Plasticization of gas separation membranes

For the investigation of the plasticizing effect of carbon dioxide on polymers used for gas separation membranes new experimental methods have been developed that measure the sorption kinetics as well as the dilation kinetics. Comparing dilation and sorption kinetics at low and elevated pressures gives information about different types of swelling behaviour depending on the pressure level. Volume relaxation in the form of a slow volume increase in time can be observed above a certain pressure, called plasticization pressure. An interpretation of these experimental facts as a process of slow loosening of densely packed entanglements is suggested. By using sorption kinetics experiments at various temperatures the plasticizing effect of C02 is apparent by a decreasing activation energy for diffusion with increasing penetrant concentration