Therefore, according to the type of reactive group in the Y group, the silane coupling agent is also called vinyl silane, amino silane, epoxy silane, mercapto silane and methacryloxy silane, etc. These several organofunctional silanes It is the most commonly used silane coupling agent.

The application of silane coupling agent can be roughly summarized into three aspects:
1. It is used for the surface treatment of glass fiber, which can improve the bonding performance of glass fiber and resin, and greatly improve the strength, electrical, water resistance, and weather resistance of glass fiber reinforced composite materials. The improvement of the mechanical properties of the material is also very significant.
At present, the use of silane coupling agents in glass fibers is quite common, and the silane coupling agents used in this aspect account for about 50% of the total consumption. Among them, vinyl silane, amino silane, Methacryloxysilane, etc.
2. Used for filling plastics with inorganic fillers. The filler can be surface treated in advance, or added directly to the resin. It can improve the dispersion and adhesion of fillers in the resin, improve the process performance and improve the mechanical, electrical and weather resistance properties of filled plastics (including rubber).
3. As a tackifier for sealants, adhesives and coatings, it can improve their bonding strength, water resistance, and weather resistance. Silane coupling agents can often solve the problem that certain materials cannot be bonded for a long time.
The principle of the silane coupling agent as a tackifier is that it has two groups; one group can be combined with the bonded skeleton material; while the other group can be combined with polymer materials or adhesives , so as to form a strong chemical bond at the bonding interface, which greatly improves the bonding strength. There are generally three methods for the application of silane coupling agents: one is used as a surface treatment agent for skeleton materials; the other is added to adhesives, and the third is directly added to polymer materials. From the perspective of giving full play to its effectiveness and reducing costs, the first two methods are better.
The specific application of silane coupling agent in the adhesive industry has the following aspects:
1. In the bonding of metal and non-metal in structural adhesives, if silane tackifiers are used, they can condense with metal oxides or condense with another silanol, so that silicon atoms can be in close contact with the surface of the glued object . If silane is added as a tackifier in the nitrile phenolic structural adhesive, the bonding strength can be significantly improved.
2. Silane has been widely used as a treatment agent at home and abroad in bonding glass fibers. It can chemically react with the interface to increase the bond strength. For example, if chloroprene glue is not used as a treatment agent, the peel strength of the glue joint is 1.07 kg/cm2, and if aminosilane is used as a treatment agent, the peel strength of the glue joint is 8.7 kg/cm2.
3. Silane tackifiers have special functions in the bonding of rubber and other materials. It significantly improves the bonding strength of various rubbers and other materials. For example, when glass and polyurethane rubber are bonded, if silane is not used as a treatment agent, the peel strength of the glue is 0.224 kg/cm2, and if silane is added, the peel strength is 7.26 kg/cm2.
4. Bonding problems that cannot be solved with general adhesives can sometimes be solved with silane coupling agents. Such as aluminum and polyethylene, silicone rubber and metal, silicone rubber and plexiglass, can all be solved satisfactorily by selecting the corresponding silane coupling agent according to the chemical bond theory. For example, vinyl triperoxy tert-butyl silane (Y-4310) can be used to bond polyethylene to aluminum foil; butadiene triethoxy silane can be used to make the peeling strength of silicone rubber and metal reach 21.6~ 22.4 kg/cm2.
Common adhesives or resins combined with coupling agents can not only improve the bonding strength, but more importantly, increase the water resistance and durability of the bonding force. For example, polyurethane and epoxy resin have high adhesion to many materials, but the durability and water resistance of the adhesion are not ideal; after adding a silane coupling agent, the performance in this area can be significantly improved .
Other applications of silane coupling agents include:
      1. Attaching the immobilized enzyme to the surface of the glass substrate;
      2. Sand control in oil well drilling;
      3. Make the masonry surface hydrophobic;
      4. Through the anti-moisture absorption effect, the fluorescent lamp coating has a high surface resistance;
      5. Improve the hygroscopic performance of the organic relative glass surface in the liquid chromatographic column.
An important newly developed application of silane coupling agents is in the production of water-crosslinked polyethylene. In recent years, in domestic experiments on woolen fabrics treated with silicone emulsions, it was found that the use of silane coupling agents and silicone emulsions can improve the wearability of woolen fabrics.
Instructions
Surface pretreatment
Make the silane coupling agent into a dilute solution with a concentration of 0.5-1%. When using it, you only need to apply a thin layer on the clean adhered surface, and glue it after drying. Most of the solvents used are water, alcohol (methoxysilane chooses methanol, ethoxysilane chooses ethanol), or water-alcohol mixture, and water without fluoride ion and cheap and non-toxic ethanol and isopropanol are suitable. Except for aminohydrocarbyl silane, solutions prepared from other silane coupling agents need to add acetic acid as a hydrolysis catalyst, and adjust the pH value to 3.5-5.5. Long-chain alkyl and phenylsilanes are not suitable for use as aqueous solutions due to their poor stability. The hydrolysis process of chlorosilane and ethoxysilane is accompanied by serious condensation reaction, and it is not suitable to be used as aqueous solution or hydroalcoholic solution, but to be used as alcoholic solution. For silane coupling agents with poor water solubility, 0.1-0.2% (mass fraction) of non-ionic surfactant can be added first, and then water can be added to process into water emulsion for use.
Migration method
The silane coupling agent is directly added to the adhesive component, generally in an amount of 1 to 5% of the matrix resin. Relying on molecular diffusion after glue coating, the coupling agent molecules migrate to the bonding interface to generate coupling. For the adhesive that needs to be cured, it needs to be left for a period of time after the glue is applied before curing, so that the coupling agent can complete the migration process, so as to obtain better results.
In actual use, the coupling agent often forms a deposition layer on the surface, but what really works is only a monomolecular layer, so the amount of the coupling agent does not need to be too much.
The use methods of silane coupling agent mainly include surface pretreatment method and direct addition method. The former is to treat the filler surface with diluted coupling agent, and the latter is to add the stock solution of coupling agent when the resin and filler are premixed.
The silane coupling agent is made into a solution, which is beneficial to the dispersion of the silane coupling agent on the surface of the material. The solvent is a solution made of water and alcohol. The solution is generally silane (20%), alcohol (72%), and water (8%). , Alcohols are generally ethanol (p-ethoxysilane), methanol (p-methoxysilane) and isopropanol (for silanes that are not easily soluble in ethanol and methanol). Because the hydrolysis rate of silane is related to the pH value, the neutral is the slowest, and it is partial Acid and partial alkali are faster, so it is generally necessary to adjust the pH value of the solution. Except for aminosilane, a small amount of acetic acid can be added to other silanes to adjust the pH value to 4-5. Aminosilane does not need to be adjusted because it is alkaline. After silane is hydrolyzed, it cannot be stored for a long time, so it is best to prepare and use it immediately, and it is best to use it up within one hour
The following are some specific applications for user reference:
Pretreatment packing method
Put the filler into a solid mixer (high-speed solid mixer HENSHEL (Henschel) or V-type solid mixer, etc.), and directly spray the above-mentioned silane solution on the filler and stir. The higher the speed, the better the dispersion effect. Generally, the stirring time is 10 to 30 minutes (the slower the speed, the longer the time), and the filler should be dried at 120 degrees Celsius (2 hours) after treatment.
Aqueous solution
(Glass fiber surface treatment agent): Glass fiber surface treatment agent often contains: film forming agent, antistatic agent, surfactant, coupling agent, water. The amount of coupling agent is generally 0.3% to 2% of the total amount of glass fiber surface treatment agent. Adjust the PH value of the 5-fold aqueous solution to a certain value with organic acid or salt, and add silane until it is transparent under full stirring, and then add For the rest of the components, isopropanol can be used to help dissolve the insoluble silane. During the drawing process, spray the glass fiber surface treatment agent on the glass fiber to dry, and remove the solvent and water.
Bottom method
Apply the 5% to 20% solution of silane coupling agent as above, apply, brush, spray, impregnate the surface of the substrate, take it out to dry at room temperature for 24 hours, preferably bake at 120°C for 15 minutes.
Direct addition method
Silane can also be directly added to the filler/resin mixture. When the resin and filler are mixed, the silane can be directly sprayed into the mixture. The amount of coupling agent is generally 0.1% to 2% of the amount of filler (determined according to the diameter of the filler). The silane loaded resin/filler is then molded (extruded, compression molded, coated, etc.).