PREPARATION AND PROPERTIES OF HYBRID ORGANIC-INORGANIC COMPOSITES PREPARED FROM POLY(PHENYLENE TEREPHTHALAMIDE) AND TITANIA

The sol-gel process was used to prepare a class of composites in which a high-temperature polymer, poly(phenylene terephthalamide), was rein forced with varying amounts of in-situ generated titania. The polymer was synthesized by reacting a mixture of p- and m-phenylene diamines w ith terephthaloyl chloride in dimethylacetamide, using stoichiometry y ielding chains with carbonyl chloride end groups. These chain ends wer e then replaced with methoxy groups using aminophenyltrimethoxysilane, and a titania network generated which should be chemically bonded to the polymer matrix through the hydrolysis of appropriate proportions o f tetrapropylorthotitanate and water. The resulting composite films ha d amounts of titania ranging from 2.5 to 40 wt%, and were characterize d with regard to their mechanical and thermal properties. The films co ntaining relatively small amounts of titania were transparent and toug h, and had tensile strengths the order of 193 MPa (relative to the 147 MPa of the pure copolymer). Thermal decomposition temperatures were i n the range 350-450 degrees C, and the weights of the samples remainin g after heating to 800 degrees C were found to be roughly proportional to the titania contents. Water absorption of the films consisting of pure Aramid was rather high (12.8 wt%), but decreased with increased a mounts of titania. Dynamic mechanical thermal analysis showed a system atic increase in the glass transition temperature with increase in tit ania content. Increased amounts of titania also caused the tan delta p eaks to shift to higher temperatures and to became broader and weaker, indicating the extent to which the mobility of the polymer chains was diminished by the titania phase. (C) 1997 Elsevier Science Ltd.