Effect of particulate fillers on thermal expansions and other critical performances of polycarbonate‐based compositions

Influence of different inorganic particulate mineral fillers on polycarbonate composites was explored. Among all the fillers assessed here only boron nitride and mica could appreciably reduce the thermal expansion of polycarbonate, particularly along the direction of flow. While measured in the normal to flow (cross‐flow) direction, the coefficient of thermal expansion (CTE) values decreased marginally in presence of boron nitride and mica as compared to the unfilled specimen. The anisotropicity in CTE is presumable due to preferential orientation of boron nitride and mica along the direction of flow in the injection molded samples. The effectiveness of fillers in reducing CTE of the polycarbonate composites was correlated to the dispersion of fillers in the polymer matrix. Better dispersion of boron nitride and mica, as observed through SEM, ensured their improved interaction with the matrix and thereby reducing the CTE. It was observed that in presence of particulate fillers the impact performance of the composites decreased appreciably with an increase in tensile modulus, in general. The flow behavior of the composites was by large dependent on the types of fillers used. In presence of some of the fillers such as BaSO₄, ZnO, ZnS, TiO₂, and alumina, flow of the composites increases significantly, primarily associated to appreciable reduction in molecular weights of the polycarbonate. On the other hand, with boron nitride flow remained almost unchanged upon its addition of 5 vol %. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012