Diffusion and sorption of vapors in ethylene–propylene copolymers. II. Diffusion

Publisher Website
Google Scholar
Abstract
The diffusion rates of methylene chloride, benzene, n‐pentane, n‐hexane, and cyclohexane in a copolymer of 51 mole‐% propylene and 49% ethylene at 23°C. and penetrant concentrations of up to 10 vol.‐% have been measured, as have the rates of benzene diffusion in copolymers containing 31–100% propylene units at 10, 23, and 40°C. Integral diffusion coefficients were calculated from the initial diffusion rates; differential diffusion coefficients from the final rates. Comparison of the two types of diffusion co‐efficients leads to the conclusion that their concentration dependence flattens out at the very lowest penetrant concentrations. The diffusion coefficients fall and the activation energies rise as the propylene content of the copolymers increases. Diffusion in low‐propylene copolymers occurs at rates comparable to those in natural rubber, while the rates in atactic polypropylene are slower by about an order of 1 magnitude. Even so, the latter are about 10 times faster than in polyisobutylene.

This publication has 15 references indexed in Scilit: