Novel epoxy–silica nano-composites using epoxy-modified silica hyper-branched structure

Abstract

Abstract Epoxy-based nano-composite films with organically modified silica reinforcement have been synthesized and characterized for their thermal and mechanical properties. Silica network generated from the sol–gel process using tetraethoxysilane (TEOS) was suitably modified to have epoxy groups within an extended silica network structure. For this purpose glycidoxypropyltrimethoxysilane and aminophenyltriethoxysilane were reacted to produce epoxide chains having alkoxy end-groups. The precursor molecules having both epoxy and alkoxide functionalities were then mixed with TEOS to produce epoxymodified silica network within a diglycidal ether of bisphenol-A (DEGEBA) matrix. Cross-linking of the matrix using jeffamine D-400 and the sol–gel process was carried out simultaneously. Epoxy–silica hybrids with different silica contents were characterized by scattering electron and atomic force microscopic techniques. Visco-elastic properties, thermal stability and coefficient of thermal expansion of the resulting hybrids were measured through dynamical thermal mechanical, thermogravimetric and thermal mechanical analyses. Large interfacial interaction between the organic and inorganic phases and the distribution of silica at nano-level using epoxy-modified silica in the matrix results in considerable improvement in mechanical properties whereas the coefficient of thermal expansion is reduced in contrast to the neat epoxy system.