Solubility and diffusivity of CO2 in polypropylene/micro-calcium carbonate composites

This work is aimed at studying the effects of the fillers and interface bonding condition between the fillers and polymer matrix on the solubility and diffusivity of CO2 in polypropylene (PP)/Micro-calcium carbonate (MicroCaCO3) composites. The solubility of CO2 in PP and its composites containing 5% and 10% MicroCaCO3 was determined precisely by using magnetic suspension balance (MSB) combined with experimental swelling correction at 200 and 220 °C and CO2 pressures up to 22 MPa. It was found that the solubility of CO2 in the PP/MicroCaCO3 composites without the interface compatibilizer increased with increasing the filler content, while the CO2 solubility remained almost unchanged in PP composites with compatibilizer. The Henryʹs law and a modified Henryʹs law were used to well correlate the solubility of CO2 in the PP composites with and without the interface compatibilizer, respectively. The diffusion coefficient of CO2 in the PP composites was found to decrease with increasing the filler content. The mutual diffusion coefficients of CO2 in the PP composites can be correlated within an average relative deviation of 10% by the free volume model proposed by Kulkarni and Stern with a parameter accounting for the barrier effect of the filler.