Preparation and Properties of Poly(Phenyleneterephthalamide)-Silica Ceramers with Interphase Bonding from Aminophenyltrimethoxysilane

Abstract

Poly(phenyleneterephthalamide) chains having carbonyl chloride end groups were prepared by reacting a mixture ofm- and p--phenylene diamines with terephthaloyl chloride, and were then end-capped with aminophenyl-trimethoxysilane. The polymer thus prepared was used to synthesize a hybrid material in which it was chemically bonded to a silica network producedin-situ by hydrolyzing tetramethoxysilane. Films prepared from this hybrid material were yellow but transparent, and quite tough. The transparency of the films and their mechanical strength were considerably improved relative to the corresponding systems in which the inorganic network was not bonded to the organic phase. Tensile strength was found to increase initially with addition of silica but then to decrease rapidly with further additions. Elongation at rupture also decreased after an initial small increase. A systematic increase in the tensile modulus and hardness with increase in the silica content and a decrease in water absorption were also observed. SEM analysis showed that the silica particle size depends on the silica content, and was 0.5 μm or less. These transparent ceramers were found to withstand tensile stresses the order of 175 MPa and had thermal decomposition temperatures around 460 - 475 ° C, and could thus be very useful in engineering applications at high temperatures.