Application of Silane Coupling Agent in Coatings（I）
Silane has been successfully used as bonding promoter and surface treatment agent for decades because of its special structure. Now silane has gradually become an indispensable component in paint and ink systems. Whether as an additive or as a separate coating primer, it will give excellent performance to coatings and inks.
Silane is a molecular structure with two functional groups.
It can be expressed as Y(CH2)nSiX3.
Y represents alkyl, phenyl, vinyl, epoxy, amino, mercapto and other organic functional groups, which are often chemically bound to the organic functional groups in the paint matrix resin.
X denotes chlorine, methoxy, ethoxy, etc. These groups are easily hydrolyzed into silanol and react with oxides or hydroxyl groups on the surface of inorganic substances (glass, silica, metal, clay, etc.) to form stable silica-oxygen bonds.
Therefore, through silane coupling agent, a "molecular bridge" can be built between the interface of inorganic and organic substances to connect two materials with completely different properties. The reaction groups of silanol functional group and silane organic functional group can determine the role of silane in paint system.
The role of silane in coatings and inks: improving the adhesion of coatings. Improve the durability of the coating. Improve the weatherability of the coating. Improve the toughness of the coating. ------- Reduce the dispersive viscosity of fillers and pigments and improve the dispersibility of pigments.
The application of silane in primers The covalent bond of silicon atom has unique ability to combine organic and inorganic substances. The inherent stable structure of silicon oxide makes it an important part of high performance paint primers. The application of silane coupling agent in primer can improve its adhesion, keep its humidity, chemistry, anti-ultraviolet ray and reinforcement, and improve the dispersion of fillers. Alkoxysilane can be compatible with many organic resins. In fact, silane is a strong polar solvent, and the polymerization of silane affects the compatibility and final properties of polymers. On the surfaces of organic polymers and inorganic substances (e.g., pigments, fillers and glass, metal surfaces), inorganic alkoxy functional groups couple a large number of organic groups in the form of covalent bonds. The organic functional groups of silane can produce excellent results as long as they are matched by organic polymers. Silane as adhesion promoter contains a small amount of silane coupling solvent. After coating, silane will migrate to the interface between coating and substrate, react with water on inorganic surface, hydrolyze to form silanol group, and then form hydrogen bond or condensation with hydroxyl groups on the surface of substrate - Si-M (M is inorganic surface), at the same time, each silane has its own surface. The intermolecular silanol groups also condense and oligomerize with each other to form a reticulated membrane covering the surface of the substrate. Even under water immersion conditions, silane coupling agent modified coatings adhere well to various inorganic substrates. In the boundary layer between the paint base and the substrate, silane interacts with the paint base to form a network structure of silane and the paint base penetrating each other, which enhances the cohesion and stability of water erosion resistance, and transfers the stress from the modulus of the substrate to the low modulus of the paint base, thus significantly improving the adhesion to the substrate.
Conversion from Ipax Coupling Agent