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  • Electronic Resource  (731)
  • 1990-1994  (731)
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  • 1992  (731)
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  • Electronic Resource  (731)
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  • 1990-1994  (731)
  • 1980-1984
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  • 1
    Electronic Resource
    Electronic Resource
    Bromierte Diphenylether — eine entscheidende Zwischenstufe auf dem Weg zu synthetischen Schmierstoffen (1992)
    Springer
    Monatshefte für Chemie 123 (1992), S. 1153-1161 
    Details
    ISSN: 1434-4475
    Keywords: Gas chromatography ; Polyphenyl ethers ; Lubricants, synthetic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The described synthesis of synthetic lubricants based on polyphenyl ethers requires an analytical characterization of the isomerization step, which is important to the process optimization. The separation of the intermediates succeeds with gas chromatography; the isomers are determined using a retention index system. The obtained results are compared with the composition of the final product, which was investigated by HPLC analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808278
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  • 2
    Electronic Resource
    Electronic Resource
    Accidental death caused by the absorption of 2,4-dichlorophenol through the skin (1992)
    Springer
    Archives of toxicology 66 (1992), S. 298-299 
    Details
    ISSN: 1432-0738
    Keywords: 2,4-Dichlorophenol ; Accident ; Fatality ; Gas chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A case involving an accidental fatality resulting from skin absorption of 2,4-dichlorophenol in a factory is presented. The compound was quantified using gas chromatography after separation on a SP-1240 DA column and detection with flame ionization. Confirmation was obtained with mass spectrometry. Blood concentration was 24.3 mg/l. Other drugs, including ethanol, were not detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02307178
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  • 3
    Electronic Resource
    Electronic Resource
    Interpretation of COHb concentrations in the left and right heart blood of cadavers (1992)
    Springer
    International journal of legal medicine 105 (1992), S. 65-68 
    Details
    ISSN: 1437-1596
    Keywords: Fire victim ; Exposure before or after death ; Carbon monoxide hemoglobin ; Gas chromatography ; Brandopfer ; Antemortale und postmortale Exposition ; Kohlenmonoxid-Hämoglobin ; Gaschromatographie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Mit Hilfe der Gaschromatographie wurde die Kohlenmonoxid-Konzentration im Blut des rechten und linken Herzens vergleichend untersucht. Das Material stammt von Leichen mit antemortaler oder nicht-antemortaler Feuer- oder CO-Exposition. Das Konzentrationsverhältnis von COHb zwischen linkem und rechtem Herzblut (L/R-Quotient) scheint ein nicht brauchbares Kriterium zu sein, um festzustellen, ob der Tod sich vor oder nach der Feuer-Exposition ereignet hat; mit der Ausnahme von solchen Fällen, wo bei makrokopischer Untersuchung kein Ruß in den Atemwegen gefunden wird und wo die COHb-Konzentration innerhalb jener Grenzen ist, welche für Zigaretten-Raucher als normal angesehen werden.
    Notes: Summary Carbon monoxide hemoglobin (COHb) concentrations in left and right heart blood samples from cadavers both exposed and not exposed to fire or CO gas were analyzed by the gas chromatographic method. The COHb concentration ratio between samples of left and right heart blood (L/R ratio) does not appear to be useful for establishing whether death has occurred before or after exposure to fire with the exception of cases where no soot can be detected in the airways by the naked eye and the COHb concentration in the blood sample is within the level considered normal for tobacco smokers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02340825
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  • 4
    Electronic Resource
    Electronic Resource
    Stereometabolism of ethylbenzene in man: gas chromatographic determination of urinary excreted mandelic acid enantiomers and phenylglyoxylic acid and their relation to the height of occupational exposure (1992)
    Springer
    International archives of occupational and environmental health 64 (1992), S. 75-78 
    Details
    ISSN: 1432-1246
    Keywords: Stereometabolism ; Ethylbenzene exposure ; R- and S-mandelic acid ; Gas chromatography ; Enantiomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ethylbenzene is an important industrial solvent and a key substance in styrene production. Ethylbenzene metabolism leads to the formation of mandelic acid, which occurs in two enantiomeric forms, and phenyl-glyoxylic acid. To decide which enantiomer is preferably formed, 70 urine samples of exposed workers were taken at the end of shifts and — after 3-pentyl ester derivatisation — gas chromatographically analysed. The R/S ratio of mandelic acid enantiomers in urine amounts to 19:1, which means that R-mandelic acid is a major metabolite and S-mandelic acid is one of the minor urinary metabolites of ethylbenzene in man. The R/S ratio is independent of ambient air concentration of ethylbenzene within the investigated range. Compared to an ethylbenzene monoexposure the height of total mandelic acid excretion is decreased in the case of coexposure to other aromatic solvents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00381472
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of fluorine substitution on the solvation properties of tetraalkylammonium alkanesulfonate phases in gas chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 551-559 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Liquid organic salts ; Alkane-and perfluoroalkanesulfonates ; Solvation mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A series of tetraalkylammonium alkanesulfonate and perfluoroalkanesulfonate liquid organic salts are studied as model solvents to characterize quantitatively the influence of fluorine substitution on retention in gasliquid chromatography. Interpretation of solvation interactions is performed using two new thermodynamic models suggested by Kollie and Poole and Abraham and co-workers. For the solvents studied any reduction in dispersive interactions accompanying the introduction of fluorine must be approximately offset by an increase in the cavity term. Of the polar interactions, orientation interactions are large but only weakly influenced by the introduction of fluorine; solvent hydrogen-bond base interactions are strong and significantly influenced by the inductive effect of fluorine on the electron density on the sulfonate group; solvent hydrogen-bond acid interactions are negligible for all salts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02262247
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  • 6
    Electronic Resource
    Electronic Resource
    Relationship between ethylene adsorption isotherms and GC retention on Carbowax-coated porous graphite (1992)
    Springer
    Chromatographia 33 (1992), S. 237-243 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Porous graphite ; Adsorption isotherms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The objective of this work was to correlate adsorption isotherms of ethylene at −78°C on porous graphitic carbon (PGC) with gas chromatographic performance, the intention being that such isotherms could be used as a quality control test for PGC's in general, whether used for GC, HPLC or other adsorptive purposes. GC of test solutes shows that severe peak tailing on bare PGC is removed almost totally by a coating PGC with as little as 0.05% by weight of Carbowax 1500. Surprisingly there is little corresponding change in the ethylene adsorption isotherms, although it is possible to distinguish small differences at surface coverages below 5% of a monolayer of ethylene. Further work is required to establish a useful QC test.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276189
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  • 7
    Electronic Resource
    Electronic Resource
    Direct aqueous injection gas chromatographic analysis of polar compounds using sorbents containing potassium fluoride dihydrate (1992)
    Springer
    Chromatographia 33 (1992), S. 279-283 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Direct aqueous injection ; KF.2H2O containing sorbents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For direct aqueous injection gas-chromatographic analysis of polar compounds present in aqueous solutions sorbents containing conventional stationary phases and potassium fluoride crystal hydrate are proposed. On such sorbents polar compounds elute with narrow symmetrical zones under gentle chromatographic conditions. In such sorbents KF.2H2O mainly deactivates the surface of the solid support. The polarity of these sorbents is compared with the polarity of molten potassium fluoride dihydrate and conventional stationary phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276195
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  • 8
    Electronic Resource
    Electronic Resource
    Improved gas chromatographic method for the determination of the individual free fatty acids in cheese using a capillary column and a PTV injector (1992)
    Springer
    Chromatographia 33 (1992), S. 351-355 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Free fatty acids ; Cheese ; Programmed temperature vaporizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic method with a capillary column and a programmed temperature vaporizer injector has been used to analyze the individual free fatty acids in cheese. The lipids were extracted from an acidified cheese slurry with diethyl ether and treated with tetramethylamonium hydroxide (TMAH) to convert the free fatty acids to tetramethylammonium soaps (TMA-soaps), which were subsequently pyrolyzed to methyl esters in the injector. Carrying out injection at the initial column temperature resulted in lower dispersion of the results, but the solvent front prevented quantitative determination of butyric and caproic acids, and an injector temperature of 300°C was therefore employed. Under the conditions tested, trimethylamine (tma) flash-off did not affect the determinations. The accuracy of the method improved at higher free fatty acid contents (coefficient of variation of 0.53% for a total free fatty acid content of 9000 mg/kg as opposed to 7.0% for a total free fatty acid content of 1400 mg/kg). The recovery rate for individual free fatty acids ranged between 91 and 103%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275917
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  • 9
    Electronic Resource
    Electronic Resource
    Unified retention indices of hydrocarbons on BP-1 dimethylsiloxane stationary phase (1992)
    Springer
    Chromatographia 34 (1992), S. 83-84 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Unified retention index ; BP-1 dimethylsiloxane ; Hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic retention indices for 23 hydrocarbons were determined on BP-1 dimethylsiloxane between 45 and 65°C. From the data measured unified retention indices were calculated. These values agree well with the corresponding experimental values. The values of unified retention indices obtained on BP-1 are compared with those determined on OV-101 and on squalane. The differences between the unified and the experimental retention indices on BP-1, OV-101 and squalane columns are shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290465
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  • 10
    Electronic Resource
    Electronic Resource
    Gas chromatographic study of the adsorption of methyl iodide on several types of carbons (1992)
    Springer
    Chromatographia 34 (1992), S. 568-572 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Carbon adsorbents ; Methyliodide ; Effect of KI on adsorption ; Thermodynamics of adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatography has been used to measure the adsorption at zero surface coverage of methyl iodide on different types of carbon. The effect on the adsorption of methyl iodide of adding potassium iodide to the carbon samples was also studied. The differences observed in the behaviour of these samples for the adsorption of methyl iodide are explained on the basis of the textural characteristics of the samples. Thermodynamic functions of adsorption of methyl iodide at zero surface coverage are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269865
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  • 11
    Electronic Resource
    Electronic Resource
    The GC separation of C2-naphthalene isomers using cyclodextrins and crown ethers (1992)
    Springer
    Chromatographia 34 (1992), S. 163-165 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Cyclodextrins ; Crown ethers ; Dimethylnaphthalene isomer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The twelve structural C2 isomers of naphthalene are resolved on a single capillary column using α, β, or γ cyclodextrin as the stationary phase. A change in elution order is seen upon going from α to β and then γ cyclodextrin which can be related to the size of the cyclodextrin cavity and the stereochemical fit of the isomer. A crown-ether column and a liquid-crystal column were found to be unable to separate all of the isomers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276131
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  • 12
    Electronic Resource
    Electronic Resource
    Pulsed discharge emission detector — Application to analytical spectroscopy of permanent gases (1992)
    Springer
    Chromatographia 34 (1992), S. 226-234 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Pulsed discharge emission detector ; Emission spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This publication contains our initial development of a pulsed discharge emission detector (PDED) (patent pending). It uses a pulsed high voltage discharge in helium, which provides a stable source for atomic and polyatomic emission spectroscopy. We have evaluated this detector for both quantitative and qualitative analysis of a range of chemical compounds. Emission spectra observed from the pulsed high voltage discharge are valuable for spectral analysis. The results obtained for selected permanent gases in the ultraviolet, visible and infrared regions of the optical spectrum indicate that these spectra can be used for compound identification after a chromatographic separation. The data are unique in our opinion and serve as a basis for the future development and investigation of the analytical significance of this detection method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268350
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  • 13
    Electronic Resource
    Electronic Resource
    Isolation of volatiles with insecticidal properties from the genusTagetes (Marigold) (1992)
    Springer
    Chromatographia 34 (1992), S. 241-248 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Natural insecticides ; Marigolds ; Isolation of volatiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The results of optimizing Soxhlet and Simultaneous Distillation-Extraction (SSDE) procedures for the isolation of natural insecticides fromTagetes erecta, Tagetes patula, andTagetes minuta, members of theCompositae family, are presented. Extraction procedures were developed and validated that produced the extract with the highest degree of biocidal activity. The highest activity was obtained with extracts isolated by SSDE using methylene chloride. Initial work was carried out on a micro-SSDE. Preparative SSDE was used to provide large quantities of extracts for bioassays. Bioassays were used to govern optimization procedures usingAedes aegypti andAnopheles stephensi adults and larvae as target organisms.Tagetes minuta was determined to be the most active of the three species studied. Evaluation of activity and recovery versus extraction time was investigated. It was determined that an extraction time of ten hours resulted in the highest activity and over 90% recovery of the oils. Finally, supercritical fluid extraction of the flowers with CO2 was compared to SSDE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268352
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  • 14
    Electronic Resource
    Electronic Resource
    Pair-wise interactions by gas chromatography. Part II: Sociation free enthalpies of some hydrogen bonding solutes with non-associated primary alcohol groups (1992)
    Springer
    Chromatographia 34 (1992), S. 249-252 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Sociation constants ; Hydrogen bonding solutes ; Nearly ideal binary solvent theory ; Isosteric solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Gas chromatographic data measured on mixtures of 19,24-dioctadecyldotetracontane, A≡C78, and 18,23-dioctadecyl-1-hentetracontanol, POH, allow the determination of the standard chemical potential of a solute on an ideal stationary phase with primary alcohol groups at ideal dilution. The Nearly Ideal Binary Solvent Theory provides the link between these data and the sociation constant of the solute with the primary alcohol. The method was applied to calculate sociation constants of a series of hydrogen bonding solutes. Results are compared with those determined by spectroscopy and calorimetry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268353
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  • 15
    Electronic Resource
    Electronic Resource
    Determination of aliphatic amines in air by membrane enrichment directly coupled to a gas chromatograph (1992)
    Springer
    Chromatographia 33 (1992), S. 77-82 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Alipharic amines in air ; Impinger sampling ; Gas membrane enrichment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for the determination of shortchain aliphatic amines in ambient air based on impinger sampling in dilute H2SO4, selective enrichment across a PTFE gas membrane and quantification by gas chromatography. The enrichment step is carried out in a flow system directly connected to the chromatograph. The separation is performed on a packed column with nitrogen selective detection. The enrichment per sample volume was in the range 7.3 to 8.2 mL−1 for C1−C6 amines. Detection limits were ca 3–10 nM with enrichment of a 2.9 mL liquid sample. After impinger sampling of 5 m3 air in 10 mL absorption solution, this corresponds, to 0.4–0.8 ng/m3 (ca 0.2–0.5 ppt by volume) in air.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276856
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  • 16
    Electronic Resource
    Electronic Resource
    Gas chromatographic behaviour of monosubstituted benzenes, benzaldehydes and acetophenones on OV polymethylphenylsilicone stationary phases (1992)
    Springer
    Chromatographia 33 (1992), S. 267-271 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Methylphenylsiloxane stationary phases ; Kovats retention indices ; Monosubstituted benzenes, benzaldehydes and acetophenones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention indices of some monosubstituted benzenes, benzaldeyhdes and acetophenones have been determined on seven OV polymethylphenylsiloxane liquid phases. The interactions and forces that affect the separation of the isomers and their elution sequences are discussed, taking into account mesomeric and inductive effects of the substituents in the benzene ring and the dipole moments of these solutes. These phases are not very selective for the separation or the accurate assessment of the effect of substituent over the benzene nucleus. This may be explained by the presence of the considerable number of benzene nuclei integral to the structure of these phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276193
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  • 17
    Electronic Resource
    Electronic Resource
    Direct determination of partition coefficients of volatile liquids between oil and gas by gas chromatography and its use in QSAR analysis (1992)
    Springer
    Chromatographia 34 (1992), S. 601-606 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Partition coefficients ; Olive oil-nitrogen partition ; QSAR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas-liquid chromatographic method has been used for direct determination of the partition coefficients (KD) of alcohols, ethers and ketones between olive oil and nitrogen. Olive oil was characterised as a stationary phase for gas chromatography. The differential molar enthalpies of solution were also calculated from retention data. Correlations between log KD for olive oil — nitrogen and molecular connectivity indices, differential molar enthalpies of solution, biological activity and partition coefficients for blood-air were obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269870
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  • 18
    Electronic Resource
    Electronic Resource
    Calculation of programmed temperature retention indices: Part 2: Optimization of temperature dependence calculation (1992)
    Springer
    Chromatographia 34 (1992), S. 636-642 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Linear programmed temperature indices ; Retention temperature ; Calculation of retention indices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Programmed Temperature Retention Indices (PTRI) of several solutes on four packed columns coated with stationary phases covering a range of polarities have been estimated for sixteen temperature programs by exploiting isothermal retention data obtained at 70–180°C. PTRI calculations have been carried out by interpolating the retention temperatures calculated according to Curvers et al. from the graphs of retention index against column temperature, matched according to polynomials of grade 1 to 3 and by hyperbolic fitting. PTRIs by the van den Doole & Kratz equation and by cubic splines have also been computed. Comparison is made of these PTRIs with those calculated from cubic splines of the measured retention temperatures throughout the various temperature programs and the retention index deviations in terms of variance and relative error are explored. The smallest variance are found for the less polar stationary phases, PS-255 and OV-105; the biggest variance values are found for OV-275. Data are given showing that about 95% of the determinations of PTRIs on the low polarity stationary phases show deviations of not greater than 2%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269876
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  • 19
    Electronic Resource
    Electronic Resource
    Determination of partition coefficients by automatic equilibrium headspace gas chromatography by vapor phase calibration (1992)
    Springer
    Chromatographia 34 (1992), S. 235-240 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Headspace sampling ; Partition coefficients ; Multiple headspace extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Equilibrium headspace gas chromatography has been applied to the determination of the partition coefficients of volatile compounds in water-air systems. Only techniques that are suited to a fully automatic headspace procedure using the pneumatic headspace sampling-technique have been considered. Particularly simple is the technique of “vapor phase calibration —VPC” where an external vapor standard is used to calibrate the concentration of the volatile analyte in the headspace, while the concentration in the sample is found from the difference in the total amount in the vial. This technique is described in detail for 2-butanone in water. Finally, the water-air partition coefficients of several selected volatile compounds at different temperatures are listed together with their temperature functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268351
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  • 20
    Electronic Resource
    Electronic Resource
    Free radical crosslinking of the gas chromatographic stationary phase containing europium chelates (1992)
    Springer
    Chromatographia 34 (1992), S. 266-268 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Stationary phases ; Crosslinking ; Europium chelates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A gas chromatographic stationary phase containing europium chelates was modified by a free radical crosslinking with 2,2′-azobis(2-methylpropionitrile). The stationary phase was characterized by injections of the McReynolds series of standard solutes. A better thermal stability and an enhanced polarity was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268356
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  • 21
    Electronic Resource
    Electronic Resource
    Hhdrodenitrogenation catalysis studied by reversed-flow gas chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 398-410 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Reversed-flow technique ; Catalysis ; Hydrodenitrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Many important parameters of surface catalysed reactions can be determined simultaneously, under nonsteady state conditions using Reversed-Flow Gas Chromatography. A simple, slightly modified gas chromatograph is required. The distorted diffusion bands, obtained experimentally for reactant and product(s), can be analysed mathematically, using simple PC programs, to give the pre-exponential factors and the exponential coefficients of a function consisting of the sum of two-four exponential functions of time. From these, and some geometrical and diffusional characteristics of the reaction cell, the values of adsorption, desorption and reaction rate constants, the overall mass transfer coefficients in the gas and in the solid catalyst, and the adsorption equilibrium constant, for both reactant and product(s) can be calculated. The above parameters were determined at various temperatures and over three catalysts for the hydrodenitrogenation of piperidine ton-pentane, an industrially important hydrotreating process. The results obtained can help to understand the mechanism of reactions on solid surfaces and to confirm experimentally theoretical calculations on adsorption and surface reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02268375
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  • 22
    Electronic Resource
    Electronic Resource
    Use of a high-pressure Soxhlet extractor for the determination of organochlorine residues by gas chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 468-474 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; High-pressure Soxhlet extraction ; Organochlorine residue analysis ; Supercritical fluid extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The operational conditions of a high-pressure Soxhlet extractor (pressure, temperature, time and amount of sample) have been optimized, using carbon dioxide as extractant for the determination of organochlorine pesticides and polychlorinated biphenyls (PCBs) in certified potato, carrot, olive oil and lyophilized fish tissue samples. Good recoveries were obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290238
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  • 23
    Electronic Resource
    Electronic Resource
    Capillary gas chromatography of some telomeric fluoroalkanols (1992)
    Springer
    Chromatographia 34 (1992), S. 475-478 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Telomeric fluoroalkanols ; Retention index ; Regression equation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of fluoroalkanols with the general formula H(CF2CF2)nCH2OH (n=1–8) on fused-silica capillary columns coated with dimethylsilicone and cyanopropylmethylsilicone stationary phases was investigated. Retention indices were determined at three temperatures. A correlation between the retention index values, the molecular weights and the number of C and F atoms in the solute molecules was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290239
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  • 24
    Electronic Resource
    Electronic Resource
    Allyl thiocyanate — Natural product or artifact in Crucifer extracts? (1992)
    Springer
    Chromatographia 34 (1992), S. 461-467 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Allyl thiocyanate and isothiocyanate ; Plant extract ; Analytical artifacts ; Isomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Allyl thiocyanate and isothiocyanate were synthesized and could be analysed by gas chromatography without isomerization by keeping the injector at, or below, 50°C. Synthetic allyl isothiocyanate contained none of the isomeric thiocyanate but allyl thiocyanate contained 0.5% of isothiocyanate. The NMR spectra indicated both compounds to be free of the corresponding isomer. Analysis of extracts of stinkweed, mustard and horseradish by GC using non-isomerizing conditions showed that only the stinkweed extract contained allyl thiocyanate. Mustard and horseradish extracts contained allyl, and other, isothiocyanates but no allyl thiocyanate. Allyl thiocyanate previously reported in extracts of mustard and horseradish was most likely an artifact caused by partial isomerization of allyl isothiocyanate under the conditions of isolation and/or analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290237
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    Electronic Resource
    Electronic Resource
    Open-tubular columns: Past, present and future (1992)
    Springer
    Chromatographia 34 (1992), S. 513-528 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Open-tubular (capillary) columns ; History of chromatography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290246
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  • 26
    Electronic Resource
    Electronic Resource
    A convenient computer program for calculation of Kováts retention indexes (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 478-479 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Kováts retention index ; GW-BASIC program ; Computer-assisted calculation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240150714
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  • 27
    Electronic Resource
    Electronic Resource
    Hydrocarbon contaminants of boiled shrimp and crab meat (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 332-334 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary column ; Volatile components of crab and shrimp ; Environmental contaminants ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary GC and GC-MS have been used for the identification and quantitation of n-alkanes, naphthalenes, and alkylben-zenes among the volatile components of crab and shrimp meat.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240150512
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  • 28
    Electronic Resource
    Electronic Resource
    A novel algorithm for chromatogram matching in qualitative analysis (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 539-547 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Neural networks ; Pattern recognition ; Simulated data ; Simulated annealing ; Essential oils ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The matching of the pattern of peaks produced during gas chromatography is of importance to many applications. At present, this task is generally performed manually, but this generates the usual problems associated with human inspection, such as a lack of objectivity and reproducibility, proneness to errors, and practical restriction of the volume of data which can reasonably be processed.This paper explores the use of a novel algorithm for automation of this task. The performance of the method on well controlled simulated data sets and real chromatograms is used to show not only how problems of manual inspection can be circumvented, but also how the existence of such a powerful method should open up the possibility of many new analyses for quality control, discrimination of varieties of sample, and the identification of specific components within a sample.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240150811
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  • 29
    Electronic Resource
    Electronic Resource
    Coupled LC-GC-MS for on-line clean-up, separation, and identification of chlorinated polycyclic aromatic hydrocarbons at picogram levels in urban air (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 745-750 
    Details
    ISSN: 0935-6304
    Keywords: On-line coupling ; LC-GC ; LC-GC-MS ; Liquid chromatography ; Gas chromatography ; Mass spectrometry ; Chlorinated polycyclic aromatic hydrocarbons ; Urban air ; Occupational exposure measurement ; Bus drivers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Coupled liquid chromatography - gas chromatography - mass spectrometry (LC-GC-MS) has been applied for on-line clean up, separation, and identification of chlorinated polycyclic aromatic hydrocarbons (CI-PAHs). A loop-type interface was used to couple the liquid chromatograph on-line with the GC-MS, and concurrent solvent evaporation was used for sample transfer.A back-flush technique was used in conjunction with a two-dimensional column system for isolation of CI-PAHs and polycyclic aromatic hydrocarbons (PAHs). This fraction was transferred on-line to the GC and separated on a capillary column. Selective and sensitive detection of CI-PAHs in the GC eluate was obtained by negative ion chemical ionization (NICI) mass spectrometry and selected ion monitoring (SIM).The combined on-line system for isolation, separation, and identification showed high precision and accuracy, and demonstrated a linear response from 1 to 1000 pg for chlorinated PAHs. The estimated detection limit was 250 fg for 1-chloropyrene and 1,6-dichloropyrene.The technique was demonstrated by analysis of urban air samples. The low detection limit made it possible to use the technique for analysis of personally carried monitoring equipment for measurement of exposure to CI-PAHs in the work environment.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240151109
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  • 30
    Electronic Resource
    Electronic Resource
    Direct patterning using metallo-organics and its application to mask repair (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1605-1609 
    Details
    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: Au patterns are formed by photographical patterning of polymeric Au mercaptoterpenes (Au resinate), followed by bakeout of the Au resinate patterns to remove carbonaceous materials. Since commercially available Au resinate is not sensitive to 436 nm (g-line) light and cannot be photographically patterned, we mixed azide (photocrosslinker) with Au resinate to give photosensitivity to the g-line. The mixture of Au resinate and azide was spun on an Si substrate, and then exposed with 436 nm (g-line) light by a standard contact printing technique. Upon exposure, Au resinate was crosslinked by the reaction with azide, and became insoluble. Au resinate patterns were generated by development with monochlorobenzene. On baking out the Au resinate patterns to remove carbonaceous materials, we obtained 2 μm line and space Au patterns. The conductivity of the Au patterns obtained was 1/4 that of bulk Au. For a mask repair application, we mixed Cr resinate with a mixture of Au resinate and azide to improve the adhesion of the resulting metal patterns onto the quartz plate. The transmittance and the adhesion were found to depend on the bakeout condition and the mixing ratios of the Cr resinate. Bakeout in vacuum with 0.1 torr oxygen gave far better adhesion and opaqueness than bakeout in air, because of residual carbon in the resultant metal. Mask repair was carried out at the optimized condition by using a spot exposure system. The clear defect was repaired with the transmittance 〈 1% and good adhesion.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322111
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  • 31
    Electronic Resource
    Electronic Resource
    Novel auto-photosensitive polyimides with tailored properties (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1623-1629 
    Details
    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: An overview is given on auto-photosensitive polyimides as introduced for the first time in 1985. It is shown how development proceeded and how the chemical basis of auto-photosensitive polyimides was extended beyond BTDA. Novel “photosensitizer tetracarboxylic dianhydrides” like 2,3,6,7-thioxanthonetetracarboxylic dianhydride (TXDA) were synthesized and copolymerized into preimidized nonphotoactive polyimides containing tetracarboxylic acids like 6FDA or ODPA. Novel photosensitive polyimides were obtained that carry all essential features of BTDA based systems plus higher photospeed. They provide the ability to better tailor material properties to specific applications.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322115
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  • 32
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    Electronic Resource
    The separate roles of phase structure and interfacial adhesion in toughening a brittle polymer (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1695-1702 
    Details
    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 effects of rubber particle size and rubber/matrix adhesion on the impact properties of a brittle polymer have been separated using polystyrene (PS)/acrylonitrile-butadiene rubber (NBR) as a model system in which interfacial chemical reaction could be controlled. It has been proven that the interfacial adhesion between the rubber phase and the PS matrix not only greatly aids in reducing the rubber particle size but also plays a further role in improving the impact properties of the matrix polymer. The impact energies of PS/NBR blends with interfacial chemical bonding are four to ten times as high as those without interfacial bonding for the same average rubber particle size. However, at temperatures below the glass transition temperature of the rubber, there is no difference in impact energies with or without interfacial chemical bonding. It has been found that the optimum rubber particle size for toughening PS is influenced by interfacial adhesion. Smaller optimum rubber particle size is observed for blends with greater amounts of interfacial chemical bonding.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322207
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  • 33
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    Electronic Resource
    Compatibilized blends of polyamide-6 and polyethylene (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1703-1710 
    Details
    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: An increasing number of polymer alloys made by reactive processing of a compatibilizer precursor (CP) to form the compatibilizer in situ have appeared in recent years. Literature reports on compatibilization studies have focused on interactions of chemistry-morphology, processing-morphology, morphology-rheology, morphology-properties, etc. In commercial alloys, the interaction of chemistry and processing results in a material that has a balance of physical properties and rheological behavior. To maximize the contribution of each phase, it is of interest to be near the phase inversion region. In this work, maleic anhydride functionalized polyethylene is used as an effective CP for polyamide/polyethylene blends. In blends containing 50% nylon 6, the melt viscosity of the alloy increases exponentially as the ratio of CP to polyethylene increases though the morphology remains dispersed polyamide 6. High ratios of CP/PE are desired for toughness, alloys containing lesser amounts of CP exhibit better processability. The balance of toughness and processability is shown to be affected by the molecular weight of the CP.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322208
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  • 34
    Electronic Resource
    Electronic Resource
    Extrudate swell of high density polyethylene. Part II: Time dependency and effects of cooling and sagging (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1750-1754 
    Details
    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: For two high density polyethylene resins, the isothermal time dependency of extrudate swell has been measured. Very minor differences in the large molecular weight part of the molecular weight distribution, hardly detectable with gel permeation chromatography and low angle laser light scattering techniques, dramatically influence the time dependency of extrudate swell as well as the maximum swell attainable. The presence of larger molecules in sample 802 than in 801 is reflected in a lower short time (after seconds) and a larger long time (after minutes) or maximum extrudate swell value. Extruding the polymers through a capillary die L:D = 30:2 mm into air at ambient temperature allows only the short time swelling behavior to be observed, because cooling and sagging of the strand.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322303
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  • 35
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    Electronic Resource
    Development of polymer blend morphology during compounding in a twin-screw extruder. Part I: Droplet dispersion and coalescence - a review (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1824-1833 
    Details
    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 theoretical and experimental data on the breakup of droplets are reviewed. Several factors influence development of droplets: flow type and its intensity, viscosity ratio, elasticity of polymers, composition, thermodynamic interactions, time, etc. For Newtonian systems undergoing small, linear deformation, both the viscosity ratio and the capillary number control deformability of drops. On the other hand, the breakup process can be described by the dimensionless breakup time and the critical capillary number. Drops are more efficiently broken in elongational flow than in shear, especially when the viscosity ratio λ ≥ 3. The drop deformation and breakup seems to be more difficult in viscoelastic systems than in Newtonian ones. There is no theory able to describe the deformability of viscoelastic droplet suspended in a viscoelastic or even Newtonian medium. The effect of droplets coalescence on the final morphology ought to be considered, even at low concentration of the dispersed phase, φd ≥ 0.005. Several drop breakup and coalescence theories were briefly reviewed. However, they are of little direct use for quantitative prediction of the polymer blend morphology during compounding in a twin-screw extruder. Their value is limited to serving as general guides to the process modeling.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322405
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  • 36
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    Electronic Resource
    Development of polymer blend morphology during compounding in a twin-screw extruder. Part II: Theoretical derivations (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1834-1845 
    Details
    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 Part II of the work, the intermeshing twin-screw extruder is briefly described and the theoretical procedures used to model its operation are summarized. Based on the microrheological considerations discussed in Part I, a predictive procedure of the morphology evolution during compounding of two immiscible polymers is proposed. In this first generation model, only the shear flow effects are considered. Furthermore, to avoid complications due to coalescence a low concentration of the dispersed phase was assumed. In the procedure, two drop breakup mechanisms are discussed. The first assumes that the drops do not break under flow while the second postulates that breakup occurs under flow. Two dispersion mechanisms are considered, the first postulating continuously increasing polydispersity of drop size and the second postulating that drop polydispersity is inversely proportional to deformation strain. The influence of the screw configuration and operating conditions on blend morphology evolution is studied. It is expected that the computed drop size distribution provides limiting values for the experimental data. Dependency of predicted morphology on operating conditions is also investigated. Increasing screw rotating speed (resulting in increasing energy consumption) and decreasing throughput (resulting in decreasing productivity) lead to prediction of finer drop size. In practice, therefore, a compromise would be required. The proposed procedure is limited to melt flow (excluding the die region) within the region of large capillary parameter values, k 〉 4kcrit.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322406
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  • 37
    Electronic Resource
    Electronic Resource
    Orientation of miscible and immiscible polymer blends (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1857-1862 
    Details
    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: Polystyrene (PS) and poly(vinylmethylether) (PVME) were used to study the orientation of miscible and immiscible polymer blends. A miscible blend containing 60 wt% PS was prepared by casting the sample from a benzene solution. The immiscible blend was made by annealing the initially miscible mixture above its lower critical solution temperature for different times and temperatures. Fourier transform infrared spectroscopy and birefringence were used to measure the orientation of PS and PVME, before and after phase separation. Stress-strain curves were also measured for the two types of systems. It was found that the two polymers orient differently and that phase separation induces an increase in the overall orientation of the mixture, in the modulus and in PS orientation. The differences observed between pure PS and PS in the blend were attributed to changes in specific interactions and density of entanglements. The variations with phase separation were attributed to a change in the morphology of the system.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322408
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  • 38
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    Electronic Resource
    Transcrystallinity phenomena in fiber-reinforced polypropylene. II: Morphology, thermal and mechanical properties relationships (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 383-391 
    Details
    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 effect of short-length carbon and Kevlar fibers on the crystallization of isotactic polypropylene (iPP) in composites prepared by compression molding has been investigated. The tendency of carbon and Kevlar fibers to nucleate the iPP during isothermal and nonisothermal crystallization has been evaluated by differential scanning calorimetry. The influence of different thermal histories used to prepare the unreinforced and reinforced samples on the crystallization parameters of iPP was examined. In addition, the tensile behavior was related to the resulting morphologies of the samples. It was observed that the crystallinity content, obtained by using different thermal treatments (slowly cooling or quenching), gives rise to different morphologies by influencing the mechanical behavior of materials as well. Moreover, the composites obtained by slow cooling seem to present a better fibber/matrix adhesion then that found in quenched samples. Possible underlying microstructures, which can explain the properties and the morphological characteristics, are also discussed.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320512
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  • 39
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    Electronic Resource
    Relationships in a bismaleimide resin system. Part I: Cure mechanisms (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 409-414 
    Details
    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 series of bismaleimide resin systems has been examined in order to identify the molecular features responsible for the mechanical response of these materials. A range of network structures was produced both by formulation of resins with different ratios of N,N′-bismaleimido-4,4′-diphenylmethane (BMI) and methylene dianiline (MDA), and by the use of different thermal processing cycles. Spectrographic and chromatographic techniques were used to study the reactions that occurred during the cure. Two principal reactions were confirmed: a Michael addition reaction which provides linear chain growth, and an addition reaction which produces crosslinking through the double bonds of the maleimide group. In general, curing at a lower temperature or increasing the MDA content served to favor chain extension over crosslinking, which might be expected to increase molecular mobility in the resin.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320604
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  • 40
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    Processing of thermotropic liquid crystalline polymers and their blends - analysis of an in-situ LCP composite system (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 400-408 
    Details
    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: Thermotropic LCP/LCP fiber blends were prepared by a combination of meltblending and hot-drawing, using a wholly aromatic copolyester KU-9211 (also called K161 from Bayer A.G.) and an aliphatic containing LCP (liquid crystalline polymer) PET/PHB60 (from Kodak Tennessee Eastman). Morphological evidence, including scanning electron (SEM) and transmission electron microscopy (TEM), showed that the dispersed phase consisted primarily of highly oriented, 0.5 to 2 μm diameter rigid-rods of aromatic fibers imbedded in a matrix of predominantly aliphatic LCP fibrils with diameters in the range of 20 to 50 nm. An interphase of approximately 50 nm strongly bonded the two phases together. The fiber blends were characterized using dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), gas chromotography/mass spectroscopy (GC/MS), and rheological measurements. It appears that the processing conditions employed for melt blending had caused PET/PHB60 to undergo chain scission, thereby creating chemical interactions between the two LCP components during the melt blending process. Differential scanning calorimetry (DSC) thermograms as well as nuclear magnetic resonance (NMR) spectra of the extracted fraction from the mixture of 30 wt% K161/70 wt% PET(PHB60) confirmed the chemical interaction between the two thermotropic liquid crystalline polymers.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320603
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  • 41
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    A pulse rheometer for reacting foams (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 426-430 
    Details
    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 foam rheometer has been developed based on the impulse theory of linear viscoelasticity. The rheometer is a large-volume parallel-plate device which operates under gap-loaded conditions, and is designed as an add-on fixture for the Materials Testing System Model 312. The rheometer provides characterization data of the pre-gel (via the zero-shear viscosity) or the post-gel (via the equilibrium modulus) properties of a foaming cellular polymer with a precision of better than ± 15%.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320607
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  • 42
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    Mechanical and rheological properties of poly(butadiene-acrylonitrile) rubber compounds reinforced with cellulosic material (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 443-447 
    Details
    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 usefulness of waste (mainly cellulosic) materials as a reinforcement for acrylonitrile-butadiene rubber (NBR) compounds is shown in this work. The materials tested are: henequen, pine, coconut, sugarcane husks, lignin, and wood sawdust. Their performance is compared with that of commercial reinforcement materials (santocel and solka), using the same copolymer composition without reinforcement as a reference compound. Uniform particle size is achieved by milling and screening. For some of the materials, 6 mm fibers and polymerfiber coupling agent are also tested. Reinforced copolymer formulations are prepared by milling. Optimum curing times are determined with a torsion rheometer. Mechanical and rheological tests (stress-strain behavior, tear resistance, hardness, interfacial strength, storage modulus, and loss tangent), show promising results for some materials, especially when looking for a reinforced product with low dissipation energy.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320610
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  • 43
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    A mixing model for multicomponent reactions in twin screw extruders applied to the polymerization of urethanes (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 457-466 
    Details
    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: To understand the performance of multicomponent reactions in twin screw extruders the mixing mechanism in the extruder had to be understood. Therefore, two new relevant mixing parameters are defined; the mixing efficiency, which is the average number of passages of material through a high shear region; and the mixing deficiency, which is the fraction of material that does not pass through a high shear region. With these parameters an analysis can be made of the mixing circumstances in the extruder. The new model was applied to the polymerization of urethanes in a counter-rotating twin screw extruder. The results agreed very well with the theoretical expectations.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320702
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  • 44
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    The grafting of maleic anhydride on high density polyethylene in an extruder (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 467-474 
    Details
    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 grafting of maleic anhydride (MAH) on high density polyethylene in a counter-rotating twin screw extruder has been studied. As the reaction kinetics appear to be affected by mass transfer, good micro mixing in the extruder is important. Due to the competing mechanisms of increasing mixing and decreasing residence times at increasing screw speed, and due to the complicated reaction scheme, various non-linearities exist that are prohibitive for simple optimization rules. The interaction diagram presented in this paper for a twin screw extruder as a MAH grafting reactor can be used for better understanding of the influence of the extruder parameters on the reaction process.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760320703
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    CO2 laser welding of polymers (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 582-585 
    Details
    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: Deep penetration welding of polymers can be carried out at high speed with relatively low laser power. This results from an efficient coupling CO2 laser radiation to polymers that leads to volume heating. A brief review of energy coupling and heat transfer effects in polymers under CO2 laser welding conditions is given. Some examples of low power (10 to 100 watt) CO2 welding of polypropylene and polyethylene at depths of up to 1.5 cm are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320903
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  • 46
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    Fatigue strength of vibration welded thermoplastic butt joints (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 593-599 
    Details
    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: Fatigue data are presented for the strengths of 120-Hz vibration-welded butt joints of four resins: the three amorphous polymers polycarbonate (PC), polyetherimide (PEI), and modified polyphenylene oxide; and the semicrystalline polymer poly(butylene terephthalate). Data are also presented for the fatigue strength of 250-Hz vibration welds of the high-temperature polymer PEI. For all the welds, fatigue strength was evaluated through 10-Hz, tension-tension, load-controlled tests at an R value (ratio of minimum stress) of 0.1. Surprisingly, for all the stress levels studied, none of the PC test specimens failed at the welds, indicating that the fatigue strength of PC welds equals that of the base resin. This is not true of the other three resins, except at relatively low stress levels. For each of the four resins, macrographs are used to highlight the differences between the failure surfaces of monolithic specimens and specimens that failed at the welds.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320905
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    Ultrasonic welding using tie-layer materials. part II: Factors affecting the lap-shear strength of ultrasonic welds (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 612-619 
    Details
    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 influence of tie-layer Melt Flow Index on the lap-shear strength of ultrasonic welds in oriented polypropylene (OPP) has been evaluated. The tie-layer Melt Flow Index was varied from 0.03 dg/min to 2600 dg/min; the highest lap-shear strength properties were obtained using tie-layers that had melt flow index values between 30 and 100 dg/min. When using low Melt Flow Index tie-layers, hot spot formation and concomitant changes in fusion zone and heat-affected-zone dimensions produced stress concentrations that promoted failure in oriented polypropylene material away from the bondline region. When very high Melt Flow Index (2600 dg/min) tie-layers were used, the mode of failure during lap-shear testing was a mix of cohesive, in oriented polypropylene, and adhesive failure. The molecular weight of material at the bondline was not markedly affected by the thermal cycle produced during ultrasonic welding. Only the flash ejected when using low Melt Flow Index tie-layers exhibited any evidence of degradation; it is suggested that the ejected flash may have been degraded because of a combination of thermal, cavitation, and thermo-oxidative processes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320907
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    Experimental characterization of processing-performance relationships of resistance welded graphite/polyetheretherketone composite joints (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 620-631 
    Details
    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 to investigate fusion bonding (welding) of AS4 graphite/polyetheretherketone (PEEK) thermoplastic composites is presented. Processing studies are conducted for resistance welding preconsolidated AS4/PEEK laminates in both unidirectional and quasi-isotropic configurations using PEEK and polyetherimide (PEI) film at the joint interface. All bonding was done under a constant displacement process. The influence of processing time, initially applied consolidation pressure, and the rate of heat generation on weld performance is examined through lap shear and Mode I interlaminar fracture toughness testing. A rapid increase in strength with processing time that asymptotically approaches the compression molded baseline is measured. Weld times for quasi-isotropic lap shear coupons are significantly shorter than those with a unidirectional lay-up. Variation of the initially applied consolidation pressure is shown to have little influence on the lap shear strength of PEEK film welded lap joints. A discussion of the mechanisms allowing void formation during the welding process is given. Bond strength test results are correlated with ultrasonic C-scans of the weld regions.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320908
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    Resin flow through fiber beds during composite manufacturing processes. Part I: Review of newtonian flow through fiber beds (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 221-230 
    Details
    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 critical part of any master model used to simulate or control a composite material manufacturing process is the description of resin flow through the fiber bed. We present here a review of both theoretical and experimental studies of fluid flow through porous media, including fiber beds. For the practical porosity range of interest in continuous fiber composites processing (0.3〈 ∊ 〈 0.6), the permeability cannot be accurately described using the Blake-Kozeny-Carman equation, even though the flow is Newtonian at very low Reynold's number. For aligned fiber situations, the Kozeny constant, k, deviates radically from theory, depends on bed nonuniformities, and is only constant over very narrow porosity ranges. Thus, one cannot experimentally determine k at high porosities and use this value to describe low porosity situations. Theoretical attempts, based on perfectly spaced and aligned arrays of cylinders, adequately describe the transverse permeability of ideal fiber beds in the high porosity range, but do not succeed at porosities below 0.6. For axial flow through aligned fiber beds, the theory yields permeabilities much lower than are experimentally observed throughout the entire porosity range. For randomly arranged fibers, random cylinder theory also predicts permeabilities that are significantly lower than are measured.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320402
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  • 50
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    Effects of thermal modification on the structural properties of thermotropic liquid crystalline copolyester and phenoxy resin blends (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 267-272 
    Details
    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 effects of thermal modification on the structural properties were studied for a poly(ethylene terephthalate-co-p-hydroxybenzoic acid) liquid crystal bended with phenoxy resin. Poor miscibility and phase separation between the blend components are observed by the temperature dependence of dynamic mechanical properties of sample molded at 260°C, over the composition range studied. The miscibility of the blends is increased by molding at 280°C, and the blends molded by increasing the processing time show a dynamic mechanical transition to a homogeneous blend. These changes are the result of an interchange reaction between the blend components. A rubbery modulus has been observed for such blends. This implies the formation of cross-linked structures that accompany the interchange reactions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320406
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    Resin flow through fiber beds during composite manufacturing processes. Part II: Numerical and experimental studies of newtonian flow through ideal and actual fiber beds (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 231-239 
    Details
    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: Proper description of the resin flow through fibrous media is an important input to the modeling of composite manufacturing processes. Based on our conclusions in a recent review of pertinent literature (see Part I, this issue), Newtonian flow through ideal cylinder arrangements has been analyzed and measured. The analytical and numerical solutions agreed well with both our own experimental observation and those of others. Experiments with actual carbon fiber beds revealed significant deviations from ideal bed behavior. These deviations include dependence of the permeability on the nature of the permeant and the applied pressure difference, both of which make questionable the use of the Blake-Kozeny-Carman (BKC) equation to describe flow in real carbon fiber beds. Experiments that simulate the autoclave process by featuring combined permeation and consolidation of fiber beds have yielded additional dependencies of the permeability on process characteristics, such as the consolidation load and the original resin-rich areas within the fiber beds.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320403
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    Numerical prediction of fiber orientation in injection molding (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 254-266 
    Details
    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 develop a numerical method for calculating fiber orientation in the midsurface of a molded part of small thickness. Two-dimensional fiber orientation is predicted on the basis of either Jeffery's equation or a constitutive equation for the orientation tensor. The calculation is fully transient; it is performed on a time-dependent flow domain. The method is based on finite elements. Updated finite element meshes are generated at every instant of filling and allow one to perform an accurate calculation of the orientation even along the boundary of the flow domain. The method is applied to several examples in plane and three-dimensional geometries.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320405
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    Stereological measurement and error estimates for three-dimensional fiber orientation (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 240-253 
    Details
    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 method is presented for measuring three-dimensional fiber orientation in fiber-reinforced polymers and placing confidence limits on the results. The orientations of individual fibers are determined from the elliptical intersections between the cylindrical fibers and a polished section. This can be done using either manual digitization or automated image analysis. Volume averages for the sample are computed using an orientation-dependent weighting function that corrects for the bias of an area-based sample. Equations are developed for nonuniform fiber lengths, using both number-average and weight-average measures of orientation. Sources of systematic, measurement, and sampling error are discussed and equations for sampling error and the propagation of measurement error are derived. The results use a second-rank tensor to characterize fiber orientation, but the error analysis can be applied to any type of orientation parameter. We implement the technique using manual digitization of optical micrographs. Our implementation accurately measures samples with known orientation, and produces identical results from two perpendicular sections of a glass fiber/nylon injection-molded sample.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320404
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    Impact resistance performances of polyamide 6 blended with different rubber phases (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 273-279 
    Details
    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 studied the impact strength, by Charpy and Izod tests, of blends of polyamide 6 with different rubbers, 10 wt% of each, or rubbers and glass fibers (8.5 wt% and 15 wt% respectively). The rubbers are from three different families: (i) a nonreactive cross-linked terpolymer, methyl methacrylate/butadiene/styrene (17/64.5/18.5); (ii) two block copolymers compatible with the matrix, poly(tetramethylene glycol)/polamide 12 (70/30 or 34/66); and (iii) two polymers containing reactive functionality, a terpolymer ethylene/ethyl acrylate/maleic anhydride (68/30.5/1.5) and a copolymer ethylene/acrylic acid (90/10). The classification of additives in regard to improved impact depends on the procedure used for the impact strength measurement, particularly on whether the samples are notched or unnotched. The results are discussed in relation to the dimensions and the adhesion of the rubber particles. The level of adhesion has been estimated from observations in scanning electron microscopy of cavities due to pullout nodules and of nonextracted rubber after treatment in boiling xylene. Strong variations in the morphologies are found, depending on the chemical nature of the rubber. The crystalline state of the polyamide in the blends has also been evaluated from differential scanning calorimetry.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320407
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    The impact performance of thermoplastic sheet composites (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 287-297 
    Details
    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: Sheet composites of polypropylene and poly(ethylene terephthalate) were produced by melt consolidation of alternating layers of polymer films and random glass fiber mats. The composites had a nominal glass content of 50 wt% (∼30 vol%). The sheets were stamped into a complex part from which test specimens were machined, and mechanical properties determined. Flexural strengths as high as 159 MPa were recorded for polypropylene composites and 313 MPa for poly(ethylene terephthalate) composites. The flexural modulus of the polypropylene composites reached 9.1 MPa, whereas the modulus of the stiffest poly(ethylene terephthalate) composite was 15 GPa. The impact properties of the composites were equally high. Polypropylene composites absorbed up to 257 J/cm during an instrumented falling dart impact test. Poly(ethylene terephthalate) composites absorbed as much as 116 J/cm in the same test.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320409
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    Masthead (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992) 
    Details
    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
    URL: http://dx.doi.org/10.1002/pen.760320501
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    Interpretation of fiber fragmentation in carbon/epoxy single fiber composites: Possible fiber pre-tension effects (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 298-304 
    Details
    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 fiber straightening pre-tension applied during the sample preparation of single fiber composites is suggested here to significantly affect the number of fragments as well as the value of the Kelly-Tyson interface shear strength obtained from single filament composite tests. This implies that fragmentation tests performed under seemingly identical conditions, but in which the fiber pre-tension is not accurately controlled during sample preparation, might yield widely differing experimental results. We present and discuss a new set of experimental results dealing with fiber pre-tension effects in carbon/epoxy single fiber composites.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320410
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    The effects of transcrystalline interphase in advanced polymer compositesThis paper has been presented in part or in full at the Materials Research Society Symposium N, Boston, November 1989; the Third International Conference on Composite Interfaces, Cleveland, May 1990; and the Textile Institute World Conference, Dundee, Scotland, November 1990. (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 280-286 
    Details
    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: Surface-induced transcrystallization in fibers has been reported in some advanced polymer composites. It is believed that transcrystalline interphase may affect stress transfer efficiency between the reinforcing fiber and the matrix. In this study, attempts were made to examine the effects of transcrystallinity on composite performance, particularly on fiber-matrix interfacial bond strength, and to investigate possible attributes of transcrystallization. Three polymer resins, poly(etherketoneketone) (PEKK), poly(etheretherketone) (PEEK), and poly(phenylenesulfide) (PPS), and four types of fiber, polyacrylonitrile (PAN)-based AU-4 (untreated AS-4) carbon, pitch-based carbon, poly (p-phenylene terephthalamide) (PPDT) aramid, and E-glass were used. It was found that PPDT aramid and pitch-based carbon fibers induce a transcrystalline interphase in all three polymers because of an epitaxial effect. Under certain conditions, transcrystallization was also observed in PAN-based carbon and E-glass fibers, which may be partially attributed to the thermal conductivity mismatch between the fiber and the matrix. Plasma treatment on fiber surface showed a negligible effect on inducing transcrystallization, whereas solution-coating of PPDT on the fiber surface showed a positive effect. The Microdebonding test, which measures the interfacial bond strength between the fiber and the matrix, consistently showed more than 40% increments for various single filament systems with transcrystalline interphase versus without. However, the effects of transcrystallinity on the interfacial bond strength appeared to decrease as the fiber content increased in composites.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320408
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    Fabrication and electrical properties of ceramic superconductor/polymer composites (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 305-309 
    Details
    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: Superconductor/polymer composites were prepared by mixing powders representing the Y-Ba-Cu-O and Bi(Pb)-Sr-Ca-Cu-O systems with high-density polyethylene. Their electrical resistivities were measured as a function of temperature. By controlling the powder preparation techniques, it was possible to fabricate composites with superconductive transition to zero resistivity in the Bi(Pb)-Sr-Ca-Cu-O system. These composites can be fabricated in certain desired shapes.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320502
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    Curing of unsaturated polyester resins: Effect of surface treatment of particulates (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 335-343 
    Details
    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 effect of surface treatment of particulates on the curing kinetics of unsaturated polyester resin has been investigated using a differential scanning calorimeter. Two coupling agents, γ-methacryloxy propyltrimethoxy silane (γ-MPS) and phenyltriethoxy silane (PTS), were employed. The former reacted with the resin; the latter did not. A kinetic model of free radical addition polymerization was used. A correction factor was used to represent the effective free radical concentration in order to account for the formation of charge transfer complex between the glass beads and the free radicals in the resin. The results indicate that (1) the resin with treated particulates showed generally faster reaction rate and conversion than the resin with untreated particulates; (2) no obvious difference on the curing kinetics was observed between these two coupling agents; the primary role of coupling agent is to inhibit the influence of particulates on the curing kinetics of the resin by effective surface coverage; and (3) a minimum aqueous concentration of 0.05 wt% was suggested for surface treatment of particulates; the reaction rate of the resin was slightly improved when the concentration of the coupling agent was 0.01 wt%; this might possibly be due to insufficient coverage of the particulate surface.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320506
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    Basic magnesium carbonate flame retardants for polypropylene (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 327-334 
    Details
    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: Magnesium hydroxide and magnesium carbonates have attracted attention as endothermic flame retardants that are sufficiently stable to be incorporated into thermoplastics without decomposition. In this survey, a basic form of magnesium carbonate, magnesium carbonate hydroxide pentahydrate [(MgCO3)4 · Mg(OH)2 · 5H2O] was evaluated as a flame retardant for polypropylene. This filler (MCHP) has a thermal stability intermediate between that of alumina trihydrate (ATH) and magnesium hydroxide, which is sufficient to allow incorporation into polypropylene without decomposition. The MCHP is most effective at high filler concentrations near 60% where it was found to impart a Limiting Oxygen Index of 28.2 with a V-O rating (no dripping). This is slightly more effective than the flammability ratings for ATH and Mg(OH)2 under the same conditions. The effectiveness of MCHP was attributed to the large endothermic loss of water of hydration, which also dilutes the combustion gases. This action was further aided by the formation of an intumescent char on the burning surface, which eventually extinguished the flame. Various combinations of magnesium oxide, magnesium hydroxide, magnesium carbonate, and MCHP were evaluated in order to clarify the mechanism of the flame retardant and improve the efficiency of the protective action. However, no synergism was evident, and the flame retardant results were found to be additive. The mechanical properties and processabilities of these highly filled compounds are very sensitive to the type of surface treatment. The method of Savides was employed to compare the burning temperature of the test specimens and to measure the rates of combustion.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760320505
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    Morphological, thermal, and rheological properties of nylon/acrylonitrile-butadiene-styrene alloys (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 878-885 
    Details
    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: Melt blends of nylon-6/modified ABS (acrylonitrile-butadiene-styrene terpolymer) have been prepared using a single screw extruder. Electron microscopic observations revealed that the rubber particles are as finely dispersed as in ABS. Both the heat of fusion and the dynamic storage modulus of the blends were linear functions of the blend composition. The melting point of nylon crystallites and glass transition temperatures of poly(acrylonitrile-co-styrene) (AS) and the rubber phase in ABS and the amorphous phase in nylon were almost independent of the composition. Very high Izod impact strength was achieved over a broad compositional range. These facts suggest that the nylon and the modified ABS are not mixed on a molecular level although there must be sufficient interaction between them. The melt viscosities were increased with an increase in the ABS component. In the region of less than 65% ABS, the viscosities bend off to the zero-shear viscosity at low shear rates. Above 65% ABS, the viscosity curves were expressed by a power law fluid. The power law index decreased with an increase in the ABS content. The activation energy of flow vs. composition curve indicated a discontinuous point between 60% and 70% ABS. The phase inversion takes place at about 65% ABS, judging from the rheological point of view.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321307
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    New wood-polymer composites containing ethyl α-hydroxymethyl acrylate polymers (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 370-375 
    Details
    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: Ethyl α-hydroxymethyl acrylate (EHMA) was synthesized and evaluated as a candidate for wood impregnation and in-situ polymerization. Southern Pine softwood was impregnated under a variety of conditions with EHMA alone and with various comonomers plus free radical initiator. Following thermal polymerization, the wood-polymer composites were tested for increased dimensional stability (water soaking swell resistance) and mechanical properties over untreated wood. The greatest increase in dimensional stability was attained using EHMA alone, while the maximum compression modulus was achieved by impregnating with 1:1 EHMA-styrene and styrene alone. The composites were further characterized by 13C CP/MAS solid state NMR and scanning electron microscopy.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320510
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    Transcrystallinity phenomena in a polypropylene/kevlar fiber system. I: Influence of crystallization conditions (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 376-382 
    Details
    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 isothermal crystallization from the melt of isotactic polypropylene in the presence of Kevlar 49 fibers has been investigated. The nucleating ability of the fibers was demonstrated, and the presence of extensive transcrystalline regions was related to crystallization parameters, such as crystallization temperature, melt precrystallization temperature, and residence time at precrystallization temperature. The results are discussed in terms of the presence of heterogeneities in the bulk and preformed self-seeded nuclei located in the anfractuosities of fiber surfaces.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320511
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    Dynamics of a continuous stirred tank reactor for styrene polymerization initiated by a binary initiator mixture. II: Effect of viscosity dependent heat transfer coefficient (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 494-505 
    Details
    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 dynamic behavior of the solution polymerization of styrene in a continuous stirred tank reactor is analyzed with a mixture of tert-butyl perbenzoate and benzoyl peroxide as an initiator system. In the modeling of the reactor, a viscosity dependent reactor wall heat transfer coefficient is used to account for the changing heat transfer efficiency as monomer conversion and polymer molecular weight increase. The steady state and bifurcation behaviors have been investigated with the reactor residence time, initiator feed composition, initiator concentration, feed solvent volume fraction, and coolant temperature as bifurcation parameters. Unlike the reactors with constant heat transfer coefficient, the present system exhibits relatively simple steady state and dynamic bifurcation behaviors. Oscillatory behavior is observed only when the solvent volume fraction in the feed exceeds 0.2. The dynamic simulation of the reactor also indicates that a feedback temperature controller may fail to maintain the reactor temperature when the heat transfer coefficient changes as a result of process disturbances.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320707
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    Characterization of blends of an amorphous polyamide with lightly sulfonated polystyrene ionomers (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 517-523 
    Details
    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: Improved compatibility of blends of polystyrene and an amorphous polyamide was achieved by lightly sulfonating the polystyrene. Hydrogen bonding between amide groups and either sulfonic acid or metal sulfonate groups lowered the interfacial tension between the two polymers, which led to a much finer dispersed phase size in blends involving the sulfonated polystyrene. At relatively high sulfonate to amide ratios, the two polymers formed a miscible blend. Improved mixing of the phases was verified by shifts in the glass transitions, and the specific interactions that occurred were characterized by Fourier transform infrared spectroscopy.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760320802
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    Shear-rate-dependence modeling of polymer melt viscosity (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 931-938 
    Details
    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: Steady-shear-viscosity data sets for commercial-grade acrylonitrile-butadiene-styrene terpolymer, nylon, polycarbonate, poly(methylmethacrylate), and polystyrence are fitted in terms of a generalized Cross/Carreau modeling for the shear-rate dependence. Based upon extensive data sets from the open literature as well as in-house measurements, it is shown that the shear-rate dependence can be more accurately described in terms of the Cross rather than Carreau model. Although the resulting viscosity fits based upon these two models might differ by 20% or more for the same well-characterized data set, the resulting effect upon simulating the injection-molding process is found to be much smaller since such predictions reflect a range of shear stresses (varying linearly from centerline to wall of cavity) over which the two models alternate in relative magnitude. This is demonstrated by detailed representative numerical predictions which are presented for both the filling and post-filling stages.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321404
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    Effects of UV exposure and thermal history on properties of a preimidized photosensitive polyimide (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 924-930 
    Details
    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 structure and properties of a preimidized photosensitive polyimide (Probimide PSPI, a copolyimide of benzophenonetetracarboxylic dianhydride with alkyl groups substituted aromatic diamines) were studied with variations of UV exposure energy and bake temperature by means of wide angle X-ray diffraction, dynamic mechanical thermal analysis, stress-strain analysis, and residual stress analysis. The X-ray diffraction patterns patterns indicate that the PSPI is amorphous in the solid state. The Tg was 378°C ∼ 410°C, depending upon the thermal history over the range of 350°C ∼ 400°C. At the glass transition region, the dynamic storage modulus E′ was very sensitive to both i-line exposure energy and thermal history. However, the mechanical stress-strain behavior at room temperature was primarily dependent on the thermal history. The mechanical properties were 2.6 GPa ∼ 2.9 GPa Young's modulus, 131 MPa ∼ 168 MPa tensile strength, 10% ∼ 12% yield strain, and 16% ∼ 74% elongation at break, depending upon the baking or annealing. These dynamic and static mechanical properties indicate that on the PSPI backbone, crosslinks are formed thermally as well as photochemically. The thermal crosslinks might be formed through thermal liberation of the labile alkyl groups of aromatic diamine moieties and subsequent coupling of the radicals. The thermal degradation was also evidenced in the mechanical properties degraded by baking above 375°C or annealing above 350°C. In addition, during baking and cooling, the residual stress was dynamically measured on Si wafers as a function of temperature. The stress at room temperature was 48 MPa ∼ 52 MPa for the PSPI films baked at 350°C or 400°C, regardless of i-line exposure.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321403
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    Blends of a chlorinated poly(vinyl chloride) compound and a thermotropic liquid crystalline copolyester: Mechanical properties of squeezed flow films (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1028-1036 
    Details
    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 mechanical properties of squeezed flow films were measured on blends of a chlorinated poly(vinyl chloride) (CPVC) compound and a thermotropic liquid crystalline copolyester of p-hydroxybenzoic acid/poly(ethylene terephthalate) (60/40), hereafter referred to as LCC. CPVC is immiscible with LCC. The most serious and unique problem of liquid crystalline polymers is their tendency to fibrillate when fabricated into films and injection molded parts, primarily because of a high degree of mechanical anisotropy. It has been found that the mechanical anisotropy of LCC and blends could be lessened using nonisothermal squeezing equibiaxial extension flow. The maximum tensile properties of LCC are achieved when processed in the vicinity of 260°C. For blends of CPVC containing LCC, the mechanical properties are dependent on the processing temperature and compositions. Blends with no more than 20 wt% of LCC exhibit significant increases in tensile properties. This is due to the possibility of frozen-in macroscopic biaxial orientation of LCC in the blends during the nonisothermal squeezing flow. Within the range of processable temperatures, the reinforcement of CPVC due to the incorporation of LCC can be achieved at a temperature below the optimum processing temperature of LCC, although the thermal history of blends never reaches that temperature.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321508
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    Kinetic model for the curing reaction of a tetraglycidyl diamino diphenyl methane/diamino diphenyl sulfone (TGDDM/DDS) epoxy resin system (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1037-1046 
    Details
    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 kinetic model based on reaction mechanisms was proposed for the description of the curing behavior of a TGDDM/DDS resin system. The characteristic of this model is the separation of the non-autocatalytic part from the autocatalytic part of the reaction, so the model can match the well-established pseudo second order reaction mechanism, as proposed by many other studies about the epoxide/amine reaction. The present model was compared with two other widely used models for the autocatalytic curing behavior of epoxide/amine system, i.e., an equation based on a single rate constant and another based on pure phenomenological analysis, by using DSC data. It was found that the reaction rate calculated from this new model can fit the DSC empirical result much better than those calculated from the other two models. Parallel studies on some other resins, such as the DGEBA/m-PDA system, also proved the superiority of this kinetic model. Results have revealed that the new model was valid for most of the epoxide/1o-amine systems studied. A discrepancy did appear as the epoxide/amine molar ratio and/or the isothermal curing temperature reached certain limits, owing to the occurrence of side reactions.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760321509
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    Masthead (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992) 
    Details
    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
    URL: http://dx.doi.org/10.1002/pen.760321601
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    Blending of poly(benzimidazole) (PBI) with a low molecular weight ether imide model compound (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1047-1051 
    Details
    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: Poly(benzimidazole) (PBI) was solution-blended with a low molecular weight ether-imide analog to Ultem 1000. The as-cast blends were found to form one-phase structures over the whole of the composition range. By the use of optical microscopy and differential scanning calorimetry, the blends were found to phase separate on heating above the blend glass transition temperature (Tg) but did not remix on cooling. It was concluded that the blends formed on room temperature casting were nonequilibrium and remained one-phase simply because they were well below Tg.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321510
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    Preface (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1053-1054 
    Details
    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
    URL: http://dx.doi.org/10.1002/pen.760321602
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    Scanning tunneling microscopy studies of single-molecule single-crystals (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1209-1212 
    Details
    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 study of single-molecule single-crystals of isotactic polystyrene was carried out by scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). It was shown that STM provided more information than TEM. By means of STM, the single-molecule single-crystals were found even in the case of aggregation. Regular strips were also found on the top surface of single-molecule single-crystals. This seems to imply regular adjacent folding.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321705
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    Mesophase structure of some flexible chain polymers (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1188-1203 
    Details
    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 mesophase structures of some flexible chain polymers, which do not contain mesogenic groups, but are able to form thermodynamically equilibrium mesomorphic states, were studied by means of the X-ray analysis, the differential scanning calorimetry, and other methods. The mesophase polyethylene in bicomponent polymer blends, mesomorphic ultra-high molecular weight polyphosphazenes, and membrane polyvinylorganosilanes were investigated. The scheme of polymer phase transitions is discussed. Besides conformational disordering, the step-by-step loss of different levels of the positional order (i.e. the multiple-step character of melting) of flexible, semiflexible, and stiff chain polymers is deduced and illustrated by examples from the authors' experience and from the literature.
    Additional Material: 29 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321703
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    On the interrelation of rubber elastic stress-strain curves under different types of strain (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1213-1216 
    Details
    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: With specially shaped samples it is possible to study the stress-strain relation σ(γ) in simple shear up to large shear deformation γ. Measurements of σ(γ) on synthetic polyisoprene, IR 305, differently crosslinked with dicumylperoxide, are reported and compared with those for uniaxial extension on the same materials. Using the simple deformation geometry including shearbands proposed in the meander model (1), both stress-strain relations can be converted into each other. These results favor the applied superstructural model and moreover show that the deformation behavior of rubbers is governed by one material law, σ(γ).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321706
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    High orientation of toughened chalk-filled isotactic polypropylene: Preparation and properties (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1217-1227 
    Details
    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: Chalk-filled isotactic polypropylene (iPP) toughened by modifying the interfaces with liquid oligomer of ethylene oxide was subjected to high deformation at elevated temperature. Oriented chalk-filled material exhibits interesting properties: high concentration of open interconnected pores, high elastic modulus, high tensile strength, ability to absorb large quantities of liquids, white color and roughness of the surface. A continuous process for the production of oriented, toughened, chalk-filled isotactic polypropylene is described. The stretching ratios which can be achieved range from 4 to 8 for modified chalk concentrations with compositions of 60 and 40 wt%, respectively. Solid state extruded, toughened, chalk-filled iPP prepared for comparison exhibits similar morphology and properties as drawn toughened chalk-filled iPP although it contains much less voids.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321707
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    Thermal properties of poly(vinyl cyclohexane) (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1228-1235 
    Details
    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: Isotactic poly(vinyl cyclohexane) (PVCH) was studied by thermal analysis. The deduced equilibrium melting point, Tm°, is 405°C (678 K). The heat of fusion, Δ Hƒ° was found to be 50.82 J/g (5.60 kJ/mol) and Δ Cp at Tg, is 0.273 J/(gK) [30.1 J/(molK)]. The glass transition temperature, Tg, of the amorphous PVCH is 80°C (353 K). In semicrystalline samples, Tg increases up to 165°C (438 K) for crystallinities 〉 40%. Beside crystalline and flexible amorphous, a rigid amorphous phase is postulated in the semicrystalline polymer.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760321708
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    Thermal characterization of high performance PBI and 6F polymers and their alloys (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1236-1241 
    Details
    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 effectiveness of thermal analysis as a technique for screening polymeric candidates for high temperature composite application is described. DSC, DMA, and TGA were employed to measure glass transition temperature, characterize blend phase morphology, and assess thermo-oxidative stability. The materials studied were polybenzimidazole (PBI), polyimide copolymer (6FCoPI), and blends of PBI with Ultem 1000™ and 6FCoPI. The potential of misinterpretation of thermal analysis as the primary screening tool was also demonstrated. It was shown that if thermal analysis was used with insufficient understanding of the chemistry and physics of the materials under investigation, highly misleading conclusions may be derived.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760321709
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    Elastic moduli of semicrystalline polyethylenes compared with theoretical micromechanical models for composites (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1242-1254 
    Details
    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 large collection of data on Young's modulus and density of unfilled polyethylenes at ambient conditions has been compared with various competing theoretical mixing rules developed for composite micromechanics. The objective was to see if such theories usefully predict the dependence of stiffness on crystalline content in an archetypal isotropic semicrystalline thermoplastic polymer above its glass trnsition temperature. It was found that the self-consistent scheme derived by Hill and Budiansky from continuum micromechanics appears to have valid application to this system. The scheme naturally and coherently incorporates information on bulk and shear moduli and Poisson's ratios, while giving a good account of the main trend in the Young's modulus data. Conversely, other theoretical models frequently invoked in the polymer literature were explicitly found to be unsuitable for representing principal features of modulus-density relationships dectated by the data.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760321710
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    Crystallite elastic constants and macroscopic moduli of isotropic semicrystalline polyethylenes (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1255-1260 
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    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: Available literature data, augmented with a few mild and plausible assumptions, have been used to derive an estimated empirical compliance matrix for orthorhombic crystalline polyethylene at ambient conditions. Compared with this representation of experimental observations, reported theoretical compliance surfaces, derived from molecular mechanics, are shown to be in quantitative disagreement, although qualitatively their shapes are not dissimilar.It is further shown that if an accurate theoretical determination were to be available, it would yield an ability to translate (in surprisingly few, and rather simple, theoretical steps) directly from interatomic forces, acting over nanometer lengths, into realistic, crystallinity-dependent, estimates of macroscopic moduli of isotropic semicrystalline polyethylenes.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760321711
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    Effect of filler concentration on the phase separation in poly(vinyl acetate)-poly(methyl methacrylate) mixtures (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1261-1263 
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    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 temperatures and kinetics of phase separation have been studied as a function of filler concentration in a polymer mixture of poly(vinyl acetate)-poly(methyl methacrylate). The filler was shown to have a marked effect on the cloud point position and the phase separation kinetics at various temperatures. The effects observed are dependent upon the component ratio.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321712
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    Thermal analysis of poly(phenylene sulfide) polymers. I: Thermal characterization of PPS polymers of different molecular weights (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1264-1269 
    Details
    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: Thermal properties of Fortron®®Registered trademark of Hoechst Celanese Corporation. poly(phenylene sulfide) (PPS) polymers of different molecular weights were studied by DSC. Crystallization studies revealed that the ability of these polymers to crystallize decreases with increasing molecular weight. The Avrami equation poorly describes the isothermal crystallization of PPS. Lamellar crystallization was observed for the lowest molecular weight sample. For the other, higher molecular weight polymers the Avrami exponent is always between 2 and 3, suggesting development of distorted spherulites with heterogeneous nucleation. The temperature dependence of the solid and melt heat capacities have been determined. The solid specific heat capacity did not exhibit a molecular weight dependence. The heat capacity increase at the glass transition, Tg, has been calculated to be 28.1 J°C-1 mole-1. The equilibrium melting point of PPS has been estimated to be 348.5°C using the Hoffman-Weeks method. The Tg of PPS increases with molecular weight. The Tg of the highest molecular weight evaluated is 92.5°C. A DMA relaxation peak corresponding to the onset of the phenylene ring rotation occurs at -92°C. Only the highest molecular weight could be quenched to a completely amorphous state.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760321713
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  • 84
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    Conformational changes in a polyethylene model under tension and compressionResearch sponsored by the Division of Materials Sciences, Office of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc., and the National Science Foundation, Polymers Program, Grant #DMR 8818412. (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1278-1285 
    Details
    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: Using a realistic model for polyethylene (PE), the molecular dynamics technique is used to simulate atomic motion in a crystal. The calculations reveal conformational disorder above a critical temperature. The rate of isomerization computed from molecular dynamics is compared to transition-state theory and leads to an activation energy under stress of ∼ 30 kJ/mol, 15 kJ/mol above the single-bond rotation value. In the unstressed case, the activation energy for the process is less.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321715
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  • 85
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    Thermal analysis of poly(phenylene sulfide). II: Non-isothermal crystallization (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1270-1277 
    Details
    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 non-isothermal crystallization of Fortron poly(phenylene sulfide), PPS, was examined to better understand its behavior during injection molding. The nonisothermal Avrami formalism was applied to this system, but this method was found to be questionable because of the sometimes severe curvature that appears in the plots of the transformed data. A method of ranking crystallization rates at low cooling rates by plotting the peak in the crystallization exotherm versus the cube root of cooling rate has been considered and shown to have limitations at the higher cooling rates of interest. The growth rate expression developed by J. D. Hoffman for polymer crystallization of chain folded lamella in three dimensions has been used to simulate crystallization exotherms. It was found that this could only fit the data at low cooling rates. At high cooling rates it was necessary to use a growth rate expression developed by Calvert and Ulhmann for polymer crystallization without chain folding. When this is used to describe a two dimensional growth geometry, close agreement in the positions of high cooling rate exotherms could be obtained. The implication is that a change in crystallization mechanism is possible as the conditions go from low to high cooling rates.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321714
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  • 86
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    Electronic Resource
    Characterization and cure of dielectric and conducting polymer thick films (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1286-1289 
    Details
    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: Polymer thick films are screenable polymer pastes which vary from electrically non-conducting to electrically conducting. These materials typically contain significant amounts of high boiling solvents, and cure therefore involves removal of solvent in addition to crosslinking of the polymer matrix. In this study thermogravimetric analysis and dynamic mechanical analysis were utilized to characterize the residual solvent and glass transition behavior, respectively, with cure of the polymer thick films. Thickness was maintained constant at approximately 25μ and 100μ by using stainless steel mesh substrates. Results showed that IR curing, although able to heat more rapidly, did not accelerate the cure beyond that expected from time at temperature. Time-temperature superposition kinetics were employed to measure activation energy of cure, generate master cure curves, and to quantify IR cure time-temperature profiles. Cure models describing Tg and residual cure as a function of time, temperature, and film thickness were developed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321716
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  • 87
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    Electronic Resource
    Indentation behavior of polymer coatings on glass (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1366-1371 
    Details
    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: For relatively soft polymer coatings on soda-lime glass substrates the indentation load increases substantially when the indenter penetrates into the glass substrate since the glass can now directly support some of the indenter load. A model for the indentation load-depth behavior is developed by accounting for the indentation load shared by the coating and substrate. This model accounts for the additional load supported by the coating due to the pile-up of coating material underneath the indenter. The model predicts the indentation behavior as a function of coating and substrate hardnesses and coating thickness. Comparison of the model to experimental data for a wide range of polymer coatings (two epoxies, epoxy acrylate, and urethane acrylate) on soda-lime glass substrates shows good agreement.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321805
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  • 88
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    The effect of cyclic stress on the physical properties of a poly(dimethylsiloxane) elastomer (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1350-1357 
    Details
    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 dynamic creep behavior of a filled poly(dimethylsiloxane) elastomer was studied under cyclic stress. The stress level was chosen such that the increase in the internal temperature was small and that microcracks were not observed. This work has demonstrated that cyclic stress in combination with high temperature accelerates the degradation of the elastomer. The results suggest that because of the applied force, breaks in the load-bearing chains of the network occur. These breaks, while relieving the mechanical stress, create highly reactive ionic fragments. It is believed that because of the subsequent reactions of the ionic fragments, changes in the specific gravity, storage modulus, effective crosslink density, and length of the sample (creep) are observed. The observed decrease in the storage modulus is thought to occur because of the reaction of the ionic fragments with moisture, which results in the formation of silanol chain ends that reduce the effective crosslink density. The results also show that contrary to the prediction of the Boltzmann's Superposition Principle, the rate of creep is greatly enhanced when the sample is subjected to a sinusoidally varying dynamic load as compared to a comparable static load. The polymer weight loss was found to be linear with time and strongly dependent on the level of applied dynamic and static force. In addition, the weight loss and rate of creep were also found to be strongly dependent upon temperature.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321803
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  • 89
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    Electronic Resource
    Effectiveness of polymer coatings on reducing indention damage in glass (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1372-1378 
    Details
    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: Polymer coatings are widely used to protect glass from indentation damage. A model for the strength degradation that occurs when a sharp indenter penetrates through the coating is developed by accounting for the indentation load shared by the coating and substrate. This model accounts for the additional load supported by the coating due to the pile-up of coating material underneath the indenter. The model predicts the strength degradation as a function of indentation load, coating and substrate hardnesses, and coating thickness. Comparison of the model to experimental data for a wide range of polymer coatings (two epoxies, epoxy acrylate, and urethane acrylate) on soda-lime glass substrates shows good agreement.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321806
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  • 90
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    Electronic Resource
    Masthead (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992) 
    Details
    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
    URL: http://dx.doi.org/10.1002/pen.760321901
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  • 91
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    NMR spectroscopy, polymer motion, and “Tack” of model printing inksPresented in part at the 33rd International Symposium on Macromolecules, International Union of Pure and Applied Chemistry, Montreal, July 1990. (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1379-1385 
    Details
    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: Polymer motion in solution and in model printing inks (as measured by NMR spectroscopy) was compared to the “tack” or tensile stress developed in the splitting of thin fluid films. For model inks based on polyisobutene, at constant pigment content, increasing the polymer content caused polymer motion to slow down, and caused the tack to increase. At constant polymer content, increasing the pigment level had much less effect on polymer motion. At 20% pigment content, tack values were little different from those of the corresponding polymer solutions. This suggests that the tensile stress developed in an ink film as it splits is related to the motion of its polymeric ingredients, but is much less dependent on the concentration of dispersed solid pigment.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321807
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  • 92
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    Assessment of oxidative thermal degradation of crosslinked polyethylene and ethylene propylene rubber cable insulationThis article is based on a Ontario Hydro Research Division Report, Report #89-172-K. (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1386-1393 
    Details
    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 procedures to monitor oxidation degradation of two commonly used cable insulations, crosslinked polyethylene (XLPE) and ethylene propylene rubber (EPR). Since the techniques described require only micro specimens, deterioration of cable insulation can be monitored without destroying the function of the cable. The techniques described are melting point, crystallinity, infrared carbonyl absorbance, gel content, relative hardness, and differential scanning calorimetry (DSC) oxidation induction time. The techniques were applied following accelerated aging over a period in excess of two years. The results from the micro specimens were directly related to embrittlement and the decrease in ultimate elongation. The previous thermal history of XLPE was determined using DSC melting peak analysis.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321808
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  • 93
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    Electronic Resource
    The yield strength of particulate reinforced thermoplastic composites (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1394-1399 
    Details
    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 effects of the filler volume fraction and strength of adhesion on the mode of tensile failure of a particulate reinforced polypropylene (PP) are investigated using finite element simulation (FES). When there is perfect adhesion between constituents, an upper bound for tensile yield strength is found to be 1.33 times the matrix yield strength above a critical volume of particulate concentration. Utilizing Sjoerdsma's model for interacting stress concentration fields, one can determine the concentration dependence of the yield strength below the critical filler volume fraction. When there is no adhesion between constituents, a modified version of an equation by Nicolais and Narkis adequately describes a lower bound for the tensile yield strength. The particulate concentration and the matrix ductility are the prime factors in controlling the brittle failure of the composite. Upper and lower bounds for brittle failure strength are characterized using a strength-of-materials approach and stress concentration factors for both “perfect” and “zero” adhesion. The properties of calcium carbonate filled PP homopolymer were measured over a wide range of filler volume fractions. CaCO3 was either treated with stearic acid to prevent adhesion between constituents or used as received. Maleic anhydride grafted PP (MPP) was used to promote adhesion. For filler volume fractions below 0.2, yielding of the composite by combined microcavitation and shear deformation was the principal failure mechanism. At vf above 0.35, a brittle failure mechanism dominated. In the range between 0.2 and 0.35, both failure modes were observed in the populations tested. Good agreement was found between the experimental results and the proposed model.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321809
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  • 94
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    Model filled polymers. XIII: Mixing and time-dependent rheological behavior of polymer melts containing crosslinked polymeric particles (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1418-1425 
    Details
    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 rheological properties of polystyrene (PS) and poly(methyl methacrylate) (PMMA) composites filled with monodisperse sized crosslinked polymeric particles are sensitive to processing history and chemical composition. Particles compatible with the matrix, such as PMMA or copolystyrene-vinylphenol in a PMMA matrix, are randomly dispersed on mixing, yielding (almost) Newtonian fluids. Particles incompatible with the matrix, such as PS or copolystyrene-acetoxystyrene in PMMA, produce composites whose steady shear viscosities depend on shear rate and whose dynamic moduli are elevated at low frequency. Particles in incompatible composites tend to cluster, producing a structure that is destroyed at high shear rates and that reforms on aging at elevated temperatures.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321904
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  • 95
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    Flow field analysis of the kneading disc region in a co-rotating twin screw extruder (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1411-1417 
    Details
    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: Co-rotating, intermeshing twin screw extruders are widely used in polymer compounding and blending. Among the different modules of the co-rotating twin screw extruder, the kneading discs are the dominant ones in determining mixing efficiency. The major difficulty in solving the flow problem in the kneading disc region arises from the complex geometry and the time-dependent flow boundaries as the discs rotate. In this work, a fluid dynamics analysis package - FIDAP - using the finite element method was employed to simulate the flow patterns in the kneading disc region of a Werner & Pfleiderer ZSK-30 co-rotating twin screw extruder. The problem of time dependent flow boundaries was solved by selecting a number of sequential geometries to represent a complete mixing cycle. The flow field was characterized in terms of velocity profiles, pressure distributions, shear stresses generated and a parameter λ quantifying the elongational flow components. The last two parameters are the most important ones in analyzing mixing efficiency. The influence of design variables (stagger angle, right or left handed configuration) and processing conditions (rpm, axial pressure gradient) on the flow characteristics was analyzed.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321903
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  • 96
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    Noncontact measurement of parison thickness profiles affected by swell and sag in continuous extrusion blow molding (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1401-1410 
    Details
    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: Optimization of final part thickness distributions is crucial in the extrusion blow molding process in order to minimize resin usage. Prediction of part thickness distributions from basic process and material parameters would be ideal. However, attempts to do so have been unsuccessful, largely because of the inability to predict parison thickness profiles. One must therefore resort to measurement of the parison thickness profile and estimation of the final part thickness distribution by computational methods. This paper describes a new technique for the noncontact estimation of parison thickness profiles in continuous extrusion blow molding. The method accounts for sag and requires no previous knowledge of rheological data. It can be employed on-line for the purposes of process monitoring and control. The approach is based on the measurement of the parison length evolution with time during extrusion, the parison diameter profile, the flow rate, and the melt temperature gradient along the length of the parison. These parameters are utilized in conjunction with a theoretical approach that describes the extrusion of a parison under the effects of swell, sag, and extrusion into ambient conditions. Results are presented for three resins of various molecular weight distributions. The degree of sag is minimal at the top and bottom of the parison, and reaches a maximum near the center of the parison. Results are also presented to demonstrate the versatility of the method under other process conditions, such as varying flow rate, die temperature, and die gap.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321902
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  • 97
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    The development of surface texture in injection stretch-blow molded polypropylene (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1426-1432 
    Details
    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 development of surface texture in biaxially deformed polypropylene is examined. Two polypropylenes formed into bottles under similar conditions by the injection stretch-blow molding process exhibit different levels of clarity. Vertical cracks of light scattering dimensions are found by optical microscopy to be the source of haze. Rheological measurements indicate the resin that develops surface cracking has a much higher extensional viscosity and exhibits a significant increase above the linear case of its extensional stress growth function. Possible mechanisms for the formation of surface texture are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321905
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  • 98
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    Electronic Resource
    Photoinitiated crosslinking of low density polyethylene. V: Orientation in stretched samples (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1433-1439 
    Details
    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 density polyethylene (LDPE) is extruded, stretched, and photocrosslinked at different temperatures with different stretch rations in a continuous production line. Three different sequences are adopted: crosslinking before drawing, crosslinking after drawing, and crosslinking during drawing. The effect of drawing is studied by measuring the tensile properties. The increase of tensile strength and the decrease of elongation at break after stretching are related to chain orientation in crystalline morphology measured by X-ray diffraction. Thermal analysis by differential scanning calorimetry (DSC) supports these results. Owing to chain relaxation, the effects of orientation by stretching are significant only when the samples are drawn at a temperature not much higher than the melting point. Annealing of the drawn samples at a temperature above the melting point shows that the orientation in a crosslinked sample is retained for a much longer time than in an uncrosslinked sample. For the crosslinked samples, it is found that crosslinking after or during drawing gives a material with lower shrinkage upon heating; however, crosslinking before drawing gives a heat-shrinkable material.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321906
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  • 99
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    Preamble (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1557-1557 
    Details
    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
    URL: http://dx.doi.org/10.1002/pen.760322102
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  • 100
    Electronic Resource
    Electronic Resource
    ARCOR, a new photolithography technique with antireflective coating on resist (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1545-1549 
    Details
    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 multiple interference effect is one of the major causes of the fluctuation in critical dimension control (CD) and in mark detection for alignment. Suppressing this effect is critical for future photolithography. We propose a new photolithography technique called anti reflective coating on resist (ARCOR), which improves linewidth accuracy and overlay accuracy by suppressing multiple interference. ARCOR consists of relatively simple processes: A clear antireflective film is spun onto the resist prior to the mark detecting for alignment and exposure. The film is subsequently removed and the resist developed in the conventional way. ARCOR differs from ARC, which suppresses the reflection at the resist/substrate interface. ARCOR suppresses the reflection at the air/resist interface. ARCOR allows mark detection and exposure without light intensity-loss and multiple interference. The experiments mainly examine polysiloxane and perfluoroalkylpolyether as ARCOR materials. It is shown that linewidth accuracy can be improved from 0.3 to 0.03 μm. The signal-to-noise ratio of the alignment signal is drastically improved, and the overlay error is about half that of the conventional method. ARCOR is also effective for directly measuring the reflectivity at the resist/substrate interface, which is a key parameter of the multiple interference effect and the halation. Using ARCOR and a thin resist film, the measured ratio of reflected light to incident light indicates the reflectivity at the resist/substrate interface. Because, the probe light does not reflect off the resist surface and the intensity-loss at the resist surface is suppressed. With perfluoroalkylpolyether film, the measurement error is ∼ 1.5%.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322018
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