A Study of Permeability to Gases. Mixtures of Natural Rubber and Other Elastomers

Abstract

Abstract An investigation of the permeability to nitrogen of various mixtures of natural rubber and synthetic elastomers has brought to light one highly important fact. The lower permeability obtained by the addition of a synthetic elastomer does not depend solely on the permeability coefficient itself of the particular synthetic elastomer. Rather, it depends in addition on another factor, which, in all probability, is a function of the internal structure of the mixture of natural rubber and synthetic elastomer. A study of this structure is not a simple problem, and mention is made only of the fact that, after having attempted unsuccessfully to analyze the structure by classic methods of microscopy, very encouraging results have been obtained with mixtures of natural rubber and Paracril-26 by measuring, at radio frequencies, the loss factor. The results indicate that, at least with natural rubber-Paracril-26 mixtures, milling brings about a certain degree of mutual diffusion of the two elastomers on a molecular scale. However, the vulcanizates give indications of a two-phase colloidal structure, one phase relatively rich in Paracril, the other phase relatively rich in natural rubber. Such a structure would be in harmony, at least qualitatively, with the conclusions drawn in the present investigation on the permeability to gases of mixtures of elastomers.