Silane coupling agents are well known and have become one of the important commonly used coating additives. Of course, it is also widely used in other fields. The application of silane coupling agents in coatings can improve the product quality of coatings, endow coatings with special functions, and reduce product costs when used reasonably. With the rapid development of composite materials such as coatings, the variety, quality, and yield of silane coupling agents have also greatly improved. China's silane coupling agent started relatively late but has developed rapidly, forming a large-scale industry. Especially in the past five years, the variety, output, and quality of silane coupling agent products have made great progress.
Silane coupling agents are a class of low molecular weight organic compounds with special structures. Although silane coupling agents have different types of structures, the most common molecular structure used as adhesion promoters in coatings is RSiX3, where R is a non hydrolyzable reactive organic functional group and X is a hydrolyzable functional group. As the name suggests, this type of silane can form molecular bridges between polymer and inorganic substrates through chemical reactions or physical interactions, firmly adhering the two together.
The mechanism of action of silane coupling agent:
1. Enhance adhesion
2. Interface between Silane and Inorganic Substrate
When organic coatings contain a small amount of silane coupling agent, after coating, silane will migrate to the interface between the coating and the substrate, react with the moisture on the inorganic surface, hydrolyze to form silanol groups, and then form hydrogen bonds or shrink to form - SiO-M (M is the inorganic surface) with the hydroxyl groups on the substrate surface. At the same time, the silanol groups between silane molecules also condense and aggregate to form a network structure film covering the substrate surface.
Even under water immersion conditions, coatings modified with silane coupling agents adhere well to various inorganic substrate surfaces.
3. Interface between silane and coating
In the interface layer between the paint base and the substrate, silane interacts with the paint base to form a network structure of silane and paint base interpenetrating, enhancing its cohesion and stability against corrosion, and transferring stress from the high modulus substrate to the low modulus paint base, thereby significantly improving adhesion to the substrate.
4. Surface modification of pigments and fillers
Silane coupling agent is used to treat pigments or fillers, making them easily wetted by the base material. The pigments or fillers disperse stably in the base material, preventing precipitation and agglomeration. After modification with silane coupling agent on the surface of the filler, the viscosity of the coating is significantly reduced. Even if the amount of pigment or filler added is increased, it will not affect the flowability of the coating, which can increase the yield of the coating and reduce production costs.
