Gas Solubility Modeling of Ethylene in Semicrystalline Polyethylenes with Different Macromolecular Architectures Based on a Thermomechanics Approach

The solubility of gases in semicrystalline polymers is a significant property with numerous applications, such as gas-phase polymerization. Although thermodynamic modeling has successfully determined gas solubility in glassy polymers or polymer melts without crystallites, predicting gas solubility in polymers with a semicrystalline morphology remains challenging. This study presents a novel multiscale modeling approach based on thermomechanics to predict gas solubility in semicrystalline polymers across different temperatures, pressures, and various grades of polyethylene. The thermomechanical framework incorporates the SL-EOS and continuum mechanics, utilizing a mechanical homogenization method to consider the semicrystalline morphology and obtain local mechanical material information. Additionally, the temperature dependence of the degree of crystallinity of polyethylene is considered. By employing this approach, the solubility of ethylene in different polyethylene grades in the semicrystalline state can be accurately predicted, demonstrating good agreement with experimental data with a relative error below 3%.