Freeze–purged–desorption method for quantitative evaluation of CO2-solubility in polymeric films

A new experimental method, named as freeze–purged–desorption (FPD) method, to evaluate quantitatively the amount of gases sorbed in polymeric films, has been developed by using carbon dioxide gas and five different films (low density polyethylene: LDPE, polypropylene: PP, polystyrene: PS, polyacrylonitrile copolymer: PAN, polycarbonate: PC). The FPD method consisted of three operational periods of time based on the stepwise change in the system temperatures, the freeze periods of sorbed CO2 at −196°C, the purging period of atmospheric CO2 at −78°C and the desorption period of the freezed CO2 in the film at −9°C. The evaluated values for LDPE, PP, PS, PAN and PC were 0.310, 0.65, 3.90, 0.098 and 6.90 (cm3(STP)/cm3 atm), respectively, which were about 20–40% higher than the reference values. The validity of the method was reconfirmed by a good reproducibility of the desorption curves of sorbed gases referring to a blank curve obtained from the non-porous glass beads.