Preparation of low-CTE composite using new alkoxysilyl-functionalized bisphenol A novolac epoxy and its CTE enhancement mechanism

Abstract

In order to prepare the epoxy material with high dimensional stability, alkoxysilyl-functionalized bisphenol A novolac epoxy was newly synthesized. The composite film of the new epoxy was prepared by adding polymer binder and its coefficient of thermal expansion (CTE) was measured. After alkoxysilyl-modification, the thermal expansion performance of the epoxy composite was significantly improved. At 80 wt% of silica added, the epoxy composite showed the CTE 1 (CTE at T < Tg) of 5.0 ppm/°C and CTE 2 (CTE at T > Tg) of 9.6 ppm/°C. The better CTE property of alkoxysilyl-functionalized epoxy system than that of the conventional epoxy system was explained to be due to the interfacial bonding mechanism between alkoxysilyl group and silica. However, the observation that CTE of alkoxysilyl-functionalized epoxy composite film was dependent on the concentration and type of polymer binder cannot be explained by the interfacial bonding mechanism. In order to understand the thermal expansion property of alkoxysilyl-functionalized epoxy composite, the new CTE enhancement mechanism was investigated for the first time.