Silicones are mainly divided into four categories: silicone oil, silicone rubber, silicone resin and silane coupling agent. They are introduced as follows:

　　Silicone oil product introduction

　　Silicone oil is a polyorganosiloxane with a chain structure of different degrees of polymerization. It is produced by hydrolyzing dimethyldichlorosilane with water to obtain a primary polycondensation ring body. The ring body is cracked and distilled to obtain a lower ring body. Then the ring body, head-capping agent and catalyst are put together and polymerized to obtain each Silicone oil can be obtained by distilling a mixture of different degrees of polymerization under reduced pressure to remove low boiling matter.

　　The most commonly used silicone oil, all organic groups are methyl groups, is called methyl silicone oil. Organic groups can also use other organic groups to replace part of the methyl groups to improve certain properties of the silicone oil and apply it to various uses. Other common groups include hydrogen, ethyl, phenyl, chlorophenyl, trifluoropropyl, etc. In recent years, organically modified silicone oil has developed rapidly, and many organically modified silicone oils with special properties have appeared.

　　Silicone oil is generally a colorless (or light yellow), odorless, non-toxic, non-volatile liquid. Silicone oil is insoluble in water, methanol, glycol and ethoxyethanol, miscible with benzene, dimethyl ether, methyl ethyl ketone, carbon tetrachloride or kerosene, slightly soluble in acetone, dioxane, ethanol and ethanol. . It has a small vapor pressure, high flash point and fire point, and low freezing point. As the number of chain segments n increases, the molecular weight increases and the viscosity also increases. Therefore, silicone oil can have various viscosities, from 0.65 centistokes to millions of centistokes. If you want to prepare low-viscosity silicone oil, you can use acidic clay as a catalyst and telomerize at 180°C, or use sulfuric acid as a catalyst and telomerize at low temperature to produce high-viscosity silicone oil or viscous materials. catalyst.

　　Silicone oil is divided into methyl silicone oil, ethyl silicone oil, phenyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil, methyl chlorophenyl silicone oil, methyl ethoxy silicone oil, methyl trifluoropropyl silicone oil according to the chemical structure. Silicone oil, methyl vinyl silicone oil, methyl hydroxyl silicone oil, ethyl hydrogen silicone oil, hydroxyl hydrogen silicone oil, cyanide silicone oil, etc.; in terms of use, there are damping silicone oil, diffusion pump silicone oil, hydraulic oil, insulating oil, Heat transfer oil, brake oil, etc.

　　Silicone oil has excellent heat resistance, electrical insulation, weather resistance, hydrophobicity, physiological inertness and small surface tension. In addition, it also has a low viscosity-temperature coefficient and high compression resistance. Some varieties are also radiation resistant. performance.

　　Silicone emulsion

　　Silicone emulsion is a form of silicone oil. The following is an introduction from two aspects: silicone oil fabric softening agent and silicone oil emulsion defoaming agent.

　　one. Silicone fabric softening agent

　　Silicone emulsion is mainly used as a silicone fabric softening agent. The first generation of silicone fabric finishes were mechanical mixtures of dimethicone and hydrosilicone (and their derivatives). The second generation of silicone fabric finishing agent is hydroxyl-terminated polydimethylsiloxane emulsion, which is emulsified from octamethylcyclotetrasiloxane monomer, water, emulsifier, catalyst and other raw materials under certain conditions. aggregated. Since polymerization and emulsification are completed in one step, it has the advantages of short working hours, high work efficiency, simple equipment, and easy operation. The obtained emulsion is very stable, the particles are very uniform, and the obtained polymer has active groups (hydroxyl groups) at both ends. ) can further react to form a film, which is beneficial to improving the application effect of the emulsion, which is beyond the reach of mechanical emulsified silicone oil.

　　Hydroxy silicone oil emulsions can be divided into several types of emulsions such as cationic, anionic, non-ionic, and complex ion based on the surfactants used.

　　1. Cationic hydroxyl silicone oil emulsion

　　The emulsifier used in cationic hydroxyemulsion polymerization is generally quaternary ammonium salts (octadecyltrimethylammonium chloride reported in foreign literature), and the catalyst is ammonium hydroxide. Cationic hydroxyl emulsion can be used in the finishing of various textiles. It has the properties of improving fabric feel, improving fabric elasticity, smoothness and crispness. Another unique advantage of it is that it is an ideal waterproofing agent for fabrics and can be used together with methyl hydrogenated silicone oil emulsion. , the waterproof performance and waterproof durability can reach a very high level, and can be used as a waterproofing agent for vinylon awning canvas, polyester card cloth, etc.

　　2. Anionic hydroxyl silicone oil emulsion

　　Anionic hydroxyemulsion is characterized by good compatibility in fabric finishing agents and very stable emulsion. In particular, most of the auxiliaries used in textile printing and dyeing are anionic. If cationic hydroxyemulsion is used, it is easy to cause demulsification and oil bleaching. Anionic hydroxyemulsion can avoid this problem, so it is more popular among users and has a wide range of uses.

　　3．Complex ionic hydroxyl silicone oil emulsion

　　Although cationic hydroxyl emulsion is an excellent fabric softening agent, this emulsion is not resistant to hard water and cannot be bathed with dimethylol dihydroxyethylene urea resin (2D) resin, catalyst magnesium chloride and anionic whitening agent. use, so there are certain limitations in use. In addition, due to the poor stability of the emulsion, the silicone polymer is easily separated from the emulsion and floats on the liquid surface, commonly known as "floating oil". If cationic and nonionic emulsifiers are used in the emulsion polymerization process, the shortcomings of cationic emulsifiers in preparing hydroxyl silicone oil emulsions can be overcome. The prepared silicone emulsions can withstand hard water and can be used with 2D resins, magnesium chloride and The whitening agent VBL is used in the same bath and has good heat resistance and freezing resistance.

　　4. Nonionic hydroxyl silicone oil emulsion

　　Nonionic hydroxyemulsion has stronger adaptability and better stability than cleaved hydroxyemulsion. Therefore, many countries are vigorously researching nonionic hydroxyemulsion. For example, UltrarateX FSA, a new product produced by Ciba-Geigy of Switzerland, is a non-ionic emulsion of hydroxyl-capped polydimethylsiloxane with a molecular weight of more than 200,000, which is more anionic than the Dc-1111 anionic emulsion of Dow Corning Company of the United States. Hydroxymilk is a step forward.

　　5. Silicone finishing agents with other reactive groups

　　In order to meet the needs of advanced finishing of various types of fabrics, improve the oil resistance, antistatic and hydrophilic properties of silicone-finished fabrics, and make chemical fiber fabrics have many advantages of natural fabrics, silicone workers have studied the introduction of other substances into silicone molecules. Reactive groups such as amino, amide, ester, cyano, carboxyl, epoxy, etc. The introduction of these groups gives silicone fabric finishing agents special effects. For example, the introduction of amino groups into silicone molecules is suitable for anti-shrinkage and soft finishing of wool fabrics; the introduction of amide groups is suitable for anti-fouling finishing, and the softness is also greatly improved: Introduction The cyano group has good oil resistance, and the copolymer of polyoxyethylene ether and silicone has a good antistatic effect; organofluorine-modified silicone has many advantages such as oil repellency, antifouling, antistatic, and water repellency.

　　two. Silicone oil emulsion defoamer

　　Silicone oil emulsion defoamer is generally an oil-in-water (O/W) emulsion, that is, water is the continuous phase and silicone oil is the discontinuous phase. It involves pre-mixing silicone oil, emulsifiers and thickeners, etc., then gradually adding water and stirring evenly, and finally grinding them repeatedly in a colloid mill until a desired emulsion is obtained.

　　Silicone oil emulsion defoamer is the most widely used and the largest amount of silicone defoamer. It is characterized by being easily dispersed in aqueous systems and can be widely used as a defoaming agent in aqueous systems. When using, add the emulsion directly into the foaming system to obtain good defoaming effect. In order to improve the defoaming effect of the emulsion and the accuracy of measurement, concentrated silicone oil emulsion with more than 10% is generally not used directly: instead, it is first diluted with cold water or directly with foaming liquid to less than 10% for use. Do not use overheated or overcooled liquids for dilution, otherwise the emulsion will break. The stability of the emulsion will become worse after dilution, and stratification (oil drifting) may also occur during storage, that is, emulsification. Therefore, the diluted lotion should be used up as soon as possible. If necessary, thickeners can be added to improve the stability of the emulsion. For intermittent operation, the silicone oil emulsion can be added all at once before the system is operated, or in batches; for continuous operation, the silicone oil emulsion should be added continuously or intermittently at appropriate parts of the system.

　　When using emulsion-type defoaming agents, special consideration must be given to the temperature of the foaming system and acid and alkaline conditions. Because silicone oil emulsions are delicate, if they exceed its use range, the emulsion will break prematurely and become inefficient or ineffective. (The dosage of silicone oil emulsion is generally 10 to 10Oppm of the weight of the foaming liquid (based on silicone oil). Of course, there are also less than 10ppm and more than 100ppm under special circumstances. The optimal dosage is mainly determined through experiments.

　　Most general silicone oil emulsion defoaming agents are oil-in-water type. Depending on the type of silicone oil, silicone oil emulsion defoamer has the following types:

　　1. Silicone oil emulsion based on dimethyl silicone oil

　　This type of defoaming agent is formulated from dimethyl silicone oil plus emulsifier and water, and can be widely used in fermentation, food, papermaking, fiber, pharmaceuticals, synthetic resins, etc.

　　2. Silicone oil emulsion based on methyl ethoxy silicone oil

　　This type of defoaming agent is made of methyl ethoxy silicone oil and compounding agents.

　　3．Silicone oil emulsion based on ethyl silicone oil

　　In recent years, silicone defoaming agents are developing in the direction of silicone-polyether block copolymerization (or graft copolymerization). This type of defoaming agent has the characteristics of both silicone and polyether, thus greatly improving the defoaming power; the silicone-polyether copolymer defoaming agent can also be called a self-emulsifying silicone defoaming agent. Block (or graft) hydrophilic ethylene oxide chain or oxyethylene oxypropylene chain in the organic silicon molecular chain, so that the hydrophobic siloxane part is combined with the hydrophilic polyether. Such molecules have larger Due to its polarity, as a defoaming agent, it has a large spreading coefficient, can be evenly dispersed in the foaming medium, and has high defoaming efficiency. It is a new type of high-efficiency defoaming agent. The defoaming effect of this type of self-emulsifying silicone oil, which does not require the use of emulsifiers, is quite satisfactory for certain systems. It is especially suitable for situations where it is not suitable to use general silicone oil emulsions and where general silicone oil emulsions are difficult to handle.

　　One of the introduction of silicone rubber products

　　High temperature vulcanized silicone rubber

　　High temperature vulcanized silicone rubber is a high molecular weight (generally 400,000 to 800,000 molecular weight) polyorganosiloxane (i.e., raw rubber) added with reinforcing fillers and various other additives. It uses organic peroxide as the vulcanizing agent and is molded under pressure. (molding, extrusion, calendering) or injection molding, and cross-linked into rubber at high temperatures. This kind of rubber is generally referred to as silicone rubber.

　　The vulcanization of high-temperature vulcanized silicone rubber is generally divided into two stages. The first stage is to mix silicone raw rubber, reinforcing agents, additives, vulcanizing agents and structural control agents, and then add the mixed materials in a metal mold. Pressure heat molding and vulcanization, the pressure is about 50 kg/cm2, the temperature is 120~130℃, and the time is 10~30 minutes. The second stage is to take the silicone rubber out of the mold and put it into the oven at 200~ Bake at 250°C for several hours to 24 hours. The rubber is further vulcanized and the organic peroxide is decomposed and volatilized.

　　The reinforcing filler of silicone rubber is various types of white carbon black, which can increase the strength of the vulcanized rubber ten times. The main purpose of adding various additives is to reduce the cost of the rubber, improve the properties of the rubber, and give the vulcanized rubber various special properties such as flame retardancy and conductivity. Cross-linking agents are various organic peroxides, such as benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, 2,5-ditert-butylperoxyhexane, etc. .Structure control agent is added to prevent the mixed rubber material from being left for too long and causing "structuring", which makes the rubber material hard and difficult to process and mature. Methylhydroxy silicone oil or diphenyldihydroxysilane can be used. As a structural control agent.

　　The side groups on the main chain of silicone rubber can be methyl, ethyl, vinyl, phenyl, trifluoropropyl, etc. The most commonly used is methyl, but other groups can also be introduced to improve processing properties and other properties. Therefore, according to the different side groups and rubber compound formulas, silicone rubber can be obtained for various purposes, which can generally be divided into the following types: general-purpose type (containing methyl and vinyl), high-temperature and low-temperature type (containing phenyl, methyl and vinyl), low compression set (containing methyl and vinyl), low shrinkage (devolatilization) and solvent resistance (fluorosilicone rubber), etc. Several important types of silicone rubber are introduced below.

　　one. Methyl silicone rubber

　　Dimethyl silicone rubber is the earliest silicone rubber put into commercial production. It can maintain good elasticity in the range of -60 to 200°C, has good aging resistance, has excellent electrical insulation properties, moisture resistance, shock resistance, and physiological inertness. characteristic.

　　Dimethyl silicone rubber is mainly used for coating strong materials, and can also be made into various extruded and calendered products for use in electromechanical, aviation, automotive, medical and other industries. However, due to the low vulcanization activity of dimethyl silicone rubber, it is difficult to vulcanize when used to manufacture thick products, the inner layer is prone to blistering, and the high-temperature compression permanent deformation is large, so it has been replaced by methyl vinyl silicone rubber.

　　2. Methyl vinyl silicone rubber

　　Since the introduction of a small amount of vinyl into the macromolecular structure of silicone rubber can greatly improve the vulcanization processing performance of silicone rubber, most of the silicone rubber currently used contains vinyl. Methyl vinyl silicone rubber is the most versatile silicone rubber and currently dominates the production of silicone rubber at home and abroad. Because it introduces partially unsaturated vinyl groups on the side chains, its processing performance and physical and mechanical properties are better than those of two-based silicone rubber. In addition to the general characteristics of dimethyl silicone rubber, it also has a wide operating temperature range and can maintain good elasticity in the range of -60 to 260°C. It is easier to vulcanize than dimethyl silicone rubber and has a smaller compression permanent deformation, good resistance to solvent expansion, stability to high-pressure steam, and excellent cold resistance. Moreover, the use of less active peroxide for vulcanization reduces the generation of bubbles and poor rubber stability during vulcanization. weakness. Therefore, methyl vinyl silicone rubber can generally be used to make thicker products. Methyl vinyl silicone rubber is the most widely used variety of silicone rubber. Various high-performance and special-purpose silicone rubbers that have emerged in recent years are mostly based on vinyl silicone rubber, such as high-strength silicone rubber, low-density silicone rubber, etc. Compression permanent deformation silicone rubber, no post-vulcanization silicone rubber, heat-resistant conductive silicone rubber and medical silicone rubber, etc. In the aviation industry, methyl vinyl silicone rubber is widely used as gaskets, sealing materials and protective layers for fragile and shock-proof components; in the electrical industry, it can be used as advanced insulating materials for electronic components and dynamic sealing rings for high-temperature potentiometers. Seals for underground long-distance communication equipment; in medicine, because methylvinyl silicone rubber has little physiological reaction to the human body and is non-toxic, it is used in plastic surgery, artificial heart valves, blood vessels, etc.

　　3. Methyl phenyl vinyl silicone rubber

　　Methyl phenyl vinyl silicone rubber is a product obtained by introducing methyl phenyl silicone chain segments or diphenyl silicone chain segments into the molecular chain of methyl vinyl silicone rubber.

　　Introducing phenyl groups to the side groups of polysiloxane destroys the regularity of the dimethylsiloxane structure, greatly reduces the crystallization temperature of the polymer, and expands the low-temperature application range of the polymer material. Therefore, in addition to the small compression permanent deformation, wide operating temperature range, antioxidant, weather resistance, shockproof, moisture-proof and good electrical insulation properties of methylphenyl vinyl silicone rubber, methylphenyl vinyl silicone rubber also has excellent Low temperature resistance, ablation resistance and radiation resistance. These properties vary with the phenyl content in the molecular chain. Generally speaking, when the phenyl content (ratio of phenyl to silicon atoms) is 5 to 10%, it is called low phenyl silicone rubber. It has unique cold resistance. Performance, it can still maintain the elasticity of rubber at -70~-100℃, which is the best low-temperature performance among all rubbers. In addition, it has the advantages of methyl vinyl silicone rubber and is not high in cost, so it has great potential to replace methyl vinyl silicone rubber. Vinyl Silicone Rubber Trends. When the phenyl content is 20 to 40%, it is called medium phenyl silicone rubber, which has the advantages of methyl vinyl silicone rubber and is not high in cost. Therefore, it has a strong tendency to replace methyl vinyl silicone rubber. When the phenyl content is 20 to 40%, it is called medium phenyl silicone rubber. It has excellent flame resistance and can self-extinguish once it catches fire. When the phenyl content is 40 to 50%, it is called high phenyl silicone rubber. It has excellent radiation resistance, and its gamma-ray resistance is 1xI08 Roentgen. Generally speaking, as the phenyl content increases, the rigidity of the silicone rubber molecular chain gradually increases, and the low-temperature resistance of silicone rubber gradually decreases. However, as the phenyl content increases, the flame resistance and radiation resistance of the vulcanized rubber are improved. Illumination.

　　Methyl phenyl vinyl silicone rubber is one of the important materials in the aerospace industry, cutting-edge technology and other sectors of the national economy. It can be used to make various molded and extruded products and is used as cold-resistant rubber in the aviation industry and for ablation resistance, Seals, gaskets, pipes and rods for heat-aging or radiation-resistant parts.

　　4. Fluorosilicone rubber

　　Fluorosilicone rubber refers to γ-trifluoropropylmethylpolysiloxane. Fluorosilicone rubber has excellent resistance to chemicals, solvents and lubricants. This kind of silicone rubber has a small expansion rate in non-polar solvents, good cold resistance and thermal stability, and good fire resistance, so it is used in aircraft. , rockets, missiles, space flight, petrochemical industry, used as hoses, gaskets, sealing rings, fuel tanks, etc. in contact with fuel oil and lubricating oil. It can also be used to make corrosion-resistant clothes, gloves, coatings, adhesives, etc. .

　　5. Nitrile silicone rubber

　　Since the side chain of the polymer molecule contains β-nitrile ethyl or γ-nitrile propyl strong polar groups, the inter-molecular force is greatly increased and the oil and solvent resistance are improved. At the same time, due to the introduction of a certain amount of nitrile alkyl groups, the regularity of the polymer structure is destroyed and the cold resistance is greatly improved. The type and content of nitrile alkyl groups have a great impact on performance. For example, silicone rubber containing 7.5 mol% of γ-nitrile propyl group has similar low-temperature properties to low phenyl silicone rubber (its glass transition temperature is -114.5°C). Oil resistance is better than phenyl silicone rubber. As the γ-nitrile propyl content increases to 33 to 50 mol%, the cold resistance decreases and the oil resistance improves. Replacing γ-nitrile propyl group with β-nitrile ethyl group can improve the heat resistance of nitrile silicone rubber and can withstand hot air aging at 250°C.

　　The main advantage of nitrile silicone rubber is that it has excellent oil resistance and bath agent resistance, and can maintain elasticity in the range of -60 to 180°C. Therefore, it can be made into oil-resistant rubber products for use in the aviation industry, automobile industry and petroleum industry; also It can be used as an environmental sealant and fuel tank sealant for high-performance aircraft, and can maintain sealing at temperatures from -54°C to over 200°C. Nitrile silicone rubber can be processed with ordinary equipment.

　　6. Phylene silicone rubber

　　The main feature of phenylene silicone rubber is its excellent radiation resistance. Its radiation resistance is 10 to 15 times that of general methyl vinyl silicone rubber and 5 to 10 times that of high phenyl silicone rubber. Therefore, it can be used It is used in the aerospace industry, atomic energy industry and nuclear reactors as cables, sheaths, gaskets and heat shrinkable tubes that are resistant to high-energy radiation.

　　7. Ethyl silicone rubber

　　Diethyl silicone rubber, which is made by introducing ethyl groups into the polysiloxane side chain, has particularly good cold resistance, and its cold resistance is better than dimethyl silicone rubber and general methylvinyl silicone rubber. The higher the ethyl content, the better the cold resistance. However, the reactivity of ethyl group is greater than that of methyl group. Therefore, as the ethyl group content increases, the heat resistance decreases. As an ethyl silicone rubber for low-temperature use, it is appropriate to contain 8 mol% of diethyl silicone chain segments in the polymer. The service temperature of ethyl silicone rubber is generally -70--200℃.

　　8. Silicone rubber

　　The main advantage of silicone rubber is its excellent thermal stability. It does not decompose at 430~480℃, and some can even withstand high temperatures above 500℃. The outstanding weakness of silicone rubber is its poor hydrolytic stability, and it was once considered to have no future. Later, it was discovered that polymers with cyclodisilazane introduced into the main chain have good thermal stability. The cyclodisilazane-containing elastomer modified with silarylene does not lose weight when heated to 425°C in air, and loses only 10% at 570°C, and has good hydrolysis stability.

　　Introduction to Silicone Rubber Products Part 2

　　Room temperature vulcanized silicone rubber

　　Room temperature vulcanized silicone rubber (RTV) is a new type of silicone elastomer that came out in the 1960s. The most notable feature of this rubber is that it can be cured on-site at room temperature without heating or pressure, making it extremely easy to use. Therefore, it has become an important part of the entire silicone product as soon as it comes out. Room temperature vulcanized silicone rubber is now widely used as adhesives, sealants, protective coatings, potting and molding materials, and has its uses in various industries. Room temperature vulcanized silicone rubber is known as liquid silicone rubber due to its low molecular weight. Its physical form is usually a flowable fluid or viscous paste with a viscosity between 100 and 1,000,000 centistokes. According to the requirements of use, the pre-vulcanized rubber can be made into self-leveling potting material or putty that does not flow but can be scratched. The fillers used in room temperature vulcanized silicone rubber are similar to those used in high temperature vulcanized silicone rubber, and are reinforced with white carbon black to give the vulcanized rubber a tear strength of 10 to 60 kg/cm2. Adding different additives can make the rubber material have different specific gravity, hardness, strength, fluidity and thixotropy, and make the vulcanized rubber have various special properties such as flame retardant, electrical conductivity, thermal conductivity, and ablation resistance.

　　Room temperature vulcanized silicone rubber can be divided into single-component and two-component room temperature vulcanized silicone rubber according to its packaging method. According to the vulcanization mechanism, it can be divided into condensation type and addition type. Therefore, room temperature vulcanized silicone rubber can be divided into three major types according to different compositions, vulcanization mechanisms and usage processes, namely single-component room temperature vulcanized silicone rubber, two-component condensation type room temperature vulcanized silicone rubber and two-component addition type room temperature vulcanized silicone rubber. .

　　The raw rubber of single-component and two-component condensation room temperature vulcanized silicone rubber is α,ω-dihydroxypolysiloxane; the addition type room temperature vulcanized silicone rubber contains alkenyl and hydrogen side groups (or end groups) Polysiloxane is also called low-temperature vulcanized silicone rubber (LTV) because it often achieves good curing effects at slightly higher than room temperature (50-150°C) during curing.

　　Each of these three series of room temperature vulcanized silicone rubber has its own advantages and disadvantages: the advantage of one-component room temperature vulcanized silicone rubber is that it is easy to use, but the deep curing speed is difficult; the advantage of two-component room temperature vulcanized silicone rubber is that it does not release heat during curing. , the shrinkage is very small, does not expand, and has no internal stress. Curing can be carried out both internally and on the surface at the same time, and can be deeply vulcanized; the vulcanization time of addition type room temperature vulcanized silicone rubber mainly depends on the temperature, so its vulcanization can be controlled by adjusting the temperature. speed.

　　1. One-component room temperature vulcanized silicone rubber

　　The vulcanization reaction of one-component room temperature vulcanized silicone rubber is initiated by moisture in the air. The commonly used cross-linking agent is methyltriacetoxysilane. Its Si-OC bond is easily hydrolyzed. The acetoxy group combines with the hydrogen group in the water to form acetic acid, and the hydroxyl group in the water is moved to the original acetoxy group. position, it becomes trihydroxymethylsilane. Trihydroxymethylsilane is extremely unstable and easily condenses with linear silicone with hydroxyl end groups to form a cross-linked structure. Usually, the organic silicone rubber containing silanol end groups and various compounding agents such as fillers, catalysts, and cross-linking agents are put into a sealed hose. When used, it is extruded from the container and vulcanized with the help of moisture in the air. Elastomers also release low molecular weight substances. In addition to methyltriacetoxysilane, the cross-linking agent can also be a silane containing an alkoxy group, an oxime group, an amine group, an amide group, or a ketone group. When it is cross-linked with an alkoxy group and releases alcohol, it is called a dealcoholized one-component room temperature vulcanized silicone rubber. When it is cross-linked with an oxime group, an oxime is generated, which is called a deoxime type room temperature vulcanized silicone rubber. Therefore, with the cross-linking Depending on the agent, single-component room temperature vulcanized silicone rubber can be of many varieties such as deacidification type, deoxime type, dealcoholization type, deamination type, deamidation type and deketone type, but the deacidification type is currently the most widely used. A sort of.

　　The vulcanization time of single-component room temperature vulcanized silicone rubber depends on the vulcanization system, temperature, humidity and thickness of the silicone rubber layer. Increasing the temperature and humidity of the environment can speed up the vulcanization process. Under typical environmental conditions, generally after 15 to 30 minutes, the surface of the silicone rubber can become non-sticky, and a 0.3 cm thick adhesive layer can be cured within one day. The depth and strength of the cure gradually builds up over about three weeks.

　　One-component room temperature vulcanized silicone rubber has excellent electrical properties and chemical inertness, as well as heat resistance, natural aging resistance, flame resistance, moisture resistance, breathability and other properties. They can maintain elasticity for a long time in the range of -60~200℃. It does not absorb or release heat when curing, has a small shrinkage after curing, and has good adhesion to materials. Therefore, it is mainly used as adhesives and sealants, but other applications include form-in-place gaskets, protective coatings and caulking materials. Many one-component silicone rubber adhesive formulations exhibit self-bonding properties on a variety of materials such as most metals, glass, ceramics and concrete, such as bare aluminum, with shear strengths up to 200 lb/in. 2. The tear strength can reach 20 pounds·feet/inch2 (0.35 Joules/cm2). When bonding is difficult, a primer can be applied on the base material to improve the bonding strength. The primer can be a reactive silane monomer or resin. When they are cured on the base material, a layer of modified suitable on silicone bonded surfaces.

　　Although one-component room temperature vulcanized silicone rubber is easy to use, its vulcanization depends on moisture in the atmosphere, so the thickness of the vulcanized rubber is limited and can only be used in situations requiring a thickness of less than 6 mm.

　　The vulcanization reaction of one-component room temperature vulcanized silicone rubber proceeds gradually from the surface to the depth. The thicker the rubber layer, the slower the curing. When the deep part needs to be cured quickly, the layered pouring and gradual vulcanization method can be used. Some rubber can be added each time and then added after vulcanization, which can reduce the total vulcanization time. Adding magnesium oxide can accelerate the vulcanization of deep glue.

　　Two-component room temperature vulcanized silicone rubber. Two-component room temperature vulcanized silicone rubber can be divided into condensation type and addition type.

　　2. Two-component condensation room temperature vulcanized silicone rubber

　　Two-component condensation room temperature vulcanized silicone rubber is the most common room temperature vulcanized silicone rubber. Its raw rubber is usually hydroxyl-terminated polysiloxane, which is combined with other compounding agents and catalysts to form a rubber compound. The viscosity range is from 100 centistokes to one million centistokes. The vulcanization reaction of two-component room temperature vulcanized silicone rubber is initiated not by moisture in the air, but by a catalyst. Usually, the silica gel, filler, and cross-linking agent are packaged as one component, and the catalyst is packaged separately as another component, or other combinations are used, but the catalyst and cross-linking agent must be packaged separately. Regardless of the packaging method, curing begins to occur only when the two components are completely mixed together. The commonly used cross-linking agent is ethyl orthosilicate, and the catalyst is dibutyltin dilaurate. And add appropriate fillers and additives based on the properties of the desired final product. In recent years, many countries have banned the addition of dibutyltin in food bags and plasma bags because dibutyltin dilaurate is a medium-toxic substance. It has basically been replaced by low-toxic octyltin.

　　The vulcanization time of two-component condensation room temperature vulcanized silicone rubber mainly depends on the type, dosage and temperature of the catalyst. The more catalyst used, the faster the sulfurization will be, and the shorter the storage time will be. At room temperature, the storage time is usually a few hours. If you want to extend the storage time of the rubber, you can use the cooling method. It takes about a day for two-component condensation type room temperature vulcanized silicone rafter glue to fully cure at room temperature, but it only takes 1 hour at a temperature of 150°C. The curing speed can be significantly increased through the synergistic effect of the accelerator γ-aminopropyltriethoxysilane. Two-component room temperature vulcanized silicone rubber can maintain elasticity for a long time in the temperature range of 165 to 250°C, and has excellent electrical properties and chemical stability. It is resistant to water, ozone, and weather aging. In addition, it is simple to use and has strong process applicability. , therefore, widely used as potting and molding materials. After coating and potting various electronic and electrical components with room temperature vulcanized silicone rubber, they can protect against moisture (anti-corrosion, shockproof, etc.) and can improve performance and stability parameters. Two-component room temperature vulcanized silicone rubber is particularly suitable for deep potting Sealing material and has a faster vulcanization time, which is better than single-component room temperature vulcanized silicone rubber.

　　Two-component room temperature vulcanized silicone rubber has excellent anti-stick properties after vulcanization, and the shrinkage rate is extremely small during vulcanization. Therefore, it is suitable for manufacturing soft molds and is used for casting epoxy resin, polyester resin, polystyrene, Molds for polyurethane, vinyl plastics, paraffin wax, low melting point alloys, etc. In addition, various exquisite patterns can be reproduced by utilizing the high simulation performance of two-component room temperature vulcanized silicone rubber. For example, in the reproduction of cultural relics, it can be used to copy ancient bronzes, and in the production of artificial leather, it can be used to copy the skin patterns of snakes, pythons, crocodiles, pangolins and other animals, achieving the effect of making fakes look real.

　　When using two-component room temperature vulcanized silicone rubber, you should pay attention to several specific issues: first, weigh the base material, cross-linking agent and catalyst separately, and then mix them in proportion. Usually the two components should be provided in different colors so that the mixing of the two components can be visually observed. The mixing process should be carefully operated to minimize the amount of trapped gas. After the rubber is mixed (even in color), the bubbles can be removed by leaving it alone or depressurizing (vacuum degree 700 mmHg). After all the bubbles are discharged, it can be vulcanized into silicon by placing it at room temperature or at a specified temperature for a certain period of time. eraser.

　　In addition to the methyl group, the side groups on the main chain of the two-component room temperature vulcanized silicone rubber siloxane can be replaced with other groups such as phenyl, trifluoropropyl, cyanoethyl, etc. to improve its low temperature and heat resistance. , radiation resistance or solvent resistance and other properties. At the same time, heat-resistant, flame-retardant, thermal conductive, and electrically conductive additives can be added as needed to produce silicone rubber with ablation resistance, flame retardant, thermal conductivity, and electrical conductivity.

　　1. Methyl room temperature vulcanized silicone rubber

　　Methyl room temperature vulcanized silicone rubber is an old variety of general-purpose silicone rubber. It has the advantages of water resistance, ozone resistance, arc resistance, corona resistance and weather aging resistance. It can be used within a temperature range of 60 to 200°C. Therefore, it is widely used as a filling and sealing material for electronic and electrical components, as well as a moisture-proof, shock-proof, high and low temperature resistant filling and sealing material for instruments and meters. It can also be used to make molds for casting polyester resin, epoxy resin and low melting point alloy parts. It can also be used as dental impression material. Coating cotton cloth and paper bags with methyl room temperature vulcanized silicone rubber can be used to make conveyor belts and packaging bags for transporting sticky items.

　　2. Methyl diphenyl room temperature vulcanized silicone rubber

　　In addition to the excellent properties of methyl biphenyl room temperature vulcanizing silicone rubber, methyl diphenyl room temperature vulcanizing silicone rubber has a wider operating temperature range (-100~250℃) than methyl room temperature vulcanizing silicone rubber. Low phenyl room temperature vulcanized silicone rubber (108-1) with a phenyl content of 2.5 to 5% can maintain elasticity under low temperature conditions of -120°C. It is currently the best low-temperature performance among silicone rubbers; the phenyl content is 10 ~20% room temperature glue (108-2) has good radiation resistance, ablation resistance and self-extinguishing properties. If a certain amount of heat-resistant additives such as Fe2O3 are added to it, the thermal aging performance can be improved, and it is suitable for 250 Used at high temperatures above ℃ or used as ablation-resistant putty coatings and encapsulating materials.

　　Methyl phenyl room temperature adhesive, like other room temperature adhesives, can be used for dipping, impression and release. If you want to increase the adhesion with other materials, you must perform surface treatment on the adhered material before using the material. The surface treatment steps are as follows: Clean the surface of the material 1 to 2 times with acetone solvent, and then treat it with a surface agent 1 ~2 times, bake in a 60°C oven for a few minutes. At this time, a layer of less sticky film will be formed on the surface of the material, and the glue can be applied.

　　3. Methyl block room temperature vulcanized silicone rubber

　　Methyl block room temperature vulcanization silicone rubber is a modified variety of methyl room temperature vulcanization silicone rubber. It is composed of hydroxyl-capped polydimethylsiloxane (107 rubber) and methyltriethoxysilane oligomer ( A copolymer with a molecular weight of 3 to 5). Under the catalysis of dibutyltin dilaurate, the hydroxyl groups in polydimethylsiloxane and the ethoxy groups in polymethyltriethoxysilane are condensed to form a three-dimensional polymer. After vulcanization, the elastic The silicone rubber has higher mechanical strength and adhesion than methyl room temperature vulcanized silicone rubber, and can be used for a long time in a temperature range of 70 to 200°C.

　　Methyl block room temperature vulcanized silicone rubber has the properties of shockproof, moisture-proof, waterproof, breathable, ozone resistance, weather aging resistance, and resistance to weak acids and weak alkali. It has good electrical insulation properties, good adhesive properties, and is low cost. Therefore, it can be widely used in potting, coating, impression, demoulding, drug carrier release and other occasions. Electronic components potted with methyl block room temperature adhesive have the functions of shockproof, moisture-proof, sealing, insulation, and stabilization of various parameters. Applying methyl block room temperature glue directly to the speaker can reduce and eliminate the mid-frequency points of the speaker. After vulcanization, the resonant frequency performance of the speaker can be reduced by about 20 Hz. After adding a certain amount of additives to the methyl block room temperature adhesive, it can be used as a paper anti-sticking agent. After applying a thin layer of methyl block room temperature adhesive on the candy and biscuit conveyor belts in the food industry, the anti-stick properties of the canvas can be improved, thereby improving the appearance of the food and increasing the utilization rate of raw materials.

　　Adding an appropriate amount of fumed silica to the methyl block room temperature adhesive can be used to install window glass, curtain walls, window frames, seams of prefabricated panels, and expansion joints of airport runways. In addition, it can also be used as an adhesive for magnetic cores and templates in electronic computer memories, and as an adhesive for conductive silicone rubber and non-conductive silicone rubber. Treating fabrics with methyl block room temperature vulcanized silicone rubber can improve the fabric's feel, softness and bending resistance.

　　4. Room temperature vulcanized silicone rubber

　　Room temperature vulcanized nitrile silicone rubber is polyβ-nitrile ethyl methyl siloxane. In addition to the light resistance, ozone resistance, moisture resistance, high and low temperature resistance and excellent electrical insulation properties of silicone rubber, room temperature vulcanization silicone rubber is mainly characterized by resistance to non-metallic acid. It has good resistance to polar solvents such as aliphatic and aromatic solvents, and its oil resistance is close to that of ordinary oil-resistant nitrile rubber. It can be used as a sealing filler for oil-contaminated parts and oil-resistant electronic components.

　　5. Room temperature vulcanized fluorosilicone rubber

　　Room temperature vulcanized fluorosilicone rubber is polyγ-trifluoropropylmethylsiloxane. Its main features are fuel oil resistance, solvent resistance and high temperature resistance to degradation, and it also has good extrusion properties. Mainly used for sealing and caulking of supersonic aircraft overall fuel tanks, fluorosilicone rubber gaskets, gasket bonding and fixation; bonding of silicone rubber and fluorosilicone rubber, as well as fuel oil resistance and solvent resistance parts in chemical engineering and general industry of bonding.

　　6. Room temperature vulcanized phenylene silicone rubber

　　Room temperature vulcanized phenylene silicone rubber is a silophenyl (biphenyl) siloxane polymer. Its outstanding advantage is its excellent resistance to high-energy rays. Tests have proven that after being irradiated by 1x109 Roentgen γ-rays or 1x1018 neutrons/cm2, the rubber can still maintain elasticity, which is 10 to 15 times greater than room temperature vulcanization methyl silicone rubber and 5 to 5 times greater than room temperature vulcanization phenyl silicone rubber. 10 times.

　　Room-temperature vulcanized phenylene silicone rubber can be used in the atomic energy industry, nuclear power plants, and spaceflight as high-temperature and radiation-resistant adhesive sealing materials and insulating protective layers for motors.

　　3. Addition room temperature vulcanized silicone rubber

　　Two-component addition type room temperature vulcanized silicone rubber can be divided into elastic silicone gel and silicone rubber. The former has lower strength and the latter has higher strength. Their vulcanization mechanism is based on the addition reaction (hydrosilylation reaction) between the vinyl group (or propylene group) on the end group of the organic silicone rubber and the silicon hydrogen group on the cross-linking agent molecule.

　　In this reaction, a hydride-functional polysiloxane is used as a cross-linking agent (vulcanizing agent) and chloroplatinic acid or other soluble platinum compounds are used as a catalyst. The vulcanization reaction takes place at room temperature. No by-products are released. Since no low molecular weight substances are released during the cross-linking process, addition type room temperature vulcanization silicone rubber does not shrink during the vulcanization process. This type of vulcanized rubber is non-toxic, has high mechanical strength, has excellent hydrolytic stability (even under high-pressure steam), good low compression deformation, low flammability, can be deeply vulcanized, and the vulcanization speed can be controlled by temperature, etc. Advantages, so it is a type of silicone rubber currently being vigorously developed at home and abroad.

　　The packaging method of addition room temperature vulcanized silicone rubber is generally divided into two components: M and N: the catalyst and the silicone polymer containing vinyl energetic groups are used as one component; the hydrogen-containing polysiloxane is Chain agent is another component.

　　High-strength addition type room temperature vulcanized silicone rubber has low linear shrinkage and does not release low molecules during vulcanization, so it is an excellent material for molding. It has been widely used in the machinery industry to make molds to cast epoxy resin, polyester resin, polyurethane, polystyrene, vinyl plastics, paraffin, low melting point alloys, concrete, etc. Utilizing the characteristics of high simulation, non-corrosion, simple molding process, and easy demoulding of addition-type thermally vulcanized silicone rubber, it is suitable for the reproduction of cultural relics and art crafts.

　　Introduction to Silicone Rubber Products Part 3

　　silicone gel

　　Addition room temperature vulcanized silicone rubber is a colorless or slightly yellow transparent oily liquid that becomes a soft and transparent silicone gel after vulcanization. This gel can maintain elasticity for a long time in the temperature range of -65 to 200°C. It has excellent electrical properties and chemical stability, is water-resistant, ozone-resistant, weather-aging resistant, hydrophobic, moisture-proof, shock-proof, non-corrosive, and has Physiologically inert, non-toxic, odorless, easy to pour, capable of deep vulcanization, low linear shrinkage, simple operation, etc., silicone gel is widely used in the electronics industry for moisture-proof, smuggling, insulation coating and Potting materials protect electronic components and assemblies from dust, moisture, shock and insulation. If you use transparent gel to encapsulate electronic components, it can not only provide shockproof and waterproof protection, but you can also see the components and use probes to detect component failures and replace them. The damaged silicone gel can be encapsulated again. repair.

　　Due to its high purity, easy use and certain elasticity, silicone gel is an ideal internal coating material for transistors and integrated circuits, which can improve the qualification rate and reliability of semiconductor devices; silicone gel can also be Used as an elastic adhesive for optical instruments.

　　In medicine, silicone gel can be used to implant organs in the human body, such as artificial breasts, and to repair damaged organs.

　　Foam silicone rubber

　　Foam silicone rubber is based on condensed hydroxyl-terminated silica raw rubber, hydroxyl hydrogen-containing silicone oil is the foaming agent, and vinyl platinum complex is the catalyst (the heated catalyst is dibutyl tin dilaurate). A porous sponge-like elastomer that is foamed and vulcanized at room temperature. In order to improve the quality of the foam, some other components should be added, such as silicone oil, to produce more gas during the vulcanization process; to improve the feel of the foam and reduce the density. Adding diphenylsilanediol can not only control the foam structure, but also control the viscosity increase during storage. However, the amount should not be too much, otherwise it will affect the electrical properties of the foam. In order to improve the physical and mechanical properties of the foam, transparent silicone rubber can also be added. The amount of vinyl complex of chloroplatinic acid as catalyst should not be too much, subject to the convenience of operation, otherwise the viscosity will increase and it is not conducive to operation; when the amount of catalyst is insufficient, the vulcanization will be incomplete, and the surface of the foam will be sticky and elastic. Good, soft and plastic, poor strength.

　　Foamed silicone rubber is liquid before vulcanization and is suitable for potting materials. The vulcanized foam can be used for a long time at -60~159℃. After aging at 150℃ for 72 hours, or ten times of alternating hot and cold use at -60~1070℃, the foam will still maintain its original properties. Foamed silicone rubber is an ideal lightweight packaging material due to its high thermal stability, good thermal insulation, insulation, moisture resistance, and shock resistance, especially at high frequencies. Used for "three defenses" protection. In addition, it can also be used as filling material for thermal insulation interlayers, floating materials and sealing materials in salt spray atmosphere. Foamed silicone rubber can also be used as filling, repairing and dressing materials in orthopedics in medicine. In order to meet the fire protection requirements of power transmission lines, the American Corning Company developed flame-retardant room temperature vulcanized foam silicone rubber DC3-6548. This kind of foamed silicone rubber is mainly used for fireproof sealing where wires and cables pass through (such as holes in roofs, walls, buildings, etc.). It has very good flame retardant properties and its limiting oxygen index reaches 39 (the limiting oxygen index of most plastics is only 20 ), with a service life of up to 50 years. At present, this kind of flame-retardant room temperature vulcanized foam silicone rubber has been widely used in nuclear power plants, electronic computer centers, offshore oil production equipment and other places with harsh environmental conditions or particularly high fire protection requirements.

　　Silicone product introduction

　　Silicone resin is a highly cross-linked network-structured polyorganosiloxane, usually made of methyltrichlorosilane, dimethyldichlorosilane, phenyltrichlorosilane, diphenyldichlorosilane or methylphenyl Various mixtures of dichlorosilane are hydrolyzed in the presence of organic solvents such as toluene at lower temperatures to obtain acidic hydrolysates. The initial products of hydrolysis are mixtures of cyclic, linear and cross-linked polymers, often containing a considerable number of hydroxyl groups. The hydrolyzate is washed with water to remove the acid, and the neutral primary condensation polymer is thermally oxidized in the air or further polycondensed in the presence of a catalyst, and finally forms a highly cross-linked three-dimensional network structure.

　　Curing of silicone resins is usually accomplished by condensation of silanol to form siloxane segments. When the condensation reaction is in progress, the silanol concentration gradually decreases, increasing steric hindrance and poor fluidity, resulting in a decrease in the reaction rate. Therefore, in order to completely solidify the resin, heating and adding a catalyst are required to accelerate the reaction. Many substances can catalyze the silanol condensation reaction, including acids and bases, soluble organic salts of lead, cobalt, tin, iron and other metals, organic compounds such as dibutyltin dilaurate or N, N, N ', N'-tetramethylguanidine salt, etc.

　　The performance of the final silicone resin product depends on the number of organic groups it contains (i.e. the ratio of R to Si). Generally, the ratio of R to Si in the molecular composition of silicone resins with practical value is between 1.2 and 1.6. The general rule is that the smaller the value of R: Si, the better the silicone resin obtained can be cured at a lower temperature; the larger the value of R: Si, the more the silicone resin obtained needs to be cured at 200 to 250 If baked for a long time at a high temperature of ℃, the hardness of the resulting paint film will be poor, but the thermal elasticity will be much better than the former.

　　In addition, the ratio of methyl to phenyl groups in the organic groups also has a great influence on the performance of silicone resin. The lower the phenyl content in the organic group, the softer the paint film will be and the faster the condensation will be. The higher the phenyl content, the harder the paint film will be and the more thermoplastic it will be. When the phenyl content is between 20% and 60%, the paint film has the best bending resistance and heat resistance. In addition, the introduction of phenyl groups can improve the compatibility of silicone resin with pigments, the compatibility of silicone resin with other silicone resins, and the adhesion of silicone resin to various substrates.

　　Silicone is a thermosetting plastic, and one of its most outstanding properties is excellent thermo-oxidative stability. After heating at 250°C for 24 hours, the weight loss of silicone resin is only 2 to 8%. Another outstanding property of silicone is its excellent electrical insulation properties, which can maintain its good insulation properties over a wide temperature and frequency range. Generally, the electrical breakdown strength of silicone resin is 50 kV/mm, the volume resistivity is 1013~1015 ohm·cm, the dielectric constant is 3, and the dielectric loss tangent value is around 10-30. In addition, silicone resin also has excellent moisture resistance, water resistance, rust resistance, cold resistance, ozone resistance and weather resistance. It has good corrosion resistance against most water-containing chemical reagents such as dilute mineral acids, but has poor solvent resistance.

　　In view of the above characteristics, silicone resin is mainly used as insulating paint (including varnish, enamel, color paint, impregnating paint, etc.) to impregnate H-class motors and transformer coils, and is used to impregnate glass cloth and asbestos cloth to make motor bushings and electrical insulation. Winding etc. Using silicone insulating paint to bond mica can produce large-area mica sheet insulation materials, which can be used as the main insulation of high-voltage motors. In addition, silicone resin can also be used as heat-resistant and weather-resistant anti-corrosion coatings, metal protective coatings, waterproof and moisture-proof coatings for construction projects, release agents, adhesives and secondary processing into silicone plastics for use in the electronics, electrical and defense industries. On the market, it is used as semiconductor packaging materials and insulating materials for electronic and electrical components.

　　There are roughly three methods for curing and cross-linking silicone resin: one is to use the hydroxyl groups on the silicon atoms to perform shrinkage polymerization and cross-linking to form a network structure, which is the main way for silicone resin to be cured; the other is to use ethylene connected to the silicon atoms. base, using organic peroxide as a catalyst, similar to the way silicone rubber is vulcanized: the third is to use the vinyl and silicon hydrogen bonds connected to the silicon atoms for addition reaction. For example, solvent-free silicone resin can be mixed with a foaming agent to make Get foam silicone. Therefore, silicone resin can be roughly divided into several categories according to its main use and cross-linking method: silicone insulating paint, silicone coating, silicone plastic and silicone adhesive.

　　Silane coupling agent product introduction

　　Silane coupling agent is obtained by the addition of silicon chloroform (HSiCl3) and unsaturated olefins with reactive groups under the catalysis of platinum chloride, followed by alcoholysis. Silane coupling agent is essentially a type of silane with organic functional groups. Its molecules have both reactive groups that can chemically combine with inorganic materials (such as glass, silica sand, metals, etc.) and organic materials (synthetic resins, etc.) Chemically bonded reactive groups. It can be represented by the general formula Y(CH2)nSiX3, where n=0~3; X-hydrolyzable group; Y-organic functional group, which can react with resin. X is usually a chlorine group, methoxy group, ethoxy group, methoxyethoxy group, acetoxy group, etc. When these groups are hydrolyzed, they generate silanol (Si(OH)3), which combines with inorganic substances to form Silicone. Y is vinyl, amino, epoxy, methacryloyloxy, mercapto or urea group. These reactive groups can react with organic substances to combine.

　　Therefore, by using silane coupling agents, a "molecular bridge" can be built between the interface of inorganic substances and organic substances to connect two materials with widely different properties, thereby improving the performance of composite materials and increasing the bonding strength. . This characteristic of silane coupling agent was first used in glass fiber reinforced plastics (glass fiber reinforced plastics) as a surface treatment agent for glass fibers, which greatly improved the mechanical properties, electrical properties and anti-aging properties of glass fiber reinforced plastics. In the glass fiber reinforced plastics industry Its importance has long been recognized.

　　At present, the use of silane coupling agents has expanded from glass fiber reinforced plastics (FRP) to glass fiber surface treatment agents for glass fiber reinforced thermoplastics (FRTP), surface treatment agents for inorganic fillers and sealants, resin concrete, water Cross-linked polyethylene, resin packaging materials, shell shapes, tires, belts, coatings, adhesives, abrasive materials (grindstones) and other surface treatment agents.

　　Among the two groups of silane coupling agents with different properties, the Y group is the most important. It has a great influence on the performance of the product and plays a role in determining the performance of the coupling agent. Only when the Y group can react with the corresponding resin can the strength of the composite material be improved. Generally, the Y group is required to be compatible with the resin and capable of coupling reaction. Therefore, a silane coupling agent containing an appropriate Y group must be selected for a certain resin. When Y is a non-reactive alkyl group or aryl group, it has no effect on polar resins, but can be used in the bonding of non-polar resins, such as silicone rubber, polystyrene, etc. When Y contains reactive functional groups, attention should be paid to its reactivity and compatibility with the resin used. When Y contains amino groups, it is catalytic and can be used as a catalyst in the polymerization of phenolic, urea-formaldehyde, and melamine formaldehyde. It can also be used as a curing agent for epoxy and polyurethane resins. At this time, the coupling agent fully participates in the reaction to form new bonds. . Aminosilane coupling agents are universal and can couple with almost all kinds of resins, with the exception of polyester resins. The type of x group has no effect on the coupling effect.

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

　　The application of silane coupling agents can be roughly summarized into three aspects:

　　one. Used for surface treatment of glass fiber, 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 wet state, it has a negative impact on the mechanical properties of composite materials. The improvement in performance is also very significant.

　　At present, the use of silane coupling agents in glass fibers has become quite common. The silane coupling agents used in this aspect account for about 50% of the total consumption. Among them, the most commonly used varieties are vinyl silane, amino silane, Methacryloyloxysilane, etc.

　　two. 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 resin, improve process performance and improve the mechanical, electrical and weather resistance properties of filled plastics (including rubber).

　　three. Used as a tackifier for sealants, adhesives and coatings to improve their bonding strength, water resistance, weather resistance and other properties. Silane coupling agents can often solve the problem of long-standing inability to bond certain materials.

　　The working principle of silane coupling agent as a tackifier is that it has two groups; one group can be combined with the adhered skeleton material; while 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 ways to apply silane coupling agents: one is 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 applications of silane coupling agents in the adhesive industry include the following aspects:

　　1. In the bonding of metals and non-metals in structural adhesives, if a silane tackifier is used, it can condense with the metal oxide or with another silanol, so that the silicon atoms are in tight contact with the surface of the adherend. For example, adding silane as a tackifier to nitrile phenolic structural adhesive can significantly improve the bonding strength.

　　2. In terms of bonding glass fibers, silane has been widely used as a treatment agent at home and abroad. It can react chemically with the interface to improve the bonding 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. If aminosilane is used as a treatment agent, the peel strength of the glue joint is 8.7 kg/cm2.

　　3．In terms of bonding rubber with other materials, silane tackifiers have special functions. 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. If silane is added, the peel strength is 7.26 kg/cm2.

　　4. Bonding problems that cannot be solved with ordinary adhesives can sometimes be solved with silane coupling agents. For example, aluminum and polyethylene, silicone rubber and metal, silicone rubber and organic glass, all can be solved satisfactorily by selecting the corresponding silane coupling agent based on the chemical bond theory. For example, vinyl triperoxide tert-butyl silane (Y-4310) can be used to bond polyethylene to aluminum foil; butadienyl triethoxysilane can be used to make the tear-off strength of silicone rubber and metal reach 21.6~ 22.4 kg/cm2.

　　The use of coupling agents with general adhesives or resins 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 bond are not ideal; after adding a silane coupling agent, this performance can be significantly improved. Improve.

　　Other applications of silane coupling agents include:

　　1. Attach the immobilized enzyme to the surface of the glass substrate;

　　2. Sand control during oil well drilling;

　　3. Make the masonry surface hydrophobic;

　　4. By preventing moisture absorption, the fluorescent lamp coating has a high surface resistance;

　　5. Improve the hygroscopicity of the organic phase in the liquid chromatography column on the glass surface.

　　An important newly developed application of silane coupling agents is in the production of water-crosslinked polyethylene. This process was developed by the American company Dow Corning and is currently commercialized. In recent years, in domestic experiments on using silicone emulsion to treat wool fabrics, it was found that the use of silane coupling agents and silicone emulsions can improve the wearing properties of wool fabrics.