ISSN:0032-3888    

DOI:10.1002/pen.760262002

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760262003

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractWe first discuss two scientific publications by Maxwell: a pioneering paper on the nature and kinetics of crazing on atactic polystyrene; and his development of a new mechanical spectrometer with a frequency range from 6 × 10−4to 1.6 × 102Hz, and storage and loss modulus obtained with it on atactic poly(methyl methacrylate). An informal association with Maxwell and his group starting in 1970 has permitted us to appreciate him as an inventor and an innovator with a broad impact on the polymer field; and also to follow him in his role of teacher/profes

ISSN:0032-3888    

DOI:10.1002/pen.760262004

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760262005

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

ISSN:0032-3888    

DOI:10.1002/pen.760262006

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractNovel segmented copolymers were synthesized using aminopropyl terminated linear poly(dimethylsiloxane) oligomers as the soft component and various diisocyanates as the hard segments. As a result of the large differences in the cohesive energy density (solubility parameter) between the two components, phase separation occurs to form a microdomain structure at relatively low oligomer molecular weights. Since chain extenders were not employed during the synthesis, the “hard” segments are strictly related to the length of the diisocyanate moiety utilized in the reaction, In this paper we utilize these copolymers as reasonable models for investigating the various methods available for determining the interfacial layer thickness between the hard and soft phase. Specifically, in these systems there is no hard segment length distribution as is the usual case for segmented urethanes. Utilizing Porod's law, and appropriate analysis, both positive and negative deviations were found in the systematic series of copolymers. The degree of positive and negative character was found to be dependent upon copolymer composition. Negative deviations were accounted for in terms of a finite interfacial thickness, which turned out to be relatively small as anticipated, while the positive deviations were assigned to isolated hard segments that reside within the soft segment matrix, i.e., concentration fluctuations. In calculating the interfacial thickness, several methods were applied and in general, close agreement was obtained. Finally, correlation function analysis in conjunction with determination of the coherent Porod lengths, etc. were determined and discussed accordingly. Cautionary comments are also provided for researchers who apply less complete small angle x‐ray scattering (SAXS) analysis to related block or segmented copolymers with regard to phase separation beh

ISSN:0032-3888    

DOI:10.1002/pen.760262007

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA new capillary rheometer incorporated in an instrumented transfer molding press has been developed. This rheometer is effective for determining the viscosity characteristics of thermoset molding compounds under both isothermal and typical molding conditions. In examples of the rheometer's utility, the power law indices of two commercial epoxy molding compounds have been determined to be approximately 0.7. Additionally it has been shown that preconditioning typical epoxy compounds at 47 percent relative humidity causes a viscosity decrease of about 40 percent owing to plasticization of the epoxy resin.

ISSN:0032-3888    

DOI:10.1002/pen.760262008

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractIn recent years there has been increasing recognition of the importance of melt elasticity in polymer processing. A new instrument has been developed that determines the elastic properties of polymers in the melt state by measuring both the stress relaxation and strain recovery characteristics as a function of applied rate of strain, temperature, and magnitude of applied strain. Data on several different polymers will be presented together with examples of the significance of melt elasticity in such processing operations as thermoforming, blow molding, and film forming. A material parameter that is very important in the processing of polymers such as polystyrene and poly(methylmethacrylate) is the transition above the glass transition,Tg, referred to as the liquid‐liquid transition,TII. At this transition there is an abrupt change in the elasticity of the melt. Processing above or below this transition produces products with very different end use propertie

ISSN:0032-3888    

DOI:10.1002/pen.760262009

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe interfacial tensions of immiscible binary blends of poly(dimethyl siloxane) (PDMS) and polybutadiene (PBD) have been determined as a function of molecular weight and temperature. The technique employed for these measurements takes advantage of recent advances in the determination and analysis of pendant fluid drop profiles. The experimental data are compared to the predictions of square gradient theories and theories based on the diffusion equation approach as developed by Helfand and co‐workers. Qualitative agreement is obtained with both types of theory when the Flory‐Huggins interaction parameter is taken to be comprised of two terms: a temperature independent term of entropic origin; and an enthalpic term that is inversely dependent upon the temperat

ISSN:0032-3888    

DOI:10.1002/pen.760262010

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe study of polymers by nuclear magnetic resonance spectroscopy has made tremendous advances in the last few years, not only with the development of superconducting solenoid magnets with increasing field strength, permitting the resolution of increasingly fine structural detail and greater sensitivity, but also in the development of new techniques. Among these is the use of two‐dimensional (2D) NMR, permitting easier and more rigorous assignment of resonances. Another important advance has been the development of means to observe high resolution spectra in the solid state, through high‐power dipolar decoupling, cross‐polarization, and magic angle spinning. A third significant development is that of deuterium quad‐rupole echo spectroscopy, permitting the study of chain dynamics in the solid state with unprecedented power and pr

ISSN:0032-3888    

DOI:10.1002/pen.760262011

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY