SOLUBILITY OF CARBON-DIOXIDE IN CELLULOSE-ACETATE AT ELEVATED PRESSURES

In the reported experiments, the solubility of carbon dioxide in symmetric (dense) cellulose 2. 4-acetate has been measured at temperatures from 0 to 70 degree C and pressures up to 45 atm. The polymer samples were prepared by slowly drying asymmetric reverse osmosis membranes. The solubility isotherms can be described satisfactorily up to 60 degree C by the ″dual-sorption″ model for glassy polymers. The model cannot represent the experimental data above 60 degree C, possibly because of a second-order transition in the polymer between 60 and 70 degree C. An analysis of the dual-sorption parameters and of the heats of solution and ″hole filling″ suggests that the polymer samples contained a relatively large volume of microcavities. Gas solution appears to occur predominantly in microcavities, a large fraction of the penetrant molecules being immobilized or partially immobilized. The solubilities obtained in this work are compared with similar data computed from time-lag measurements of other investigators, and the validity of the dual-sorption model is examined for the present case.