摘要:

AbstractThe kinetics of the emulsion polymerization of styrene are developed on the basis of the Harkins' theory of reaction loci. Only that portion of the reaction is considered in which essentially no polymer nuclei are formed. Agreement is obtained between experiment and theory when the reaction in the monomer‐polymer particle is considered three‐halves order with respect to monomer. This treatment is further substantiated by the fact that the concentration of monomer in the polymer, when a separate monomer phase exists, is correctly predicted by the kinetic theory. The activation energy for the polymerization of styrene in the monomer‐polymer particle is calculated as 22,600 calories per mole. A dilatometer for the precise determination of monomer conversion rates in emulsion polymerization is desc

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020301

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractIn this paper experimentally determined values are reported for the thermal diffusivity (k) of various rubberlike polymers. Corresponding values of the thermal conductivity (W) can be computed from the well‐known relationship, W = kpcp, where p and cp denote the density and specific heat at constant pressure of the composition. Measurements were made on (a) pure gum stocks prepared with natural rubber, Butyl (GR‐I), Perbunan 18, Perbunan 26, Perbunan 35, Buna S (GR‐S), polybutadiene, neoprene GN, polyisoprene, Silastic 160, and Silastic 180; (b) pure gum stocks of the first five rubbers listed under (a) containing in addition 20 parts of a hydrocarbon softener (Bardol), based on 100 parts by weight of the polymer; and (c) the Bardol stocks containing in addition 54 parts of carbon black (Kosmobile 66). From measurements of the rate of change of temperature within a rubber sphere suddenly subjected to a change in its surface temperature, it was found possible to determine the dependence of k on temperature. A satisfactory definition of the “mean” temperature of a sphere under these conditions is described. In a discussion of the effect of chemical composition and structure on heat conduction, the bearing of hindered rotation, cross linking and branching and interatomic bond strength on the results is pointed out. Values are derived for certain other properties of some of the polymers, including their characteristic Debye temperatures, specific heats at constant volume, flexibility of the main valence chains, compressibilities, and sound v

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020302

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractTetrachlorophthalic anhydride (TCPA) was reacted with cellulose diacetate and with cellulose diethyl ether in dioxane solution to produce esters with rather low tetrachlorophthalyl contents. Phthalic anhydride was found to be considerably more reactive than was TCPA with these cellulose derivatives, especially if pyridine was used as the reaction solvent. Acylations could not be executed with TCPA in the presence of pyridine as solvent, however, because this material decomposed the anhydride, removing chlorine from it. The TCPA derivatives were more limited in solubility than were the corresponding esters made from phthalic anhydride.

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020303

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThis paper is the first part of a review on some recent advances in pectin chemistry. Part I reviews recent work on the constitution and structure of pectin, the characterization of pectin, x‐ray diffraction studies on sodium pectate, and the acid dissociation of pectinic acid

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020304

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractAn attempt has been made in this communication to formulate explicitly the dependence of the frictional coefficients of threadlike molecules in solution upon the centrifugal field applied to them in the usual velocity ultracentrifuges. This quantitative treatment, using the Kuhn and Kuhn odel for randomly coiled free‐draining thread molecules, verifies the assumption generally made that the effect considered is negligible. Since the molecular weight of the particles and the magnitude of the centrifugal field applied to them vary inversely with each other, the constant,\documentclass{article}\pagestyle{empty}\begin{document}$\overline {\beta h_0^2 }$\end{document}rarely attains values which are significant, and the effect produced by orientation of the threads is balanced by the effect due to stretching them. Moreover, by a suitable change of parameters, this treatment could be extended to account for the action of other tensile forces acting on thread molecules in soluti

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020305

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe thermal polymerization of styrene in vacuo has been followed by measuring the change of its magnetic rotatory power. The degree of polymerization was determined from measurements of the refractive index, viscosity, and density. The Verdel constant of the monomer at 25 °C. was found to be 0.0338 minute per gauss per cm.; furthermore, it showed no appreciable change on polymerization. Because of experimental difficulties the measurements could not be made beyond 25% polymerization

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020306

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractIn contradistinction to the usual methods, the diffusion of water into a polymer has been investigated by starting from a disk of the material surrounded by water. In this way, actual service conditions are often closely approached. Since a theoretical basis is desirable, equations are given for this type of diffusion, and experiments with a wood flour containing phenol‐formaldehyde material were performed from which values for the permeation constant could be derive

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020307

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractMethods for the preparation of fiber‐forming polymeric amides from polymethylene diamines and polymethylene dicarboxylic acids, and the stabilization of these polymers against viscosity changes, have been described. The variation in physical properties, particularly melting points, of the polymeric amides with increasing chain length of the components has been discusse

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020308

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractIt is shown that molecules of benzidine dyes can diffuse into cellulose fibers only perpendicular, not parallel, to the fiber axis.

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020309

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY

摘要:

AbstractThe variation of the x‐ray reflection to the interchain separation in sodium pectate has been determined as a function of moisture content. The crystalline regions in sodium pectate have been found to sorb about 24% water (dry basis) at a relative humidity of 95% at 25°C. The sample as a whole under these conditions has a water content of 64%. At high water contents, therefore, a large difference in water content must exist between the crystalline and amorphous regions of sodium pectate. A marked change in degree of crystallinity occurs, as determined by the number and sharpness of the x‐ray reflections, at an average water content of about 6% on desorption and on sorption at an average water content of about

ISSN:0022-3832    

DOI:10.1002/pol.1947.120020310

出版商:Interscience Publishers, Inc.    

年代:1947

数据来源: WILEY