Study on cell nucleation behavior of HDPE–wood composites/supercritical CO₂ solution based on rheological properties

In this study, the shear viscosities of wood–plastic composites (WPC)/supercritical CO₂ (sc-CO₂) solutions at different die temperatures and sc-CO₂ contents were measured by a slit die attached on a single-screw extrusion system. A theoretical model based on the Carreau-Yasuda model and Arrhenius equation was then developed to describe the shear-thinning behavior of the WPC/sc-CO₂ solution. This model was incorporated into a finite element method software, POLYFLOW, to simulate the pressure and velocity field of WPC/sc-CO₂ solution flowing through a foaming die. Based on the simulation results, the pressure drop rate and the location of the supersaturation point were estimated to investigate the cell nucleation. The saturation pressure of sc-CO₂ in WPC was determined by a magnetic suspension balance and corrected by the Sanchez Lacombe Equation of State.