Investigating the rheological and thermomechanical properties of SiO2/epoxy nanocomposites: Probing the role of silane coupling agent

In our study, three different silane coupling agents with various functional groups, (y-aminopropyl) triethoxysilane (KH550), γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH560) and trimethoxyoctadecylsilane (TMOS) were added into the SiO₂/epoxy composites respectively, and their effects on the rheological and thermomechanical properties of nanocomposites were investigated systematically. The incorporation of coupling agents alter the rheological properties of nanocomposites depending on functional group of the silane which is responsible for interacting with the polymer matrix, and the viscosities were increased by the addition of coupling agents except for the KH560 coupling agent. In addition, the incorporation of coupling agents into epoxy matrix decreased the cross-link densities of nanocomposites due to the “plastic effect” of coupling agents, which consequently leaded to poorer thermal stabilities, increased glass transition temperatures (Tg) and coefficient of thermal expansion (CTE) of nanocomposites as evidenced from TGA, DMA and TMA, respectively. We believe that the different structures of coupling agents as well as their corresponding filler-matrix interfacial interactions are responsible for the resulting properties of nanocomposites.