Predicting gas solubility in semi-crystalline polymer solvent systems by consistent coupling of Sanchez-Lacombe EOS with a continuum mechanics approach

Abstract

Solubility of gases in polymers plays a crucial role in several industrial sectors. This spans from chemical, pharmaceutical to polymer industry. While, in last years thermodynamic models have been successfully developed to predict the solubility of fluids in polymers, which are above the melting temperature or in a glassy state, thermodynamic models for predicting the fluid solubility in semi-crystalline polymer solvent mixtures are rare and even controversially discussed in literature. In this work a new theoretical framework based on a consistent coupling of SL-EOS with a continuum mechanics approach is developed to explain phenomena occurring due to gas solubility in semi-crystalline polymers on the one hand and predict gas solubility in semi-crystalline polymer solvent mixtures with a high accuracy on the other hand. Herein, the framework is applied to a n-butane/linear low density polyethylene mixture as well as to an i-butane/linear low density polyethylene mixture. The solubility of n-butane in the respective polymer is predicted for various temperature and pressure states, where the polymer is due to temperature variations in the molten as well as in the semi-crystalline state. A very good agreement between predicted and experimental solubility data could be achieved.