Classification and application of silane coupling agents

 Silane coupling agents are used in large amounts and come in many varieties, and their structure is usually represented by Y-R-SiX3. Among them, X is a halogen or alkoxy group. Under the action of water, Si-X changes into Si-OH to realize the connection between the inorganic surface and the silane. R is a long-chain alkane, and Y is an organic functional group such as amino group, vinyl group, methacryloyloxy group, mercapto group, epoxy group, etc., which is easy to react with polymers. Silane coupling agents are widely used in surface modification of nanoparticles, anti-corrosion surface treatment of glass fibers and metals, and as tackifiers for coatings and sealants, which can greatly improve material performance.

silane coupling agent

Classification of silane coupling

Sulfur-containing silane coupling agent

The development of the automobile industry has promoted the development of the rubber industry. Butadiene rubber is used in the production of tires due to its excellent cold resistance, wear resistance, aging resistance and elasticity. However, butadiene rubber has poor tear resistance and poor slip resistance, so it is often necessary to fill butadiene rubber with a certain amount of silica. However, silica has a large surface energy, is easy to agglomerate, and is difficult to wet and disperse in the organic phase, so it must be surface modified. Currently, the most commonly used surface modifiers in the tire industry are sulfur-containing silane coupling agents. The sulfur-containing silane coupling agent combines the sulfur in the structure with the rubber and the alkoxy groups with the silicone hydroxyl groups on the surface of the white carbon black to form a strong network structure, which greatly reduces the rolling resistance of the tire.

Amino silane coupling agent

As a universal coupling agent, aminosilane coupling agents can couple with almost all kinds of polymer resins. Due to the presence of free amino groups, this type of silane coupling agent is highly alkaline and has high reactivity, and the flexural strength of the molding material increases with the increase of amino groups. The disadvantage of this type of silane coupling agent lies in the use process Premature reactions may occur and the expected results may not be achieved. γ-Ureidopropyltriethoxysilane (A-1160), as a new type of ureido-containing silane coupling agent, is a neutral water-soluble compound with a pH value of around 7, which can be used with most resins. Carry out reactions with slightly reduced activity at low temperatures while maintaining certain extreme working performance. As representative varieties of heat-resistant silane coupling agents, Y-5475 and Y-5669 have heat-resistant temperatures 60 to 100°C higher than traditional products due to the combination of silicon atoms and benzene rings.

Epoxy silane coupling agent

Traditional silane coupling agents are prone to pre-crosslinking reactions with water, which limits their application in polyester materials. With the development of research technology, epoxy silane coupling agents represented by 3-(2,3-epoxypropoxy)propyltrimethoxysilane (A-187) can be stored at room temperature for more than 12 months. It still maintains good physical properties and adhesion, thus showing good long-term storage stability in water-based solutions.

Application of silane coupling agent

Glass fiber surface treatment

As an inorganic non-metallic material, glass fiber has good insulation, heat resistance, corrosion resistance and high mechanical strength. It is often used as reinforcing materials, electrical insulation materials and thermal insulation materials in composite materials. However, the surface polarity of glass fiber makes it difficult to be compatible with non-polar resins, greatly reducing its filling effect. In order to improve the bonding performance between resin and glass fiber and improve the strength, electrical and weather resistance properties of glass fiber reinforced composite materials, it is necessary to surface modify the glass fiber. At present, the most commonly used surface modifier in glass fiber surface modification is silane coupling agent, and its varieties mainly include: vinyl silane, amino silane, methacryloxy silane, etc.

Inorganic filler surface treatment

Polymer materials such as plastics and rubber need to be added with different inorganic fillers to meet their different performance properties. Composite materials can realize the compounding of materials through direct interface contact. Therefore, the properties and microstructure of the interface directly affect its physical properties and bonding force. The surface of general inorganic fillers is hydrophilic and cannot be well dispersed in resin and rubber during use, which will seriously affect the performance of composite materials. In practical applications, by surface modification of the filler to make the filler hydrophobic, the function of the inorganic filler can be fully exerted. Using silane coupling agents for surface treatment of inorganic fillers can form a non-polar molecular film on the surface of the fillers, improve the stability, dispersion and adhesion of the fillers in rubber and plastics, and improve the performance of filled plastics (including rubber) electrical, mechanical and weather resistance properties, and promote the improvement of process performance.

Nanopowder surface modification

Nanopowder has the characteristics of small particle size and large specific surface area, so it has unique small size effect, tunnel effect and surface effect. Therefore, it is favored for its excellent reinforcement, stability and thickening properties. It is used in plastics, rubber, It is widely used in coatings and other fields. Since nanopowder has a large surface energy and is easy to agglomerate, which limits its ultrafine effect and is difficult to disperse and infiltrate in the organic phase, it must be surface modified to improve its compatibility and binding force with organic molecules. . It is a commonly used nanopowder modification method to use coupling agent molecules to carry out a certain chemical reaction with the surface of nanopowder to evenly cover the surface of nanopowder with the coupling agent to improve the hydrophobicity of nanopowder. Silane coupling agents, titanate coupling agents and aluminate coupling agents are commonly used. PF-1S, surface Coated Fine Aluminum Hydroxide power and the first of its kind in China is a highly advanced product manufactured by the latest surface modifying technology. The patent was solely developed and owned by Pengfeng. This technology enables Aluminum Hydroxide particles with high absorbability to reach their potential and generate optimized results in the process of surface modification. Therefore, it fundamentally resolves the problems of ultrafine particle ions aggregation, the inadequacy of surface modification, and the maldistribution of ions or particles.

Used as a tackifier for sealants, coatings, etc.

As a tackifier, silane coupling agent is widely used in adhesives, sealants, coatings and other fields to improve their bonding strength, water resistance and weather resistance. Introducing functional silane coupling agents into coatings can allow the silane to form an interpenetrating network polymer (IPN) with the film-forming polymer of the coating or undergo a cross-linking reaction with the film-forming polymer of the coating, thereby promoting the wetting of the substrate by the coating , improve the adhesion of paint. In addition, alkyl and aryl silanes can also improve coating film gloss, hiding power, miscibility, and pigment wetting and dispersing properties.

In other aspects, silane coupling agents are also widely used in metal surface treatment and other industries.

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