Lowering of Water Absorption for Epoxy Resin by The Addition of Silica Particles and Silane Coupling Agent

Abstract

Lowering of water absorption for epoxy resin by the addition of silica particle and silane coupling agent (SCA) was investigated. The water absorption decreased with the increase of silica content. Bonding, hydrocarbon, and fluorocarbon type SCAs were employed. The bonding type has glycidoxy or amino groups that react with epoxy resin, whereas the other types have only hydrophobic chains. The water absorption was lower for the hydrocarbon type than the bonding type. The fluorocarbon type SCA was also effective at zero and low silica content. Modification of the epoxy phase by SCA addition had a more dominant effect than interfacial adhesion for the lowering of water absorption, whereas it had been conventionally considered that interfacial adhesion had a more dominant effect. Two addition methods were compared, a pre-treatment method and an integral blend method in which all components were mixed simultaneously. The integral blend method was found to be superior to the pre-treatment method for water absorption contrary to the conventional view.