THE SOLUBILITY OF HYDROGEN IN GLASSY POLY(VINYL ACETATE) AT ELEVATED PRESSURES

The solubility of H2 in glassy poly(vinyl acetate) (PVAc) has been determined by a gravimetric technique at 5.0 and -5.0°C in the pressure range from 1 to 20 atm. The solubility is a nonlinear function of the gas pressure and can be described by the "dual-mode" sorption model. The solubility decreases with increasing temperature. The values of the solubility coefficient (S) vary from a maximum of 6.5 x 10-2 cm3 (STP)/(cm3 polym.-atm) at 1.5 atm and -5.0°C to a minimum of about 1.9 x 10-2 (in the same units) at 19 atm and 5.0°C. The fact that the H2/PVAc system exhibits dual-mode sorption behavior was anticipated from the observation of Meares that a plot of log S versus 1/T, the reciprocal absolute temperature, exhibits changes in slope in the glass-transition region of the polymer. The possible effect of the size of penetrant gas molecules on dualmode sorption is discussed. © 1990.