CO2 solubilities in low-density polyethylene (LDPE) in its molten state over high temperatures and pressures conditions

This study investigates the solubility behavior of carbon dioxide (CO₂) in low-density polyethylene (LDPE) under molten conditions across a broad temperature range (398–473 K) and pressures up to 20 MPa. CO₂ solubility was determined using a magnetic suspension balance and quantitatively modeled with the Sanchez–Lacombe equation of state. Results indicate that CO₂ solubility increases linearly with pressure and decreases with temperature, consistent with typical condensable gas behavior. The model achieved high accuracy, with an average relative deviation of less than 0.9 %. Derived Henry’s constants and interaction parameters further clarify the thermodynamic interactions between CO₂ and LDPE, providing critical insights for optimizing polymer foaming processes. For comparison, nitrogen solubility was also measured, exhibiting lower values and an opposite temperature dependence, which highlights the distinct dissolution mechanisms of the two gases.