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  • 1995-1999  (1.794)
  • 1995  (1.794)
  • Engineering General  (737)
  • Chemical Engineering  (730)
  • Genetics  (327)
  • Nuclear reactions
Datenquelle
Materialart
Erscheinungszeitraum
  • 1995-1999  (1.794)
Jahr
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    Characterization of Japanese families with early-onset type 2 (non-insulin dependent) diabetes mellitus and screening for mutations in the glucokinase and mitochondrial tRNALeu(UUR) genes (1995)
    Springer
    Acta diabetologica 32 (1995), S. 17-22 
    Details
    ISSN: 1432-5233
    Schlagwort(e): Maturity-onset diabetes of the young (MODY) ; Genetics ; Diabetes mellitus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Genetic linkage studies of families with earlyonset type 2 diabetes have facilitated the identification of diabetes-susceptibility genes. In order to assess the feasibility of using linkage approaches to identify genes responsible for the development of type 2 diabetes in Japanese subjects, we examined our clinical records for multigenerational families suitable for genetic studies. We identified 16 families in which at least one subject was diagnosed with type 2 diabetes before 25 years of age. Seven of these families had a pattern of inheritance consistent with a diagnosis of maturity-onset diabetes of the young (MODY) and nine families showed a complex pattern of inheritance of type 2 diabetes with transmission of diabetes-susceptibility genes from both parents. The glucokinase and mitochondrial tRNALeu(UUR) genes were screened for mutations in at least one affected subject from each family in order to assess the contribution of mutations in these genes to the development of the diabetes. No mutations were found, which suggests that the diabetes in these families resulted from mutations in other genes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00581039
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  • 2
    Digitale Medien
    Digitale Medien
    Identification of genomic regions affecting plant height in sorghum and maize (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 380-388 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Genetics ; Breeding ; Sorghum bicolor Zea mays
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The objective of this study was to use restriction fragment length polymorphisms (RFLPs) to determine the genetic location and effects of genomic regions controlling plant height in sorghum. F2 plants (152) from the cross CK60 x PI229828 were used. Genomic and cDNA clones (106) identified 111 loci distributed among ten linkage groups covering 1299 cM. Interval mapping identified four regions, each in a separate linkage group. These regions may correspond to loci (dw) previously identified by alleles with qualitative effects. Also, these regions identified in sorghum may be orthologous to those previously reported for plant height in maize. Gene effects and gene action varied among genomic regions. In each region, PI229828 alleles resulted in increased plant height. Each region accounted for 9.2–28.7% of the phenotypic variation. Positive, additive effects ranged from 15 to 32cm. Tallness was dominant or overdominant and conferred by alleles from PI229828 for three quantitative trait loci (QTL). At the fourth QTL, PI229828 contributed to increased plant height, but short stature was partially dominant. One digenic interaction was significant. The presence of a PI229828 allele at one region diminished the effects of the other region. A multiple model indicated that these four regions collectively accounted for 63.4% of the total phenotypic variation. The utility of this information for germplasm conversion through backcross breeding is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00221980
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  • 3
    Digitale Medien
    Digitale Medien
    Mixed desmoplastic primitive neuroepithelial tumor of infancy: a light microscopic, immunocytochemical, ultrastructural and genetic study (1995)
    Springer
    Acta neuropathologica 89 (1995), S. 99-104 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Primitive neuroepithelial tumor ; Desmoplastic small cell tumor ; Brain tumor of infancy Immunocytochemistry ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We describe a case of a desmoplastic brain tumor which was initially resected from the right fronto-temporal region in a 2 year-old boy. This nodular, calcified tumor was vascularized by the internal carotid artery and the middle meningeal artery branches. Grossly, it contained several mucoid cysts. Light microscopy showed cords or nests of small cuboidal cells surrounded by a loose connective tissue and desmoplasic areas containing fibers and spindle cells. The cuboidal cells expressed epithelial, neuronal and neuroendocrine markers. Some foci of spindle cells showed glial differentiation. The tumor recurred 16 months later and displayed some characteristics of the small cell neuroepithelial component, mitoses being conspicuous. Electron microscopy revealed undifferentiated clear cells, some containing neurosecretory granules. Karyotyping demonstrated the following formula: 〈 15 〉 46, t(8;11) (a13; q11). The chromosome 11 breakpoint was different from that described in Ewing's sarcoma. This isolated translocation has not been previously reported to our knowledge. These unusual features lead us to report this case and to discuss its pathogenesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00294266
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  • 4
    Digitale Medien
    Digitale Medien
    Fetal brain disruption sequence in sisters (1995)
    Springer
    European journal of pediatrics 154 (1995), S. 654-657 
    Details
    ISSN: 1432-1076
    Schlagwort(e): Key words Fetal development ; Brain diseases ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We report two female siblings with the fetal brain disruption sequence. Extensive investigation of both children failed to define a definitive aetiology but clinical and laboratory findings are consistent with a hitherto unknown storage disease. We postulate that the accumulation of a neurotoxic metabolite may be responsible for the disease phenotype observed. This is the first report of recurrence of the fetal brain disruption sequence and supports the existence of a genetic form of this condition. Previous reports have emphasized possible environmental aetiologies. Infants with fetal brain disruption sequence should be investigated exhaustively and, in the absence of definitive evidence of an environmental cause, the possibility of a genetic aetiology should be considered. In some families the recurrence risk may be as high as one in four.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004310050366
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  • 5
    Digitale Medien
    Digitale Medien
    Floating-Harbor syndrome: description of a further patient, review of the literature, and suggestion of autosomal dominant inheritance (1995)
    Springer
    European journal of pediatrics 154 (1995), S. 658-661 
    Details
    ISSN: 1432-1076
    Schlagwort(e): Key words Floating-Harbor ; syndrome ; Growth retardation ; Dysmorphology ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The Floating-Harbor syndrome is a growth retardation syndrome with delayed bone age, speech development, and typical facial features. The face is triangular with deep-set eyes, long eyelashes, bulbous nose, wide columella, short philtrum, and thin lips. We present an additional patient and review 16 cases from the literature. The possible phenotype in the patient's mother suggests a dominant mode of inheritance for the syndrome. Conclusion The Floating Harbor syndrome is a growth deficiency syndrome characterized by proportionate short stature, characteristic face and delayed speech development. Inheritance is possibly autosomal dominant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004310050367
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  • 6
    Digitale Medien
    Digitale Medien
    Genetic counselling on brittle grounds: recurring osteogenesis imperfecta due to parental mosaicism for a dominant mutation (1995)
    Springer
    European journal of pediatrics 154 (1995), S. 123-129 
    Details
    ISSN: 1432-1076
    Schlagwort(e): Key words Osteogenesis imperfecta ; Collagen I ; Mosaicism ; Genetics ; Recurrence risk
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Osteogenesis imperfecta (OI), a dominantly inherited connective tissue disorder, is usually caused by defects in collagen I. There is growing evidence for parental mosaicism that results in affected children born to unaffected parents. This situation poses a difficult task for the geneticist because a mosaic parent may appear clinically healthy while carrying the mutation in a fraction of her or his gonadal cells. To illustrate this problem, we report a Swiss couple whose first child was affected with severe OI. The unexpected recurrence of the disorder in the second child raised the suspicion of a recessive trait or, rather, of parental mosaicism. We identified the responsible collagen mutation in the COL1A2 gene (Gly688Ser in the α2(I)-chain) in both children and demonstrated the father to be a somatic mosaic for this mutation and to have subtle clinical signs such as soft skin and short stature that may be a result of his mosaic state.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004310050261
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  • 7
    Digitale Medien
    Digitale Medien
    Fetal brain disruption sequence in sisters (1995)
    Springer
    European journal of pediatrics 154 (1995), S. 654-657 
    Details
    ISSN: 1432-1076
    Schlagwort(e): Fetal development ; Brain diseases ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We report two female siblings with the fetal brain disruption sequence. Extensive investigation of both children failed to define a definitive aetiology but clinical and laboratory findings are consistent with a hitherto unknown storage disease. We postulate that the accumulation of a neurotoxic metabolite may be responsible for the disease phenotype observed. This is the first report of recurrence of the fetal brain disruption sequence and supports the existence of a genetic form of this condition. Previous reports have emphasized possible environmental aetiologies. Infants with fetal brain disruption sequence should be investigated exhaustively and, in the absence of definitive evidence of an environmental cause, the possibility of a genetic aetiology should be considered. In some families the recurrence risk may be as high as one in four.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02079071
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  • 8
    Digitale Medien
    Digitale Medien
    Floating-Harbor syndrome: description of a further patient, review of the literature, and suggestion of autosomal dominant inheritance (1995)
    Springer
    European journal of pediatrics 154 (1995), S. 658-661 
    Details
    ISSN: 1432-1076
    Schlagwort(e): Floating-Harbor syndrome ; Growth retardation ; Dysmorphology ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Abstract The Floating-Harbor syndrome is a growth retardation syndrome with delayed bone age, speech development, and typical facial features. The face is triangular with deep-set eyes, long eyelashes, bulbous nose, wide columella, short philtrum, and thin lips. We present an additional patient and review 16 cases from the literature. The possible phenotype in the patient's mother suggests a dominant mode of inheritance for the syndrome. Conclusion The Floating Harbor syndrome is a growth deficiency syndrome characterized by proportionate short stature, characteristic face and delayed speech development. Inheritance is possibly autosomal dominant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02079072
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  • 9
    Digitale Medien
    Digitale Medien
    Genetische Faktoren bei der Entstehung und Progression maligner Melanome (1995)
    Springer
    Der Hautarzt 46 (1995), S. 394-399 
    Details
    ISSN: 1432-1173
    Schlagwort(e): Schlüsselwörter Malignes Melanom ; Genetische Instabilität ; Genetik ; Syndrom der dysplastischen Nävi ; Xeroderma pigmentosum ; Key words Malignant melanoma ; Genetic instability ; Genetics ; Dysplastic nevus syndrome ; Xeroderma pigmentosum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary Exposure of the skin to ultraviolet irradiation is an important risk factor for the development of malignant melanoma, with UVA possibly playing an important role. Hereditary factors are also relevant. In the dysplastic nevus syndrome a genetic instability has been shown by different methods. In xeroderma pigmentosum the DNA repair defect is thought to be responsible for the high incidence of malignant melanoma. Frequent and non-random changes in certain chromosomes have been demonstrated in melanoma cells. These might contain sequences that control melanoma growth or melanoma suppressor genes. Especially the short arm of chromosome 9 is thought to contain one of these genes. This hypothesis is supported by a genetic linkage analysis in melanoma families and the demonstration of a germ line deletion of the locus 9p21 in a patient with eight primary melanomas. Changes in known tumor suppressor genes and oncogenes have also been reported in melanoma, but no consistent sequence of genetic events is known.
    Notizen: Zusammenfassung Die Exposition der Haut mit ultravioletten Strahlen ist ein wichtiger Risikofaktor für die Entwicklung eines malignen Melanoms. Möglicherweise spielt hierbei UVA-A eine besondere Rolle. Daneben sind hereditäre Faktoren von Bedeutung. Während beim Syndrom der dysplastischen Nävi eine genetische Instabilität mit verschiedenen Methoden nachgewiesen wurde, wird bei Xeroderma pigmentosum der DNA-Reparaturdefekt für die hohe Melanominzidenz verantwortlich gemacht. In Melanomzellen sind überzufällig häufig karyotypische Veränderungen in bestimmten Chromosomen gefunden worden. Diese enthalten möglicherweise Melanomwachstumsregulierende Sequenzen oder Melanom-Suppressorgene. Insbesondere der kurze Arm des Chromosoms 9 steht in Verdacht, eines dieser Gene zu enthalten. Diese Hypothese wird auch unterstützt durch eine genetische Kopplungsanalyse an Melanomfamilien und dem Nachweis einer Keimbahndeletion des Lokus 9p21 bei einer Patientin mit 8 primären Melanomen. Veränderungen an bereits bekannten Tumorsuppressorgenen oder Onkogenen sind ebenfalls in Melanomen beschrieben worden, ohne daß jedoch eine konsistente Reihenfolge von genetischen Ereignissen bekannt wäre.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001050050272
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  • 10
    Digitale Medien
    Digitale Medien
    Allelic relationships between genes for resistance to tomato spotted wilt tospovirus in Capsicum chinense (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 146-149 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Capsicum chinense ; Resistance gene ; Genetics ; Pepper ; Tomato spotted wilt virus ; Tospoviruses
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Pepper (Capsicum chinense Jacq.) has been reported to be an important reservoir of resistance genes to tomato spotted wilt virus (TSWV). The genes for TSWV resistance present in three C. chinense lines (‘PI 152225’, ‘PI 159236’ and ‘Panca’) were investigated for allelism. All resistant lines were crossed with each other. Parents, F1, backcrosses and F2 populations (including reciprocals) developed from those crosses were mechanically inoculated with a highly virulent TSWV isolate. Susceptible C. annuum cv ‘Magda’ was used to check inoculum virulence. Fifty plants of the F1 hybrids; ‘Magda’ x ‘PI 152225’, ‘Magda’ x ‘PI 159236’, and ‘Magda’ x 'Panca, were also inoculated with the TSWV isolate. The resistance response in all C. chinense sources was associated with a localized, hypersensitive-like reaction that was phenotypically expressed as a prompt formation of large local lesions accompanied by premature leaf abscission. All F1 generations presented a final score of resistant; indicating that the expression of resistance to TSWV is conditioned by a dominant gene regardless of the source. The absence of segregation for resistance to TSWV that was observed in all generations of the crosses between C. chinense lines indicated that either a tightly linked group of genes exists or that the resistance is governed by the same single major gene (probably the already described Tsw gene). Previous reports have indicated that the Tsw gene is not effective against tospovirus members of serogroup II, i.e. tomato chlorotic spot virus (TCSV) and groundnut ring spot virus (GRSV). In the assay described here, all of the C. chinense lines showed, after mechanical inoculation, an identical susceptibility response to the TCSV and GRSV isolates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00221009
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  • 11
    Digitale Medien
    Digitale Medien
    Diallel analysis for mineral element absorption in tropical adapted soybeans [Glycine max (L.) Merrill] (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 707-713 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Mineral stress ; Nutrient efficiency ; Aluminium tolerance ; Inheritance ; Genetics ; Breeding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Brazilian tropical adapted soybeans contains, in addition to superior morphological characters, genetic factors for tolerance to cultivation in acidic, mineral-stressed soils. However, the selection process for these hindrances has been empirical, and information on the genetics of mineral element uptake by the plant is necessary. The objective of this investigation was to identify the mode of inheritance for the absorption of phosphorus, potassium, calcium, magnesium, iron, aluminium, manganese, zinc and copper in a 9 × 9 diallel cross. General combining ability (GCA) was higher than specific combining ability (SCA), with the exception of copper, manganese and zinc, indicating predominantly additive effects. The ratios of GCA/SCA varied between 3.4 (calcium) and 8.5 (magnesium). The regression of covariance (Wr) on variance (Vr) showed that the additive-dominance model explained the genetic differences in this germ plasm. However, the detection of overdominance could be related to possible heterozygosity in the parental varieties for mineral absorption. Broad-sense heritability values were higher than narrow sense heritability values for aluminium, iron, potassium, calcium and magnesium, being in the range of 67.9–86.9% and 42.0–56.6%, respectively. This is an indication that soybeans can be further improved to efficient utilisation of nutrients and to tolerate toxic factors in the soil.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00222137
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  • 12
    Digitale Medien
    Digitale Medien
    Opioid operant self-administration, analgesia, stimulation and respiratory depression inμ-deficient mice (1995)
    Springer
    Psychopharmacology 117 (1995), S. 23-31 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Opioid ; Genetics ; Self-administration ; CXBK/ByJ ; Reinforcement
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract It is commonly thought thatμ-receptors play an important role in the reinforcing effects of opioids. In the present study, inbred strains widely divergent in CNS opiate receptor densities were used to investigate the influence of genetic variation in receptor concentration on opioid-reinforced behavior. In particular, the CXBK/ByJ mice were used as an investigative tool because of their significantly lower number of CNSμ opioid receptors. The behavioral pharmacology of opioids in theμ-deficient CXBK/ByJ mice was compared to other commonly used inbred mouse strains, C57BL/6J and BALB/cJ, and the opiate receptor rich CXBH/ByJ mice. Operant opioid reinforced behavior, opioid-induced locomotor stimulation, analgesia and respiratory depression were investigated in all four inbred strains. To assess the acquisition and maintenance of opioid reinforced behavior, oral self-administration of the potent benzimidazole opioid, etonitazene, was determined using an operant fixed-ratio schedule of reinforcement (FR 8). Acquisition of etonitazene-reinforced behavior was established in all four strains including theμ-deficient CXBK/ByJ mice. However, there were significant genetic differences in the amount of drug intake during the maintenance of opioid-reinforced behavior and extinction behavior following vehicle substitution. For example, drug intake was significantly greater in the BK versus BH mice during the maintenance phase and an extinction burst was seen in the BH but not the BK mice following vehicle substitution. Thus,μ-receptor density may not account for individual variability in the acquisition of opioid-reinforced behavior under these conditions. Sensitivity to etonitazene-induced respiratory depression, stimulation of locomotor activity and analgesia were unrelated to drug intake during self-administration sessions across these four inbred strains. These data indicate that inherited differences in CNSμ-opiate receptor concentrations do not affect acquisition of etonitazene-reinforced behavior.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02245094
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  • 13
    Digitale Medien
    Digitale Medien
    Chromosomal mapping of loci influencing sensitivity to cocaine-induced seizures in BXD recombinant inbred strains of mice (1995)
    Springer
    Psychopharmacology 117 (1995), S. 62-66 
    Details
    ISSN: 1432-2072
    Schlagwort(e): Cocaine ; Quantitative trait loci ; Seizure ; Recombinant inbred strains ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Among inbred mice, genetic factors mediate differences in sensitivity to the convulsant properties of cocaine; however, the gene(s) underlying cocaine's effects have not been identified. To help elucidate the gene(s) responsible for cocaine seizure susceptibility, we used recombinant inbred-quantitative trait loci (RI-QTL) analyses to identify chromosomal loci associated with cocaine-induced seizures. RI-QTL analyses seek to identify associations between a quantitative measure of a particular phenotype and one or more previously mapped marker genes across a panel of RI strains. This report describes an RI-QTL analysis of cocaine seizure susceptibility among 26 BXD RI strains. These strains showed a skewed, bimodal range of seizure susceptibility which could be the result of one or more modifying genes acting in concert with a major gene to influence cocaine sensitivity. Correlating the percent seizures displayed by each strain following 60 mg/kg cocaine with chromosomal marker data for these strains revealed a number of significant correlations clustered in two regions on chromosomes 12 and 6. This is the first identification of putative chromosomal loci associated with a cocaine-related phenotype and should facilitate identification of the gene(s) underlying cocaine toxicity and other cocaine-related phenotypes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02245099
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  • 14
    Digitale Medien
    Digitale Medien
    Sex segregation ratio and gender expression in the genus Actinidia (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 129-132 
    Details
    ISSN: 1432-2145
    Schlagwort(e): Sex control ; Disomic segregation ; Dioecy Kiwifruit ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The sex segregation ratio was checked in bi-parental families of Actinidia deliciosa (2n=6x=174) obtained by crossing four females (A12, Mo3, Br4, Hw1) with two males (T2, M1) and one fruiting male (M3h, subandroecious) according to a factorial mating design. The M3h fruiting male was also selfed. The sex ratio was checked in maternal families of A. kolomikta (2n=2x) and A. chinensis (2n=2x) as well as in A. deliciosa. Seedlings of both diploid species took 3–4 years to progress beyond juvenility, whereas a noticeable number of seedlings from biparental crosses of A. deliciosa involving A12 and Hw1 as seed parents were still non-flowering after seven growing seasons. Open-pollinated families of both diploid and hexaploid species as well as most families from biparental crosses showed a sex segregation ratio approaching 1∶1. Subandroecious lines with different degrees of ovary and pistil development appeared in proportions of 0–4.2%, depending on the cross, but only 6 of the 2567 male vines checked were capable of setting fruit. No case of self-fertility or apomixis was detected among 1866 bagged female vines. Selfed M3h progenies gave only female and male phenotypes in a ratio of 1 female to 3 males. No off-type vines were found among these progenies. The same disomic sex segregation ratio seems to be operating at different ploidy levels in the genus Actinidia. Since selfed fruiting males produced both female and male individuals, the male sex appears to be the heterogametic one. Such evidence indicates that a monofactorial system based on one or more linked genes or on an X/Y chromosome set must be controlling sex expression. How a monofactorial sex-determining mechanism could operate in polyploids to give a 1∶1 female: male ratio is discussed. Minor modifying gene(s) seem to be responsible for the feminization of males, and their expression appears enhanced by environmental conditions. Masculinizing gene(s) seem to be lacking in female genotypes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00242255
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  • 15
    Digitale Medien
    Digitale Medien
    Genetic mapping of adrenergic receptor genes in humans (1995)
    Springer
    Journal of molecular medicine 73 (1995), S. 299-306 
    Details
    ISSN: 1432-1440
    Schlagwort(e): Adrenergic receptors ; Human genetics ; Restriction fragment length polymorphism ; Chromosome mapping ; Linkage ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We have genetically mapped the genes encoding four human adrenergic receptors (ARs) of subtypes α1C, α2A, α2B, and β1, which are prototypic G protein coupled receptors that mediate the physiological effects of neurotransmitters, hormones, and drugs. We placed these genes onto the Cooperative Human Linkage Center (CHLC) and Genethon framework maps, within confidence intervals with greater than 1000∶1 odds. With multipoint analysis the α1C gene (locus ADRA1C) mapped to the interval between NEFL and D8S283; α2-C4, the gene encoding the α2C AR (locus ADRA2C), mapped to the interval between D4S126 and D4S62; and the α2-C10 (α2A AR)/β1 haplotype (loci ADRA2A/ ADRB1) mapped to the interval between D10S259 and D10S187. A fifth AR gene, β2, yielded significant LOD scores with markers on the long arm of chromosome 5; however, this locus (ADRB2) could not be mapped to any specific interval with odds of greater than 1000∶1. The two AR genes that are completely linked, α2-C10 and β1, were oriented on their shared 225-kb genomic fragment relative to the direction of transcription, with β1 being 5′ to α2-C10. The positioning of these genes on high-density framework maps allows them to be tested as candidates in a spectrum of diseases that might involve AR dysfunction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00231616
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  • 16
    Digitale Medien
    Digitale Medien
    Insertion/deletion polymorphism in the angiotensin-converting enzyme gene associated with macroangiopathy and blood pressure in patients with non-insulin-dependent diabetes mellitus (1995)
    Springer
    Journal of molecular medicine 73 (1995), S. 307-311 
    Details
    ISSN: 1432-1440
    Schlagwort(e): Atherosclerosis ; Hypertension ; Type 2 diabetes ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In the search for new risk factors for diabetic macroangiopathy the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme gene was studied in 237 consecutive patients (125 men and 112 women) with non-insulin-dependent diabetes. The female population showed an excess of ischemic electro-cardiographic changes or definite myocardial infarctions in the patients homozygous for the deletion [D/D; odds ratio (OR) 2.8; 95% confidence interval (CI) 1.4–5.3] and in the insertion/deletion heterozygotes (I/D; OR 1.8; CI 1.1–3.1) compared with the patients homozygous for the insertion (I/I). In the total series coronary heart disease, cerebrovascular disease, and claudication were more often observed in the patients with I/D (OR 1.5; CI 1.0–2.2) or the D/D genotype patients (OR 1.7; CI 1.1–2.6) than in those with the genotype I/I. The systolic blood pressure was lower in patients with genotype I/I (138±19 mmHg) than in those with the genotype I/D (149±22 mmHg) or D/D (150±21 mmHg; P〈0.02). The prevalence of hypertension and the median urinary albumin excretion rate also tended to be lowest in the I/I genotype patients. Multiple logistic analysis revealed that in women the angiotensin-converting enzyme D/D genotype is independently associated with coronary heart disease. Our findings suggest that variation at the angiotensin-converting enzyme gene locus is one of the factors involved in the predisposition of diabetic patients to the development of arterial disease and hypertension.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00231617
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  • 17
    Digitale Medien
    Digitale Medien
    A genetic study of idiopathic focal dystonias (1995)
    Springer
    Journal of neurology 242 (1995), S. 508-511 
    Details
    ISSN: 1432-1459
    Schlagwort(e): Dystonia ; Torticollis ; Blepharospasm ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The inheritance of focal dystonias was investigated in 43 families containing 43 index cases with torticollis (n = 21), blepharospasm (n = 18) and writer's cramp (n = 4). They generated a potential population of 235 first-degree relatives, and 168 out of 179 living first-degree relatives were examined. Ten relatives with dystonia were identified in ten families. Another two parents from two of the same group of ten families were affected according to the family history. The majority of the secondary cases (six patients, five siblings, and one child) were not aware of any dystonia. The tendency for affected relatives to have the same type of dystonia as index patients was observed only for torticollis. Overall, 23% of index patients had relatives with dystonia. Segregation analysis suggested the presence of an autosomal dominant gene or genes with reduced penetrante underlying focal dystonia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00867421
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  • 18
    Digitale Medien
    Digitale Medien
    Characterization of B-cell lines from SLE patients and their relatives (1995)
    Springer
    Rheumatology international 15 (1995), S. 89-93 
    Details
    ISSN: 1437-160X
    Schlagwort(e): SLE Lupus ; BBV transformation ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Epstein-Barr-virus (EBV)-transformed lymphoblastoid B-cell lines were generated from peripheral blood lymphocytes of 55 patients with systemic lupus erythematosus (SLE) and 44 healthy relatives. All donors have previously been extensively characterized with regard to clinical, serologic, and genetic parameters. Here, peripheral blood lymphocytes and lines were characterized for cell surface antigens. Furthermore, autoantibody production and proliferation rate of the cell lines were monitored. A significant difference between patients and relatives was the lower proliferation rate of EBV-transformed cell lines of the SLE patients. All SLE cell lines are available for interested researches and can be obtained from the European Cell Bank, Salisbury, UK.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00302123
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  • 19
    Digitale Medien
    Digitale Medien
    Industrial mycology and the new genetics (1995)
    Springer
    Journal of industrial microbiology and biotechnology 14 (1995), S. 355-364 
    Details
    ISSN: 1476-5535
    Schlagwort(e): Transformation ; Fungi ; Yeast ; Genetics ; Biotechnology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary The genetic investigation of fungi has been extended substantially by DNA-mediated transformation, providing a supplement to more conventional genetic approaches based upon sexual and parasexual processes. Initial transformation studies with the yeastSaccharomyces cerevisiae provided the model for transformation systems in other fungi with regard to methodology, vector construction and selection strategies. There are, however, certain differences betweenS. cerevisiae and filamentous fungi with regard to type of genomic insertion and the availability of shuttle vectors. Single-site linked insertions are common in yeast due to the high level of homology required for recombination between vectored and genomic sequences, whereas mycelial fungi often show a high frequency of heterologous and unlinked insertions, often in the form of random and multiple-site integrations. While extrachromosomally-maintained or replicative vectors are readily available for use with yeasts, such vectors have been difficult to construct for use with filamentous fungi. The development of vectors for replicative transformation with these fungi awaits further study. It is proposed that replicative vectors may be inherently less efficient for use with mycelial fungi relative to yeasts, since the mycelium, as an extended and semicontinuous network of cells, may delimit an adequate diffusion of the vector carrying the selectable gene, thus leading to a high frequency of abortive or unstable transformants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01569951
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  • 20
    Digitale Medien
    Digitale Medien
    Genetic research, adolescents, and informed consent (1995)
    Springer
    Theoretical medicine and bioethics 16 (1995), S. 347-373 
    Details
    ISSN: 1573-1200
    Schlagwort(e): Genetics ; human research ; adolescence ; child ; informed consent ; decision making ; medical ethics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Philosophie
    Notizen: Abstract The participation of adolescents in genetic research engenders unusual problems concerning the nature of their informed consent. In this study we analyze 70 consent documents collected from genetics investigators in the United States who conduct research with children and adolescents. We find that many consent documents do not reflect either the current or the developing ethical and legal standards for research with adolescents and that in many cases the documents are simply confusing or unclear. We make recommendations for change to reflect more adequately the changing perspective concerning the autonomous decision-making capacity of adolescents.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00995481
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  • 21
    Digitale Medien
    Digitale Medien
    Have fishes had their chips? The dilemma of threatened fishes (1995)
    Springer
    Environmental biology of fishes 43 (1995), S. 1-27 
    Details
    ISSN: 1573-5133
    Schlagwort(e): Conservation ; Extinction ; Rarity ; Biodiversity ; Breeding guilds ; Endemism ; Speciation ; Habitat degradation ; Environmental management ; Invasive fishes ; Genetics ; Ecology ; Stenotopy ; Captive propagation ; Legislation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Synopsis The conservation status and factors threatening fishes worldwide are reviewed in order to introduce a series of one-page articles on ‘Threatened fishes of the world’, and to encourage the incorporation of information on threatened fishes into international conservation programmes. Information on fish extinction and threat rates are compared with those of other animal groups, and the unique characteristics of fish conservation problems are highlighted. At present 979 species of fishes are listed as threatened in the IUCN Red List and at least 36 species and three subspecies are listed as recently extinct. It is argued that these figures are probably gross underestimates and that they may mislead conservation authorities and resource users about the seriousness of the situation. Freshwater fishes may be the most threatened group of vertebrates after the Amphibia. Urgent action is required to save many narrowly endemic, stenotopic species from extinction, especially in Africa, Asia and South America. The conservation of common species that drive essential ecological processes is also important. Anthropogenic pressures, especially habitat degradation, the introduction of invasive species and pollution, on inland and coastal waters are particularly severe and many major fish communities are threatened with elimination throughout the world. The conservation of marine fishes is complicated by the fact that it is difficult to ascertain their rarity. The importance of the retention of genetic variation is highlighted, and both orthodox and innovative conservation measures are encouraged. Further research on minimum viable populations, genetics, and the factors that cause fishes to become vulnerable to extinction, is urgently required.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00001812
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  • 22
    Digitale Medien
    Digitale Medien
    Domestication via hybridization of the wild tetraploid oats Avena magna and A. murphyi (1995)
    Springer
    Theoretical and applied genetics 91 (1995), S. 639-646 
    Details
    ISSN: 1432-2242
    Schlagwort(e): Gene introgression ; Genetics ; Linkage ; Taxonomy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The wild tetraploid (2n=28) oat species Avena magna and A. murphyi have been domesticated by having been transferred from the common oat, A sativa (2n=42), the characteristics of non-shedding spikelets glabrous and yellow lemma, and reduced awn formation. Domestication has been achieved by crossing the common oat with either of the tetraploid species and then backcrossing the pentaploid hybrids with pollen of the tetraploid wild parent. Among the BC plants obtained only a few produced some seeds. Fertile tetraploids exhibiting the domesticated syndrome have been selected for in the F2 generation. Although morphologically they were almost indistinguishable from the common oat, they were tetraploids. Wild x domesticated A. magna hybrids were vigorous and fertile. They retained their spikelets at maturity, lemma color and pubescence were intermediate between the parental lines, and awns were formed only on the lower floret of the spikelet. Each of these characteristics segregated in a 3∶1 fashion, indicating single gene control, as in the common oat. These four characteristics formed a linkage group in one F2 family and two linkage groups in the other two families. The usefulness of the domesticated tetraploids for oat research and production has been discussed. Taxonomically, the domesticated tetraploids were ranked as subspecies: A. magna ssp. domestica, and A. murphyi ssp. rigida.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00223291
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  • 23
    Digitale Medien
    Digitale Medien
    Blockiness of olefin copolymers and possible microphase separation in the melt (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 18-27 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Solid-catalyzed copolymerization reactions of ethylene and α-olefins can produce complex mixtures generally regarded as “polyethylenes” (including linear low-density polyethylene). The selective nature of those catalysts can lead to block-like character in segments of polymer molecules, and these segments are sufficiently dissimilar (from a thermodynamic viewpoint) to allow for the possibility of microphase separation in the melt. Such a molecular-level phase separation would substantially alter the melt rheology, the crystallization process, and hence the mechanical and optical properties of the resulting product. It would, in principle, be identical to those occurring in conventional well-defined block copolymers, allowing the thermodynamic models developed for those systems to be extended to block-like polyolefins.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350104
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  • 24
    Digitale Medien
    Digitale Medien
    Influence of processing history on the properties of a thermotropic copolyester/polycarbonate blend (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 52-63 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Relationships between the rheological, morphological, and tensile properties of an immiscible blend of 25 wt% of a thermotropic liquid crystalline polymer (LCP) with polycarbonate are presented. The shear viscosity of the blend is intermediate between the two constituent materials, and indicates immiscibility in the melt. Extrudate swell behavior is examined and found to be closely related to that of polycarbonate. The morphology of the dispersed LCP phase varies between droplets and oriented fibrils, and is highly correlated with changes in tensile properties. Fibrils are associated with increased tensile modulus, and their development is favored in the elongation flow fields present in the spinline and in the die convergence section. In all cases, blend stiffness is less than that predicted for a continuous fiber-reinforced composite. Enhanced tensile modulus is associated with both extrusion from shorter length dies and increases in spinline draw ratio, with the latter proving the most important in fibril formation.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350108
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  • 25
    Digitale Medien
    Digitale Medien
    Ultrasonic behavior of polymer blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 79-91 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: During the last few years, improvements in control strategies became a necessity, with controls being targeted on material properties. The ever-increasing demand for polymer blends spells the need for in-line instrumentation capable of monitoring blend properties such as morphology. Since ultrasonics have proved to be sensitive to properties of multiphase materials, their performance for discriminating blend morphology was explored here. In-line and off-line (static, with no flow) ultrasonic measurements were made on different blends of polystyrene (PS), polyethylene (PE), and polypropylene (PP) for various viscosity ratios, and over the entire range of composition. Blends were compounded on a ZSK-30 Werner & Pfleiderer intermeshing co-rotating twin-screw extruder. In-line ultrasonic measurements were performed on both single-screw and twin-screw extruders. Ultrasonic properties (velocity and attenuation) were found to vary approximately linearly with composition. Mixing rules were evaluated for the description of ultrasonic behavior. For the attenuation measurements, the positive deviations from these rules were found significant. The additional attenuation was attributed to scattering generated by the presence of the minor phase inclusions.
    Zusätzliches Material: 23 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350111
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  • 26
    Digitale Medien
    Digitale Medien
    Rheo-Optical behavior of binary polymer blends: The effect of simple shear flow on phase behavior (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 92-99 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The phase behavior of polymer blends under simple shear flow has been studied using a custom-designed rheo-optical system consisting of a two-dimensional small-angle light scattering (SALS) device incorporated into a conventional rheometer. Two-dimensional SALS images were gathered for model polymer blend systems with different quiescent phase behavior: polystyrene/polyisobutylene (PS/PIB) that exhibits upper critical solution temperature phase behavior and polystyrene/poly(vinyl methyl ether) (PS/PVME) that shows lower critical solution temperature phase behavior. For the PS/PIB blend, shear-induced phase mixing occurred at a critical shear rate. Below that critical shear rate, the dispersed phase was highly elongated parallel to the flow direction. For PS/PVME blends, a streak scattering pattern was observed even though the sample became optically clear after shearing. We observed, apparently for the first time, the development of a bright-streak pattern from a transient dark-streak pattern for a polymer blend system under shear. Rheo-microscopy studies revealed an intriguing wave pattern that developed coincident with the observation of a streak pattern by SALS. The relationship between the two phenomena has not yet been established.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350112
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  • 27
    Digitale Medien
    Digitale Medien
    Milligrams to kilograms: An evaluation of mixers for reactive polymer blendingPresented in part at: ACS Annual Meeting 1993 Chicago. Presented at: Polyblends '93 Conference 1993 Montreal. (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 100-114 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The dispersions of both reactive and nonreactive polymer-polymer blend systems achieved in three different mixers are compared. The dispersions are prepared using an industrial scale twin-screw extruder, a laboratory internal mixer, and a miniature cup and rotor mixer. The morphology development in the three mixers is remarkably similar: The dispersed phase is stretched into sheets and ribbons; these sheets and ribbons then break into cylinders, which subsequently break into droplets via Rayleigh-type instabilities. Drop size distributions can be accurately predicted if we know the size of cylinders formed in the high shear fields of the mixer. There is a significant effect of quenching time on blend morphology - i.e, to properly evaluate mixing, blends must be quenched extremely quickly (well within a minute). Otherwise, we need to consider the morphology development during the quenching time, which may not be relevant to the mixing. There is a uniform shear stress in the miniature mixer, unlike the other mixers, which have varying stress levels. It is shown that a high stress level followed by a lower stress level is required in polymer blending to achieve efficient mixing. In the high stress level, the dispersed phase is stretched into extended shapes, which undergo instabilities and break up upon entering the low stress level. In the miniature mixer, the dispersed phase sees only one stress level, and thus very extended shapes persist at the end of mixing. The final dispersions in the twinscrew extruder and internal mixer at matched maximum shear rates are almost identical. For similar shear rates in the miniature mixer, the final dispersion of reactive blends is comparable to the other mixers. However, the miniature mixer does a poor job in dispersing high viscosity uncompatibilized blends, and the mixing conditions must be altered to obtain efficient mixing.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350113
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  • 28
    Digitale Medien
    Digitale Medien
    Instrumented impact evaluation of a toughened carbon fiber epoxy composite (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 129-136 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Instrumented impact testing and analysis were performed on an interlaminartoughened carbon fiber epoxy composite (Toray 3900-2/T800H) and a conventional (untoughened) epoxy composite (Fiberite 934/T300). Severity of impact was varied by using a wide range of impact energy. The effect of difference in the tup of the impact instrument was discussed. The residual compressive strengths after compact (CAI's) were measured by using a universal mechanical tester. The impact damage and delamination resistance of the toughened and conventional composites were quantitatively compared. At the same impact energy, the extent of damage was much less severe and the CAI was higher for the toughened composite. Relationships between the CAI's, the state of impact damage, and impact energy were investigated. Impact damage mechanisms for these two composites were not exactly the same. The impact damage of the conventional composite exhibited much greater extents of delamination. By contrast, interlaminar delamination in the toughened composite was found to be significantly suppressed, and the impact damage was more dominated by controlled matrix cracking/fiber damage, instead of catastrophic delamination. As a result, the CAI's of the toughened composite exhibited a monotonous decrease with increase in the impact energy and in the linear dimension of extents of damage.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350202
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  • 29
    Digitale Medien
    Digitale Medien
    Melting behavior and thermal properties of high density polythylene (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 151-156 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Thermal diffusivity of high density polyethylene (HDPE) was studied over a wide range of temperatures (25 to 200°C) by melting powdered HDPE in a cylindrical mold at several pressures (101.3 to 5065 KPa gage) and recording the temperature profiles at several radial positions. The energy equation was solved numerically for cylindrical geometry. The thermal diffusivity of HDPE was fit as a function of temperature, porosity, and pressure.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350205
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  • 30
    Digitale Medien
    Digitale Medien
    Re-examination of a proposed model for nonisothermal crystallization kinetics (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 170-172 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This communication is a theoretical re-examination of the model proposed by Choe and Lee for the nonisothermal crystallization kinetics of semicrystalline polymers.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350208
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  • 31
    Digitale Medien
    Digitale Medien
    Crosslinking in halogen containing novolac electron beam negative resists (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 180-183 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Halogenophenol novolac (HPN)-based negative resists exhibit excellent sensitivity and pattern resolution properties. The HPNs act as synergists for crosslinking with other irradiation labile compounds such as naphthoquinone diazide and bisazide vs. hydrogen halide (HX) elimination reaction, resulting in additional crosslinking, probably by aryl radical recombination and/or addition. We describe a new resist formulation based on HPN binder and melamine crosslinker (Cymel 303). In this case the irradiation induced HX elimination additionally catalyzes the melamine crosslinking.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350210
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  • 32
    Digitale Medien
    Digitale Medien
    Some relationships for the orientational drawing of polymersPart of the experimental data in this article was presented at the 4Th Rolduc Polymer Meeting, April 1989, Kerkrade, The Netherlands. (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 173-179 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The orientational drawing of films from different thermoplastics has been studied. The value of the activation energy of drawing in the regions of forced elasticity (necking), high elasticity, and viscous flow (ΔE1, ΔE2, ΔE3) has been found to vary directly with the activation energy for viscous flow of the melt (ΔEη). Here ΔE1 〈 ΔE2 〈 ΔE3 = ΔEη. Thus Δ Eη characterizes the potential of thermoplastics for orientational drawing under different deformation conditions, since it reflects simultaneously both the intermolecular interaction level and chain flexibility. For maximum chain orientation, the calculated values for the change in the entropy are close to that of the entropy change during crystallization (melting) of the same polymer. The deformation of polymer may be described as a deformation of an entanglement network from the standpoint of classic elasticity theory. Some parameters for an entanglement network were calculated from the results of the drawing experiments. The density of the entanglement network (DEN) depend on the polymer composition: For flexible-chain polymers the DEN is less, for rigid-chain polymers (with coiled chains) it is higher. The DEN affects the maximum (prebreak) drawing ratio: The greater the DEN, the smaller the ratio to which a film can be drawn. At high orientation, the tensile strength of different polymer films tend to be similar, if drawing is not accompanied by crazing.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350209
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  • 33
    Digitale Medien
    Digitale Medien
    Block copolyetherester. Part 3: Preparation of block copolyetheresters by a terephthalic acid process in the presence of salts (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 190-194 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The block copolyetheresters with hard segments of poly(butylene terephthalate) and soft segments of poly(tetramethylene ether) were prepared by a terephthalic acid (TPA) process in the presence of some salts. The preparations of a block copolyetherester under various conditions were first studied in a 1 L stainless steel reactor to find the best method. Then, the preparations of four block copolyetheresters were run in a pilot plant comprising a 200 L polyesterification reactor and a 200 L polymerization reactor under the suitable condition. The presence of some salts reduced the formation of tetrahydrofuran (THF), and also reduced the total reaction time in the pilot plant. The thermal properties and various mechanical properties of the block copolytheresters prepared by the pilot plant were investigated to evaluate the feasibility of this method.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350212
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  • 34
    Digitale Medien
    Digitale Medien
    Microwave processing of two-phase systems: Composites and plymer blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 144-150 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The objective of the current paper was to extend the relationships between complex polymer structures and microwave absorptivity that were formulated in the first three papers of this series (1-3). The microwave processing of composite and polymeric blends via a cylindrical resonance wave cavity and a rectangular standing wave applicator is described. These polymeric materials were irradiated in a low power (〈 100W) electric field at 2.45 GHz. Graphite-epoxy laminates were processed in both standing and traveling wave applicators. Rapid heating and curing were achieved in both cases. An observation of significance was that, with proper tuning of the traveling wave device (the precursor of a protable repair tool), it proved to be highly effective in processing. Additionally, a compatible blend of poly(methyl methacrylate) and poly(vinylidene fluoride) was heated in and applicator and the rates of temperature rise were demonstrated to depend upon morphology.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350204
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  • 35
    Digitale Medien
    Digitale Medien
    Stress-strain behavior and dynamic mechanical properties of poly(1,1-dimethyl-1-sila-cis-pent-3-ene), poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) and of these polymers after crosslinking with sulfur (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 157-164 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Mechanical properties of polymers can be described by their stress/strain curves and by their behavior under dynamic mechanical thermal analysis (DMTA). The purpose of this paper is to report such mechanical properties for two unsaturated polycarbosilanes: poly(1, 1-dimethyl-1-sila-cis-pent-3-ene) (I) and poly(1-methyl-1-phenyl-1-sila-cis-pent-3-ene) (II). Tensile strength, elongation at break, modulus, bending modulus, Tg, and tan δ for I, II and for sulfur crosslinked I and II have been measured. The influence of polymer molecular weight, quantity of crosslinking agent, cure time, presence of carbon black filler, the effect of crosshead speed, and frequency on these properties was investigated.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350206
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  • 36
    Digitale Medien
    Digitale Medien
    The effects of physical aging on the brittle fracture behavior of polymers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 165-169 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The effects of physical aging on the failure behavior of a typical brittle polymer, polystyrene, have been studied. Properties examined were creep rupture lifetimes, fatigue lifetimes, and environmental stress cracking in ethanol. Fractured samples were examined both optically and by scanning electron microscopy to determine the degree of crazing. It was found that a longer physical aging time produced shorter lifetimes in all cases. The main reason for this is the reduction in craze strength caused by a reduced toughness due to physical aging. A long aging time was found to delay craze formation, but once formed, these crazes were much less stable than those formed with a short aging time. The effects of aging are important on failure prediction criteria and on testing methodologies, and the implications are discussed.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350207
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  • 37
    Digitale Medien
    Digitale Medien
    Investigation of cure in epoxy acrylate resins using rheological and dielectric measurements (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 184-189 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Dielectric and rheological measurements are reported for the cure in a series of mixtures of an epoxy-acrylate with n-butyl methacrylate. The level of the initiator and properties of the epoxy acrylate and n-butyl methacrylate influence the cure characteristics and morphology of the film formed. Analysis of the rheological data indicates that during the curing process, microphase separation occurs within the mixture. The changes in the dielectric relaxation behavior with composition of the completely cured material is also consistent with microphase separation occurring in these resins while they are cured.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350211
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  • 38
    Digitale Medien
    Digitale Medien
    Monomer chain cross-transfer constants and cross termination factor evaluations on styrene-acrylonitrile copolymerization (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 195-201 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Using low conversion bulk copolymerization experimental data and the apparent rate constant model, the monomer chain cross-transfer rate constants and the cross-termination coefficient were evaluated. It was found that the dependence of the cross-termination coefficient on composition is a function of initiator efficiency and that monomer chain cross-transfer rate constant are relevant for the theoretical estimation of the molecular weights and molecular weight distributions.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350213
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  • 39
    Digitale Medien
    Digitale Medien
    Rheology of thermoplastic starch: Effects of temperature, moisture content, and additives on melt viscosity (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 202-210 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The melt viscosity of thermoplastic starch has been investigated as a function of temperature, moisture content, and processing conditions. The effects of various low molecular weight additives have also been studied. Starch melts exhibit power law behavior over the range of shear rates studied. Melt viscosity decreased with increasing temperature and moisture content (MC). The power law index m increased with increasing temperature. The consistency K decreased with increasing temperature and increasing moisture content. Moisture content during the pelletizing step influenced melt viscosities measured after equilibration to different MCs. All additives studied except glycerol monostearate (GMS) significantly lowered the melt viscosity of starch, some more effectively than water relative to starch with 15% MC. Starch with GMS had viscosities essentially the same as, or slightly higher than, starch/water. This behavior may be due to the presence of unmelted helical inclusion complexes of starch and GMS. Starch formulations at 160°C exhibited melt visocosities similar to an LDPE of melt index 1.8.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350214
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  • 40
    Digitale Medien
    Digitale Medien
    Preface (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 289-290 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350402
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  • 41
    Digitale Medien
    Digitale Medien
    On the phenomenology of yield in bisphenol-a polycarbonate (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 291-303 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The phenomenology of yield in bisphenol-A polycarbonate is explored through tensile tests on thin rectangular specimens and through pressure-induced bulging of thin, clamped circular disks. In a tensile test, while the nominal critical stress at which yield initiates and the nominal draw stress at which a stable neck propagates along a specimen depend on the temperature and the strain rate, the ratio of the draw stress to the critical stress is shown to be approximately 0.75 over a temperature range of 22 to 65°C and strain-rates in the range of 10-4 to 100 s-1. Specimens subjected to constant tensile loads between the draw and critical stresses are shown first to creep till stretches on the order of 1.06 are attained and then are shown to undergo stable necking. Tensile tests on thin, wide rectangular specimens show that yielding initiates through shear bands that broaden and intersect to generate necks, which subsequently propagate along the specimen. In pressure-induced bulging of clamped disks, biaxial stretching progresses monotonically under increasing pressures; strain localization does occur near the outer edges of the specimens, however. Heating of a specimen with a substantial stably necked region shows that the temperature-induced recovery of the specimen from its deformed state begins well below the transition temperature Tg of the material, although most of the recovery occurs at Tg.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350403
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  • 42
    Digitale Medien
    Digitale Medien
    Plastic behavior and deformation textures of poly(etherether ketone) under uniaxial tension and simple shear (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 317-330 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Samples of poly(etherether ketone) (PEEK) were subjected to large plastic deformations under uniaxial tension and simple shear by means of a new video-controlled testing method at constant true strain rate. The “equivalent” stress-strain curves obtained under the two loading modes are close at the yield point, but diverge drastically at large strains, with a rapidly increasing hardening in tension and a moderate hardening under simple shear. X-ray diffraction goniometry shows that these contrasting behaviors are associated with the different textures developed in the crystallite orientations. Under tension, the PEEK lamellae are progressively tilted in such a way that the chain axis becomes oriented parallel to the tensile axis; in the other mode, the final chain orientation is near to the shear axis. DSC analyses of deformed samples in both modes are carried out. The results show that the tension loading induces a fragmentation of the thin lamellae, while the shear mode generates less fragmentation. A quantitative model is presented that involves a composite approach: (i) the viscoplastic deformation of the crystalline lamellae, which is controlled by chain slip and transverse slip systems on planes parallel to the c axis, and (ii) the hyperelastic deformation of the amorphous phase, which depends on the affine unfolding of statistically distributed subchains. A discussion of the influence of the CRSS values on the stress-strain curves and textures is developed by means of this model.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350406
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  • 43
    Digitale Medien
    Digitale Medien
    Mechanical response of beams of a nonlinear viscoelastic material (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 345-350 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A constitutive equation for nonlinear viscoelasticity is used to model the mechanical response of solid polymers such as polycarbonate. The nonlinearity arises from a reduced time which causes stress relaxation to accelerate with increasing strain. The constitutive equation can account for the occurrence of yield in a homogeneous uniaxial constant strain rate test. The constitutive equation is used in a study of the pure bending of beams. It is assumed that the classical assumption of beam theory is valid, i.e., plane sections remains plane. At each fixed time, the strains vary linearly through the depth of the beam. At a fixed material element the strain varies in time with the curvature. This spatial variation of the strains combined with the nonlinear dependence of the reduced time on strain leads to a significantly different response from that given by traditional beam theory. The implications of this for the bending moment history, stress distributions, and other factors that relate to beam design are discussed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350408
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  • 44
    Digitale Medien
    Digitale Medien
    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350501
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  • 45
    Digitale Medien
    Digitale Medien
    Preface (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 385-386 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350502
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  • 46
    Digitale Medien
    Digitale Medien
    The evolution of material properties during physical aging (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 403-410 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Aging experiments using the NIST (National Institute of Standards and Technology) torsional dilatometer have been performed in which the temperature of an isothermally equilibrated epoxy glass was abruptly changed to a new temperature T0 and the evolution of the volume and torsional relaxation responses recorded. The results of down-jump and up-jump experiments were found to differ dramatically. Not only is the normal asymmetry of volume approach to equilibrium found, but the mechanical responses are found to evolve differently from the volume response, contrary to simple free volume models of the physical aging process. It is found that the torsional modulus changes with increasing time after the T-jump. In the case of the down-jump the evolution of the modulus ceases prior to that of the volume of the sample. In the up-jump experiment, the contrary is true, viz., the modulus continues to evolve after the volume has attained its equilibrium value. The implications of this for the description of material behavior are discussed.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350505
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  • 47
    Digitale Medien
    Digitale Medien
    An investigation into the three-dimensional stress-birefringence-strain relationship in elastomers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 395-402 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The statistical theory of the birefringence of an individual non-Gaussian elastomer chain is used together with a chain network description of rubber elasticity to develop a relationship among the strain, birefringence, and stress in elastomers, valid for large deformations under generalized strain states. The result is a fully three-dimensional internal variable based constitutive model of rubber elasticity in which measurement of the elastomeric birefringence during straining in one deformation state characterizes the optically anisotropic response of the elastomer. Simultaneous measurement of the stress vs. strain response provides the rubbery modulus and limiting network extensibility properties needed to completely characterize the mechanical anisotropy of the material. Once characterized using the single, large deformation experiment, the birefringence and stress responses of the elastomer in other deformation states may then be predicted without adjusting any model parameters. The theory is compared to experimental studies from the literature of large strain deformations of elastomers in uniaxial tension and compression for which the exhibited birefringence and stress responses of deforming elastomers have been simultaneously recorded.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350504
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  • 48
    Digitale Medien
    Digitale Medien
    A constitutive theory for rigid polyurethane foam (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 387-394 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Rigid, closed-cell, polyurethane foam consists of interconnected polyurethane plates that form cells. When this foam is compressed, it exhibits an initial elastic regime, which is followed by a plateau regime in which the load required to compress the foam remains nearly constant. In the plateau regime, cell walls are damaged and large permanent volume changes are generated. As additional load is applied, cell walls are compressed against neighboring cell walls, and the stiffness of the foam increases and approaches a value equal to that of solid poyurethane. When the foam is loaded in tension, the cell walls are damaged and the foam fractures. A constitutive theory for rigid polyurethane foam has been developed. This theory is based on a decomposition of the foam in two parts: a skeleton and a nonlinear elastic continuum in parallel. The skeleton accounts for the foam behavior in the elastic and plateau regimes and is described using a coupled plasticity with continuum damage theory. The nonlinear elastic continuum accounts for the lock-up of the foam due to internal gas pressure and cell wall interactions. This new constitutive theory has been implemented in both static and dynamic finite element codes. Numerical simulations performed using the new constitutive theory are presented.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350503
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  • 49
    Digitale Medien
    Digitale Medien
    Measurement of the J integral in polycarbonate using the method of caustics (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 426-431 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The nonlinear fracture behavior of polycarbonate is investigated. The feasibility of measurement of the J integral through the optical method of reflected caustics is demonstrated. Significant increase in the crack growth resistance during small amounts of crack extension is observed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350508
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  • 50
    Digitale Medien
    Digitale Medien
    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350601
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  • 51
    Digitale Medien
    Digitale Medien
    Effect of the pressure drop rate on cell nucleation in continuous processing of microcellular polymers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 432-440 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Microllular plastics are cellular polymers characterized by cell densities greater than 109 cells/cm3 and cells smaller than 10 μm. One of the critical steps in the continuous production of microcellular plastics is the promotion of high cell nucleation rates in a flowing polymer matrix. These high nucleation rates can be achieved by first forming a polymer/gas solution followed by rapidly decreasing the solubility of gas in the polymer. Since, in the processing range of interest, the gas solubility in the polymer decreases as the pressure decreases, a rapid pressure drop element, consisting of a nozzle, has been employed as a continuous microcellular nucleation device. In this paper, the effects of the pressure drop rate on the nucleation of cells and the cell density are discussed. The experimental results indicate that both the magnitude and the cell density are discussed. The experimental results indicate that both the magnitude and the rate of pressure drop play a strong role in microcellular processing. The pressure phenomenon affects the thermodynamic instability induced in the polymer/gas solution and the competition between cell nucleation and growth.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350509
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  • 52
    Digitale Medien
    Digitale Medien
    Effects of variable viscosity on the steady melting of thermoplastics during spin welding (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 441-459 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The steady melting of several amorphous and semicrystalline polymers during spin welding is analyzed by solving a simplified set of momentum and energy balance equations, assuming a shear-rate and temperature-dependent viscosity. A numerical model is developed for predicting the flow field and the temperature distribution in the molten film. It is shown that the steady melting rate of the thermoplastic solid is affected by the variable viscosity, by the pressure applied on the parts to be joined, and by a balance between the viscous heat generation in the melt and the convection of colder material into the molten film. The convection of heat in the outflow direction is shown to have a much smaller effect on the melting process.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350510
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  • 53
    Digitale Medien
    Digitale Medien
    Enhanced polycarbonate toughness. II: Mechanisms (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 477-482 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Glassy shell-rubbery core polymer particles, 0.1 to 0.2 μm in diameter, increase the plane strain JIC values of 3.175 mm thick polycarbonate from 3.05 kJ/m2 (no particles) to 9.5 kJ/m2 (7.5 phr particles) at 23°C. Some modest decreases in these values are caused by tests at -20°C in samples 9.525 and 3.175 mm thick. If only the particle concentration is varied, JIC increases monotonically to 7.5 phr (by wt), then levels off or decreases slightly at 10.0 phr. The total volume of 1 to 2 μm diameter cavities formed in the matrix by the apparently unbonded particles behaves similarly; cavity volume and JIC are directly related. With increasing particle concentration the tensile modulus is unchanged, the yield stress and strain decrease modestly, the strain at fracture decreases appreciably, and the heat recoverable orientation in the fractured samples decreases. Few cavities are formed. The particles reduce the extent of shear deformation in the tensile samples.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350604
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  • 54
    Digitale Medien
    Digitale Medien
    A process model for nonisothermal photopolymerization with a laser light source. I: Basic model development (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 483-492 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A mathematical model for a laser-induced photopolymerization process has been developed. This model simulates important aspects of stereolithography, a rapid prototyping process used for the production of three-dimensional plastic parts. The model consists of a set of coupled partial differential equations and considers irradiation, chemical reaction, and heat transfer in a small zone of material exposed to a stationary UV laser source. Numerical techniques are used for an approximate solution of the model equations, and the output includes spatial and temporal variations in the conversion of monomer to polymer, depletion of photoinitiator, and local variations of temperature in and around the region contacted by the laser light. Maximum conversions of approximately 60% and peak temperature rises of approximately 35° C were calculated for the cylindrical exposed region. Results have provided insights concerning laser dwell time, depth penetration, and the uniformity of polymer formed during the stereolithography process.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350605
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  • 55
    Digitale Medien
    Digitale Medien
    The relationship between structure and deformation behavior of sulfone polymers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 499-505 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The deformation of three types of sulfone polymers - polysulfone (PSF), poly(ether sulfone) (PESF), and polyarylsulfone (PASF) - was performed with a mechanical testing system (MTS). The result and samples were studied using a transmission electron microscope (TEM), a dynamic mechanical analyzer (DMA), and a dielectric thermal analyzer (DETA). Stripes on TEM micrographs for small deformations increase with the fracture toughness (GIc). The activation energy (Ea) of the α-transition was determined from DETA. The results show that both Ea and TEM micrographs can be used to qualitatively estimate the order of GIc of sulfone polymers. An energy model was proposed to explain this phenomenon.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350607
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  • 56
    Digitale Medien
    Digitale Medien
    Molecular weight dependence of the fracture toughness of glassy polymers arising from crack propagation through a craze (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 419-425 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: We investigate criteria for craze failure at a crack tip and the dependence of craze failure on the molecular weight of the polymer. Our micromechanics model is based on the presence of cross-tie fibrils in the craze microstructure. These cross-tie fibrils give the craze some small lateral load bearing capacity so that they can transfer stress between the main fibrils. This load transfer mechanism allows the normal stress on the fibrils directly ahead of the crack tip in the center of the craze to reach the breaking stress of the polymer chains. We solve for stress field near the crack trip and use it to relate craze failure to the external loading and microstructural quantities such as the craze widening (drawing) stress, the fibril spacing, the molecular weight, and the force to break a single polymer chain. The relationship between energy flow to the crack tip due to external loading and the work of local fracture by fibril breakdown is also obtained. Our analysis shows that the normal stress acting on the fibrils at the crack tip increases linearly as the square root of the craze thickness, assuming that the normal stress distribution is uniform and is equal to the drawing stress acting on the craze-bulk interface. The critical crack opening displacement, and hence the fracture toghness is shown to be proportional to [1-(Me/qMn)]2, where Me is the entanglement molecular weight, Mn is the number average molecular weight of polymer before crazing, and q is the fraction of entangled strands that do not undergo chain scission in forming the craze.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350507
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  • 57
    Digitale Medien
    Digitale Medien
    Enhanced polycarbonate toughness. I: Measurement methodology (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 471-476 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The JIC values for core-shell-particle-toughened polycarbonate were determined at different temperatures and at 0, 2.5, 5.0, 7.5, and 10.0 phr particle content by six similar methods, using compact tensile specimens. At the 2.5 phr toughener level, the JIC values ranged from 2878 to 6100 J/m2, and at 7.5 phr, they ranged from 6125 to 10,760 J/m2, dependent only upon how the same JI-Δ a data were interpreted. This indicates that more work will be required before a reliable method of JIC measurement that can be applied to tough polymers is achieved.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350603
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  • 58
    Digitale Medien
    Digitale Medien
    Kinetics modeling and time-temperature-transformation diagram of microwave and thermal cure of epoxy resins (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 461-470 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Stoichimetric mixtures of a diglycidyl ether of bisphenol A (DGEBA)/ diaminodiphenyl sulfone (DDS) and a DGEBA/meta phenylene diamine (mPDA) were cured using both microwave and thermal energy. Fourier transform infrared (FTIR) was used for the measurement of the extent of cure and thermal mechanical analysis (TMA) was used for the determination of the glass transition temperature (Tg). The cure kinetics of the DGEBA/mPDA and DGEBA/DDS systems were described by an autocatalytic kinetic model up to vitrification in both the microwave and thermal cure. For the DGEBA/mPDA system, the reaction rate constants of the primary amine-epoxy reaction are equal to those of the secondary amine-epoxy reaction, and the etherification reaction is negligible for both microwave and thermal cure. For the DGEBA/DDS system, the reaction rate constants of the primary amine-epoxy reaction are greater than those of the secondary amine-epoxy reaction and the etherification reaction is only negligible at low cure temperatures for both microwave and thermal cure. Microwave radiation decreases the reaction rate constant ratio of the secondary amine-epoxy reaction to the primary amine-epxy reaction and the ratio of the etherification reaction to the primary amine-epoxy reaction. Tg data were fitted to the DiBenedetto model. A master curve and a time-temperature-transformation (TTT) diagram were constructed. The vitrification time is shorter in microwave cure than in thermal cure, especially at higher isothermal cure temperatures. For the DGEBA/mPDA system, the minimum vitrification time is two to five times shorter in the microwave cure than in the thermal cure. For the DGEBA/DDS system, the minimum vitrification time is 44 times shorter in the microwave cure than in the thermal cure.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350602
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  • 59
    Digitale Medien
    Digitale Medien
    A process model for nonisothermal photopolymerization with a laser light source. II: Behavior in the vicinity of a moving exposed region (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 493-498 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A mathematical process model that stimulates important aspects of stereolithography, a rapid prototyping technique used for the production of three-dimensional plastic parts, has been developed. The model consists of a set of coupled partial differential equations and considers irradiation, chemical reaction, and heat transfer in a vat of photomonomer exposed to a moving UV laser source. Laser motion occurs in a straight line (vector path), and the model thus simulates the production of a single strand of plastic. Numerical techniques are used for approximate solution of the model equations, and output includes spatial and temporal variations in conversion of monomer to polymer, depletion of photoinitiator, and variations of temperature along the line of exposed material. The formation of a temperature wave that moves along the line of plastic is observed, together with the fact that the leading edge of the wave is steeper than the trailing edge, i.e., the material heats considerably faster than it cools. The maximum temperature of the wave reaches a pseudo-steady state after a short time. The results have provided useful information concerning the temperature at which the majority of the polymerization occurs; provided information on overall transient temperature behavior; allowed computer prediction of stereolithography working curves (cure depth and cure width vs. laser scan rate); and afforded a means for evaluating the amount of reaction that occurs in the dark period after light exposure.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350606
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  • 60
    Digitale Medien
    Digitale Medien
    Correlations between relaxation time spectrum and melt spinning behavior of polypropylene. 1: Calculation of the relaxation spectrum as a log-normal distribution and influence of the molecular parameters (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 513-517 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The linear viscoelastic behavior of commercial broad-distribution polypropylenes is studied. The samples underwent different controlled peroxide degradation rates, so they exhibit different molecular distributions. The relaxation spectrum is obtained by assuming that it takes the shape of a Log-Normal distribution. It is in agreement with the linear viscoelasticity theory by providing limiting values, contrary to other models. Moreover, the ratio τw/τn which takes place in this law is very useful to distinguish the synthesis differences of the samples when the Melt Flow Index alone cannot.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350609
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  • 61
    Digitale Medien
    Digitale Medien
    A study of creep and creep rupture of polycarbonate (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 546-554 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The creep characteristics of polycarbonate at elevated temperatures are investigated. The onset of glass transition temperature of polycarbonate is determined. An Arrhenius type relationship is used to describe the creep process and the concept of property retention index as applied to creep is discussed. An attempt is made to construct the master rupture curves for polycarbonate. The onset of glass transition temperature of polycarbonate was placed at around 110°C. It is concluded that the Arrhenius theory and the concept of property retention index are extremely useful in the construction of master rupture curves and that they require further investigation.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350613
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  • 62
    Digitale Medien
    Digitale Medien
    Morphology and mechanical properties of liquid crystalline copolyester and poly(ethylene 2,6-naphthalate) blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 538-545 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Blends of poly(ethylene 2,6-naphthalate) (PEN) and a liquid crystalline copolyester (LCP), poly(benzoate-naphthoate), were prepared in a twin-screw extruder. Specimens for mechanical testing were prepared by injection molding. The morphology and mechanical properties were investigated by scanning electron microscopy (SEM) and an Instron tensile tester. SEM studies revealed that finely dispersed spherical domains of the liquid crystalline polymer (LCP) were formed in the PEN matrix, and the inclusions were deformed into fibrils from the spherical droplets with increasing LCP content. The morphology of the blends was found to be affected by their composition and a distinct skin-core morphology was found to develop in the injection molded samples of these blends. Mechanical properties were improved with increasing LCP content, and synergistic effects have been observed at 70 wt% LCP content whereas the elongation at break was found to be reduced drastically above 10 wt% of LCP content. This is a characteristic typical of chopped-fiber-filled composites. The improvement in mechanical properties is likely due to the reinforcement of the PEN matrix by the fibrous LCP phase as observed by scanning electron microscopy. The tensile and modulus mechanical behavior of the LCP/PEN blends was very similar to those of the polymeric composite, and the tensile strength and flexural modulus of the LCP/PEN 70/30 blend were two times the value of PEN homopolymer and exceeded those of pure LCP, suggesting LCP acts as a reinforcing agent in the blends.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350612
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  • 63
    Digitale Medien
    Digitale Medien
    Coefficients of dynamic friction as a function of temperature, pressure, and velocity for several polyethylene resins (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 557-563 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The coefficient of dynamic friction is often the controlling factor for solids conveying, pressure generation, and thermal decomposition of a resin in the feed section of a single-screw plasticating extruder. The coefficients of friction are, however, very poorly understood, and the interpretation of the measurements are complicated by the dissipation of frictional energy at the sliding interface. A new instrument was recently built to help understand dynamic friction, and a numerical technique was developed to estimate the interface temperture. Coefficients of dynamic friction for several polyethylene resins are presented in this paper as a function of the surface temperature, pressure, and velocity. The relationship of the data with respect to the extrusion process is discussed.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350702
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  • 64
    Digitale Medien
    Digitale Medien
    A flow model for non-newtonian liquids inside a slot die (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 577-586 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A one-dimensional flow model for non-Newtonian liquids inside a dual-cavity slot die is presented. The model is capable of analyzing slot dies of any cavity shape, cavity taper, slot-length variations, and slot-gap variations. The proposed model incorporates a truncated-power-law model for the viscosity of non-Newtonian liquids. According to flow models with power-law approximation for liquid viscosity, the distribution of non-Newtonian liquid through a slot die depends on the slot Reynolds number only. With our model, we find that the zero shear viscosity and the relaxation time of a non-Newtonian liquid have large effects on its distribution. For non-Newtonian liquids which are expected to experience shear-thinning over portion of a slot die, it is concluded that a flow model with a truncated-power-law approximation for liquid viscosity be used to predict the liquid distribution from the die.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350704
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  • 65
    Digitale Medien
    Digitale Medien
    Residence time distribution in non-intermeshing counter-rotating twin-screw extruders (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 598-603 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This paper deals with the residence time distribution (RTD) in a non-intermeshing counter rotating twin screw extruder.The RTDs were measured in three vent zones of the extruder sparately, and in the adjacent zones combined, using a soluble dye as the tracer. Assuming that the RTDs in the adjacent zones are independent of each other, the overall RTD was also calculated using a previously developed statistical theory. The theory has also confirmed the consistency of the present measurements.A predictive RTD model for the non-intermeshing twin screw extruder, based on the flow analysis of the individual screw zones and their statistical superposition, was also developed. The predictions are in good agreement with experiment.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350706
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  • 66
    Digitale Medien
    Digitale Medien
    The flow-induced phase morphology of fluoroelastomer and polycarbonate blends during extrusion (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 619-636 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The flow-induced phase morphological development under different extrusion conditions was studied in terms of the rheological property and interfacial tension of various elastomers and thermoplstics. The interfacial tension for elastomers and thermoplastics was investigated by using a breaking thread method (1-4). We found that the method is suitable for measuring interfacial tension without degradation. The droplet-fibrillation transition phenomenon was observed in various extrudates of fluoroelastomer/polycarbonate blends. The criteria for the flow-induced morphology, in particular the droplet-fibrillation transition, are critically discussed in this paper.
    Zusätzliches Material: 23 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350708
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  • 67
    Digitale Medien
    Digitale Medien
    The conducting behavior and stability of conducting polymer composites (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 637-641 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Results of measurements of the electrical conductivity of low density polyethylene/polypyrrole and polystyrene/polypyrrole composites are reported. It is observed that the electrical conductivity of the composite vs. concentration follows the power law predicted by the percolation theory. The manufacturing process influences the homogeneity of the composite at microscopic scale and thus the percolation threshold. Annealing studies show that the stability of the electrical conductivity of the composite is related to the thermal expansion of the polymers and the relaxation of the polymer chains. The decrease of the electrical conductivity of the composite is attributed to the interruption of the percolation path.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350802
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  • 68
    Digitale Medien
    Digitale Medien
    The effect of a partly hydrolyzed styrene-tert-butyl acrylate diblock copolymer on the properties of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and polyamide-6 (PA) blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 648-657 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The compatibilizing effect of a polystyrene-hydrolyzed poly(t-butyl acrylate) diblock copolymer (SBAH) on the phase structure, rheological properties, and mechanical properties of immiscible poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and polyamide-6 (PA) blends was investigated. The SBAH was prepared by sequential anionic polymerization of styrene and t-butyl acrylate, followed by acid-catalyzed hydrolysis of t-butyl acrylate block. Scanning electron micrographs show that the blends exhibit a more regular and finer dispersion when the SBAH of 47% hydrolyzed t-butyl acrylate block is added. By addition of small amount of the block copolymer, the blends show non-Newtonian power-law behavior, and the contribution of storage modulus (G′) to the total response increases. Solubility tests support the formation of graft copolymer by chemical reaction between amine groups of the PA and carboxyl groups of the SBAH. Both modulus and strength are improved about 20% with addition of the 3 wt% SBAH, while the elongation at break decreases notably; thus, the blends fail in a brittle manner.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350804
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  • 69
    Digitale Medien
    Digitale Medien
    A study on interfacial adhesion of poly(vinylidene fluoride) with substrates in a multilayer structure (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 666-672 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The peel force of a PVDF/3-APS/Si joint and a PVDF/3-APS/Al joint can reach the same level by treating the Si substrate with ≥ 0.3% 3-aminopropyltriethoxy silane (3-APS) solution and treating the aluminum substrate with NH3 solution (pH 10.5) first and then with ≥ 3% 3-APS solution. Scanning electron micrographs show that the interfacial adhesion mechanisms of PVDF/3-APS/Si joints and PVDF/3-APS/Al joints are different. In the peel test, the PVDF [poly(vinylidene fluoride)] break surfaces from PVDF/3-APS/Si joints reveal striations on the surface and less plastic deformation. The significant plastic deformation of the PVDF at the break surface may result from the deeper interpenetration of 3-APS with PVDF in the PVDF/3-APS/Al joint than in the PVDF/3-APS/Si joint. The peel force of PVDF film/substrate joint depends on many factors: film thickness, peel rate, concentration of coupling agent, the treatment time of the coupling agent on the substrate, and the substrate pretreatment.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350806
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  • 70
    Digitale Medien
    Digitale Medien
    Morphologies of mechanically mixed amorphous blends before and after annealing (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 693-702 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The morphologies of amorphous polymer blends produced by extrusion were investigated by transmission electron microscopy. Polymers with similar viscosities, i.e. poly(methyl methacrylate) (PMMA), polystyrene (PS), and random copolymers P(SxMMA1 - x) were mixed pairwise, in different compositions. Finely dispersed phase structures were produced in the blends, with domains in the submicron range. The structure patterns were considerably perturbed by the stress fields in the extruder. Domain-matrix and co-continuous morphologies were obtained, in a distribution controlled mainly by the viscosity ratio. Annealing after extrusion led to structure coarsening, whereby the patterns were changed until a steady state was established. Sometimes, matrix inversion was observed.
    Zusätzliches Material: 17 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350809
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  • 71
    Digitale Medien
    Digitale Medien
    Morphology and barrier properties of oriented blends of poly(ethylene terephthalate) and poly(ethylene 2,6-naphthalate) with poly(ethylene-co-vinyl alcohol) (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 680-692 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Morphology and oxygen permeability studies were carried out for blends of poly(ethylene terephthalate), PET, and poly(ethylene 2,6-naphthalate), PEN, with poly(ethylene-co-vinyl alcohol), EVOH. PET/EVOH blends are seen as a possible substitute for poly(vinylidene chloride)-coated PET packaging films. The effects of several processing parameters such as draw temperature and draw ratio on blend morphology and barrier properties suggest that the morphology of the EVOH phase dictates to a large extent the oxygen permeabilities of these blends. The relationships between morphology and oxygen permeability and explained are explained by consideration of two-phase conduction models. The model of Fricke is found to be a good predictor of the barrier properties of the PET/EVOH system. The oxygen permeability of PET was reduced by a factor of 4.2 with the addition of 20 wt% EVOH and that of PEN by a factor of 2.7 with the addition of 15 wt% EVOH. Water vapor permeabilities and mechanical properties of PET and PEN were only slightly affected by the addition of 15 wt% EVOH.
    Zusätzliches Material: 18 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350808
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  • 72
    Digitale Medien
    Digitale Medien
    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350901
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  • 73
    Digitale Medien
    Digitale Medien
    Application of statistical experimental strategies to the process optimization of waterborne polyurethane (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 722-730 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A modified acetone process for the preparation of aqueous polyurethane (PU) dispersion is investigated. PU dispersions were prepared by polyaddition of isophorone diisocyanate (IPDI) to poly(tetramethylene ether glycol) (PTMG) and dimethylolpropionic acid (DMPA), followed by neutralization of pendant COOH groups with triethylamine (TEA). The resulting prepolymer chain was then extended through reaction with an ethylenediamine (EDA) derivative bearing sulfonate groups. The effect of such preparation conditions as catalyst (dibutyltin dilaurate, DBTDL) concentration, the acetone/PU ratio, phase-inversion temperature, agitation rate, and water-addition rate on the average particle size of aqueous PU anionomer dispersions is systematically studied using fractional factorial design and response surface methodology. Fractional factorial analysis indicates that the effects of the acetone/PU ratio, phase-inversion temperature, water-addition rate as well as the two factor interactions of DBTDL concentration and phase-inversion temperature, of the acetone/PU ratio and phase-inversion temperature, and of acetone/PU ratio and agitation rate are the key variables influencing average particle size of PU dispersions. Empirical models for average particle size are fitted and plotted using central composite experimental design as contour diagrams in order to facilitate examination of the average particle size results. The results show that for a 100 g PU anionomer containing 0.311 wt % COOH and 1.51 wt % SO3H groups, a minimum number-average particle size of the dispersion ∼ 25 nm can be obtained under an acetone/PU ratio, water-addition rate, phase-inversion temperature, catalyst concentration, and agitation rate of 3.65, 2 mL/min, 50°C, 150 ppm and 350 rpm, respectively.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350812
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  • 74
    Digitale Medien
    Digitale Medien
    Master curve approach to polymer crystallization kinetics (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 733-740 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Nonisothermal crystallization kinetic data obtained from differential scanning calorimetry (DSC) for a poly(ethylene terephthalate) are corrected for the effects of temperature lag between the DSC sample and furnace using the method of Eder and Janeschitz-Kriegl which is based on experimental data alone without resort to any kinetic model. A method is presented for shifting the corrected nonisothermal crystallization kinetic data with respect to an arbitrarily chosen reference temperature to obtain a master curve. The method is based on experimental data alone without reference to any specific form of kinetic model. When the isothermal crystallization kinetic data for the same material are shifted with respect to the same reference temperature, a master curve is also obtained which overlaps to a large extent the corresponding master curve from nonisothermal data. It follows that nonisothermal DSC measurements provide the same crystallization kinetic information as isothermal DSC Measurements, only over a wider range of temperatures. The shift factors obtained from experimental data alone are compared in turn with the corresponding values calculated from the Avrami equation, the Hoffman-Lauritzen expression, and the Nakamura equation as a means of evaluating these models individually. It is concluded that the Avrami equation is very good at describing isothermal crystallization kinetics, the Hoffman-Lauritzen extrapolation of the limited isothermal data to a wide range of temperatures is quite good, and the Nakamura equation yields reliable crystallization kinetic information over a narrower range of temperatures than nonisothermal data alone without using any specific model.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350902
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  • 75
    Digitale Medien
    Digitale Medien
    The effect of curing of unsaturated polyester resin on the dynamic relaxation time (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 754-758 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The effect of hot curing of unsaturated polyester resin on the dynamic relaxation time was studied using dielectric measurements along with two dynamic mechanical measurement methods. It was found that the dynamic response during cure was a material frequency dependent property and did not depend on the measurement method. All relaxation times, measured during cure, by all three measurement methods used, converged to a single equation: τ(t)av=atb where t= curing time, a, b=constants. The increase of the relaxation time during cure followed the same trend as a friction factor, which was found to increase with conversion. The crosslinking density was found to increase slowly with conversion, while the relaxation time increased exponentially. These two different modes of behavior during cure explain the high resolution of dynamic measurements as a cure monitoring tool, which can easily detect small curing changes. This behavior of the relaxation time was explained by the sharp rise of activation energy due to a parallel decrease of free volume at high conversion.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350904
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  • 76
    Digitale Medien
    Digitale Medien
    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351001
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  • 77
    Digitale Medien
    Digitale Medien
    Effect of matrix ductility on the fracture behavior of rubber toughened epoxy resins (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 778-785 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This paper investigates the effect of matrix ductility on toughness in a carboxyl-terminated butadiene-acryionitrile copolymer (CTBN) toughened diglycidyl ether of bisphenol-A (DGEBA)-piperidine system. Two kinds of epoxides were blended separately into this system to change the matrix ductility. One was a rigid and polyfunctional 4,4′-diaminodiphenol methane (MY720), and the other was a flexible diglycidyl ether of propylene glycol (DER732). The matrix Tg was significantly changed, but without alteration of the microstructure of the dispersed rubbery phase. The result of fracture energy tests reveals that the toughness of the neat epoxy resins increases slightly with the increase in the resin ductility. The toughness of the rubber-modified epoxy resins increases strongly with matrix ductility. Studies on the morphology of the toughened systems and their fracture surfaces indicate that the size of the plastic deformation zone under constant rubbery-phase morphology is determined by the multiple but localized plastic shear yielding. Increasing matrix ductility increases the size of the plastic deformation zone by inducing more extensive shear yielding. In addition, fracture surfaces reveal that as the matrix rigidity is increased, an increasing proportion of the fracture energy is dissipated by rubber cavitation during crack initiation.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760350907
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  • 78
    Digitale Medien
    Digitale Medien
    Quiescent nonisothermal crystallization kinetics of isotactic polypropylenes (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 797-804 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Recently, a model was developed for the nonisothermal crystallization of normal alkanes with chain lengths between 30 and 50. The model was derived based on the fundamental equation of Ozawa for nonisothermal crystallization, the surface nucleation theory, and the growth rate theory for extended chain crystals. In this paper, the proposed model is modified and extended to the case of polymer crystallization. Experimental differential scanning calorimetry data for three isotactic polypropylene resins with different molecular weights are presented at five cooling rates from 2 to 40 K/min. Model predictions are in excellent agreement with the experimental data for the three polymers at low and high supercoolings.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351002
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  • 79
    Digitale Medien
    Digitale Medien
    The effect of particles on failure modes of filled polymers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 813-822 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The effect of rigid particles on the fracture mode of polymers that yield with necking was analyzed theoretically with a model of regularly arrayed spherical particles. The adhesion between a polymer and particles was assumed to be weak, and particles were assumed to debond from the polymer before necking. A linear decrease in engineering draw stress with an increase in the filler content was derived. An increase in filler content leads to a transition in deformation mechanism. The transition depends on the ability of the polymer to strain-harden. If the ability to strain-harden is insignificant and the engineering fracture stress (strenght) of the polymer is lower than its yield stress, the transition is from ductile to brittle fracture. If the ability to strain-harden is essential and the strength of the unfilled polymer is higher than its yield stress, the transition (ductile-to-ductile) is from neck propagation to uniform ductile yield. The critical filler contents were determined for both transitions from the properties of an unfilled polymer. The ductile-to-ductile transition without embrittlement is possible if the strength of the unfilled polymer is higher than its yield stress. Results for polymers filled by weakly bonded particles were compared with polymers filled by particles that debond after the yield stress.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351004
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  • 80
    Digitale Medien
    Digitale Medien
    Micro scale flow behavior and void formation mechanism during impregnation through a unidirectional stitched fiberglass mat (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 837-851 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Liquid composite molding (LCM) processes such as resin transfer molding (RTM) and structural reaction injection molding (SRIM) have been perceived as high potential processes for the near-net-shape manufacturing of composite parts. This paper addresses two major issues in LCM technology: fiber wetting and void formation during mold filling. Flow visualization experiments were carried out to develop a better understanding of the flow induced voids. The formation and elimination of voids were studied using several liquids and a unidirectional stitched fiberglass mat. Void formation was correlated to capillary number and liquid-fiber-air contact angle.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351006
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  • 81
    Digitale Medien
    Digitale Medien
    An overview of the basic aspects of polymer adhesion. Part I: Fundamentals (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 957-967 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Adhesion between two substrates is a complex phenomenon which at present is still not well understood. The important existing adhesion models (electrical, diffusion, thermodynamic adsorption, chemical, etc.) are reviewed in order to try to explain their mechanisms. Thermodynamic adsorption is now believed to be one of the most importnat mechanisms by which adhesion is achieved. Difusion and wetting are kinetic means in attaining good adsorption of a polymer at the interface. In the case of this model (thermodynamic adsorption), the notion of surface energy is developed and the importance of this property in the understanding of adhesion phenomena is emphasized. The methods of determining the surface characteristics of low and high energy solids are presented. The role played by acid-base interactions in adhesion is also mentioned.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351202
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  • 82
    Digitale Medien
    Digitale Medien
    Copolymerization of t-butoxycarbonyloxystyrene and sulfur dioxidePresented at the 205th National Meeting of the American Chemical Societry, Denver, Colorado, March 28, 1993 (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 989-999 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The reaction kinetics of radical chain copolymerization of t-butoxycarbonyl-oxystyrene (TBS) and sulfur dioxide have been studied using a reaction/sampling apparatus that permits accurate determination of the reaction mixture concentrations during polymerization. The results are compared with the styrene-sulfur dioxide copolymerization kinetics. The influence of temperature and reactant concentrations on the polymerization rate and copolymer composition are reported. With increasing reaction temperature, the amount of SO2 incorporated and the molecular weight fo the copolymer are found to decrease. For a constant TBS concentration in the reaction solutio, raising the SO2 concentration causes an increase of SO2 incorporation in the copolymer, up to a maximum SO2 content corresponding to a TBS:SO2 mole ratio of 2:1. However, for a constant SO2 concentration, the amount of TBS incorporated in the copolymer increases with decreasing TBS concentration in the reaction solution. The polymerization rate and copolymer molecular weight increase proportionally with monomer concentration as expected for a normal radical chain polymerization mechanism. Comparison of these findings with various kinetic models for styrene-SO2 copolymerization indicates good agreement with models proposed by Barb (1-3) and Walling (4); however, the data do not agree with the predictions of Matsuda et al. (5) The understanding of the kinetics and reaction mechanism provided in this study will aid in the manufacture of this lithographically important copolymer.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351205
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  • 83
    Digitale Medien
    Digitale Medien
    Indentification of plastic waste using spectroscopy and neural networksBased on a Dupont Company Internal Report Issued in February 1992 (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1011-1015 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: In this paper we investigate a new approach for the automated sorting of post-consumer plastic waste. We show that rapid and relible identification of polymers can eb achieved using a combination of fixed-filter near-infrared spectroscopy and neural network data analysis, and we demonstrate the effectiveness of the proposed method for sorting polyethylene terephthalate, high density polyethylene, and poly(vinyl chloride). Finally, we discuss a proposed compact, rugged instrument based on the new sorting method. Owing to the flexibility gained by incorporating neural networds in our system, thismethod can easily be extended to include additional polymers.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351208
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  • 84
    Digitale Medien
    Digitale Medien
    Analysis of titanium dioxide agglomerate dispersion in linear low density polyethylene and resulting properties of compounds (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1037-1045 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The dispersion of titanium dioxide agglomerates within linear low density polyethylene (LLDPE) melts has been investigated by using a cone-and-plate device installed within a temperature controlled oven. Observation of fragment evolution indicates that erosion is the predominant mechanism of dispersion. The erosion rate of titanium dioxide agglomerates in LLDPE was consistenty with the results obtained in previous dispersion studies of titanium dioxide in polydimethyl siloxane (PDMS). The effect of agglomerate dispersion on the optical, tensile, and dynamic mechanical properties of compounds incorporating titanium dioxide was also investigated. Changes in compound properties were correlated with observed morphology changes of agglomerates in order to clarify the effect of dispersion.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351212
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  • 85
    Digitale Medien
    Digitale Medien
    Dynamic simulation of flow-induced fiber fracture (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1022-1030 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A dynamic simulation method has been developed of the fracture process of a fiber in a flow field using the particle simulation method proposed i a previous paper. The fiber is modeled with bonded spheres as a fiber model. The flexibility of the fiber model is altered by changing three parameters of the stretching, bending, and twisting constants between adjacent spheres. The stress induced in each bond of the fiber model as a result of deformation is formulated using displacement of the bodn distanc, bond angle, and torsion angle fr each pair of spheres. After deformation, the fiber model fractures at the bond at which the stress surpasses the strength of the fiber. The motion of the fiber model in a flow field is determined by solving the translational and rotational motion equations for individual spheres under the hydrodynamic force and torque exerted on them. The correctness of the method and formulation was verified by comparing the simulated deflection curve of a cantilever beam (with a concentrated load at the end) with the theoretical curve. Good agreement was found in both the deflection and slope of the beam. The fracture process of a fiber after bending deformation in a two-dimensional siimple shear flow was simulated under assumptions of an infinitely dilute system, no hydrodynamic interaction, and a low Reynolds number of a particle. The calculated critical conditions of the flow field for fiber fracture were compared with Forgacs and Mason's theoretical ones. Simulated values of the fracture condition of the fluid shear stress related to the Young's modulus of a fiber agree with theoretical ones over an aspect ratio of 15.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351210
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  • 86
    Digitale Medien
    Digitale Medien
    Masthead (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995) 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351301
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  • 87
    Digitale Medien
    Digitale Medien
    On the structure/properties relationships in photoinitiators of polymerization (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1061-1065 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The choice of photoinitiators is partly governed by the requirement of a high curing speed. Many reactive monomers and efficient photoinitiators have been synthesized and are commercially available. However, improved photoinitiator systems, exhibiting increasingly faster curing speeds and/or increased photosensitivity, are increasingly required. The intrinsic reactivity in the exicited states determines te interest of a given photoinitiator with reference to its efficiency. However, other factors e.g. high molecular absorption coefficients and a broad spectral absorption range, synergistic effects, yellowing, extractability, and th effect on the long-term stability, must be considered as important. An attractive field of research and development is found in the role played by decisive parameters affecting the reactivity of a given structure, such as chemical substitution in well-chosen positions, the character of water solubility, acid release ability, and copolymerization potential. Laser spectroscopy proved a most convenient tool for the real time investigation of the excited state dynamics and the processes involved.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351215
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  • 88
    Digitale Medien
    Digitale Medien
    Morphology and mechanical properties of epoxy resins containing functionalized perfluoroether oligomers (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1069-1076 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Chain extended perfluoroether oligomers were found to be miscible with bisphenol epoxy resins at all concentrations. These were evaluated as modifiers for anhydride cured resin systems, taking advantage of the carboxylic acid functionality at the chain ends. By altering the mixing and curing procedure different two-phases morphologies could be obtained varying from fine co-continuous networks, which produced transparent castings, to opaque systems consisting of precipitated heterogeneous particles. While the Tg and flexural modulus were found to be slightly lower than the control cure resin, the addition of the fluoroligomer modifier produced large increases in flexural strength, ductility, and fracture toughness. Samples with an IPN type morphology were found to exhibit an increase in ductility after aging at 200°C for three weeks proportionally to the concentration of fluoroligomer used.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351302
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  • 89
    Digitale Medien
    Digitale Medien
    The leveling of thermosetting waterborne coatings. Part II: Drying of coated wet films (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1098-1105 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Evaporation behavior of water/solvent blends was estimated using the universal functional activity coefficient, UNIFAC, method. The evaporation rate from a free surface of a waterborne coating, WBC, containing a co-solvent was experimentally determined. These results were used to estimate the evaporation rate from wet films of a WBC containing a variety of co-solvents with a range of initial thickness. Knowing the composition of the WBC during the drying process, the change in the viscosity and the surface tension was determined. The results strongly support the development of a surface tension gradient in the film. It is also suggested that a surface tension gradient would accelerate the leveling of the ribs if a proper co-solvent were employed.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351305
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  • 90
    Digitale Medien
    Digitale Medien
    Effect of casting solvent on the heterogeneity of films of polymer blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1113-1116 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The miscibility window of the 50/50 w/w poly(styrene-co-4-vinylphenyl)-dimethylsilanol/poly(n-butyl methacrylate) (ST-VPDMS/PBMA) blends prepared from toluene was studied and determined to be in the VPDMS composition range of 4 to 18 mole% in the copolymers. The observed miscibility window was to be compared to the range of 9 to 34 mole% found for the blends prepared from methyl ethyl ketone which was capable of competing for hydrogen bonding. The fact that the observed miscibility windows are influenced by the choice of solvents illustrates that an equilibrium state of polymer mixing is not always attained in solvent casting films and that caution needs to be exercised in studying polymer miscibility when solvent cast films are used.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351307
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  • 91
    Digitale Medien
    Digitale Medien
    The double yield in the tensile deformation of the polyethylenes (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1117-1123 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Double yields, as well as other complex yielding behavior, that are observed during the tensile deformation of the polyethylenes have been studied in a systematic manner. The conditions under which such yielding is observed were established by studying a set of linear polyethylenes and well-characterized ethylene copolymers of narrow molecular weight and composition distributions. A wide range in crystallinity levels were developed and the rate of deformation and the deformation temperature were varied. These experimental results make clear why such complex yielding processes are not always observed. A qualitative explanation, based on the postulate of a partial melting-recrystallization process during deformation, is given that encompasses all of the experimental data.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351308
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  • 92
    Digitale Medien
    Digitale Medien
    Discrete strength levels in modified polypropylene tapes (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1133-1136 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A statistical study of the strength of unmodified and modified uniaxially drawn polypropylene tapes was carried out. The results show that the curve representing the distribution of strength for unmodified tapes reveals seven discrete levels corresponding to microdefects in the form of microcrazes and submicrocrazes. On introduction of modifying additive, three discrete strength levels were observed, corresponding to submicrocrazes. The strength of the modified polypropylene tape increase approximately twice compared to the strength of the initial material. The polyfunctional effect of the additives as artificial nucleators and regulators of the structure leads to an increase of the degree of crystallinity which in turn restrains the submicrocrazes development into microcrazes. The method used could be applied for objective analysis of the tensile characteristics of polymeric materials.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351402
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  • 93
    Digitale Medien
    Digitale Medien
    Aging characteristics of oriented ply(ethylene terephthalate) (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1145-1154 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The physical aging characteristics of oriented poly(ethylene terephthalate) (PET), have been studied ad functions of storage time and temperature below the glass transition temperature (Tg) of PET. The free volume relaxation, associated with aging, has been characterized by the enthalpy at Tg, as measured by differential scanning calorimetry. The effects of the free volume relaxation on mechanical properties and the mode of failure have been investigated. It has been determined that a correlation exists between the enthalpy of relaxation and the ductile-to-brittle failure transition. Molecular orientation reduces significantly the enthalpy of relaxation, resulting in the disappearance of the ductile-to-brittle transition when highly oriented samples are aged over time. It has been established that a minimum amount of orientation is required to reduce or eliminate the effects of PET aging. Molecular orientation has also been found to reduce craze formation when oriented PET is exposed to a stress-cracking medium at constant stress.
    Zusätzliches Material: 18 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351404
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  • 94
    Digitale Medien
    Digitale Medien
    The effect of crystallinity on the light scattering of regenerated cellulose tubular filmsPresented at the First Annual Meeting of the European Optical Society. Saragossa, Spain (July 1993). (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1155-1160 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: An experimental study of the effect of crystallinity on the light scattering of regenerated cellulose tubular films is reported. Several films were prepared by varying manufacturing conditions, so that thickness and surface roughness were maintained approximately constant and the degrees of crystallinity varied between 38 and 66%. The scattered radiation intensity, measured between 220 and 550 nm decreases with the increasing wavelength. It was demonstrated that for the polymeric films studied, there was excellent agreement between crystallinity and scattering radiation intensity for a given wavelength. It was found that for crystallinity values less than around 57%, scattered radiation intensity decreases with increasing crystallinity, the reverse of that for crystallinity values greater than that percentage.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351405
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  • 95
    Digitale Medien
    Digitale Medien
    Tesile toughness of microcellular foams of polystyrene, styrene-acrylonitrile copolymer, and polycarbonate, and the effect of dissolved gas on the tensile toughness of the same polymer matrices and microcellular foams (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1167-1177 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: This paper reports on the tensile properties of microcellular foams of three different thermoplastics, since there have been several reports in the literature, but with indefinite conclusions so far, that microbubbles act in a manner similar to rubber particles in toughening thermoplastics. Polystyrene (PS), styreneacrylonitrile copolymer (SAN), and polycarbonate (PC), were selected based on their different intrinsic ductilities. The gas supersaturation technique was used to generate samples with microbubbles. The effect of the presence of microbubbles inside the polymer matrix was separated from the effects of the pressure and thermal history experienced by the samples. Nitrogen gas dissolved into PS, and to a lesser extent into SAN, caused and increase of the tensile toughness, but this increased decayed with time as nitrogen gas diffused out of the samples. Furthermore, microcellularly foamed PS samples showed some limited improvement in terms of tensile toughness after all the nitrogen gas diffused out. SAN and PC showed deterioration of the tensile toughness in the presence of microbubbles.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351407
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  • 96
    Digitale Medien
    Digitale Medien
    Water sorption and diffusion in starch/polyolefin blends (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1184-1190 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The kinetics of water sorption by starch filled polyolefins has been investigated using blends of commercial starch masterbatch with low density polyethylene (LDPE), high density PE (HDPE), and copolymers of ethylene with methyl acrylate (EMA), ethyl (EEA), AND n-butyl acrylate (EBA). Transient state diffusion coefficients (D) of water in the blends were determined using Fickian analysis of the initial stages of the sorption isotherms. Measured D values were several orders of magnitude lower than values reported for either pure starch of LIDPE by various investigators. Resin effects on D were on the order DHDPE 〈 DLDPE ≪ DEBA 〈 DEEA 〈 DEMA. The resin effects diminished as the starch content increased. The lower magnitude of D in the blends relative to pure LDPE was attributed to the sorption of water by the dry starch particles, in a manner similar to dual-mode sorption in glassy polymers. Copolymer effects were consistent with reduction in crystallinity caused by the comonomers. The dependence of the diffusion coefficient on starch content was not described by mixing models of heterogeneous systems of percolation theory.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351409
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  • 97
    Digitale Medien
    Digitale Medien
    Ballistic performance of polycarbonate/polyester and polycarbonate/styrene-acrylonitrile microlayer sheets (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1191-1195 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Extruded microlayer sheets of Polycarbonate/Polyester (PC/PCTG) and Polycarbonate/Styrene-acrylonitrile (PC/SAN) were tested for ballistic performance. Composition of the microlayer sheets ranged from 60 to 100 percent polycarbonate. The number of layers in the approximately 3 mm thick sheets ranged from on for the blend control samples to 3713 layers in the PC/PCTG sheets. The normalized ballistic test results showed that some samples performed as well as as and slightly better than injection molded polycarbonate samples. The failure mechanism was affected by the composition and the number of layers. Increasing composition of polycarbonate and number of layers decreased the percent of brittle failures.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351410
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  • 98
    Digitale Medien
    Digitale Medien
    Esterification in reactive extrusionPresented at Regional Meeting of the Polymer Processing Society, Morgantown W.Va., August 8, 1993. (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1197-1205 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A condensation type reaction has been studied for reactive extrusion in a twin-screw extruder. The esterification reaction is to graft a nonylphenyl-ethoxylate (NP8) onto a pre-maleated ethylene-propylene (EPRMA). The kinetics were initially characterized in the static mixture using a thermally controlled call in a FTIR spectrometer. These were then used to predict the conversion along the length of the extruder screws, having determined the residence time distribution at various sampling locations. A reasonable fit with the data was obtained, although the kinetics seem to be slightly faster in the flowing medium than those predicted. Over short screw distances, the equilibrium rapidly approached equilibrium. Moreover, the NP8 was shown to penetrate the EPRMA within screw distance of less than 1.3 L/D, despite using conveying elements known for their minimal mixing capacity. Within the molten medium, a mixing model showed that obtaining the expected conversion in a product does not imply that the reactants in the product have in fact been well mixed.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351502
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  • 99
    Digitale Medien
    Digitale Medien
    Semianalytical solution of isothermal nylon-6 polymerization in batch reactors (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1231-1240 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Nylon 6 polymerization in batch reactors has been assumed to consist of important reactions of ring opening, step growth and polyaddition steps and a set of ordinary differential equations (initial value problem) for the concentrations and moments of the various reacting species has been derived. We have proposed a series solution for these variables in terms of conversion of ε-caprolactam. A technique similar to the finite element method for boundary value problems is used to divide the conversion domain into subdomains. The size of these is determined by a convergence criterion and the results determined at the end of conversion domain through sequential computations. This technique of solution involves the evaluation of constant coefficients of the series only and gives comparable results with those of Runge Kutta or Gear's algorithm (which involves evaluation of functions) in fewer steps. The scheme can easily be implemented on a personal computer and is considerably faster and more efficient.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351506
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  • 100
    Digitale Medien
    Digitale Medien
    Experimental and theoretical studies of shrinkage, warpage, and sink marks of crystalline polymer injection molded parts (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1222-1230 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: An integrated theory and computer program were developed in this study for simulation of shrinkage, warpage, and sink marks of crystalline polymer injection molded parts. The basic theory considers the following items: (1) mold cooling analysis; (2) analysis of the polymeric filling, packing, and cooling processes; (3) viscoelastic behavior of polymeric fluid; (4) influence of thermal and mechanical properties of polymer; (5) pressure-volume-temperature relationship of polymer; (6) crystallization kinetics of crystalline polymer; and (7) solid mechanics analysis. Considered are the origins of defects, e.g. nonuniform cooling process, nonuniform volume shrinkage, flow-induced residual stress, thermal induced residual stress, and crystallization behavior. The boundary element and the finite difference method were applied toward calculating the mold cooling analysis for obtaining the temperature profile at the cavity surface as the boundary conditions in filling and packing analysis. A hybrid finite-element and finite-difference methods were employed for simulating the injection molding filling, packing, and cooling processes. A control volume method was applied towards both finding the melt front position and also calculating the temperature and pressure profile at any instant during the filling process. A modified Tait equation provided a description of the pressure-volume-temperature relationship of crystalline polymers. The Malkin's kinetics model was employed to describe the behavior of polymer crystallization. The flow-induced and thermal induced-residual stresses employed as the initial conditions in the solid mechanics analysis were obtained with the linear thermo-viscoelastic model. The displacements, including the thickness direction of part, which could not be calculated by the traditional bending moment method, were solved by using the numerical solid mechanics analysis with the three dimensional finite element method. These methods were applied to predict the shrinkage, warpage, and sink marks of crystalline polypropylene and amorphous ABS for the plate cavity. Both the qualitative results for the theoretical prediction correlated sufficiently with the experimental data. The theoretical results were also correlated using the commercial software C-MOLD.
    Zusätzliches Material: 20 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760351505
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