Effect of tensile deformations on gas transport in glassy polymer films

An exploratory study has been undertaken to determine the effect of simple tensile deformations, applied stepwise, on the permeability and diffusion coefficients (P and D) of gases in glassy polymers. For nitrogen in a polycarbonate film at 73°C, it was found that ( 1 P) dP dε{lunate} {reversed tilde equals} 13 and ( 1 D) dD dε{lunate} {reversed tilde equals} 5 to 8, where ε{lunate} is the strain. Also, P and D were found to decrease with time at constant strain and to depend somewhat on strain and thermal histories. A calculation of ( 1 D) dD dε{lunate}, based primarily on considerations of free volume and its strain dependence, gives 11.8 or 8.5, depending on the assumptions made. Progressive stepwise application of strain to a polyimide (Kapton) film at 72° and 125°C caused P and D for carbon dioxide to increase. But above 2% strain at 125°C, they decreased until at 6% strain they became smaller than those for the undeformed specimen, a reflection of a straininduced relaxation process. © 1981.