Polycarbonate/mica extrusion using mixing elements: Improvement of transparency and thermal, mechanical and water and gas barrier properties

Abstract

Polycarbonate (PC) was loaded with mica fillers by melt mixing process using a twin-screw extruder. The influence of the mica content on the PC properties was analyzed. Also, the presence of mixing elements of grid shape on the mica distribution during the PC extrusion was discussed. These elements allowed us to significantly improve the fillers dispersion in the polymer matrix. As a consequence, the transparency of the PC films was maintained up to 5 wt% of mica due to reducing the aggregates formation and the homogeneous mica dispersion. Despite a slight decrease of the polymer molar mass, a strong improvement of the PC thermal stability, mechanical resistance as well as barrier properties towards water and gases (N2, O2 and CO2) was obtained due to the reinforce and tortuosity effects induced by mica fillers in the PC matrix. The gas and water transport properties of the PC/mica films were well-fitted using a predictive empirical model, that took into account the double tortuosity and immobility effect of mica particles. In addition, mica fillers were found to have specific interactions with water molecules, that led to enhancement of the moisture resistance of PC, thus improving its performance.