摘要:

The temperature dependence of the optical anisotropy and of the mean square end-to-end distance of polydimethylsiloxane chains have been derived from photoelastic measurements. The rotational isomeric chain model, including the interaction of neighboring bond rotations, is insufficient to interpret the data completely.

ISSN:0022-2348    

DOI:10.1080/00222346808212870

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Systematic infrared studies of a series of polyhexamethylene adipamides (nylon 66) have resulted in the assignment of two bands to the regularly folded polymer chain. Utilizing this assignment and long-period measurements by small-angle X-ray diffraction, a method has been developed to compare the amount of regular chain folding in solution-crystallized samples precipitated at different temperatures. At high supercoolings in solution, only 60% of the chain folding which occurs has a regular structure. Annealing of the solution-crystallized samples not only produced a longer fold period but also regularized the folds. Melt-crystallized samples when annealed do not show much increase in fold period or regularization of the folds. Glass-crystallized samples show a rapid initial increase with time at a particular temperature in long period and regular folding. For the glass-crystallized samples crystallized at different temperatures for the same period of time, higher temperatures of crystallization produce longer fold periods and greater fractions of regular folds. The infrared fold bands disappear when samples consisting of regular folds are deformed but reappear after annealing.

ISSN:0022-2348    

DOI:10.1080/00222346808212871

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

Stress-relaxation data are presented for two commercial grades of ABS and an ABS-polycarbonate blend over a temperature range which includes the glassy, transition, and entanglement regions. Reduced master curves and the shift factor, aT, are obtained and compared to data for fractionated polystyrene and polycarbonate; the principle of time-temperature superposition is shown to be as applicable to the relaxation data for these heterogeneous polymers as to similar data for homogeneous polymers. Compared with homogeneous polymers, the reduced curves for the composites are different in several ways: A slightly larger negative slope in the glassy region, a more diffuse transition region, a higher and broader entanglement plateau, and a smaller negative slope in the flow region are noted. For the two ABS polymers, the temperature dependences of aTare about that of a homogeneous polymer with an equivalent Tg, indicating that the discrete rubber particles do not alter the relative relaxational behavior of this heterogeneous system. For the ABS-polycarbonate blend (both phases continuous), the temperature dependence of aTis close to that of the polycarbonate component. suggesting that in this case the continuous phase with the longest relaxation times dominates the relaxational behavior of the composite.

ISSN:0022-2348    

DOI:10.1080/00222346808212872

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The Maron theory of nonelectrolyte solutions was used to analyze available osmotic pressure data for solutions of polyisobutylene in benzene, chlorobenzene, toluene, and cyclohexane and to evaluate the interaction parameters, μ, for these systems. The results obtained show that for the benzene and chlorobenzene solutions the μ's are linear functions of volume fraction and temperature, but they are not dependent on molecular weight. On the other hand, the solutions of polyisobutylene in toluene and cyclohexane show a dependence of μ on molecular weight and, in all probability, also on volume fraction and temperature. However, the data available are insufficient to establish the exact dependence of μ on v2and T for the latter two systems.

ISSN:0022-2348    

DOI:10.1080/00222346808212873

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The Maron theory of nonelectrolyte solutions has been used to examine the vapor pressure behavior of solutions of polyisobutylene in benzene and in cyclohexane between 25 and 65°C and in n-pentane between 25 and 55°C. The results show that the theory can predict the vapor pressures of these solutions over the full concentration range, provided the polymers involved are amorphous. When the polymers are not completely amorphous, then discrepancies between theory and experiment are observed at high solution concentrations which are due to persistence of polymer order in the highly concentrated solutions. A method is described by means of which these discrepancies can be used to obtain on an absolute basis both the degree of polymer order in solution and in the original polymer samples used.

ISSN:0022-2348    

DOI:10.1080/00222346808212874

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The location of vinyl end groups in monolayer polyethylene crystals (specially prepared to have surfaces highly accessible to gaseous reactants) has been investigated by exposing the crystals to ozone and determining the extent of reaction by infrared spectroscopy. It was found that, for the type of crystals used, about nine-tenths of the chain ends reacted very rapidly and it is deduced that these are excluded from the crystal lattice and should lie on the crystal surfaces. The remaining fraction of ends were, by comparison, highly resistant to oxidation.

ISSN:0022-2348    

DOI:10.1080/00222346808212875

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

An attempt to categorize the low-temperature dispersions of the swollen polymethacrylates is given and discussed in connection with recent measurements of Shen and Strong.

ISSN:0022-2348    

DOI:10.1080/00222346808212876

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

A comparison has been made of the morphology of fibrillar polyethylene crystals prepared by shear-induced crystallization and heterogeneous Ziegler-Natta catalysis under similar solvent and temperature conditions. Both specimens had a shish-kebab superstructure consisting of lamellar overgrowths on a filamentary backbone. For polyethylenes stirrer-crystallized at small supercoolings, the overgrown lamallae were removed by nitric acid oxidation followed by selective dissolution, leaving naked filamentary ribbons. Thermal analysis of these specimens suggested a dual molecular conformation of both folded and extended chains. The fact that these fibrils did not deform easily under uniaxial stress conforms with a core of extended chains. Thermal and oxidative behavior of polyethylenes prepared at lower crystallization temperatures suggested a greater content of chain folds in the central thread as the degree of supercooling increased. The Ziegler-Natta fibrils were degraded into lamellar fragments on oxidation and their thermal behavior suggested a predominantly folded-chain conformation. Uniaxial deformation occurred on stretching the Ziegler-Natta specimens in harmony with a core of folded chains. Molecular models have been proposed to account for the observed phenomena.

ISSN:0022-2348    

DOI:10.1080/00222346808212877

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor

摘要:

The Research Group of Polymer Physics in Japan, in cooperation with the Research Group of Polymer Solutions, publishes an annual summary of the work done on high polymer physics in Japan. The publication consists of short reports (2 to 4 pages) describing current or recently completed research. This journal, in cooperation with Professor S. Oka, Chief Editor of the Report, publishes the table of contents of each issue as soon as it is available. Papers on biophysical matters are also included since Annual Reports of the Research Group on Biophysics in Japan has been discontinued. Copies of the complete report (and back issues) can be obtained from the publisher.

ISSN:0022-2348    

DOI:10.1080/00222346808212878

出版商:Taylor & Francis Group    

年代:1968

数据来源: Taylor