摘要:

AbstractThe problem of tensile failure is discussed in terms of the conditions for mechanical stability. Data are not available for detailed examination of the usefulness of this approach. However, some measurements on plasticized polyvinyl chloride, cellulose acetate, and polymethyl methacrylate suggest that the arguments may have some validity. The toughness and brittleness of materials are also considered briefly in the same terms. Attention is called to the complications that may arises from the adiabatic character of the failure process.

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189001

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe osmotic molecular weight of a copolymer of 5 mole per cent methacrylic acid and 95 mole per cent methyl methacrylate in benzene at 29.8°C. indicates considerable molecular association, with the size of the molecular aggregate constant over a wide range of solution concentration. This behavior is consistent with a model in which the copolymer contains on the average less than two carboxyls free to participate in intermolecular association, which proceeds virtually to completion. It is shown that equilibrium constants for the association of the carboxyl groups of the polymer with cosolvents can be estimated from the dependence of the apparent molecular weight on cosolvent concentration

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189002

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe degradation at 150°C. of polyvinyl chloride in the presence of base is studied by means of ultraviolet, visible, and infrared spectra. The reaction of polyvinyl chloridebase systems at 150°C. is viewed as a base accelerated dehydrochlorination of polyvinyl chloride proceeding through initiation, propagation, and termination phases. Polyene units with sixteen double bonds in conjugation are considered to be the most probable component of polyene structures contributing to the longest wave length absorption maxima recorded at 550 mμu. Dichroism to polarized light is observed in a plasticized, oriented, base degraded polyvinyl chloride film. This dichroism is considered a confirmation of the assigned polyene structure. The infrared spectra obtained reveal the development, as the reaction progresses, of conjugated carbon‐carbon double bonds, conjugated carbonyl groups, bonded hydroxyl groups such as from hydroperoxides and/or alcohols, and the eventual formation of carboxyl groups. The mechanism of the oxidative degradation at 150°C. is attributed to the attack, after dehydrohalogenation, by molecular oxygen at the olefinic double bonds to form peroxide radicals which by radical chain transfer yield hydroperoxides that degrade to carbonyl containing pro

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189003

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractThe effect of various added simple electrolytes upon the solution viscosity of polymethacrylic acid and hydrolyzed polyacrylonitrile was studied. The viscosity behavior of these polymers in water and in the presence of added NaCl was typical of that of polyelectrolytes. The addition of multivalent anions (sulfate, diacid phosphate, oxalate, and succinate) to solutions of polymethacrylic acid decreasesd the viscosity at low added salt concentrations, but a reversal in the reduced viscosity–concentration curve was obtained as the ionic strength was increased. This increase in viscosity can be partly explained on the basis of increased ionization originating from the behavior of the added multivalent anions. However, this is not the complete explanation since the relative efficiency of these anions in increasing the viscosity is not consistent with the values of the dissociation constants. A possible alternative explanation involves the formation of associated complexes of the polyions. It is further demonstrated that the limiting intrinsic viscosities at infinite ionic strength is dependent upon the initial polymer charg

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189004

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractA study of the dynamic mechanical properties of several high polymers has been made over a temperature range from 80°K. to above room temperatures and at frequencies in the range from 200 to 4000 cps. For amorphous polymers such as polystyrene the mechanicalloss rises sharply in the neighborhood of 80°C. but over the rest of the temperature range studied exhibits no relaxation peaks. For partly crystalline polymers such as polymethylene, polytetrafluoroethylene, and nylon the loss curve exhibits one or more definite internal friction peaks in the temperature range studied. The observed relaxation behavior is discussed in terms of possible molecular mechanisms and the results correlated with specific heat measurements and other mechanical loss measurements where such data are availabl

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189005

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractMonomer reactivity ratios for the system polyethylene fumarate/methyl methacrylate have been determined. The experimental methods used in measuring these ratios for simple linear systems had to be severely modified. While the technique evolved does not give results of great accuracy, the ratios obtained are in agreement with those expected from consideration of the radicals involved. Ethylene fumarate polymers have been characterized in several different ways, and it was shown that, although prepared from maleic anhydride, substantial conversion to the isomeric fumarate form had occurred.

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189006

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractPolymerizations of styrene have been carried out in solution using as initiators benzoyl peroxide or ammonium persulfate. It has been shown that the ammonium persulfate initiated polymerizations proceed at a faster rate and produce polymers of higher molecular weight than those initiated by benzoyl peroxide, although all the conditions for polymerization remained identical in both cases. This behavior is explained in terms of a reduced rate of termination. It is suggested tentatively that the reduction in the rate of termination may be due to the mutual electrostatic repulsion of the chains caused by the presence of electrically charged end groups arising from initiation by the sulfate ion radical. Calculations are presented showing the essential conditions that have to be fulfilled to make the explanation tenable.

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189007

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractAn approximate method is developed to calculate the velocity of a polymer molecule in a centrifugal and in an electric field. The model used is a porous sphere. The hydrodynamic interaction between the polymer segments is described by means of Oseen's equations. It is assumed that the force acting on the liquid has spherical symmetry and that the flow derived from this force may be replaced by its average over a spherical surface. The results of the calculation show that this approximation is legitimate. For the sedimentation velocity an equation is obtained which is similar to Debye's though somewhat simpler. In the theory of electrophoresis all relaxation effects are ignored, while for the charge density due to the small ions an expression is used that has been derived on the basis of the Debye‐Hückel approximation for electrolytes. The expression derived for the electrophoretic mobility is quite simple and leads to results almost identical with those obtained in previous work by a straightforward extension of the theories of Brinkman and Debye and Buec

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189008

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractViscosities of polyacrylate ion in the presence of potassium bromide, sodium bromide, lithium bromide, sodium iodide, sodium hydroxide, and hydrochloride acid in aqueous solution were measured over the approximate ranges 0.0–0.6% polymer and salt up to saturation with respect to polyacrylate or to salt. The general initial effect of added electrolyte is to reduce the ratio ηsp/cand to convert the curve characteristic of polyelectrolytes into a straight line, which can be extrapolated to zero polymer concentration to given [η], the intrinsic viscosity of the polymer in the presence of excess salt. Sodium hydroxide and sodium bromide produce minima in plots of [η]against salt concentration. Sodium iodide precipitates polyacrylate at 1.5Niodide as a translucent gel, which redissolves at 3.0Nand finally reprecipitates at 6N. In the latter range of concentration, [η] exhibits a maximum. Both by‐ions and counter‐ions have specific effects on the viscosity of th

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189009

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY

摘要:

AbstractIn an attempt to increase the intermolecular attraction between polyorganosiloxane chains and rings, polar groups have been introduced into methyl groups attached to the silicon atoms. To avoid the usual weakening of the CSi bond by negative polar substituents, positive substituents of the type (CH3)3M (where M is Si, Ge, or Sn) were employed in this study. Cyclic trimers and extended linear polymers were prepared, both from the pure polar‐substituted monomers and from mixtures of these monomers with octamethyltetrasiloxane. Intermolecular attraction was estimated by measuring viscositities and activation energies of viscous flow. The preparations also were compared in these respects with pure dimethylsiloxanes and with neopentylsiloxanes. The results show that intermolecular attractionisincreased by the positive polar substitutents, and that the CSi bond is rendered more stable toward OH−attack by such positive substituents than by negative. More detailed analysis indicates that the effects of the groups on the viscosity of the polymers depends on: (1) the dipole attraction of the polar groups, (2) the bulk or steric effect of the enlarged group, and (3) the effect of the metal M upon the ease of rotation of the methyl groups (the characteristically free intramolecular motion of silicon polymers). The trends of these effects oppose each other in the CSiGeSn series, and so limit the observed increase

ISSN:0022-3832    

DOI:10.1002/pol.1955.120189010

出版商:Interscience Publishers, Inc.    

年代:1955

数据来源: WILEY