摘要:

AbstractThe sorption of solvent and nonsolvent by polyvinyl alcohol from water–acetone and water–n‐propanol mixtures was measured by using the dipping refractometer to follow changes in concentration of the liquid phase. Beyond about 15% acetone no selective sorption was observed. The values calculated forn‐propanol and water sorbed are a function of then‐propanol concentration of the equilibriu

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811801

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe principal complication arising out of free radical‐initiated polymerizations involving vinyl acetate has been the chain transfer to monomer and polymer which results in a highly branched polymer chain. Some evidence has also been presented to show that the degree of branching in polyvinyl esters increases with an increasing number of carbon atoms in the vinyl ester. It was of interest, therefore, to obtain a relative measure of the chain transfer constants for successive members of the homologous series of vinyl esters and to relate the constants to the actual structure of the respective polyvinyl ester. Accordingly, the study of the chain transfer in the benzoyl peroxideinitiated polymerizations of vinyl acetate in the presence of a homologous series of ethyl esters of fatty acids was made. Chain transfer constants versus number of carbon atoms in the carboxylate portion of the fatty acid ester resulted in a linear relationship which can be expressed as\documentclass{article}\pagestyle{empty}\begin{document}$$C_{tr,s} = 4.0 \times 10^{ - 3} + n \times 0.7 \times 10^{ - 3}$$\end{document}wherenis the number of non‐α‐methylene groups in the side chain. A concurrent study of the influence of monomer chain lengths of selected vinyl esters on molecular weight of the derived homopolymer was also carried out. The results obtained provide a basis for predicting the trends for changes in branching and degree of polymerization within the homologous series of vinyl

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811802

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe degradation of an addition polymer sample (polystyrene) has been studied. In conformity with theory, the process of degradation does not proceed below a limiting chain length. A rate constant has been derived. The experimental size distributions of the polystyrene at different stages of the degradation have been determined and compared with their corresponding theoretical distributions. The experimental values of the number of broken links at the early stages of degradation have been determined photometrically and compared with their corresponding theoretical values as derived from the theory of ultrasonic degradation. Satisfactory agreement has been found between experiment and theory for the main features of the degradation.

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811803

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe effect of ultrasonic intensity on degradation parametersKandyfor a polystyrene in benzene sample was investigated. The results are discussed in relation to a theory previously developed for the degradation of addition polymers by ultrasonic waves. It is shown that for a constant ultrasonic frequency the experimental results can be explained by theories which assume that degradation is caused by frictional or impact forces.

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811804

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractPolyvinyl chloride when heated loses HCl, presumably by a “zipper” mechanism. The loss of each molecule of HCl from the polymer results in the formation of a double bond, which activates adjacent chlorine and causes the decomposition reaction to propagate along the resin chain. Virgin and degraded resins were subjected to ozonization in order to ascertain the type and location of the labile structures responsible for initiating the “zipper” HCl loss. The molecular weight decrease and formation of carbonyl structures (detected by infrared) produced by ozone indicate that unsaturated chain ends are primarily responsible for HCl loss. Tertiary chloride chain branches contribute to a lesser degree in the initial stages but become more important as dehydrochlorination proceeds. Stability measurements on simple prototypes of structures presumed to be present in polyvinyl chloride provide additional information which is in essential agreement with this me

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811805

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractStress relaxation in the systems PVAc (polyvinyl acetate)‐water, PVAc‐methanol, PMA (polymethyl acrylate)‐water, and PMA‐methanol was measured at several temperatures above the glass‐transition points of the pure polymers in ranges of sufficiently low concentrations of diluents. It was found that the time‐concentration superposition principle as proposed by Ferry is applied successfully to these data to obtain master relaxation curves of the pure polymers at fixed temperatures. The master relaxation curves so obtained at different temperatures were further superposed with each other by horizontal shift along the log time axis, in agreement with the time‐temperature superposition principle. The concentration shift factoracas a function of diluent concentrationCat fixed temperature was well interpreted in terms of the modified Doolittle's free volume equation for the viscosity of supercooled systems on the assumption that the fractional free volume of the system increases linearly withC. The proportionality coefficient, β, of this linear relation provides a measure of the plasticizing effect of a given diluent on a given polymer. It was found that β is practically independent of temperature at sufficiently smallCand is larger for water than for methanol in both polymers studied. On the basis of Doolittle's viscosity equation modified to account for the concentration effect, it is shown that the glass‐transition temperatureTgof a given polymer‐diluent pair decreases withCin a linear fashion in the range of smallC. The value of β can also be calculated from the slope of this linear relation. Values of β determined in terms of this procedure from literature data on a variety of polymer‐diluent pairs are given in a tabular form. For a given polymer the β values generally become smaller as the size of diluent molecule is increased, but no unique relation can be obtained between the two quantities. Equilibrium sorption and integral sorption processes were studied on the four pairs of polymer and diluent mentioned above, not only to obtain data needed for analyzing the present stress‐relaxation data but also to find information which will serve a study described in Part III of this series which is concerned with diffusion‐controlled stress‐relaxation in amorphous linear polymers. Some correlation (though not definite) appears to exist between the diffusion coefficientD(at zero concentration) and the plasticizing parameter β for a given polymer. This may be expected because bothDand β are quantities depending on the frequency at which polymer segments jump cooperatively in the presence o

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811806

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractAn approximate theory of the relaxation of stress in amorphous linear polymers accompanying sorption of a low molecular weight penetrant is worked out on the assumption that the relaxation time of each Maxwellian relaxation mechanism involved is changed in the presence of penetrant by a factor dependent on penetrant concentration. A method is derived from the theory which permits approximate evaluation of the integral diffusion coefficientD̄of the penetrant in the polymer from stress‐relaxation data on swelling systems. The theory is checked on experimental data for the systems polymethyl acrylate‐water and polymethyl acrylate‐methanol at 40°C., and it is found that, for both systems studied, the values ofD̄computed from mechanical data agree reasonably with those evaluated directly from usual sorption experiments. The theory described presents only a first attempt to the quantitative interpretation of the phenomenon discussed. Further improvement and modification of it is apparently desirable, in view of some drastic approximations incorporated in its mathematical dev

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811807

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractA particular kind of plot has been used, yielding graphs tending toward straight lines, to compare the fractionation and viscometry data of eight high pressure polyethylene samples with the distribution formula deduced by Beasley. These graphs are equivalent, except for an additive constant in the abscissas, to the log‐log plots of intrinsic viscosity versus molecular weights. In this way an evaluation of the distribution parameters defined by Beasley can be obtained for all the investigated samples. By means of these parameters and the absolute determination of the (number‐)average molecular weight of a single sample, an evaluation of all the molecular weights and of their distribution in the given samples has been proposed. Within the limits of experimental uncertainty of the measurements of high pressure polyethylene in diluted solutions, these results are in some agreement with the experimental findings of other auth

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811808

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

Abstractp‐Isopropenylstyrene was synthesized and its polymerization characteristics are essentially the same as those of divinylbenzene. A soluble prepolymer can be separated from polymerization in a solvent having chain transfer properties but polymerization in bulk or in an inert solvent gives crosslinked infusible polyme

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811809

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811810

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY