Inter-Phase Bonding in Poly(hyroxyamide)-silica Hybrids: Effect of Isocyanto‐propyltriethoxysilane Addition on the Structure and Properties

Abstract

Novel aramid‐silica ceramers with increased inter‐phase bonding have been prepared via the sol‐gel process. The aramid chains with pendant alkoxy groups were synthesized by reacting poly(hyroxyaramid) chains with isocyanato‐propyltriethoxysilane (ICTOS). The sol‐gel process was carried out in this matrix after mixing an appropriate amount of tetraethoxysilane (TEOS) to produce a silica network structure chemically bonded to the matrix. The effect of ICTOS addition on morphology, thermal and mechanical properties of the composites has been studied. Properties of the composites were compared with the hybrid system where a similar matrix was used but the silica network was developed using a mixture of ICTOS and TEOS or TEOS alone. The hybrid materials in which ICTOS was added prior to TEOS in the matrix showed better mechanical and thermal properties as compared to the system in which ICTOS and TEOS were used together or where only TEOS was used in the pure aramid matrix. The glass transition temperature was found to increase and the coefficient of thermal expansion was considerably reduced in chemically bonded ceramers as compared to those having no interfacial bonding.