A silane coupling agent is a compound that can combine with both polar and non-polar substances. They are characterised by having both a polar and a non-polar part in the molecule and can be represented by the formula Y(CH2)nSiX3, where Y represents organic functional groups such as alkyl, phenyl, vinyl, epoxy, amino, mercapto, etc. They are also usually chemically bound to organic functional groups in the adhesive base resin. and is usually chemically bound to the organic functional groups in the adhesive matrix resin. x represents a chlorine group, methoxy, ethoxy, etc. These groups are readily hydrolysed 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 agents, a "molecular bridge" can be built between the interface of inorganic and organic materials, linking two completely different materials and thus effectively increasing the bond strength of the interfacial layer.

The addition of silane coupling agents to adhesives not only improves the bond strength, but also improves the durability and resistance to heat and moisture ageing of the adhesives. 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 agents to the epoxy adhesives used in their study of the damp heat durability of titanium adhesives, which increased the shear strength retention of the adhesives after damp heat ageing 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 (e.g. 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 pre-treated with silane coupling agent, 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. However, not all fillers are treated with coupling agents, different types of fillers have different effects, and some even have no effect. For silica, glass, aluminium 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.