John Rehner

Statistical Mechanics of Cross‐Linked Polymer Networks II. Swelling

The interaction of solvents with cross‐linked network structures, such as occur in vulcanized rubber, is subjected to a statistical mechanical treatment based on the model and procedure presented in the preceding paper. The activity of the solvent is expressed as a function of its concentration in the swollen network, and of the degree of cross‐linking. The maximum degree of swelling of the network in contact with the pure solvent is related to the degree of cross‐linking. The heat of interaction of the solvent with the network can be calculated from the temperature coefficient of maximum swelling. The theory leads to the conclusion that the swelling capacity should be diminished by the application of an external stress. Furthermore, the modulus of elasticity should decrease inversely with the cube root of the swelling volume.

Statistical Mechanics of Cross‐Linked Polymer Networks I. Rubberlike Elasticity

A model is proposed for the structure of a cross‐linked network, such as exists in a vulcanized rubber, which is amenable to statistical treatment. Expressions are derived for the structural entropy of the network, and for the entropy change on deformation. The latter is in agreement with the relationship derived by Wall and others by a different treatment.

Effect of Deformation on the Swelling Capacity of Rubber

Elongation of swollen vulcanized rubber, or other polymeric materials possessing random network structures, should increase the amount of liquid absorbed (dissolved) at equilibrium with an excess of the swelling agent. According to a previously published equation relating to the thermodynamics of stretching and swelling of rubber, the relative volume of the swollen rubber at equilibrium should equal the square root of the relative stretched length. Experiments with butyl rubber vulcanizates in xylene support these predictions of theory.

Theory of Filler Reinforcement in Natural and Synthetic Rubber. The Stresses in and about the Particles

An attempt is made to develop a general theory of filler reinforcement by determining the stresses occurring in and about a spherical particle imbedded in a rubberlike medium subjected to an applied tension. For a system containing a single particle rigidly attached to the adjacent medium, an application of the theory of elasticity shows that, for infinitesimal deformations, the stress components within the particle are independent of the radial distance from the origin, taken at the center of the particle. The stress components at a given point in the surrounding medium depend on the elastic constants both of the particle and of the medium, on the radius of the sphere, on the distance from the origin, and on the angle between the direction vector and the applied tension. Expressions are given for the average stresses in media containing many (independent) particles. Theoretical values of the bulk moduli of the synthetic rubbers considered in the treatment are derived from sound velocity data. Curves show...

Vulcanization Reactions in Butyl Rubber. Action of Dinitroso, Dioxime, and Related Compounds

Abstract Experiments have been carried out to determine the chemical reactions that occur when Butyl rubber is vulcanized by quinone dioxime or related compounds. Observations have been made of the reactions of these substances with simple olefins, and of the effect of oxidizing agents on the dioxime-type of vulcanization of Butyl in solution. The theory is proposed that, in the vulcanization of Butyl by quinone dioxime or its esters, in presence of oxidizing agents, the active agent is p-dinitrosobenzene formed by oxidation of the dioxime. Chemical reactions are suggested for the subsequent cross-linking or vulcanizing steps, and the results of confirmatory experiments are presented. p-Dinitrosobenzene and other polynitroso compounds are active vulcanizing agents for Butyl, natural rubber, Buna-S, Buna-N, and Neoprene, and do not require the addition of an oxidizing agent. It is suggested that vulcanization of natural rubber by polynitro compounds involves their reduction to corresponding nitroso compoun...