摘要:

AbstractA series of poly(vinyl formal) membranes was synthesized by formalization of poly(vinyl alcohol) membranes. Representative pieces were selected for this study. Some cellulose acetate membranes cast from dioxane were used for comparison. The main experimental techniques employed included water absorption measurements and direct osmosis measurements. Aqueous solutions of sodium chloride at various concentrations were used for the studies of permeation through the membranes by direct osmosis.The plot of water permeability coefficientPwversus volume fractionVwof water absorbed in a membrane was interpreted in terms of the effect of two different types of absorbed water molecules. The individual diffusion coefficients were evaluated from asymptotic slopes of the curves. Similar analyses applied satisfactorily to data found in the literature.

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120101

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe thermoelastic behavior of poly(vinyl alcohol)–poly(acrylic acid) networks was evaluated in pure water and CaCl2solution. The ratiofe/fof the energy component of the force to the total force, evaluated without taking into account polymer–diluent specific interactions, ranged from −0.75 for networks swollen in pure water to −5.7 in 0.1MCaCl2. However, an analysis based on Flory's theory of polyelectrolyte gels yieldsfe/fconstant at −1.32 when specific interactions are accounted for. In addition, the variation of In (r2)0with CaCl2concentration is 2000 times that with water. In neither pure water nor CaCl2solution can specific interactions be

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120102

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractDSC traces and specific heat data for poly(p‐diphenyl acrylate) (PPBA) and poly(p‐cyclohexylphenyl acrylate) (PPCPA) obtained by radical polymerization are reported. The results indicate the existence of a definite ordered phase and of a reversible firstorder solid–liquid transition in both polymers although x‐ray diffraction studies showed that they are not crystalline in the conventional sense. The extent of the ordered phase present in each polymer is calculated, and the problems involved in such determination by thermal measurements are discussed. On the basis of the experimental results reported here in conjunction with the x‐ray data, models are proposed for the morphology of these

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120103

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA theoretical study is presented of the dependence of the vapor permeability of suitable nonhomogeneous polymer membranes on the sense of flow This is based on a simple model of a binary membrane in which the component phases A, B are either intimately mixed, with the composition of the mixture varying continuously across the membrane, or formed into a laminate AB. The influence of various parameters (which represent either properties of the component phases or the experimental conditions) on the magnitude of these flow reversal effects has been investigated. The results have proved useful as an indication of the capability of such membrane valves and of the conditions for optimum performance, as well as for the understanding of the behavior of experimental systems.

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120104

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractSolubilities of several solvents were measured in four molten polymers by using an isobaric vapor‐pressure apparatus. Solvent concentration ranged from 0.5 to 15 wt‐%. The systems polyisoprene–benzene and polyisobutylene–benzene were studied at 80.0°C; polyisobutylene–cyclohexane was studied at 100.0°C; ethylene–vinyl acetate copolymer (EVA)–cyclohexane, EVA–isooctane, and poly(vinyl acetate)–isooctane were studied at 110.0°C. Of six polymer–solvent systems studied, all except poly(vinyl acetate)–isooctane appear to exhibit hysteresis in a single sorption–desorption cycle starting with dry polymer. The desorption curves of solvent activity plotted versus solvent weight fraction show an inflection point, suggesting localized adsorption of solvent molecules. Experimental data were analyzed with a theory which takes into account adsorption of solvent by polymer in addition to differences in free volumes and intermolecular forces. The theory gives a semiquantitative representatio

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120105

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractData from the literature are analyzed to show that decay of the chain‐end radical of PMMA in the regime of 80–130°C and 1–13000 atm occurs by two mechanisms operating in parallel. These processes are characterized by activation volumes of ca. 70 Å3(I) and ca. ∼7.5 Å3(II), suggesting that decay by process I occurs by chain‐end diffusion and decay by process II occurs by unzipping of the polymer radical to

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120106

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractStress–strain relationships are calculated for three models of the deformation of monocrystalline polytetrafluoroethylene,\documentclass{article}\pagestyle{empty}\begin{document}$ \rlap{--} ({\rm CF}_{\rm 2} \rlap{--} )_n $\end{document}. The physical models comprise either sliding one molecule or one plane of molecules parallel to the molecular chain axis past its stationary neighbors. The potential energy is calculated for each stage of deformation by semiempirical methods by use of 6‐exp and dipole–dipole interactions. Application of Eyring's activated complex theory leads to stress–strain relationships. These are compared with results of friction measurements

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120107

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractPoly(ethylene 2,6‐naphthalene dicarboxylate) exhibits thermally stimulated chemiluminescence after exposure to ultraviolet radiation and oxygen. The chemiluminescence spectrum is essentially the same as the fluorescence spectrum of the polymer with a maximum intensity at 430 nm. Upon heating, the decay of the luminescence follows a first‐order law with an activation energy of 26.3 ± 0.3 kcal/mole. A comparison of the ultraviolet absorption spectra of the polymer before and after exposure to ultraviolet light and oxygen indicates that the naphthalene ring is oxidized. Heating the polymer above 80°C causes decomposition of the initial photo‐oxide to produce lumin

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120108

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractNew data are reported for the permeation of inert gases through polyethylene, polytetrafluoroethylene, and silicone and natural rubbers. Additional data are compiled from the literature. The relative solubilities of these gases are practically insensitive to chemical variations in the homopolymer. Hence variations in structure at the glass transition (Tg) and melting (Tm) temperatures that affect diffusion also unambiguously affect permcation. Consequently an equivalence results between permeation at a given temperature for different polymers and permeation at different temperatures for a given polymer. Although the diffusion coefficient changes continuously with temperature, the Arrhenius parametersDoandEdapparently change discontinuously atTgandTm. Their magnitudes and variations with atomic weight reach maxima at aboutTg. These data indicate a dependence of the classical correlation betweenDoandEdon polymer properties. A perturbed diameter for the permeant, specific for each polymer, is proposed for correlating theDoandEddata. This correlation makes the changes observed atTgandTmmore perceptible.

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120109

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractEffects of neutralization on butadiene–methacrylic acid copolymers have been studied. In Hycar CTB with 2% acid groups, small‐angle x‐ray scattering gives evidence of some cation clustering and leads to a value of the mean radius of 5.6 Å for the clusters and a value of the distance between them of 70 Å. When the concentration of salt is increased there is no appreciable change in the distance between clusters or in their size, but their number increases. The structure of clusters has been studied by electron paramagnetic resonance in copolymers neutralized with copper salts. The appearance of a line as in the monohydrated acetate salt permits one to define the structure of clusters consisting of two Cu2+and four RCOO−ions with two H2O or RCOOH molecules. When the temperature is increased, the signal corresponding to Cu2+–Cu2+pairs disappears. In high molecular weight butadiene methacrylic acid copolymers with 9% acid groups, we have found the ion pair clusters gathered into larger clusters. In dynamic mechanical properties, a relaxation peak appears at 340°K. We interpret this as due to breaking and possible re‐forming of dipola

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120110

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY