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.