THE SILANE SIZING COMPOSITE INTERPHASE

Silane coupling agents are but one of many ingredients in commercial s izings that are applied to glass fibers. The chemistry of a silane cou pling agent alone allows it to react with both the glass fiber surface and the epoxy matrix to increase the fiber/matrix adhesion. However, the action of a commercial sizing system containing a silane coupling agent along with other components is not well understood. Research has been conducted in which the physical properties have been measured of blends of epoxy-compatible silane/sizing made with bulk matrix at con centrations representing likely compositions found at the fiber-matrix interphase as a result of processing and fabrication. It has been sho wn that the silane/sizing interaction with the epoxy matrix produces a material with vastly different properties than those of the bulk matr ix. In this particular system, the model interphase has a lower T(g), higher modulus, and greater tensile strength, but lower toughness. The results from the present study show that a chemical interaction theor y of adhesion alone is not sufficient to explain the role of silane co upling agents in glass fiber-epoxy matrix adhesion. Consideration must be given to the interphase and its mechanical properties.