Effects of pressure ratio and pressure difference on the gas permeation properties of rubbery and glassy membranes

Abstract

The dependence of permeance and ideal separation factor on pressure ratio and pressure difference across the membrane was studied for a rubbery and a glassy membrane. The membranes tested included commercially available silicone rubber and polyimide. The experimental gases included helium, oxygen, and nitrogen. The experiments were performed using an automated constant volume gas permeation system where the rise of the downstream pressure was accurately converted into permeance using a computer program. All experiments were performed at room temperature.The results indicated that the permeance of the rubbery membrane increased with pressure ratio and decreased with pressure difference. The ideal separation factors of the three experimental gases were not affected by pressure ratio, but increased with pressure difference. On the other hand, the permeance and ideal separation factors of the gases through the glassy membrane remained unaffected by either pressure ratio or pressure difference.