29 - Adhesion Promoters: Silane Coupling Agents

Abstract

Adhesion promoters, or coupling agents, are chemicals that act at the interface between an organic polymer and an inorganic surface to enhance adhesion between the two materials. This chapter discusses the inherent chemical and physical nature of organosilane coupling agents that are used as adhesion promoter. A silicon-based chemical that will function as an adhesion promoter, or a coupling agent, has a general structure of four substituents attached to a single silicon atom. The most common structure has three inorganic-reactive alkoxy groups, methoxy or ethoxy, and one organic group, although sometimes it may contain only two alkoxy groups and two organic groups. Silane coupling agents act in the interphase region, the area between an inorganic substrate and an organic substrate, and act as a bonding, or bridging, agent to improve the adhesion between the two dissimilar materials. Silane couplings are used for various purposes such as: surface treatment of fiberglass, surface treatment of minerals in plastics, mineral fillers in rubber reinforcement and adhesion promoters for paints, Inks, Coatings, and adhesives.