A simple preparation method of epoxy resin/silica nanocomposite for Tg loss material

Abstract

Nanocomposite materials of epoxy resin and silica were prepared by a simple procedure wherein diglycidyl ethers of bisphenol-A (DGEBA) as the pre-polymer of epoxy resin, tetraethoxysilane (TEOS) as silica source, and hexahydrophthalic anhydride (HHPA) were mixed together and heated at 170 °C in a sealed autoclave. HHPA played two roles in this reaction system: one role is as a well-known curing reagent of epoxy resin; the other is as the condensation reagent of alkoxysilane, since transesterification promotes this reaction. These two reactions occurred simultaneously in homogeneous solution, and organic–inorganic composite materials were readily obtained. Field emission SEM/EDX images showed that silica particles of nano size (below 50 nm) were included in the epoxy resin matrix. Some of these epoxy resin/silica nanocomposite materials displayed high thermal stability. When DGEBA bearing about three bisphenol-A units and five molar equivalents of TEOS were reacted, the obtained composite displayed no T_g point below 300 °C in the DSC (differential scanning calorimetry) thermogram. This high thermal stability is likely to be derived from the interaction of hydroxyl groups of DGEBA with silica.