Introduction to Silane Coupling Agent

Silane coupling agent was developed by United Carbide Corporation, which is mainly used for glass fiber reinforced plastics. The molecular structure of the silane coupling agent is generally: Y-R-Si(OR)3 (wherein Y-organofunctional group, SiOR-siloxy group). The siloxy group is reactive with inorganic substances, and the organic functional group is reactive or compatible with organic substances. Therefore, when the silane coupling agent is interposed between the inorganic and organic interfaces, a bonding layer of an organic matrix-silane coupling agent-inorganic matrix can be formed. Typical silane coupling agents are A-151 (vinyltriethoxysilane), A-171 (vinyltrimethoxysilane), A-172 (vinyltris(β-methoxyethoxy)silane), and so on.

Here, n = 0 ~ 3; X---hydrolyzable group; Y---organic functional group, which is capable of reacting with a resin. X is usually a chloro group, a methoxy group, an ethoxy group, a methoxyethoxy group, an acetoxy group, or the like. When these groups are hydrolyzed, silanol (Si(OH)3) is formed and combined with an inorganic substance to form a siloxane. Y is a vinyl group, an amino group, an epoxy group, a methacryloxy group, a decyl group or a ureido group. These reactive groups can be combined with an organic substance to react. Therefore, by using a silane coupling agent, a "molecular bridge" can be established between the interface of the inorganic substance and the organic substance, and the two materials with disparate properties can be joined together to improve the performance of the composite material and increase the bonding strength. This property of silane coupling agent was first applied to glass fiber reinforced plastic (glass reinforced plastic) as a surface treatment agent for glass fiber, which greatly improved the mechanical properties, electrical properties and anti-aging properties of FRP. Its importance in the FRP industry has long been recognized. The use of silane coupling agents has expanded from glass fiber reinforced plastics (FRP) to glass fiber surface treatment agents for glass fiber reinforced thermoplastics (FRTP), surface treatment agents for inorganic fillers, and sealants, resin concrete, water crosslinks, polyethylene, resin encapsulating materials, shell molding, tires, belts, coatings, adhesives, abrasives (grinding stones) and other surface treatment agents. Among the two groups of silane coupling agents with different properties, the Y group is the most important, and it has a great influence on the properties of the product, which determines the performance of the coupling agent. The strength of the composite can only be increased when the Y group reacts with the corresponding resin. It is generally required that the Y group be compatible with the resin and capable of undergoing a coupling reaction.

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