Mechanical and Thermal Behavior of Polycarbonate Composites Reinforced with Aluminum Borate Whiskers

Inorganic aluminum borate (Al₁₈B₄O₃₃) whisker was employed in this study to reinforce polycarbonate (PC). The composites were prepared in a single-screw extruder, followed by injection molding. The whiskers were pretreated with tetrabutyl orthotitanate prior to compounding. The tensile, dynamic mechanical, impact, and thermal properties of the composites were studied. Tensile results showed that the modulus of PC-Al₁₈B₄O₃₃ composites increased markedly with increasing whisker content. However, the tensile stress of the composite decreased slightly with the addition of 5 wt % whisker; thereafter, it increased slowly with increasing whisker content. Differential thermal analysis and thermogravimetric measurements showed that the glass transition temperature (T_g) and 5% weight loss temperature (T_-5%) of the composite shift rapidly to lower temperature regimes with the addition of Al₁₈B₄O₃₃ whiskers up to 10 wt %. Thereafter, the T_g and T_-5% of PC-Al₁₈B₄O₃₃ composites tended to decrease slowly with increasing whisker content. The mechanical and thermal properties of PC-Al₁₈B₄O₃₃ composites were compared with those of PC-potassium titanate (K₂Ti₆O₁₃) whisker composites. The reinforcing effect of Al₁₈B₄O₃₃ and K₂Ti₆O₁₃ whiskers on PC was discussed and contrasted. © 1999 John Wiley & Sons, Inc.