Organofunctional Silane Coupling Agents

Abstract

The development and increasing use of organ-ofunctional silanes has closely pilralleled the growing use of composite materials in expanding and diverse applications. From the crude laminates developed to meet the material shortages of World War II, composite materials have evolved into sophisticated products that are required to meet ever increasing performance demands. In addition to providing a wide range of mechanical properties, many of today's composites are asked to furnish specific electrical characteristics, lend themselves to various fabrication techniques, maintain their properties after exposure to hostile environments , and accomplish this in an economically viable manner. The challenge is indeed great. The composites of this discussion are combinations of organic polymers and glass fibers and/or particulate fillers. Included among the useful organic polymers are both thermosetting and thermoplastic resins and elastomers. Glass fibers are used in many forms including continuous roving, chopped strand, mat, and woven fabric, the choice indicated by fabrication method and/or property requirements. The particulate fillers encompass a wide range of materials including refined natural minerals and synthetic products. Prominent among these are clays, silicates, and silicas. The high strength and modulus of glass fibers 536 have made them obvious candidates as reinforcements for organic polymers; however, the function of particulate fillers has evolved with time. Originally, except for the use of selected fillers as reinforcements for elastomers, fillers were used to control rheology and to lower the cost of the composite. More recent developments have shown that fillers can, particularly with surface modification, make positive contributions to composite properties while continuing to affect rheology and costs. Common to all of the composites discussed is a large interfacial area between the organic polymer and the fiber and/or filler. To optimize both the ease of fabrication and the resulting composite properties, it is necessary that as a minimum the organic polymer wet the fiber or filler surface and ideally that it bond to it. This chapter is concerned with the use of organo-functional silicon compounds to promote the wetting of the fiber/filler surface, establish bonds between the polymer and the fiber/filler, and retain these bonds under a hostile environment. THEORY. The matrix resin of a modem mineral reinforced organic resin composite serves many functions. It influences the method used to fab-I. Skeist (ed.), Handbook of Adhesives