EFFECT OF PREPARATION AND FILLER SURFACE ON DYNAMIC MECHANICAL-PROPERTIES OF EPOXY-RESIN COMPOSITES FILLED WITH SILICA MICROBALLOONS

Dynamic mechanical properties and thermomechanical properties of epoxy resin composites filled with silica microballoons were studied by varying degas time and mixing procedure of components and fillers. The glass transition temperature (T(g)) of the composites was high when the resin and the filler were mixed prior to the addition of curing agent. But T(g) of the composites was lower when the resin and the curing agent were mixed prior to the addition of the filler. The T(g) decreased with further degassing. These facts indicates the preferential absorption of curing agent on fillers. The storage modulus depends on the surface area of the filler corresponding to the pores with radius larger than 3.75 nm. T(g), impact strength, flexural strength and linear thermal expansion coefficient of composites filled with silica microballoons pretreated with silane coupling agent (SC) were higher than those of composites filled with untreated fillers. This results indicates that the SC pretreatment might prevent the absorption of curing agent on the filler.