Silane coupling agents usually have the following general formula:
YSiX₃YSiX₃
Y represents a non-hydrolyzable group, usually an organic functional group, such as amino, thiol, epoxy, vinyl, cyano, and methacryloxy.
X represents a hydrolyzable group, such as halogen, alkoxy, acyloxy, etc.

Under the action of water, the hydrolyzable group X hydrolyzes into silanol (Si-OH), which then undergoes a condensation reaction with the hydroxyl group on the surface of the inorganic material.

Hydrolysis solvent
The hydrolysis solvent of silane coupling agent can be divided into three types: deionized water, alcohol, and deionized water + alcohol. If deionized water is used alone to dissolve the silane coupling agent, the solution will be divided into two layers: one is the water phase; the other is the mixed phase of the silane coupling agent and water3. Using alcohol or deionized water + alcohol as a solvent can improve solubility and hydrolysis efficiency.

Practical application
There are two main methods for the actual use of silane coupling agents: pretreatment method and overall blending method. The pretreatment method includes dry method and wet method, in which the inorganic filler is surface treated with a coupling agent to make an active filler, which is then added to the polymer.