Silane coupling agent is a compound that can combine with both polar and nonpolar substances. It is characterized by having both polar and non-polar parts in the molecule and can be expressed by the general formula Y(CH2)nSiX3, where Y represents organic functional groups such as alkyl, phenyl, vinyl, epoxy, amino, mercapto, etc. It is also usually chemically bound to organic functional groups in the adhesive base resin. and are usually chemically bound to organic functional groups in the adhesive matrix resin. x represents chlorine groups, methoxy, ethoxy, etc. These groups are readily hydrolyzed to silanols, which react with oxides or hydroxyl groups on the surface of inorganic substances (glass, silica, metals, clay, etc.). and are inherently stable silicone oxygen bonds. Therefore, by using silane coupling agent, it is possible to build a "molecular bridge" between the interface of inorganic and organic materials, connecting two materials with completely different properties, thus effectively improving the bonding strength of the interface layer.

Adding silane coupling agent in the adhesive can not only improve the bonding strength, but also improve the durability of the adhesive and resistance to heat and humidity aging properties. For example, polyurethane has high adhesion to many materials, but the durability is not ideal, adding silane coupling agent can significantly improve the durability. Chen et al. added silane coupling agent to the epoxy adhesive used in the study of the damp heat durability of titanium alloy adhesive, so that the shear strength retention rate of the adhesive after damp heat aging increased from about 80% to about 97%. Silane coupling agents can even be used directly as adhesives for bonding metals such as silicone rubber, fluoroelastomers, and nitrile rubber. For example, the adhesives CK-1 and Chemlock 607 (USA) are silanes.

In order to improve certain properties of organic adhesives (such as heat resistance, self-extinguishing properties, dimensional stability, etc.) , or to reduce the cost of organic adhesives, some inorganic fillers are often added to the adhesives. If the filler is treated with silane coupling agent in advance, the polar groups on the surface of the filler will react with the silane coupling agent, thus greatly reducing the structural effect between the filler and the resin, which not only greatly improves the compatibility and dispersion of the filler to the adhesive base resin, but also significantly reduces the viscosity of the system, thus increasing the amount of filler. But not all fillers are treated with coupling agents, different types of fillers have different effects, and some even have no effect. For silica, glass, aluminum powder and other fillers with a large number of hydroxyl groups on the surface, the best effect, while for calcium carbonate, graphite, boron and other fillers without hydroxyl groups on the surface, there is no effect.