Introduction to the Application Fields of Silane Coupling Agents

Aug 30, 2021

Silane coupling agent is a chemical agent mainly used for glass fiber reinforced plastics. The molecular structure of the silane coupling agent is generally Y-R-Si(OR)3 (where Y is an organic functional group and SiOR is a siloxy group). Siloxy groups are reactive to inorganic substances, and organic functional groups are reactive or compatible to organic substances. Therefore, when the silane coupling agent is between the inorganic and organic interface, a bonding layer of organic matrix-silane coupling agent-inorganic matrix can be formed. [1] Typical silane coupling agents include  (vinyltriethoxysilane),(vinyltrimethoxysilane),  (vinyltris(β-methoxyethoxy)silane) and the like.

The coupling agent is an organosilicon compound with a special structure. In its molecule, there are both reactive groups that can be combined with inorganic materials (such as glass, cement, metals, etc.) and reactive groups that can be combined with organic materials (such as synthetic resins, etc.). Commonly used theories include chemical bond theory, surface wettability theory, deformation layer theory, restraint layer theory and so on. Coupling agents are used as surface modifiers to improve the dispersibility and adhesion of inorganic fillers when filling plastics.

The role and effect of silane coupling agents are recognized and affirmed by people, but why a very small amount of coupling agent on the interface has such a significant impact on the performance of composite materials, there is no complete set of coupling mechanisms to explain it. The mechanism of the coupling agent on the interface between two materials with different properties has been studied a lot, and explanations such as chemical bonding and physical adsorption have been proposed. Among them, the chemical bonding theory is the oldest but is considered to be a relatively successful theory so far. .

Application field
The application of silane coupling agent can be roughly summarized into three aspects:
Surface treatment
It can improve the bonding performance of glass fiber and resin, greatly improve the strength, electrical, water resistance, weather resistance and other properties of glass fiber reinforced composite materials. Even in the wet state, it can improve the mechanical properties of composite materials, and the effect is very significant. . The use of silane coupling agents in glass fibers has been quite common. The silane coupling agents used in this area account for about 50% of the total consumption. Among them, the more used varieties are vinyl silane, amino silane, and methyl. Acryloyloxysilane, etc.
Filled plastic
The filler can be surface treated in advance, or directly added to the resin. It can improve the dispersion and adhesion of the filler in the resin, improve the compatibility between the inorganic filler and the resin, improve the process performance and improve the mechanical, electrical and weather resistance properties of the filled plastic (including rubber).Used as a tackifier for sealants, adhesives and coatings

It can improve their bonding strength, water resistance, weather resistance and other properties. Silane coupling agents can often solve the problem that certain materials cannot be bonded for a long time. The principle of action of silane coupling agent as a tackifier is that it has two groups; one group can be combined with the frame material to be adhered; and the other group can be combined with polymer materials or adhesives , Thereby forming a stronger chemical bond at the bonding interface, greatly improving the bonding strength. There are generally three methods for the application of silane coupling agents: one is as a surface treatment agent for the framework material; the other is to add it to the adhesive, and the third is to add it directly to the polymer material. From the perspective of giving full play to its effectiveness and reducing costs, the first two methods are better.