Principles for selecting silane coupling agents

Among the two types of functional groups with different properties in silane coupling agents, the Y group is the most important, which directly determines the application effect of silane coupling agents. Only when the Y group can react with the corresponding matrix resin can the adhesive strength of organic adhesives be improved. Generally, it is required that the Y group be soluble in the resin and capable of coupling reaction, so for different resins, silane coupling agents containing appropriate Y groups must be selected.

When Y is a non reactive alkyl or aryl group, it does not work on polar resins, but can be used in the bonding of non-polar resins such as silicone rubber, polystyrene, etc. When Y contains reactive functional groups, attention should be paid to its reactivity and compatibility with the resin used. When Y contains amino groups, it belongs to catalytic properties and can act as a catalyst in the polymerization of phenolic, urea formaldehyde, melamine formaldehyde, as well as a curing agent for epoxy and polyurethane resins. At this time, the coupling agent fully participates in the reaction and forms new bonds. Aminosilane coupling agents are universal and can almost couple with various resins, except for polyester resins. The type of X group has no effect on the coupling effect. Therefore, based on the types of reactive groups in the Y group, silane coupling agents are also referred to as vinyl silane, amino silane, epoxy silane, mercapto silane, and methacryloyloxy silane, among others. These organic functional silanes are the most commonly used silane coupling agents.