A predictive approach based on the Simha-Somcynsky free volume theory for the effect of dissolved gas on viscosity and glass transition temperature of polymeric mixtures

The gas concn. and pressure effects on the shear viscosity of molten polymers were modeled by using a unified approach based on a free vol. theory. A concn. and pressure dependent "shift factor," which accounts for free vol. changes assocd. with polymer-gas mixing and with variation of abs. pressure as well as for diln. effects, has been herein used to scale the pure polymer viscosity, as evaluated at the same temp. and atm. pressure. The expression of the free vol. of the polymer/gas mixt. was obtained by using the Simha and Somcynsky equation of state for multicomponent fluids. Exptl. shear viscosity data, obtained for poly(e-caprolactone) with nitrogen and carbon dioxide were successfully predicted by using this approach. Good agreement with predictions was also found in the case of viscosity data reported in the literature for polystyrene and poly(dimethylsiloxane) with carbon dioxide. Free vol. arguments have also been used to predict the Tg depression for polystyrene/carbon dioxide and for poly(Me methacrylate)/carbon dioxide mixts., based on calcns. performed, again, with the Simha and Somcynsky theory.