摘要:

AbstractDeuterium and tritium exchanges were performed on the aromatic groups of polystyrene using DCl or TCl and TiCl4. Up to 5 deuterium atoms per monomer unit could be placed on the aromatic groups depending upon time, DCI pressure, and TiCl4concentration. Tritiated polystyrene mixed with zinc sulfide phosphor produced 1.06 Cd/m2of luminance.

ISSN:0021-8995    

DOI:10.1002/app.1991.070420701

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractClassical morphological analysis has been performed on novel PET fibers of high modulus and low shrinkage (HMLS). As expected, amorphous orientation controls the degree of shrinkage and tenacity. The uniqueness of these materials is derived from a high “effective” crosslink density which results in a high retractive force during elevated temperature shrinkage and significant stress‐amplification during room temperature extension. Although the morphological origin of the high effective crosslink density is unknown, it is speculated that the interfibrillar regions contribute to the observed behavior by suppressing yie

ISSN:0021-8995    

DOI:10.1002/app.1991.070420702

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe evolution of organic vapors from encapsulants at elevated temperatures has been implicated as the source of the degradation of the gold–aluminum intermetallic of the wire that connects the bond pad to the leadframe in an integrated circuit. Gas chromatography/infrared spectroscopy/mass spectrometry were used to study the decomposition of three commercial epoxy‐novolac thermosetting compounds. Outgassing products have been identified and their origins discussed. Insight into the types of initiators used in encapsulants and their possible influence upon ball bond failure rates has been gai

ISSN:0021-8995    

DOI:10.1002/app.1991.070420703

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe modification of polyacrylonitrile membrane with ethanolamine was carried out, and the permeation characteristics in pervaporation were examined using the aqueous alcohol solutions. In pervaporation of a water/alcohol solution, preferential permeation of water was observed for all these membranes because of the hydrogen‐bonding interaction. The selectivity of the modified polyacrylonitrile (PAN) membrane depended on operating temperature, but was independent on the thickness of the membrane. Furthermore, it was found that the membrane with more ethanolamine content had a higher affinity to water. The effect of feed concentration and the molecular size of the permeating species on the separation factor and permeation flux was also investigate

ISSN:0021-8995    

DOI:10.1002/app.1991.070420704

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractStress relaxation behavior of short Kevlar fiber‐reinforced thermoplastic polyurethane (TPU) is studied with respect to strain level, strain rate, fiber loading, and fiber orientation and temperature. The existence of a two‐step relaxation mechanism for unfilled stock and a three‐stage relaxation mechanism for the fiber‐filled stock is r

ISSN:0021-8995    

DOI:10.1002/app.1991.070420705

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe FT IR spectra for different degrees of neutralization of ionomers based on poly(ethylene–methacrylic acid) copolymer were obtained. They involve the alkali metal ions (such as lithium, sodium, potassium, rubidium, and cesium), the alkaline earth metal ions (such as magnesium, calcium, strontium, and barium), and the transition metal ions (zinc and copper). Through the analysis of these spectra it can be deduced that there are two formation mechanisms and corresponding models for the ionomers: a cluster–multiplet model and a coordinated complex model. Also, it can be seen that the metal cations play an important role in the structure of an ionomer. By comparing the spectra of the metal ionomers at different temperatures as well as the spectra of the metal ionomers before and after water immersion, the existence of the two formation mechanisms and models can be inferred furt

ISSN:0021-8995    

DOI:10.1002/app.1991.070420706

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe Fourier transform infrared (FTIR)in situmethod was developed for the investigation of photopolymerization. Ultraviolet (UV) cure of a mixture of a cycloaliphatic epoxide, a 2‐ethylhexyl acrylate, and photoinitiators, which forms simultaneous interpenetrating polymer network (IPN), was monitored while the sample was irradiated with UV light. Triphenylsulfonium salt and benzoin ether were used as photoinitiators. For the sake of comparison, similar experiments were performed for the epoxide with the triphenylsulfonium salt photoinitiator and the acrylate with the benzoin ether photoinitiator. The epoxy photopolymerization was monitored using an epoxy CH stretching band at 3005 cm−1and a ring vibration band at 790 cm−1. The acrylic photopolymerization was monitored using a CC stretching band at 1637 cm−1. The epoxy conversion was less than 60% when the acrylic polymerization was completed i

ISSN:0021-8995    

DOI:10.1002/app.1991.070420707

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe rate coefficient for entry of radicals into the polymer particles and the radical exit rate coefficient were estimated in seeded emulsion polymerization of styrene. The dependence of both coefficients on the particle size was used in an attempt to discriminate between the models proposed for these coefficients. The results obtained were found to be consistent with a model in which the entry of radicals into the polymer particles occurs by the propagational mechanism and the radicals desorb from the polymer particles by diffusion. A comparison between the estimated values of the coefficients and those calculated theoretically using the equations derived from the corresponding mechanisms was performed.

ISSN:0021-8995    

DOI:10.1002/app.1991.070420708

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe relaxation processes and thermal properties of a series of blends of a highly linear high‐density polyethylene (HDPE) with several branched high‐density, linear low‐density (LLDPE) and low‐density polyethylenes (LDPE) have been measured. For the sake of comparison, all the samples were subjected to the same thermal treatment, that is, a rapid quenching from the molten state. The mechanical properties have been analyzed, taking into consideration the crystallization behavior of each sample. The existance of cocrystallization provides a bigger change in the dynamic mechanical properties than when segregation takes place. The observed changes in the end‐corrected storage modulus supports this conclusion as well as those associated with the α, β, and γ relaxation

ISSN:0021-8995    

DOI:10.1002/app.1991.070420709

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY

摘要:

AbstractThe molecular weight distribution of iPP and its copolymers with ethylene have been studied using cyclohexane/decalin as eluent at 333 K. The fractionation of the polymers using the same solvent system was also investigated. Reproducible and reliable molecular weight distribution and averages have been obtained.

ISSN:0021-8995    

DOI:10.1002/app.1991.070420710

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1991

数据来源: WILEY