Using Supercritical CO2 for Viscosity Reduction of Polymers: A Data-Driven Modeling Approach for Predicting the Diffusive Properties of Polystyrene Melt

This study investigates the influence of supercritical CO₂ on the rheological properties of polystyrene (PS) through a comprehensive rheological analysis. By generating time-dependent viscosity curves and the corresponding torque profiles, we accurately assess the progressive plasticization effects of CO₂. Results show that CO₂ can significantly lower the viscosity of PS, achieving up to a 96% reduction when transitioning from atmospheric to subcritical conditions and an additional 56% decrease when moving from subcritical to supercritical states. These findings highlight the effectiveness of supercritical CO₂ in enhancing the processability of polymers through viscosity reduction. Furthermore, we develop a universal viscosity model that incorporates temperature, shear rate, and CO₂ concentration effects for PS-CO₂ melts. This model in combination with CO₂ solubility models offers a robust framework for accurately predicting CO₂ diffusion coefficients. This methodology not only deepens our understanding of CO₂–PS interactions but also provides a reliable tool for future research and industrial applications, presenting a more efficient and environmentally friendly alternative to traditional methods.