Among the two types of silane coupling agent having different properties, the Y group is the most important, which directly determines the application effect of the silane coupling agent
. The bonding strength of the organic adhesive can be improved only when the Y group can react with the corresponding matrix resin. It is generally required that the Y group be compatible with the resin and can undergo a coupling reaction, so for different resins, a silane coupling agent containing an appropriate Y group must be selected.
When Y is an unreactive alkyl or aryl group, it is ineffective for polar resins, but can be used for bonding of non-polar resins such as silicone rubber, polystyrene, and the like. When Y contains a reactive functional group, it should be paid attention to its reactivity and compatibility with the resin used. When Y contains an amino group, it is catalytic, which can be used as a catalyst in the polymerization of phenolic, urea-formaldehyde, melamine formaldehyde, and can also be used as a curing agent for epoxy and polyurethane resins. At this time, the coupling agent fully participates in the reaction to form a new bond. Aminosilane-based coupling agents are of a general-purpose type and can be coupled to various resins, except for polyester resins. The type of X group has no effect on the coupling effect. Therefore, depending on the kind of the reactive group in the Y group, the silane coupling agents are also referred to as vinyl silane, amino silane, epoxy silane, mercapto silane, and methacryloxy silane, which is the most commonly used silane coupling agent.