摘要:

AbstractTemperature dependences of diffusion and permeation coefficients of hydrogen and deuterium in glassy and rubbery polymer films have been measured. The size of the free volume element in rubbery polymers has been calculated according to the theory of Frisch and Rogers for the quantum isotope effect, but the free volume is too large for precise calculation below the glass‐transition temperature. The cooperative movement of segments is also discussed using the ratio of preexponential factors for diffusion mechanisms above and below the glass‐transition temperat

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180201

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractAn extension of Hartel's theory for multiple scattering has been applied to the case of small‐angle light scattering from polymer films with random two‐phase morphology. The scattering is treated in terms of Debye–Bueche theory from which values of the correlation length, an average phase size, and mean‐square fluctuation in polarizability are determined. It is shown that multiple scattering leads to a reduction in the angular dependence of scattering due to an enhancement of scattering at high angles. This leads to an underestimate of the correlation length and an overestimate of the magnitude of the mean‐square polarizability fl

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180202

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe morphology of linear polyethylene ofMw/Mn1.19 crystallized isothermally from the melt has been investigated. Electron microscopy (EM) of stained thin sections gave exceptionally well‐defined images. There were no qualitative differences between Regime I and Regime II crystallization, but the lamellae grown at lower supercooling were thicker, larger, and had fewer spiral growths per unit area of fold surface. Small‐angle x‐ray scattering indicated a much sharper distribution of lamellar thicknesses than EM and Raman LAM did. This is evidence of the complementary nature of the techniques and not a contradiction. EM also revealed nonrepresentative features in detail. There were extremely thin lamellae formed on cooling, indicating molecular weight segregation even in this fractionated material, and there were extremely thick lamellae, attributed to isothermal thickening. As the representative lamellae are also supposed to have thickened isothermally, this raises the issue of when and how the lamellae which are theprimaryproducts of crystallization can be ident

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180203

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe thermal expansion of epoxy‐resin (Epikote 828)/particle composites has been measured in the range 77 to 450 K. The fillers used were Cu spheres (seven sizes from 5 to 150 μm diameter) and glass ballotini spheres (three sizes from 3.5 to 200 μm diameter). The volume concentrations used were 0.3 and 0.5 for Cu and 0.3 for glass. The experiments show that the addition of filler raises the glass transition temperatureTg, especially for fine particles. Below the normal value ofTgthe thermal expansion is independent of particle size while aboveTgthe expansion is considerably smaller for samples containing the smaller particles. The effect is more pronounced for Cu than for glass filler. In addition a rapid heating rate reduces the expansion for specimens containing smaller particles but it does not effect the expansion for those containing large particles. The results, which are discussed in the light of the work of other authors, suggest that the addition of particles increasesTgby changing the nature of the polymer not only immediately at the particle surface but also for a considerable distance into the polymer itself. This probably occurs because the epoxy bonds strongly to the particles and this inhibits segmental rotations of the polymer even at considerable distances from the particle surf

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180204

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractQuantitative comparison of previously published NMR spin‐relaxation data for polydiethylsiloxane with theoretical predictions for a variety of motional processes allowed both the nature and time scale of molecular motions to be identified. At the lowest temperatures, methyl reorientation produced aT1minimum and was found to proceed with an activation energy of 2.4 kcal/mole in both amorphous and crystalline phases. Reorientation of the ethyl groups in the amorphous phase was observed at a higher temperature with an activation energy of 9.3 kcal/mole. Relaxation in the melting region was influenced by flexing and stretching of the helical polymer chain. The maximum angular displacement of the chain was estimated to be 24°, with an activation energy for this process of 2.6 kcal/mo

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180205

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractMolecular structural changes of a vinyl functional silane coupling agent onE‐glass fibers, induced during the immersion test in hot water, have been studied using Fourier transform infrared spectroscopy. The amount of the coupling agent on the glass fibers is reduced by hydrolytic degradation. Silanol groups formed by the hydrolysis of the siloxane groups have been detected in the FT‐IR difference spectrum in the range 930–840 cm−1due to the SiO stretching mode of the SiOH groups. Heat treatment produces partial reformation of the siloxan

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180206

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe course of melting of melt‐crystallized polyethylene fractions and of a poly(ethylene oxide)‐polystyrene‐poly(ethylene oxide) triblock copolymer has been followed by small‐angle x‐ray scattering (SAXS). Changes in the intensity and shape of the SAXS curves indicated that both surface melting and melting over the full crystallite thickness (full‐strand melting) take place. Full strand melting is the final, irreversible process. Comparison with an analytical model indicates that in the earlier stages of the irreversible, full‐strand process the crystallites melt out randomly throughout the bulk. Later stages may occur by the simultaneous melting of a larger stack of

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180207

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractPolyalkane imides based on 3,3′,4,4′‐diphenyloxidetetracarboxylic, pyromellitic and 1,4,5,8‐naphthalenetetracaboxylic acids, and aliphatic diamines containing 4, 6, 8, 10, or 12 methylene groups have been studied. Relations governing the effect of structure on solubility, heat resistance, density, and crystallizability have been established. Conformation analysis has been carried out and models of the macromolecules have been constructed. The morphology of the crystalline polymers has been studied. For the polymers of the given class, crystallization capability is shown to be associated with the conformational flexibility of the macromolecular unit determining a given acid moiety by the number of methylene groups in the diami

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180208

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractDouble‐exposure speckle patterns created by scattered light were used to study tensile deformation of isotactic polypropylene film. The method makes possible a quantitative investigation of the deformation process (relative magnitude and orientation of the displacement vector, Poisson's ratio μ) by means of a simple optical analysis of stepwise deformations covering the desired range. The displacement vector and Poisson's ratio have been determined with an accuuracy of ± 5% in the range of small deformations (up to 18% relative deformation); and the role of stress relaxation has been examined. Limitations of the method, such as the range of measurable displacements, effect of prestressing, and stability of the system, etc., are discussed. Among advantages of the method are comparative simplicity and accuracy, and the possibility of its application to other systems studied by the small‐angle light scattering m

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180209

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe thermally stimulated current (TSC) technique has been used to investigate three anionic polystyrenes of M̄n17,000, 71,700, and 1.55 × 106, i.e.,MTgappears to be theTllprocess and is designatedTMll. Relaxation times for it follow a Vogel equation.TMgandTMllvary with molecular weight, increasing belowMcand leveling off aboveMcat a temperature of about 170°C. Values ofTMgandTMllare compared with values ofTgandTllobtained from torsional braid analysis, which involves melt flow; and with differential‐scanning‐calorimetric values on fused films, where there is no transport of polymer. It is concluded from such cross‐comparisons that TSC, at least for polystyrene, is a quasistatic test which may involve microscopic viscosity. Macroscopic viscosity does not play a role. The ratioTMll/TMgis in the range 1.10–1.16, similar toTll/Tgvalues by other methods. A few comments aboutTllin atactic poly(methyl methacrylate) by the TSC meth

ISSN:0098-1273    

DOI:10.1002/pol.1980.180180210

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY