Sorption and diffusion in crystalline elastomers. Part I. Solubility of isomeric hydrocarbons in stretched rubber

Abstract

AbstractThe solubility coefficients of n‐ and isobutane for stretched crosslinked natural rubber have been measured for simple elongations of 0–400% in the temperature range 30–50°C. To minimize the effect of penetrant on the degree of crystallinity, regions of low concentration were chosen. The sorptive capacity of the rubber was not significantly altered by elongation until the extension was sufficient to permit crystallization to take place. For both stretched and unstretched samples temperature—hysteresis effects were absent and Henry's law was obeyed. The data indicate that the difference in solubility between stretched and unstretched rubber can be taken as a measure of the degree of crystallinity. A slight decrease in the solubility over extended periods of time was attributed to a corresponding slow increase in the degree of crystallinity. The dependence of the degree of crystallinity on temperature and elongation was well represented by that deduced from Flory's theory of strain‐induced crystallization.