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  • Articles: DFG German National Licenses  (10,842)
  • 2000-2004  (43)
  • 1990-1994  (3,803)
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  • Chemical Engineering  (9,432)
  • Life Sciences (general)
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  • Articles: DFG German National Licenses  (10,842)
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  • 1
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The increasing requirements in wastewater treatment have led to the development of new wastewater treatment processes based on the know-how and experience in reaction and process engineering of the chemical industry. Due to their compactness, closed operation and high flexibility, these new processes show a large potential for process integration and significant cost reduction in particular for highly polluted industrial wastewaters.This paper discusses the HCR (high-performance compact reactor) - process, developed at the Mass Transfer Laboratory of the Technical University of Clausthal within the last decade. This process has been realized in more than 30 technical applications with a volume loading of up to 70 kg COD/m3 d and an energy consumption of about 0.4 kWh per kg CODelim.
    Additional Material: 10 Ill.
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  • 2
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 169-174 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Nitrogen fixing Anabaena azollae strains isolated from four different Azolla cultures were characterized based on their total protein profile and RAPD profile to study the existing variation among them. As expected, the isolates showed almost similar protein banding patterns, but exhibited differences in 40-70 KDa protein subunits. Polymerase chain reaction of the DNA of the isolates, using four different primers, amplified specific sequences of DNA and showed clear polymorphism among the isolates. The RAPD profile generated the fingerprinting pattern characteristic of each strain based on the sequence of the primers used. Common band sharing observed between the strains A. azollae-RS-KK-SK-AM and A. azollae-RS-KK-SK-RP probably represents maternal inheritance of DNA to the progeny. The polymorphic bands were generated specifically for the isolates A. azollae-RS-KK-SK-RP and A. azollae-RS-KK-SK-AM with primers numbered 2 and 4, respectively, which could be developed as possible markers for these isolates.
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 175-183 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mature seed-derived callus from an elite Chinese japonica rice cv. Eyl 105 was transformed with a plasmid containing the selectable marker hygromycin phosphotransferase (hpt) and the reporter β-glucuronidase (gusA) genes via particle bombardment. After two rounds of selection on hygromycin (30 mg/l)-containing medium, resistant callus was transferred to hygromycin (30 mg/l)-containing regeneration medium for plant regeneration. Twenty-three independent transgenic rice plants were regenerated from 127 bombarded callus with a transformation frequency of 18.1%. All the transgenic plants contained both gusA and hpt genes, revealed by PCR/Southern blot analysis. GUS assay revealed 18 out of 23 plants (78.3%) proliferated on hygromycin-containing medium had GUS expression at various levels. Genetic analysis confirmed Mendelian segregation of transgenes in progeny. From R2 generations with their R1 parent plants showing 3:1 Mendelian segregation, we identified three independent homozygous transgenic rice lines. The homozygous lines were phenotypically normal and fertile compared to the control plants. We demonstrate that homozygous transgenic rice lines can be obtained via particle bombardment-mediated transformation and through genetic analysis-based selection.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 202-202 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 219-233 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The GRAM-positive bacterium Rhodococcus erythropolis K2-3 and the GRAM-negative Ochrobactrum anthropi K2-14 are capable of synergistically degrading 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB). The two strais execute this task in a symbiotic manner, but the nature of the interaction involved in the degradation is only partially understood as yet. An essential first step in elucidating the interaction is to be able to monitor the two strans separately, at the cellular level, within mixed populations. Therefore a method exploiting fluorescently labelled lectin probes was developed. Since Concanavalin A (Con A) binds specifically to R. erythropolis K2-3, it was selected and linked to the fluoresent dye Bodipy 630/650, which has an excitation maximum in the red part of the visible light spectrum. Forward light scatter (FSC) and DNA fluorescence from both strains were also measured to obtain simultaneous information about their physiological states. The three parameters were conveniently monitored by dual and triple excitation flow cytometry in conjunction with double fluorescent staining techniques. In addition, the strains were identified using an epifluorescence microscope. These techniques were found powerful tools for the population analysis of this mixed bacterial system.
    Additional Material: 7 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 235-274 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: A quite unconventional, innovative scientific methodology called “macroscopic pattern analysis” is presented in this paper. This approach is more adequate in the case of complex systems than the well-known microscopic, mechanistic approach. Complex systems are not only attracting more engineering interest, but their scientific treatment is increasingly wanted by society due to the manifold problems in Earth's ecosphere. The macroscopic pattern approach will be explained in depth and illustrated in some case studies from the ecosphere (sustainability, hurricanes and avalanches), where nature serves as a teacher for the solution of the sustainability problem. Then, a series of case studies on macropatterns are described showing the problem-solving capacity for anthropo- and technosphere: sustainability in society with an index of sustainability, the eco-social market economy with eco-tech as an instrument, biokinetics, bioreactor mixing and integrated bioprocessing with models, design of cars and houses and even quality of life as an attempt to quantify macropatterns.The innovations are briefly compared in their problem-solving capacity with known approaches such as the microscopic method in science, technology and society (free market economy), including the evaluation of other indices and cleaner production, industrial ecology and zero emission initiative. Finally, a deeper integration of sciences, ethics, arts and nature will be introduced based on the vision with macroscopic pattern analysis, where the different domains of human life are integratable to effect a reconciliation.
    Additional Material: 22 Ill.
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  • 9
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 17-29 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dynamic behaviour of biofilters intended to remove toluene and xylene from air was studied during transient states. Laboratory scale biofilters were filled with a mixture of peat, bark and wood and inoculated with a mixed microbial population. Toluene and xylene were applied both as single pollutants and as mixtures. Attention was focused on the evaluation of the following transients: the response of biofilters to step changes and peaks in pollutant concentrations, the effect of changes between single and multiple pollutant loadings and the response to shutdown periods.The biofilters demonstrated a good dynamic stability during transient states induced by change in inlet pollutant concentrations. Their time periods did not exceed three hours. No interaction between xylene and toluene degradation was observed during changes in loading with single pollutants or their mixture. The performance interruptions lasting less than 24 hours were found to have no significant influence on the removal efficiency of biofilters. When the biofilters were reacclimated after longer starvation periods, a short temporary decrease in efficiency whose minimum and duration were proportional to the length of a preceding shutdown period was observed. The longest starvation period (7 days) resulted in a reacclimation lasting 7 hours only. Adaptations of a microbial population to new operating conditions as well as sorption/desorption processes were suggested as the main factors influencing the dynamic reponse characteristics.
    Additional Material: 10 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 31-38 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this paper, the in vivo decolourization of the polymeric dye Poly R-478 by semi-solid-state cultures of Phanerochaete chrysosporium BKM-F-1767 (ATCC 24725) was investigated, employing corncob as a support. In order to stimulate the ligninolytic system of the fungus, the cultures were supplemented with veratryl alcohol (2 mM) or manganese (IV) oxide (1 g/l).Maximum manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP) activities of around 2,000 U/l and 400 U/l were attained by the former, whereas the activities reached by the latter were of about 1,500 U/l and 200 U/l, respectively. Furthermore, laccase activity (around 150 U/l) was only detected in manganese (IV) oxide supplemented cultures.The polymeric dye Poly R-478 (0.02 w/v) was added to three-day-old cultures. A percentage of biological decolourization of about 85% was achieved using cultures supplemented with veratryl alcohol, whereas MnO2 cultures showed a rather lower percentage of around 58% after nine days of dye incubation. Moreover, a correlation between MnP activity and Poly R-478 decolourization could be observed, indicating that this enzyme is mainly responsible for dye degradation.In the present work, the in vivo decolourizing capability of the ligninolytic complex secreted by P. chrysosporium was investigated under the above-mentioned cultivation conditions, employing a model compound, such as the polymeric dye Poly R-478.
    Additional Material: 2 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 187-187 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 189-201 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Desulfovibrio vulgaris strain PY1 was isolated from a 3-chlorobenzoic acid (3CBA) degrading anaerobic enrichment culture, using anaerobic Percoll density centrifugation. When grown on pyruvate (20 mM), in the absence of sulphate and under strict anaerobic conditions, this organism converted not only the co-substrates benzoate (BA), 3-amino-BA and 3CBA to the corresponding alcohols but also ten other different halogenated benzoic acids, viz., 4-Cl-, 3-Br-, 4-Br-, 3-I-, 3-F-, 4-F-, 2,4-di-Cl-, 2,5-di-Cl-, 3,4-di-Cl- and 3,5-di-Cl-BA. This was verfied with HPLC and GC/MS spectrometric analyses. The yields of the co-substrate converted after 30 days of growth were between 20% and 88%, depending on the compounds which had been added at initial concentrations of 500 μM. Sulphate, sulphite, thiosulphate and disulphite inhibited the formation of 3-Cl-benzyl alcohol (3CBOH), i.e. a 97 to 99% inhibition, and nitrate and sulphur had no effect (a 7-10% inhibition). In cell-free extracts, the reduction of 3CBA to 3CBOH required strict anaerobic conditions, pyruvate or H2 as electron donors and the addition of methylviologen (MV), FAD, FMN or ferredoxin as electron carriers. The specific activity of the reduction of 3CBA to 3CBOH in crude extract was 5.3 nmol/(mg protein min). The reaction was not inhibited by additions of sulphate or sulphite (5 mM), but was completely inhibited at concentrations of 10 mM 3CBA or 50 mM BA. A carboxylic acid reductase (aldehyde dehydrogenase), which acted on non-activated 3CBA and was responsible for the reduction of 3CBA to 3-Cl-benzaldehyde, was found in the solube fraction (94% of the total activity). These results demonstrate that strain PY1 was able to effectively reduce a wide range of halogenated benzoic acids to the corresponding alcohols.
    Additional Material: 3 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 203-218 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The recent upsurge in information technology has provided the international community with an easy access to professional journals (e.g. Electronic Journal of Biotechnology at http://www.ejb.org; etc.), discussion groups (e.g. bioenergy@cret.org; digestion@crest.org; etc.) and recently to electronic international conferences (e.g. ICIBS; http://www.cid.harvard.edu/cidbiotech, etc.) as well as a series of biotechnological information material (e.g. http://www.psrast.org, etc.) to stay in contact and receive up-to-date information in biotechnology. There is no doubt that this new technology will be more cost effective in future and reach more people in communities around the globe.This review reports on one such an electronic conference aiming at bridging the communication gap between developed and developing countries. This conference dealt with integrated biosystems and has provided an excellent forum for more than 100 active participants from all regions of the world. As has been demonstrated in this review, the conference was able to show the very different approaches towards the use of biotechnology in developed and developing countries, cold and tropical climate regions owing to their different ecological, economical and societal problems. It also demonstrated very clearly that the field of molecular genetics and/or genetic engineering is not a priority issue in developing countries, but rather the need for clean technologies, multiproduct formation through socio-economic integrated biosystems, e.g. incorporating microbial waste management into agro-industries, in human activities and their roles in creating better health conditions, a better environment and sustain development.It is hoped that this review will lead to a greater use of the electronic facilities available to inform and educate both the northern and the southern communities more readily of their needs and requirements to improve understanding and efforts for a sustainable future.
    Additional Material: 4 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 275-288 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The purpose and scope of this article is to introduce capable zeolites into downstream processing of natural compounds, especially flavour compounds like 2,5-dimethyl-4-hydroxy-3(2H)-furan-3-one (Furaneol®Furaeol is a registered trademark of FIRMENICH, Ch). The synthesis and the recovery of Furaneol from L-rhamnose are presented. Therefore adsorption isotherms of the zeolites ZSM5 and DAY with varying modules have been determined and adsorption experiments using model and reaction mixtures of Furaneol synthesis were performed and will be discussed.
    Additional Material: 11 Ill.
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  • 16
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fermentation process for manufacturing 1,4-piperazinium-(L,L)-dilactate from renewable raw materials and a method for processing this product into L,L-dilactide are described. Lactic acid fermentation with Lactobacillus paracasei was modified in such a way that pH control occurred by using an aqueous solution of piperazine as a correcting agent instead of sodium hydroxide solution. The production of a stoichiometrically composed piperazinium lactate was possible when the pH was 5.0. From 5.0 kg of glucose and 2.15 kg of piperazine, 6.65 kg of 1,4-piperazinium-(L,L)-dilactate were formed in the fermentation process. Separation from fermentation broth, purification and concentration of the product in aqueous solutions were carried out by means of ultrafiltration, nanofiltration and electrodialysis. Total product retention by the membranes used was about 33%. The crystalline salt was obtained by vacuum evaporation. Processing of the 1,4-piperazinium-(L,L)-dilactate into L,L-dilactide was performed in a special glass reactor. A product yield of 70% was achieved. The purified product was characterized by elementary analysis, as well as solubility behaviour, polarity and spectroscopic data. An overall process consisting of the stages fermentation, purification and concentration of piperazinium dilactate as well as cyclization of the latter to dilactide is described.
    Additional Material: 9 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 161-168 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Five different chemical reagents and γ-rays were tested for the sanitization of immobilized biocatalysts with high penicillin G acylase (PGA) activity. The most effective chemical reagents were N-cetyl-N,N,N-trimethylammonium bromide (CTAB) and 2-isopropyl-5-methylphenol (thymol). The optimum concentration of CTAB for the treatment of the immobilized enzyme was 0.25% [w/v] and 1 h, for immobilized cells 0. [w/v] and 3 h. The optimum concentration of thymol for the immobilized enzyme was found to be 0.1% [w/v] and 1 h, for immobilized cells 0.27% [w/v] and 2 h. The optimum dose of γ-rays for the sanitization of the immobilized enzyme was established as 3.2 kGy, for immobilized cells as 4.5 kGy.
    Additional Material: 5 Tab.
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  • 18
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 53-64 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: An advanced primary treatment process for a municipal waste water was systematically studied, using a bio-flocculation-adsorption, sedimentation and stabilzation process (BSS). It was shown that the organic removal efficiency was higher than that of the traditional primary treatment processes but lower than that of the traditional secondary treatment processes. Both adsorption and bio-flocculation played an important role in the removal of pollutants. The activated sludge within the bio-flocculation-adsorption tank could be considered a bio-flocculent which improved the quality of the effluent from the primary treatment process. As the effluent of the BSS process did not meet the requirements for a typical secondary effluent, the process may be regarded as an advanced (or enhanced) primary treatment process, suitable for waste water containing a high concentration of suspended solids and colloidal particles.
    Additional Material: 7 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 67-73 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The concentration of airborne fungal spores and bacteria as related to room temperature, humidity and occupancy levels within a library building in Singapore was determined. Measurement of indoor air quality with respect to microorganisms is of particular importance in tropical environments due to the extensive use of air-conditioning systems and the potential implications for human health. This study has revealed a number of interesting relationships between the concentrations of fungal spores and bacteria in relation to both environmental and human factors. The levels of fungal spores measured in the indoor environment were approximately fifty times lower than those measured outside, probably because of the lowered humidity caused by air-conditioning in the indoor environment. The variation in fungal spore concentration in the outdoor environment is likely to be due to the diurnal periodicity of spore release and the response to environmental factors such as light temperature and humidity. The indoor concentration of fungal spores in air was not clearly correlated to concentrations measured in air outside of the library building and remained relatively constant, unaffected by the difference in the numbers of occupants in the library. In contrast, the indoor concentrations of bacteria in air were approximately ten times higher than those measured outdoors, indicating a signficant internal source of bacteria. The elevated levels of indoor bacteria were primarily attributed to the number of library occupants. Increased human shedding of skin cells, ejection of microorganisms and particulates from the respiratory tract, and the transport of bacteria on suspended dust particles from floor surfaces probably accounts for the strong positive correlation between occupancy levels and the concentration of bacteria in internal air.
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  • 21
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000) 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 22
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 96-96 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
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  • 23
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 87-96 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Preliminary results on the novel use of the bacterium Thiobacillus ferrooxidans (ATCCJ 3598 and ATCC33020) for the micro-machining (or biomachinig) of metals are reported. Biomachning is a controlled microbiological process to selectively form microstrucutures on a metal work-piece by metal removal (or dissolution) using microorganisms. Applying copper and mild steel as work-pieces, it was shown that the mass removed increased proportionately with machining time. In another experiment, the work-pieces were coated with organic photo-resistive materials to mask (i.e. protect) certain regions of the metlas, thereby defining the microstructure to be formed. The unmasked regions were successfully biomachined; the final machined profile was shown to be similar to the coating image on the original metal. Although biomachining proceeded at a slower rate than chemical machining, the undesired leaching of the metal in the region under the masked area (termed undercutting) was not as severely encountered when compared with the latter. This work demonstrates the potential use of microorganisms for the biomachining of metals. As a “green process”, the innovative use of T. ferrooxidans for the micro-machining of metals opens up the possibility of biomachining as an alternative to conventional metal processing.
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  • 24
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: During the microbial treatment of a sandy model soil artificially contaminated with polycyclic aromatic hydrocarbons (PAHs), a large residual pollution was found. The remainig PAHs were sorbed into the micropores of the soil and were therefore not bioavailable. Using a lab-scale precolator, the microbially pretreated soil was subjected to aftertreatment with surfactants with the aim of further degradation of its pollution. Two commercial nonionic surfatants of the polyethoxylate type, Präwozell F1214/5 N and Sapogenat T-300, were used. The surfactants differ both in their physicochemical properties (CMC value, PAH solubilization capacity, adsorption onto soil) and in their microbial degradability. During aftertreatment under permanently aerobic conditions, only a weak PAH accumulation in the liquid phase was observed, which was due to a low solubilization rate as well as to simultaneous microbial degradation of the dissolved PAHs. Temporary anaerobiosis successfully suppressed the microbial degradation of both the surfactant and the solubilized PAHs, resulting in a more intensive PAH accumulation. But the PAH content of the soil - the essential criterion for evaluating the efficiency of surfactant application - was not decreased to a larger extent with surfactants than without them. To find out why the surfactants failed to act, the surfactant and hydrocarbon distribution among the liquid and solid phases was studied in mixtures of phenantherne-spiked solis and Präwozell-containig liquids; at heavy phenanthrene loading, the aqueous phase was saturated with PAH; at weak loading, it was unsaturated. Model-aided data analysis showed that the soil may contain PAH in two fractions: strongly sorbed into soil pores and, in the case of heavy loading, also weakly attached to the soil surface. The latter is easily extractable, resulting in a PAH-saturated liquid, while strongly adsorbed PAH is only partially dissolved due to competition between the micelles and the soil pores for the PAH. The microbially pretreated soil contains only strongly bound PAHs, which are as difficult to extract by surfactants as they are poorly accessible for microbes.
    Additional Material: 8 Ill.
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  • 25
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Autochthonous bacteriocenoses in semiarid soils in Patagonia were found to be capable of rapidly adapting to high contamination with crude oil. This adaptation at community level is due to the selective enrichment of hydrocarbon-utilizing bacteria always present in these soils. Immediately after a heavy contamination with crude oil, the authochthonous bacteriocenosis contained about 28% hydrocarbon-utilizing bacteria which could be classified into eight ecotypes with characteristic metabolic profiles. Mainly n-alkanes were used as growth substrates of representative strains. After seven months' exposure to crude oil, the bacteriocenosis consisted almost entirely of hydrocarbon-utilizing bacteria. At least fourteen ecotypes were distinguishable, and the majority of representative strains were able to metabolize a broad spectrum of aliphatic and aromatic hydrocarbons. Corresponding to the significant alteration of the physiological diversity, drastic changes to the taxonomic diversity were also found. Whereas at the beginning of the study the autochthonous bacteriocenoses were dominated by GRAM-positive genera of the Actinomycetales (Dietzia, Gordona, Nocardia, Rhodococcus, Streptomyces) with high ecological potency, after just two months' exposure to crude oil, GRAM- negative bacteria (especially Pseudomonas stutzeri) became predominant within the hydrocarbon-utilizing bacteriocenoses accompanied by some GRAM-positive genera of the Actinomycetales with a significantly lower abundance. These findings underline the importance of Pseudomonas and some genera of Actinomycetales for processes of natural attenuation and the technically supported in situ bioremediation of soil polluted by crude oil in Patagonia.
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  • 26
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 149-159 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Some parameters of the production of an alkaline protease by Rhizopus oryzae in the solid state fermentation of wheat bran were optimized. Using the optimum parameters of an inoculum age of 7 days, an incubation time of 9 days, an amount of CZAPEK-DOX (liquid medium) of 6 ml/g bran and an incubation temperature of 33°C, an activity of 50 U/g bran was achieved. The initial pH of the CZAPEK-DOX medium had little effect. Re-incubation of mouldy bran with only fresh CZAPEK-DOX yielded 3 times total activity compared to single-cycle fermentation. As for the effect of the amount CZAPEK-DOX medium, the water constituent contributed more to activity increase than did the salt component. The ARRHENIUS activation energies were 23 and 7.9 kcal/mole below and above the optimum of 33°C, respectively. In all the studies, along with protease production, variation of protein content and specific activity were also observed. Attempts were made to explain the effects and also gauge their implications for large-scale production.
    Additional Material: 4 Ill.
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  • 27
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 28
    Electronic Resource
    Electronic Resource
    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000) 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 29
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Because of the growing utilization of renewable raw materials, the technical use of lignocellulosic fibres from wood and other annual plant materials is becoming increasingly important. The conventional production process of fibreboards is characterized by high-energy consumption and use of ecologically insecure synthetic lesins. Approximately 40 to 45% of the total energy expenditure are used for the thermo-mechanical pulping. Because of high plastication temperatures, an inactive lignin crust on the fibre surface is formed. For that reason, for glueing of the fibres, urea formaldehyde and melamin resins are usually used. The costs for the resin amount to approximately 50% of the entire material costs. In addition, environmental problems are caused. The aim of our investigation is the reduction of energy and resin consumption by enzymatic modification of wood chips and the enzymatic activation of the inherent bonding strength of the material. The first industrial use of fungi for the modification of wood was in the production of “Myco wood”. Pleurothus ostreatus and Trametes versicolor were applied for nonsterile delignification of beech wood. The present investigation of the authors deals with the mycological pre-treatment of wood chips in order to reduce the energy consumption during wood pulping. The screening results favour the brown rotter Gleophyllum trabeum for pinewood (Pinus silvestris) and the white rotter Trametes hirsuta for beech (Fagus silvatica). Both species show resistance against mould fungi. The use of submerged inoculum of these fungi has the advantage over wheat inoculum that the lag phase is less than 12 hours and that the addition of nutrients or fungicides is not necessary. Short-time wood chip incubation results in a 40% decrease of energy consumption during thermo-mechanical pulping and in improved fibreboard properties. Lignin reduction could not be determined by gravimetrical and x-ray microanalysis.Comparative investigations of fibre incubation using laccase, a submerged culture of Trametes versicolor and rape straw fibres show a high increase in bending and tensile strength and an improvement in the hygroscopic properties of glue-free fibre boards for the last two incubation kinds. Similar effects have been obtained incubating pine wood fibres for the production of fibre sheets with enzyme medium of Trichoderma reseei.
    Additional Material: 4 Ill.
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  • 30
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    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 335-350 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: During the 20th century, important relationships developed between the oil industry and both microbiological and biotechnological research. Basic microbiological research has played an important role in both the exploration and production sectors of the oil industry, but as the maturity of the industry has progressed, such contributions have been relegated with respect to their importance. With respect to refining and petrochemicals manufacture, process routes have been extensively researched, but only rarely have the biotechnological solutions developed satisfied the economic criteria that resulted in major investment. In fact, situations exist where investment has occurred, but project life was unrealistically short, suggesting a need for extreme caution when evaluating biotechnological processes for the oil industry. However, as far as engineered processes for both biotreatment and bioremediation are concerned, the fundamental research that has underpinned other areas of hydrocarbon microbiology will finally prove to be of both technical and economic value, in ensuring that the essential needs of treatment, rather than disposal, and restoration, rather than environmental destruction, can be satisfied by the oil and other industries involved in both geochemical manipulation and natural resource exploitation.
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  • 31
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of different growth-limiting factors - namely the sources of carbon, nitrogen and phosphorus and the dilution (growth) rate - on the ice-nucleation activity of Pseudomonas syringe CCM 4073 was studied. A higher ice-nucleation activity was observed at a lower dilution (growth) rate (D = 0.1 h-1) than at a higher dilution (growth) rate (D = 0.3 h-1). Remarkable differences in ice-nucleation activity were found in its dependence on the growth-limiting factor. The highest ice-nucleation activity was observed under carbon limitation (T90 = -2.7°C), a medium activity under nitrogen limitation (T90 = -5°C) and lowest activity under phosphorus limitation (T90 = -12.3°C). After the addition of excess nitrogen or phosphorus to steady-state cultures, the ice-nucleation activity was restored.
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  • 32
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
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  • 33
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    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 65-65 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
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  • 34
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
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  • 35
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    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 41-52 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Studies were carried out to evaluate the feasibility of using coffee industry residues, viz. coffee husk, coffee leaves and spent coffee ground as substrates in solid state fermentation (SSF) to cultivate edible mushrooms Pleurotus. Eight strains of Pleurotus ostreatus and two strains of Pleurotus sajor-caju were screened on a medium prepared from aqueous extract of coffee husk and agar. Based on best mycelial growth (9.68 mm/day) and biomass production (43.4 mg/plate in 9 days at 24°C), the strain P. ostreatus LPB 09 was selected for detailed studies. SSF was carried out using these substrates under different moisture conditions (45-75%) and spawn rates (2.5-25%). In general, although a 25% spawn rate appeared superior, the 10% spawn rate was recommended for all the three substrates in view of the process economics, as there was not any significant difference in the increase with 10 to 15%. The ideal moisture content for mycelial growth was 60-65% for coffee husk and spent coffee ground, and 60-70% for coffee leaves. The biological efficiency (BE), which is defined as the ratio of the weight of fresh fruiting bodies to the weight of dry substrate, multiplied by 100, and which indicates the fructification ability of the fungus for utilizing the substrate, was best with coffee husk. With coffee husk as the substrate, the first fructification occurred after 20 days of inoculation, and the biological efficiency reached about 97% after 60 days. When coffee leaves were used as the substrate, no fructification was observed even upon prolonged cultivation. With spent ground as the substrate, the first fructification occurred 23 days after inoculation and the biological efficiency reached about 90% in 50 days. There was a significant decrease in the caffeine and tannin contents (61 and 79%, respectively) of coffee husk after 60 days. It was remarkable to observe that caffeine was adsorbed onto the fruiting body (0.157%), indicating that it was not completely degraded by the fungal culture. However, no tannins were found in the fruiting body, indicating that the fungal strain was capable of degrading them. The results showed the feasibility of using coffee husk and spent coffee ground as substrates without any pre-treatment for the cultivation of edible fungi in SSF, and provided one of the first steps towards an economical utilization of these otherwise unutilized or poorly utilized residues.
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  • 36
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    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 75-81 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Serratia marcescens biovar A2/A6 is able to produce a red pigment as a secondary metabolite which has antimicrobial activity. This paper describes its growth and biopigment formation in batch cultures, in media containing different concentrations of lactic acid and beef extract as carbon and nitrogen sources, respectively. An unstructured model has also been developed to describe its growth, lactic acid uptake and biopigment formation. The comparison of simulated and experimental data shows that the proposed model predicts reasonably well the system behaviour over a range of conditions.
    Additional Material: 2 Ill.
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  • 37
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    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 97-98 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
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  • 38
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    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000) 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
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  • 39
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    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 334-334 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
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  • 40
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The impact of hydrocarbon remediation on several enzyme activities (catalase, dehydrogenase, lipase, protease, urease, alkaline phosphomonoesterase, fluorescein diacetate hydrolysis) and microbial properties (biomass-C, respiration, N-mineralization, qCO2, microbial counts) was evaluated in a laboratory study over a period of 10 weeks. A pristine soil was contaminated with diesel oil (10 mg/g soil) or with a mixture of phenanthrene and naphthalene (total amount 1 mg/g soil) and supplemented with inorganic nutrients to give a C:N ratio of 20:1. The corresponding controls consisted of uncontaminated nutrient-supplemented soil. Oil contamination caused a significant initial increase of all biological parameters measured. In the presence of PAHs, biomass-C, respiration, protease activity and heterotrophic counts were significantly enhanced, while urease activity was depressed. N-mineralization was initially, however, reversibly inhibited in the presence of oil and PAHs.The measured parameters behaved differently over time: Biomass-C, respiration and alkaline phosphomonoesterase activity reached a maximum activity after about 2-5 weeks, corresponding to the period during which the majority of hydrocarbons disappeared, and declined thereafter to the background level. Activities of catalase and dehydrogenase also followed this pattern, however, were characterized by fluctuations. Activities of lipase, protease, urease and fluorescein diacetate hydrolysis increased and remained almost constant throughout the incubation period.
    Additional Material: 10 Ill.
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  • 41
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    Berlin : Wiley-Blackwell
    Acta Biotechnologica 20 (2000), S. 351-368 
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The action resonance theory (ART), a hypothesis based on a logical extension of EINSTEIN's theory of Brownian movement, suggests that the genotype × environment interaction can be modelled as forceful encounters of the gene-products of an organism with its environment. This model has implications for molecular and cell biology, morphogenesis, evolutionary development via mutation, the mechanism of natural selection and overall function of ecosystems, extending SCHRÖDINGER's programme for molecular biology. Action, a thermodynamic property with the same physical dimensions as angular momentum and PLANCK's quantum of action, is proposed to be reversibly generated as a result of the molecular exchange of quanta, which become resonant at equilibrium, corresponding to an optimum degree of entropy and action for living systems. Because the theory can potentially predict solutions to unsolved problems such as the folding of proteins it has strong implications for successful genetic modification of organisms and for biotechnology in general; the design of a programme of research to test this theory is proposed. A key element in this research programme, improving productivity and sustainability, would be the need to select genetically modified strains in the ecological environment or niche in which they are required to function.
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  • 42
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
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  • 43
    ISSN: 0138-4988
    Keywords: Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous counter-current chromatographic processes have been successfully used in the petrochemical and sugar industry over the last 30 years. Only recently has simulated moving bed (SMB)-technology attracted widespread interest in the pharmaceutical industry, mainly as a very efficient system for chromatographic enantioseparation. The application of this technique to the downstream processing of biotechnological products requires some specific changes to meet the special demands of bioproduct isolation. Production processes are set up on an multi-ton scale, for example, for the purification of fructose with both yield and purity higher than 90%. Examples for other mono- and oligosaccharides are reported. In the purification of fatty acids or fat soluble vitamins, SMB technology under supercritical fluid conditions gives additional benefits and increases the productivity by a factor of four when a pressure gradient is applied. Another field of operation is the isolation of drug compounds from natural sources where different batch- and SMB-chromatographic steps could be successfully combined. First examples are reported for cyclosporine A and paclitaxel isolation. Finally, step-gradient elution modes can be used continuously, as demonstrated for the isolation of monoclonal antibodies.
    Additional Material: 6 Ill.
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  • 44
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 6-11 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new class of materials based on a spirodilactam structure has been recently synthesized as part of research into new polymeric materials. Not only is the spirodilactam structure novel, but it was not even the intended product in the synthesis as originally designed. The polymerization process discovered by the reaction of 4-ketopimelic acid or its corresponding spirodilactone with primary amines opened a new field of polysprodilactam chemistry. This paper describes the chemistry leading to the discovery of spirodilactam-based polymers and initial applications in the area of thermoplastics and thermosets. Most recent developments to be covered include aromatic spirodilactams and isomeric spirodilactams.
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  • 45
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 12-16 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Spirodilactam bisallylether is a new high temperature performance monomer. It melts at 154°C, and is thermally inactive in forming a homopolymer. However, it reacts readily with a bismaleimide via “ene” reaction. Therefore, it could be used as a comonomer and an effective toughening modifier for bismaleimide. The properties of the blends of spirodilactam bisallylether and 4,4'-bismaleimidodiphenyl-methane were studied. The cocured resins have high glass transition temperature, 〉 300°C. By adding 30 to 40 mole % of the bisallylether, the compact tension toughness of the bismaleimide was improved to 0.7 MPa-m1/2. Therefore, the resins have a combination of high glass transition temperature and toughness. They also showed good flexural properties. Despite the high water absorption, 5 to 7%, the resins retained high hot/wet flexural properties because of the high glass transition.
    Additional Material: 3 Ill.
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  • 46
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 59-68 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Four immiscible blend systems, styrene-maleic anhydride/styrene-acrylonitrile (SMA/SAN). styrene-maleic anhydride/acrylonitrile-butadiene-styrene (SMA/ABS), poly(vinylidene fluoride)/SAN (PVF2/SAN), and PVF2/ABS, were investigated. The effect of adding up to about 10 wt% of a third polymer that is miscible with each blend component, poly(methylmethacrylate) (PMMA), was determined. In every case, the addition of PMMA led to the improvement of properties such as tensile strength, tensile elongation, and notched impact strength. Furthermore, the addition of PMMA resulted in finer, more uniform dispersions of the primary blend components. The experimental results are interpreted in terms of interfacial activity of the common phase component, PMMA.
    Additional Material: 13 Ill.
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  • 47
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 81-85 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Differential scanning calorimetry (DSC) was used to investigate the solid-state cure process of poly(phenylene sulfide)(PPS) resin. Virgin PPS resin in an open sample pan was cured in DSC cell. Either air or oxygen was used as a curing atmosphere. Cure temperatures were in the range of 200 and 250 °C, which are below the melting point of PPS resin. Cure temperature as well as atmospheric condition influenced the cure behavior of PPS in the solid state. Both the rate and the amount of cure increased with increasing cure temperature. On the other hand, the time to reach the maximum cure rate was independent of cure temperature. Changing the atmosphere from air to oxygen increased both the cure rate and the amount of cure. The size effect of PPS particles on the cure reaction was also discussed.
    Additional Material: 9 Ill.
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  • 48
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 109-115 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Slow crack growth was measured in the perpendicular and parallel directions relative to the extrusion direction of the pipe. For five pipes from different manufacturers, the anisotropy factor, the lifetime to fracture in the perpendicular direction divided by lifetime in the parallel direction, varied from 1.2 to 4.7 for complete fracture and 1.4 to 4.0 for crack initiation. The degree of molecular orientation was determined by measuring the shrinkage that occured when a pipe specimen was heated near its melting point. The amount of shrinkage correlated with the anisotropy factor for slow crack growth. The shape change after shrinkage was related to the flow pattern of the resin during extrusion and the cooling rate after extrusion.
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  • 49
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 135-140 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The complex Young's modulus, E*(ω), and the complex strain-optical coefficient, O*(ω), of poly(ether sulfone) (PES), polysulfone (PSF), and polyethermide (PEI), were measured over the frequency range 1 to 130 Hz. The data were analyzed with a modified stress-optical rule: The Young's modulus was decomposed into two complex functions, EG*(ω) and ER*(ω); the modified stress-optical coefficient, CR and CG, associated with the rubber (R) and glass (G) components, respectively, were determined. The results for six polymers, including polystyrene, poly(α-methyl styrene), and bisphenol A polycarbonate were compared with each other. One of the coefficients, CR, equivalent to the stress-optical coefficient in melts, mainly depended on the way in which phenyl groups were connected to the chain. The other, CG, was in the range of 20 to 40 Brewsters, and did not strongly depend on the details of polymer structure. The component function, EG*(ω), which was located in the glassy region and originated from the high glassy modulus, was almost the same in shape when plotted against ω with double logarithmic scales. The R component, ER*(ω), located at the long time end of the glass-to-rubber transition zone, was slightly sensitive to the molecular structure of polymers.
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  • 50
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 159-165 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: While there is abundant evidence that the molecular weight distribution (MWD) of a linear polymer has an influence on the shape of the viscosity function, the ability to convert the viscosity function to an MWD has been questioned. Using strictly numerical techniques, we have shown that the viscosity function can be transformed to the MWD, but always with some distortion. However, distinct bimodality can be qualitatively preserved through both the MWD-viscosity and viscocity-MWD transforms.
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  • 51
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 169-173 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In microcellular plastics, an unfoamed skin that is integral with the foamed core can be created by allowing the nucleating gas to diffuse from the surfaces of a gas saturated specimen prior to foaming. In this paper, a semi-empirical model is proposed that predicts the skin thickness variation in microcellular foams as a function of gas desorption time. The model shows good agreement with experimental results on the polycarbonate-carbon dioxide system.
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  • 52
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 174-189 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The present paper proposes “Deformation Characteristics” (DC) as a new deformation measure of screw extrusion processes, based on the Green deformation tensor. In contrast to previous strain measures heuristically proposed by Mohr, et al., Mckelvey, and Pinto and Tadmor, the new DC can naturally incorporate the demixing phenomena and systematically take into account the three-dimensional circulatory flow with the screw flight effect. Therefore, DC can be regarded as an improved strain measure. “Weighted Average Deformation characteristics” (WADC) is also proposed to indicate the overall deformation characteristics as a quantitative measure to the “goodness of mixing” of the extrusion process. The present paper includes discussion on delicate differences between DC and several other strain measures in case of the two-dimensional velocity approximation, and on the application of DC into a general three-dimensional velocity field obtained by a quasi-three-dimensional finite element analysis of extrusion processes. In determining WADC in the three-dimensional application, the residence time distribution function, including the three-dimensional circulatory flow effect, is used.
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  • 53
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 229-237 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Non-isothermal flow is simulated in the screw and kneading disc elements in a modular co-rotating twin screw extruder. Methods of calculating mean temperature rises for individual elements are discussed and results are presented. The implications of non-isothermal operation for scale-up is discussed. A method is then described for making calculations in a modular co-rotating machine, that contains many different elements. Example calculations are given showing the tendency of larger machines to buildup greater temperatures when viscous heating is included.
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  • 54
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 221-228 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study of the influence of a compatibilizing agent on phase morphology development in a 75/25 polyethylene/polyamide-6 blend in a modular co-rotating twin screw extruder is presented. The development of phase morphology along the axis of the modular screw was observed by cooling the extruder and removing the polymer from the screw channels. Changes in phase morphology due to the addition of a compatibilizer have been investigated using scanning electron microscopy. Sufficient quantities of compatibilizing agent produce significant increases in the rate of mixing and also reduce the scale of the phase morphology. Much larger quantities (5%) than actually required for interface coverage are needed for rapid mixing. This seems to be due to the high viscosity of the matrix.
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  • 55
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 251-251 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 56
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 57
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 260-265 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Penrose states that quantum effects can occur even in relatively large systems when energy differences remain small. This is just the situation with polymer materials. A quantum description by Penrose of the formation of quasi-crystals can be rewritten to apply to polymer crystallization. The implications of the need to take account of quantum effects are discussed. Another approach based on the quantization of energy levels in clusters of atoms offers a possible explanation of heat setting in nylon and polyester fibers. Finally some problems of the interpretation of quantum theory are discussed.
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  • 58
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A novel approach to a truly dynamic thermodynamics is proposed in which equilibrium is defined in terms of explicit time, distance, and acceptable error scales. This approach involves reformulating the second law of thermodynamics in terms of an excess energy that vanishes at equilibrium instead of an entropy that assumes some unknown maximum value. Excess energy is defined mathematically as the total Legendre transform of energy with respect to an independent set of extensive variables. Excess energy is effectively the free energy functional of a nonequilibrium system and is a function of the time, distance, and acceptable error scales. Elimination of entropy from thermodynamics requires recognizing temperature as a thermal stress, proportional to the antimetric component of the stress tensor that is neglected when one assumes the validity of Cauchy's second law of motion. The inclusion of temperature as part of the stress-strain couple completes the science of thermomechanics and opens the way for a practical unification of chemistry and physics in strictly mechanical terms.The last sentence of the abstract shows how high the goals that Lindem meyer set for himself were. I personally do not agree with the idea that mechanics is the queen of all sciences, and that given deep enough probing one could achieve “a practical unification of chemistxy and physics in strictly mechanical terms”; for instance, electromagnetism has full citizenship's rights in physics, and it is hard to conceive that it could be reduced to mechanics.
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  • 59
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The interfacial strength of two paper-polypropylene-paper laminates used for electrical power transmission cable insulation has been measured using a peel test after a variety of conditionings that simulate the service thermal stress conditions. Immersion in dielectric oil at 23°C causes little decrease in peel strength, but heating in the oil at 90°C causes a rapid initial loss followed by a slow loss of strength. Cyclic and static heating show that cyclic fatigue is not a factor as the initial loss of strength occurs in a time comparable to the first two test cycles and further heating causes much less loss of strength. Tensile and compressive stresses resulting from cable winding have no effect on the loss of bond strength during heating in oil. Vacuum drying of the laminate and oil (as in cable manufacture) before heating results in less decrease in peel strength than heating without prior drying. Optical and electron microscopy show minimal wetting of the paper fibrils by the polypropylene with only a few having been either normal to or at a steep angle to the polypropylene surface. That is, the fibrils appear to be parallel to the interface and only partially immersed in the polypropylene. Micrographs show little, if any, differences between the interfaces on the two sides as well as little paper on the polypropylene after delamination and vice versa. It is suggested that the bonding mechanism is a combination of weak mechanical interlocking and secondary bonds. It is also suggested that swelling of the polypropylene relative to the paper by the dielectric oil at 90°C weakens the interfacial bond.
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  • 60
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 290-300 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Variations of stress with temperature for stretched networks of trans-polyisoprene networks in the crystallization region are reported. Such profiles are characteristically U-shaped with the stress at lower temperatures often climbing to high levels. Valley widths of the profiles narrow as annealing temperature increases to about 50°C, then widen at yet higher temperatures. The degree of crystallization at 22°C is 37% and independent of deformation and annealing temperature. The β crystal form is overwhelmingly present with traces of other crystal forms appearing only at high deformations. The theory of stress-induced crystallization provides a good description of experimental results provided the nucleation parameter σ is dependent upon deformation. Therefore, the data provide good qualitative support for the theory in its current form.
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  • 61
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyalkylenebenzoxazoles of high molecular weight (inherent viscosity values from 0.76 to 2.95) were prepared from 4,6-diaminoresorcinol dihydrochloride and aliphatic diacids in polyphosphoric acid by heating at 180 to 200°C for 3-5 h. Melting points of the polymers ranged from 148 to 423°C, depending on the length of the alkylene chain. Glass transition temperatures were relatively low, ranging from 50 to 100°C and did not show the pronounced odd/even effect noted for melting points. In all cases, rapid weight loss occurred above 400°C. No evidence for the formation of a molecular composite was observed in an attempt to prepare in situ a rod-like polybenzoxazole in a polyalkylenebenzoxazole.
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  • 62
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 63
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    Polymer Engineering and Science 34 (1994), S. 93-101 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Low levels of oligomer molecules are generally desirable in polymeric materials. It is known that several reactor variables can affect the oligomer distribution, and therefore it is useful to have predictive models for molecular weight distribution. The normal approach of a differential equation-based model is very complex to set up if it is applied rigorously to include all the non-Flory aspects of the step growth polycondensation and in particular the interfacial polycarbonate polymerization. In this paper, simple methods based on the Monte Carlo method and Stockmayer distribution are applied to simulate the effects of mass-transfer, unequal reactivity, and the starting stoichiometry of the polycondensing functional groups on the oligomer distribution. It is shown that these parameters can have a significant effect on the oligomer weight distribution and polydispersity of the final polymer.
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  • 64
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    Polymer Engineering and Science 34 (1994), S. 308-317 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The true crystallite modulus of polyoxymethylene (POM) was evaluated experimentally and thoeretically as a function of temperature. The mechanical deformation mechanism of POM was lattice-dynamically predicted and confirmed by measuring the stress-induced vibrational frequency shifts of the infrared and Raman spectra, which were interpreted on the basis of anharmonic potential field.
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  • 65
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    Polymer Engineering and Science 34 (1994), S. 141-152 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The ultra-high strength/modulus, extended chain polyethylene fiber (Spectra® fiber) composite has shown great potential as a lightweight armor material with its extraordinary capability of absorbing the kinetic energy of projectiles. But the relatively low melting point of this fiber (∼ 145°C) has caused concerns regarding the effect of temperature rise during the impact/penetration process on the performance as armor material. In this article, an analysis of temperature rise in projectile and the fiber composite during the impact/penetration process is described. Combining the simulation of impact deformation by finite element analysis and the simulation of temperature rise by a finite difference approximation of the related dynamic equations, the temperature rise caused by the projectile/composite interaction was estimated. Results show that there is a significant temperature rise at the projectile/composite interface due to the friction but that the short length of time involved in the process and the low thermal conductivity of Spectra fiber composite keep the temperature rise in a very small region (in the order of 0.001 cm) around the interface during the impact/penetration process. Consequently, the volume that is affected by the temperature rise is very small, in the order of total 0.001 cm3 around the projectile, and this is too small to generate any detectable effect on the armor performance. After the projectile is stopped, however, substantial heating of fiber composite can occur under specific conditions as the result of heat flow from the hot projectile embedded in the composite. This heating of fibers, however, is a postmortem effect and hence inconsequential to the ballistic performance of the composite armor.
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  • 66
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 67
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    Polymer Engineering and Science 34 (1994), S. 190-200 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A mathematical model of a polycondensation reactor that can be used in the final stage for poly(ethylene terephthalate) (PET) is established and compared with experimental data obtained from a laboratory scale reactor with film renewal. Detailed side reactions are considered along with the diffusional removal of the small molecules through thin film. Among several kinetic constants, the polycondensation reaction rate constant k1(= k8) and diester group degradation reaction rate constant k7 have an influence over the degree of polymerization. The values of k1(= k8) and k7 for 0.05 wt% Sb2O3 were obtained as curve-fit values: (1) k1(= k8) = 3.4 × 106 exp(- 18.500/RT′) (L/mol-min); (2) k7 = 1.3 × 1011 exp(- 37,800/RT′) (min-1). Effects of the film exposure time, reduced pressure of vacuum, temperature, the initial terephthalic acid (TPA)/ethylene glycol (EG) mole ratio, the initial degree of polymerization, and catalysts were well explained by the model.
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  • 68
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    Polymer Engineering and Science 34 (1994), S. 209-212 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Entrance pressure losses for the creeping flow of a power-law fluid are calculated for an abrupt contraction of ratio 2, 4, 8 and ∞ for both the axisymmetric and planar cases using P2P1 and P+2P1 finite elements. Contrary to some earlier findings in the literature, the entrance pressure loss obtained by using the two different types of finite elements, both of which satisfy the Babus̆ka-Brezzi condition, are found to converge to the same results. The present results also confirm that the variational method of Duda and Vrentas gives excellent upper bounds for both the axisymmetric and planar cases with infinite contraction ratio.
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  • 69
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    Polymer Engineering and Science 34 (1994), S. 405-413 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The curing of epoxy-amine polymer has been modeled by the reaction of functional groups, and the mole balance of these is governed by a set of six nonlinear differential equations. In this work, we have first developed a complete analytical solution for isothermal curing. For nonisothermal curing, we have divided the domain of hydroxyl group concentration β into small increments Δβ and adopted our analytical results for this domain. In addition, we solved the energy balance equation analytically and obtained the temperature rise for Δβ. We have compared our results with those obtained from the Runge Kutta numerical solutions. We have shown that our semianalytical technique is about a thousand times more efficient and faster.
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  • 70
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    Polymer Engineering and Science 34 (1994), S. 513-518 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A shear test is proposed as a complement to the tensile test in order to characterize the short time mechanical behavior of thermoplastic polymers. The proposed test geometry makes the test easy to perform and to evaluate and gives relevant information about anisotropy, plastic deformation, crack initiation, and propagation properties. Three different materials have been tested and the results are discussed.
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  • 71
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    Polymer Engineering and Science 34 (1994), S. 500-506 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Material property models for poly(etheretherketone) (PEEK) have been combined with a residual stress model to provide a means for investigating the effect of crystallization process on the residual stress development in semicrystalline materials. The analysis shows that crystallization causes an increase in the residual stress levels. This increase is affected through an increase in the resin modulus values and through the resin modulus build-up at higher temperatures. The shrinkage due to crystallization was found to have no effect on the residual stress development in neat PEEK.
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  • 72
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    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Temperature sweeps of dynamic viscoelastic properties have shown that phydroxybenzoic acid (PHB)-based liquid crystalline polyesters, specifically in this case those copolymerized with poly(ethylene terephthalate) (PET), can be subjected to considerable supercooling if initial heating curves are compared to subsequent cooling curves, indicating that this type of material can be in quite different states even at the same temperature, depending on thermal history. Utilizing this supercooling behavior, viscoelastic properties of a 60 mol% PHB/40 mol% PET material produced by Unitika were monitored before and, particularly, after large-scale shear deformation to determine how potential structure changes induced by the shear are reflected in viscoelastic properties immediately, and with time. According to dynamic viscoelastic temperature sweep data four quite different initial states were employed including conditions with, as well as largely free of, crystallites. However, in all cases, post-shear monitoring showed decreased G′ and G″ values with almost no evidence of return towards initial values within approximately 25 min. These results, in addition to furthering somewhat the fundamental understanding of the flow and relaxation properties of liquid crystalline polymers, may be useful in polymer processing, where large-scale shear deformations employed in forming processes appear to be capable of changing considerably the subsequent behavior of such materials.
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  • 73
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    Polymer Engineering and Science 34 (1994), S. 507-512 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A thermodynamic model was proposed to correlate the phase behavior of a swelling polymeric gel (vinyl alcohol-sodium acrylate copolymer) and the volume phase transition in alcohol (methanol, ethanol or propanol)-water solutions. The model is based on the Flory-Huggins formula for polymer solution coupled with the osmotic pressure by rubber elasticity proposed by Flory. The volume change behavior and the equilibrium concentrations inside and outside the gel were successfully correlated using the present model.
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  • 74
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    Polymer Engineering and Science 34 (1994), S. 528-531 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Terpolymerization was investigated by dilatometry for zincacrylate (ZnA2), acrylonitrile (AN), and styrene (St), radically initiated by a As2S3-styrene complex (I) in dimethyl sulphoxide (DMSO), at 90 ± 0.1°C for 1 h under inert atmosphere. The system follows non-ideal kinetics, due to primary radical termination as well as a degradative chain transfer reaction. The kinetic expression for the system is Rpα(I)0.27 (St)0.31 (AN) 0.22[ZnA2]0.12. The value for the activation energy and kp2/kt are 55 kJ mol-1 and 1.87 × 10-7 1 mol-1 s-1 respectively. The terpolymer has been characterized by IR and NMR spectroscopy. The thermal stability and solubility of the terpolymer have also been studied.
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  • 75
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    Polymer Engineering and Science 34 (1994) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 76
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    Polymer Engineering and Science 34 (1994), S. 551-558 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The intermeshing counterrotating twin screw extruder is widely used for compounding, devolatilization, blending, and reactive extrusion. A fluid dynamics analysis package-FIDAP, using the finite element method, was implemented to simulate the 3-D flow patterns in the region of conveying elements and shearing discs of a Leistritz LSM30.34 twin screw extruder. The rheological behavior of the fluid was described by a power law model. The flow fields were characterized in terms of velocity profiles, pressure distributions, shear stresses generated, and a parameter λ quantifying the elongational flow components. The influence of screw rotational speed and axial pressure difference on the flow characteristics was also analyzed. A comparison between the flow characteristics in the shearing discs operated in a corotating or counterrotating mode was also presented.
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  • 77
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    Polymer Engineering and Science 34 (1994), S. 532-540 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A model for the phase distribution and evolution of the heterogeneous (suspension) polymerization of vinyl chloride is presented. Experimental information on pressure, temperature, and conversion has been obtained from a 34 liter bench reactor reproducing reaction conditions and product properties typical of industrial operation. A calculation procedure based on simple plant data is proposed for the description of the phase compositions and their evolution over the entire process. Results based on classical Flory-Huggins theory of solutions are presented and compared with existing data.
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  • 78
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    Polymer Engineering and Science 34 (1994), S. 559-569 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A mathematical model is presented for the computer simulation of multilayer flow of polymer melts in coexitrusion. The proposed model can handle an arbitrary number of layers. The viscosity of each layer is shear-rate and temperature dependent. Given the material properties, die dimensions, and process conditions, the model determines the flow field throughout the die gap. Computer simulations and experimental data are presented for a three-layer polyester/EVA/polyester film coextrusion, with emphasis on the interfacial instability and its effects on optical properties of the film. The rsults are discussed in the context of the critical interfacial shear stress criterion that has been proposed by Schrenk, et al. (1) for the onset of interfacial instability. It appears that elasticity differences between layers contribute to the interfacial instability. It is conjectured that minimizing interfacial shear stress and matching elasticities of adjacent layers is an appropriate criterion in coextrusion analysis.
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  • 79
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    Polymer Engineering and Science 34 (1994), S. 541-550 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A simple unified lubrication approach has been proposed to design a coat-hanger die that can deliver wide and uniform liquid sheets. This approach requires that the wall stress in the manifold be constant. With this constraint, any inelastic non-Newtonian fluid model can be used to describe the liquid motion inside the die. Fluid models that can represent the pseudoplastic or viscoplastic behavior of polymeric liquids have been selected for illustration. A general equation that can be solved to determine the effect of production variations on flow uniformity inside the die has also been derived.
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  • 80
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    Polymer Engineering and Science 34 (1994), S. 570-579 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this paper we address the aspects associated with shear modification of low density polyethylene by extrusion. By successive passes of the polymer through an extruder it can be shown that both the melt viscosity and melt elasticity are reduced by shear modification. These reversible variations are not accompanied by significant changes in molecular weight distribution. The major effects of extrusion are to decrease the amount of elastically effecitve material. Study of proton relaxation times at 150°C shows that the melt comprises regions of relatively ordered, entangled, and unentangled polymer. Shearing reduces the proportion of more ordered material. The elastically effective anchors that are reduced by shearing are regions with restricted segmental mobility rather than conventional entanglements or intermolecular knots. Successive extrusions produce a relatively small decrease in the number of such constraints to molecular motion. Repeated shearing has a diminishing effect on the proportion of more ordered material in the polyethlene melt. This parallels observations of the effects of repeated shear modification on the properties of polyethylene films and other extrudates.
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  • 81
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    Polymer Engineering and Science 34 (1994), S. 585-597 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper presents the design and analysis of a process control strategy for a reactive extrusion polypropylene degradation process. The primary control objective is to continuously produce polypropylene with desired properties (viscosity) despite variations in the properties of the feed material. The viscosity of the polypropylene, measured using an In-line Wedge Rheometer, is controlled by manipulating the feed concentration of the peroxide which acts as the initiator for the degradation reaction. An empirical model of the reactive degradation process is developed which describes the process dynamics and the characteristic process disturbances. Minimum variance (MV), constrained minimum variance (CMV), and pole placement (PP) controllers are first evaluated and compared in simulation. Then, a pole placement controller is implemented on the actual reactive extrusion process, with results being presented for the response of the controlled process to load disturbances due to feed material changes.
    Additional Material: 14 Ill.
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  • 82
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 83
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 580-584 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A sliding plate rheometer has been developed to measure the normal thrust of a molten plastic in large amplitude oscillatory shear. The normal thrust of a molten plastic in large amplitude oscillatory shear is a significant nonlinear effect that has previously been unobtainable. Normal thrust measurements may now be used to help understand and characterize nonlinear viscoelastic behavior inherent in most molten plastics. The new rhemoeter incorporates a piezoelectric pressure transducer in a very stiff plate that minimizes compliance. Normal thrust measurements with cone and plate rheometers are made by measuring the total force on the plate (or cone) and are subject to error due to edge effects. The new rheometer measures the local pressure in the sample and is therefore unaffected by sample size or edge effects. Normal thrust measurements in large amplitude oscillatory shear are reported for both molten Phillips TR480 high density polyethylene pipe resin which contains 2% by weight of carbon black filler and IUPAC LDPE X. Crosstalk due to shear stress on the active face of the pressure transducer causes signal error which for oscillatory shear is filtered out using a discrete Fourier transform.
    Additional Material: 7 Ill.
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  • 84
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 613-624 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: At 75/25 concentration ratio, bisphenol a polycarbonate (PC)/styreneacry-lonitrile copolymer (SAN) blend has poor impact resistance compared to PC/ABS. A rubber phase methacrylate-butadiene-styrene (MBS) of core/shell type was dispersed in PC/SAN blend. The morphology of the unmodified and modified blend was investigated. The influence of the acrylonitrile ratio in the SAN on the microstructure was studied. It clearly shows that core/shell resides at the interface between PC and SAN. It seems that core/shell particles enhance the adhesion between the different phases. Their presence influences the interface mobility; i.e., the coalescence of the dispersed phase observed in pure PC/SAN is considerably reduced when the MBS particles are added. The impact resistance of the samples was correlated with the morphology.
    Additional Material: 14 Ill.
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  • 85
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 598-612 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper presents the development of a model for free radical initiated polypropylene degradation during reactive extrusion that combines a kinetic model of the polypropylene degradation reaction with a simplified model of the melting mechanism in the extruder. The free radical initiated degradation of polypropylene is characterized by a narrowing of the molecular weight distribution (MWD) and a decrease in the molecular weight averages. A high temperature SEC is used to determine MWD's for three different commercially available polypropylenes degraded at various initiator concentrations in a 1.5 inch single screw extruder (L/D = 24:1). The predictions of the kinetic model alone and the combined kinetic-melting model are compared with the experimentally determined MWD's and molecular weight averages for the degraded polypropylenes. The predictions of a modified kinetic model that includes the possibility of termination by combination are also examined. The kinetic-melting model is found to provide significantly improved predictions of the experimentally determined MWD's and molecular weight averages in comparison to the original kinetic model. A viscosity-molecular weight relationship is also developed, which is then used to determine the gain of the degradation process as a function of the initiator concentration from the molecular weight averages predicted by the kinetic-melting model. Earlier work has shown such prior knowledge of the process gain can be used to significantly improve the performance of process control schemes for the degradation process.
    Additional Material: 11 Ill.
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  • 86
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 625-631 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The curing and vitrification effect during the reaction of ATBN modified epoxy resin was studied through the dynamic differential scanning calorimetry method and a new reaction kinetic equation containing generalized WLF equation was developed to describe the reaction rate at both glassy and rubbery state. An autocatalytic mechanism was found to describe adequately the cure kinetics of the rubber modified epoxy resin and the overall order of reaction was assumed to be 2. The kinetic parameters were determined from the DSC data through the Marquardt's multivariable nonlinear regression method and Runge-Kutta integration technique. The presence of rubber indicated minor effect on the cure kinetics of epoxy resin. The Arrhenius type viscosity function was employed to establish a relationship between viscosity data measured by RMS and chemical conversion calculated from the reaction kinetic equation.
    Additional Material: 12 Ill.
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  • 87
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    Polymer Engineering and Science 34 (1994), S. 642-649 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyurethane foam formation involves both polymerization and expansion processes. The dynamics of the water and R-11 blown foams depend on the rates of chemical and physical blowing processes, along with the rate of viscosity increase of the reacting mixture. Experiments were carried out to study the dynamics of free rising, water and R-11 blown rigid polyurethane foams. The density and temperature change during the foam formation were monitored. A theoretical model was developed to predict the density and temperature variation with time. In the model, the physical blowing agent (R-11) evaporation process is assumed to be heat generation-controlled and the carbon dioxide generation process to be controlled by the rate of the water-isocyanate reaction. The kinetic parameters of the reactions of isocyanate with polyol and water were obtained separately and were asssumed to be independent of each other. The water-isocyanate reaction appears to follow first-order kinetics with respect to concentration of water. The theoretical predictions of the model show good agreement with the experimental data for density variation with time. The model predictions for temperature rise also match experimental data, except at the later stages of foaming when it is found to be slower than the experimental measurements. However, this deviation does not affect the dynamics of density change since it occurs after the completion of the expansion process.
    Additional Material: 7 Ill.
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  • 88
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 657-664 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A good extrusion die must distribute the polymer melt in the flow channel such that the material exits from the die with a uniform velocity and temperature. Coathanger dies are commonly used for the extrusion of plastic sheets and films. The die is usually provided with a straining bar allowing a regulation of the flowrate in the case of a poor design. But this, in turn, can affect temperature uniformity. Therefore, the design of coathanger die is a complex task which is mainly accomplished by trial and error in industry. Analyses of the flow in coathanger dies have been reported in the literature. Analytical and numerical approaches are used to solve this problem. The first one involves many simplifying assumptions: the most important ones being the unidirectional and isothermal flow of the polymer. Most numerical methods deal with a 2-D geometry, but only a few of them have considered the non-isothermal flow. A new model has been developed using a modified FAN method (Flow Analysis Network introduced by Tadmor) for the calculation of the 2-D flow, coupled with a finite-difference scheme for the calculation of temperature. The overall model can run on a PC with only a few minutes of calculation. Good agreement was obtained between experimental data and simulations.
    Additional Material: 16 Ill.
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  • 89
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    Polymer Engineering and Science 34 (1994), S. 650-656 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new finite element model named Corrected Slice Method (CSM) has been developed to cope with three-dimensional vacuum cooling calibrator problems. Such problems appear whenever the cooling channel lay-out comprises transverse channels in the calibrator. The CSM is an extension of the 2D approach (8), which takes into account the axial heat fluxes within the calibrator. The proposed model was validated by comparing the numerical results obtained on a test problem with a rigorous finite element approach. Moreover, a real complex profile-calibrator system was simulated in order to illustrate the full performance of the porposed method.
    Additional Material: 15 Ill.
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  • 90
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 665-670 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The use of bend testers for the determination of critical strains in the study of environmental stress cracking has been assessed. Using the combination of polystyrene in ethanol, various factors affecting the measurement of critical strains were investigated, including the strain applied during the bend testing, the time of immersion in the liquid prior to straining, the surface finish, and the extent of physical aging. It was concluded that the best determination of critical strain is the strain at which a sample just shows signs of crazing, rather than the strain at the outer edge of a band of crazes. The measured value of critical strain increases with increased prior immersion time, decreased surface roughness, and decreased physical aging time. Reasons for these variations are discussed. It is concluded that although the use of bend testers is valuable for qualitative testing, careful testing methodologies need to be adopted for it to be a useful quantitative test.
    Additional Material: 11 Ill.
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  • 91
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    Polymer Engineering and Science 34 (1994), S. 632-641 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dynamics of R-11 blown polyurethane foam formation depend on the rates of viscosity increase of the reacting mixture and R-11 evaporation, and both are controlled by the polymerization process. Detailed experiments were carried out to study the dynamics of foaming and the measurements made included the cream and rise times, the density change of the expanding foam with time, and the temperature rise during reaction. Dynamic temperature measurements at different points in the foaming mixture were also made to study the spatial variation of the temperature in the foam. The experimental results showed the rate of foaming, the final density, and the maximum temperature decreased with increasing R-11 concentration. The heat losses from the foam were also found to be significant towards the later stages of foaming when density was low. Theoretical models were developed to predict the temperature and density change with time and spatial variation of temperature in the foam due to heat losses, by considering the foaming dynamics to be either heat generation controlled or heat and mass transfer controlled. In the former, the foam was assumed to be a pseudohomogeneous phase and the approach was similar to that of Rojas, et al. (5). New features accounted for in the model were dilution of the reactant concentration due to the presence of liquid blowing agent and heat loss from the foam due to radiation. While excellent agreement between theoretical predictions and experimental results was obtained for temperature variation with time at different locations in the foam, the model gave a much sharper reduction in density with time as compared to the experimental data. In the second model, the rate of foaming was assumed to be controlled by the rate of heat and mass transfer to a single bubble in the foam. Assuming a film model for heat and mass transfer, the theoretical predictions for both temperature and density were found to be in very good agreement with experimental data.
    Additional Material: 11 Ill.
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  • 92
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    Polymer Engineering and Science 34 (1994), S. 821-826 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: When diffusion coefficients are measured with the cup method, the exposed area is often less than the area of the sample. Because of this masking effect the measured diffusion coefficient is overestimated. The present article presents simple formulas based on two-dimensional analytical solutions to correct for this in cylindrical cup samples. Different cases of anisotropical diffusion are dealt with. The error in the analytical solutions is determined by numerical computer simulations.
    Additional Material: 6 Ill.
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  • 93
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    Polymer Engineering and Science 34 (1994), S. 815-820 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A comparative study of warpage, global shrinkage, and residual quench stresses developed in rotational molding is made for a series of thermoplastics including various polythylenes, polypropylene, polyamide-6, polycarbonate, and polystyrene. The influence of rate of quench on uniaxial stress strain and impact behavior of rotomolded parts was also studied. Generally, warpage, global shrinkage, and residual stresses increase with increasing quench rate for all the polymers. Further, the levels of warpage and global shrinkage increases with extent of crystallization, i.e., products from glassy polymers exhibit little warpage and those from highly crystalline polymers are highly warped. Increasing rate of quench tends to increase elongation to break and impact strength.
    Additional Material: 10 Ill.
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  • 94
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    Polymer Engineering and Science 34 (1994), S. 799-803 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Measurements of melt strength and breaking stretching ratio of several blends of thermoplastic polymers with liquid crystalline polymers are presented. The melt strength behavior depends not only on the viscosity of the blends but also on the temperature dependence of the viscosity. In particular, even if the viscosities of the blends are, at the extrusion temperature, lower than that of the thermoplastic matrices, the melt strength can be larger than that of the pure thermoplastics if its viscosity-temperature curve exceeds that of the matrices far from the solidification temperature. This behavior allows one to spin or film blow these blends despite the low viscosity.
    Additional Material: 9 Ill.
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  • 95
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    Polymer Engineering and Science 34 (1994), S. 804-814 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A mathematical model of the high pressure polymerization of ethylene in tubular reactors was tested with experimental data obtained from an industrial size tubular reactor. Series of experiments involving changes in operating conditions were carried out, and process data and polyethylene samples were collected. The collected samples were characterized for their molecular weight distributions and various rheological material functions involving shear and extensional flows. The findings of the model were compared against the generated process data and the molecular weight distributions of the samples. The determined rheological behavior exhibited strong dependence on the primary characteristics of the resins. Overall, this study should introduce a better understanding of the interactions between high pressure reaction conditions and the primary properties of polyethylene, including moments of molecular weight distribution and extent of branching on one hand and the interrelationships between primary properties and the rheological behavior of the high pressure polyethylene product on the other hand.
    Additional Material: 11 Ill.
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  • 96
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    Polymer Engineering and Science 34 (1994), S. 827-834 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The Galerkin finite element method has been applied to study the three-dimensional flow field of power-law fluids inside an extrusion die. Two inlet designs, i.e., center-fed and end-fed, have been considered. The effects of inertial force as represented by the Reynolds number Re, inlet geometry, and the power-law index n on lateral flow uniformity and vortex formation in the entrance region have been examined. A flow visualization technique has been carried out to experimentally verify the theoretical prediction of the three-dimensional flow field inside a die. It has been found that increasing Re or decreasing n will deteriorate flow uniformity. Depending on the direction of the inlet jet stream, the inertial force may create a flow peak in the central region of a center-fed die, or the maximum flow rate will appear close to the end of the die for an end-fed die. For highly shear-thinning fluids, lower flow rates are always observed close to the end of the dies. It is concluded that creating a plug flow in the inlet tube of the extrusion die is advantageous for both center-fed and end-fed designs.
    Additional Material: 13 Ill.
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  • 97
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    Polymer Engineering and Science 34 (1994), S. 835-846 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A two-phase model is presented for simulating the post-filling stage of injection molding of amorphous and semicrystalline materials. A finite-element scheme with quadratic shape function for the pressure is proposed. The melt is considered in terms of Hele-Shaw flow for a non-Newtonian fluid using a modified-Cross model with either an Arrhenius-type or WLF-type functional form to describe the viscosity under nonisothermal conditions; the compressible behavior of the polymer is assumed to obey either a double-domain Tait or single-domain Spencer Gilmore equation of state. The interfacial energy balance equation including the latent-heat effect for semicrystalline materials is coupled with the transient energy equation for the solid and melt phases in order to predict the solidified layer and temperature profile. Two well-characterized materials, namely a commercial-grade PP and PS, were used in the present work. Good agreement is obtained between the present simulation and experimental pressure traces from this study and from previous investigation in the literature. The effects of compressibility, viscosity model, and thermal properties upon the predicted pressure field are also considered.
    Additional Material: 10 Ill.
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  • 98
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 99
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 100
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    Polymer Engineering and Science 34 (1994), S. 1148-1156 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We have generated microcellular polymeric foam structures using a pressure induced phase separation in concentrated mixtures of supercritical CO2 and poly(methyl methacrylate). The process typically generates a microcellular core structure encased by a nonporous skin, the thickness of which decreases with increasing saturation pressure. This trend can be described by a model for skin formation that is based on the diffusion rate of gas out of the sample. Significant density reductions on the order of 30 to 70% can be achieved by changing the pressure and temperature conditions in the foaming process. There are several ways in which the saturation pressure affects the average cell size, with the net effect that cell size decreases sharply with increasing pressure above 2000 psi, leveling out at higher pressures. Cell size increases with increasing temperature from 40°C to 70°C. A model for cell growth, based on a cell model of Aremanesh and Advani, modified to include the effect of CO2 on model parameters, reproduces these trends.
    Additional Material: 15 Ill.
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