摘要:

AbstractMeasurements are described of the rate and final extent of crystallization at a temperature of −25°C. in natural rubber which has been modified by the chemical combination of sidegroups to the rubber molecule. The substances added were six thiol acids. Their efficiencies in retarding crystallization are compared with that previously reported for peroxide crosslinking and with the value predicted by a simple banned volume treatment for crystal nucleus formation. They are found to be generally greater than the large value predicted theoretically. Possible reasons for this are discuss

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811701

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractOn exposure to Co‐60 γ‐radiation, mixtures of natural rubber and methyl methacrylate yield almost exclusively rubber‐polymethyl methacrylate graft polymers. An appreciable amount of free polymethyl methacrylate is formed only in the presence of a transfer agent or following radiation‐induced degradation of the interpolymer. Structural characterization of the products has been made. The findings are not consistent with random grafting of the synthetic polymer on linear rubber molecules of random molecular size distribution—the rubber component appears to comprise several crosslinked molecules. The influence of the purity of the rubber, monomer concentration, field intensity, the presence of transfer agent, and the gel effect on the rate of formation, yield, and structure of the interpolymer ar

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811702

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe elastic modulus of highly oriented crystalline polymers is discussed in terms of a series model. As has been shown previously, if a polymer has fully extended chain configurations within the crystalline regions, the modulus of this phase may be expected to be high. In this case the macroscopic elastic modulus is limited primarily by the characteristics of the amorphous phase and the degree of crystallinity. Where the fiber identity period (FIP) indicates a contracted chain configuration, the crystalline regions, themselves, may be extensible and their modulus may not be much greater than that of the unoriented amorphous phase. In this case the macroscopic elastic modulus is much less dependent upon orientation and crystallinity. The elastic moduli of eight chemically different polymers have been determined from measurements of their macroscopic moduli and the extensions of their FIP when subjected to small strains. Where the degree of crystallinity could also be determined the modulus of the amorphous phases were also determined from these same measurements. The moduli of some of these systems are discussed in terms of their structure as deduced from birefringence measurements and x‐ray diffraction pattern

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811703

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe lattice model is used to predict the solution properties of graft and block polymers. It is found that the solubility of a graft polymer is critically dependent on the heat of interaction of the various components of the polymers with the solvent. Furthermore, the precipitates from fractionations of graft polymer solutions are no longer simple functions of the over‐all molecular weigh

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811704

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractBranching frequencies have been determined by dilute solution measurements through evaluation of the radius of gyration, either directly by light scattering or indirectly through the intrinsic viscosity. A third possibility is presented by the decrease in the second virial coefficient,A2, with branching. Through use of a semi‐empirical relation betweenA2and [η], it is shown that a reasonable approximation over a wide range of branching frequencies should be furnished by:\documentclass{article}\pagestyle{empty}\begin{document}$ h^3 = {{\left[ \eta \right]_\theta ^* } \mathord{\left/ {\vphantom {{\left[ \eta \right]_\theta ^* } {\left[ \eta \right]_\theta }}} \right. \kern-\nulldelimiterspace} {\left[ \eta \right]_\theta }} \cong {{A_2^* } \mathord{\left/ {\vphantom {{A_2^* } {A_2 }}} \right. \kern-\nulldelimiterspace} {A_2 }} $\end{document}where the quantities designated by an asterisk refer to the branched polymer, and the corresponding unmarked quantities to a linear polymer having the same molecular weight. The validity of the approximate relation betweenA2and branching is confirmed using the data of Thurmond and Zimm for linear and branched polystyrene, and using data for linear and branched polyethylene presented here. This procedure should prove useful inasmuch as the molecular weight of a branched polymer must be determined by an absolute method, and the branching frequency can be estimated through theA 2*/A2ratio from these same

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811705

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe dynamic tensile modulus and energy loss have been measured for nylon 6‐6 at 35°C. over a wide range of humidity in forced longitudinal vibration experiments. The frequency range covered was about 3 to 30 cps. (radian frequency 20 to 200 sec.−1). Dispersion of mechanical properties was observed with changing humidity, the maximum in the loss factor, tan δ, occurring at about 70% RH. Small variation of energy dissipation with change in frequency is such as to suggest that the dispersion region extends over a wide frequency range and that at low humidity an energy loss maximum should be expected at a frequency below one cycle per second. Increase in the amount of water adsorbed by the nylon with increasing relative humidity leads to plasticization of the fiber and consequent increase in freedom of motion of chain segments in the amorphous region of the fiber. Examination of individual runs shows that the dynamic modulus tends to increase with increasing frequency and that the increase is of a reasonable order of magnitude for the relaxation phenomena inv

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811706

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractThe Gordon‐Taylor equation relating the glass transition temperature θ of a copolymer to the glass transition temperatures θ1and θ2of the homopolymers is equivalent to\documentclass{article}\pagestyle{empty}\begin{document}$$A_1 c_1 (\theta - \theta _1 ) + A_2 c_2 (\theta - \theta _2 ) = 0 $$\end{document}wherec1andc2are the weight fractions of the constituents andA1andA2are constants. It can be recast into the following forms suitable for linear plots\documentclass{article}\pagestyle{empty}\begin{document}$ \theta = k\left( {\theta _2 - \theta } \right)\left( {{{c_2 } \mathord{\left/ {\vphantom {{c_2 } {c_1 }}} \right. \kern-\nulldelimiterspace} {c_1 }}} \right) + \theta _1 $\end{document}and\documentclass{article}\pagestyle{empty}\begin{document}$ \theta = - \left( {{1 \mathord{\left/ {\vphantom {1 k}} \right. \kern-\nulldelimiterspace} k}} \right)\left( {\theta - \theta _1 } \right)\left( {{{c_1 } \mathord{\left/ {\vphantom {{c_1 } {c_2 }}} \right. \kern-\nulldelimiterspace} {c_2 }}} \right) + \theta _2 $\end{document}wherek=A2/A1. Data from the literature on 10 copolymer systems, including butaciene‐styrene copolymers, give linear plots, verifying the equation within experimental error. However, the observed value ofkis in most cases significantly smaller than the ratio of the differences of the volume‐temperature coefficients for each homopolymer in the rubbery and glassy states, as required by the derivation of Gordon and Taylor. The glass transition temperature (in °C.) for a butadiene‐styrene copolymer prepared by emulsion polymerization at 50°C. may be calculated from the weight fractionc2of bound styrene as\documentclass{article}\pagestyle{empty}\begin{document}$ \theta = {{\left( { - 85 + 135c_2 } \right)} \mathord{\left/ {\vphantom {{\left( { - 85 + 135c_2 } \right)} {\left( {1 - 0.5c_2 } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {1 - 0.5c_2 } \right)}} $\end{document}and for a similar 5° copolymer as\documentclass{article}\pagestyle{empty}\begin{document}$ \theta = {{\left( { - 78 + 128c_2 } \right)} \mathord{\left/ {\vphantom {{\left( { - 78 + 128c_2 } \right)} {\left( {1 - 0.5c_2 } \right)}}} \right. \kern-\nulldelimiterspace} {\left( {1 - 0.5c_2 } \right)}} $

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811707

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

Abstract2,6‐Dioxymethyl‐4‐methylphenol wird bei 130°C derart kondensiert, dass hierbei fast ausschliesslich Polyoxybenzyläther entstehen. Die Konstitution dieser Polyätherketten wird durch die quantitative Bestimmung der Spaltprodukte bei der Polykondensation und durch die Bromwerte der HBr‐Hydrolysate der Polykondensate bewiesen. Verhältnismässig hochmolekulare Polyoxybenzyläther lassen sich in Benzol als Losungs‐ und mit Petroläther als Fällungsmittel durch Fällringstitration in Fraktionen zerlegen, wobei jeder Fraktion eine Fällbarkeit γ*zugeordnet werden kann. Für diese Fraktionen gilt logM=a−b· γ*im Molekulargewichtsbereich von 2500 bis 20000. Die Molekulargewichte wurden mit einem Osmometer nach Owens und Immergut osmotisch twstimmt. Sind die Polyoxybenzyläther genügend hochmolekular, so können unter Vernachlässigen der Anteile mit Molekulargew‐icht unter 2500 (P = 17) integrale und differentielle Massenverteilungen ermittelt werden. Es lässt sich nicht eindeutig feststellen, ob oder wie stark die experimentell ermittelten von den statistisc

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811708

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractFour of the new high‐density polyethylenes and one conventional high‐pressure, low‐density polyethylene have been fractionated by a fractional solution technique. The number‐average molecular weights, infrared absorption spectra, and densities of the fractions were measured by standard techniques, modified where necessary to accommodate the low solubility of the new high‐density polyethylenes. The results show: (1) The solubility of polyethylene is determined primarily by a shape parameter—number of methyl groups per hundred carbon atoms—rather than molecular weight. (2) Crystallinity is not a reliable index of the solubility of polythene unless considered in relation to molecular weight. (3) The unusual physical properties of the new high‐density polyethylenes arise from their having an essentially unbranched molecular structure rather than high mo

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811709

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY

摘要:

AbstractIsopiestic measurements have been made on aqueous solutions of Sky Blue FF and of sodium polymethacrylate, and the relevant activity coefficients estimated.

ISSN:0022-3832    

DOI:10.1002/pol.1958.1202811710

出版商:Interscience Publishers, Inc.    

年代:1958

数据来源: WILEY