(368d) Property Prediction of Poly(Propylene) Plasticized by CO2

Micro-cellular plastic (MCP) producing using supercritical CO2 has attracted much attention due to its environmentally friendliness and also excellent material features such as low density, low heat conductivity, etc. The supercritical CO2 MCP equipments are composed of an extruder, a supercritical CO2 feeder, and a molding/injection unit. The extruder is the most important unit that achieves various important phenomena in this technique; melting polymer, dissolving CO2 into melt polymer, mixing for homogenous solution and phase separation leading to forming. Designing the above mentioned processes requires quantitative information under these phenomena in accordance with the physical-chemical properties of the polymer mixtures involving CO2. There have been proposed a lot of equation of states (EoS) with the aim of accurately calculating the equilibrium and also transport properties. Among proposed EoSs, the Sanchez-Lacombe (S-L) equation has been widely used for calculating physical properties of polymers under supercritical CO2 because of its applicability to both CO2 and polymers. However, the calculation accuracy by S-L equation is strongly dependent on the EoS parameters which are normally determined from the experimental P-V-T data. For polymers whose PVT data sometimes do not cover the temperature range of MCP processing, the EoS parameters used may provide insufficient results. In this work, we have measured the P-V-T of molten polymer and swelling ratio under pressurized CO2 for poly(propylene) and redetermined the S-L EoS parameters from the measured data. Using the three sets of the S-L EoS parameters, the effect of the parameter values on the prediction ability of the EoS was discussed for P-V-T, viscosity, solubility and surface tension. In addition, the EoS was applied to estimate the degree of crystalline of polymer+CO2 mixtures.