Thorough understanding of silicone rubber, how to distinguish the material of silicone rubber products.teethers silicone toys price

　　High-temperature vulcanized silicone rubber is a polyorganosiloxane (that is, raw rubber) with high molecular weight (molecular weight is generally 400,000 to 800,000), adding reinforcing fillers and other various additives, using organic peroxide as a vulcanizing agent, and press molding (Molding, extrusion, calendering) or injection molding, and cross-chained into rubber at high temperature. This 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 the raw silicone rubber, reinforcing agent, additive, vulcanizing agent and structure control agent, and then add the mixed material in the metal mold. Pressure heating molding and vulcanization, the pressure is about 50 kg/cm2, the temperature is 120 ~ 130 ° C, and the time is 10 ~ 30 minutes. Bake at 250°C for several hours to 24 hours. The rubber is further vulcanized, while the organic peroxide is decomposed and volatilized.

　　The reinforcing filler for silicone rubber is various types of silica, which can increase the strength of the vulcanizate tenfold. Adding various additives is mainly to reduce the cost of the rubber, improve the properties of the rubber, and give the vulcanized rubber various special properties such as flame retardant and electrical conductivity. The cross-linking agent is various organic peroxides, such as benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, 2,5-di-tert-butylperoxyhexane, etc. .Structure control agent is added in order to avoid the long time of mixing the rubber compound, resulting in "structure" and making the rubber compound hard and hard, and difficult to process and mature. Methyl hydroxy silicone oil or diphenyl dihydroxy radane can be used. as a structural control agent.

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

　　1. Methyl silicone rubber

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

　　Dimethyl silicone rubber is mainly used for the coating of strong objects, and can also be made into various extrusion and calendering products for electromechanical, aviation, automobile and medical industries. However, due to the low vulcanization activity of dimethyl silicone rubber, when it is used to manufacture thick products, it is difficult to vulcanize, the inner layer is easy to foam and the permanent deformation of high temperature compression is large, so it has been replaced by methyl vinyl silicone rubber at present.

　　2. Methyl vinyl silicone rubber

　　Since the introduction of a small amount of vinyl groups into the macromolecular structure of silicone rubber can greatly improve the vulcanization processability of silicone rubber, most of the currently used silicone rubbers contain vinyl groups. Methyl vinyl silicone rubber is the most common type of silicone rubber and currently dominates the production of silicone rubber at home and abroad. Due to the introduction of a partially unsaturated vinyl group on the side chain, its processability and physical and mechanical properties are superior to those of two-base 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, better solvent expansion resistance and high pressure steam resistance stability and excellent cold resistance, etc., and because of the use of peroxides with lower activity for vulcanization, it reduces the generation of bubbles during vulcanization and poor rubber stability. weakness. Therefore, methyl vinyl silicone rubber can generally be used to make products with larger thicknesses. Methyl vinyl silicone rubber is the most widely used variety of silicone rubber. In recent years, various high-performance and special-purpose silicone rubber products have emerged, mostly based on vinyl silicone rubber, such as high-strength silicone rubber, Low compression set silicone rubber, no post-vulcanization silicone rubber, heat-resistant conductive silicone rubber and medical silicone, etc.

　　In the aviation industry, methyl vinyl silicone rubber is widely used as a protective layer for gaskets, sealing materials and fragile and shock-proof parts; in the electrical industry, it can be used as advanced insulating materials such as electronic components, dynamic sealing rings for high temperature potentiometers, Sealing ring for underground long-distance communication equipment; in medicine, because methyl vinyl silicone rubber has little physiological response to the human body and is non-toxic, it is used for surgical plastic surgery, artificial heart valves, blood vessels, etc.

　　3. Methylphenyl vinyl silicone rubber

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

　　Methylphenylvinyl 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 silicone products and extruded silicone products. Sealing rings, gaskets, pipes and rods for ablation, heat aging or radiation resistant parts.

　　4. Fluorosilicone rubber

　　Fluorosilicone rubber refers to γ-trifluoropropyl methyl polysiloxane. Fluorosilicone rubber has excellent chemical resistance, solvent resistance and lubricating oil resistance. 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 used as contact hoses, gaskets, seals, fuel tanks, etc. with fuel oil and lubricating oil, and can also be used to make corrosion-resistant clothes, gloves, coatings, adhesives, etc. .

　　5. Nitrile Silicone Silicone Rubber

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

　　6. Phenylene silicone rubber

　　The main feature of phenylene silicone rubber is that it has 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 for Aerospace industry, atomic energy industry and nuclear reactors are used as cables, sheaths, gaskets and heat shrinkable tubes that are resistant to high-energy radiation.

　　7. Ethyl silicone rubber

　　The diethyl silicone rubber prepared by introducing an ethyl group into the side chain of polysiloxane has the outstanding performance of particularly good cold resistance, which is better than dimethyl silicone rubber and general methyl vinyl silicone rubber. The higher the ethyl content, the better the cold resistance. However, the reactivity of ethyl group is higher than that of methyl group, so the heat resistance decreases with the increase of ethyl group content. As the ethyl silicone rubber used at low temperature, it is preferable that the polymer contains 8 mol% of diethylsiloxane mers. The use temperature of ethyl silicone rubber is generally -70--200 ℃.

　　Eight, silicon nitrogen rubber

　　The main advantage of silicon nitrogen rubber is that it has excellent thermal stability, it does not decompose at 430-480 °C, and some can even withstand high temperatures above 500 °C. The outstanding weakness of silicon-nitrogen rubber is its poor hydrolytic stability, which was once considered to have no future. It was later found that the polymer with cyclodisilazane incorporated into the main chain has good thermal stability. The cyclodisilazane-containing elastomer modified with silicon arylene does not lose weight when heated to 425°C in air, but only loses 10% at 570°C, and has good hydrolytic stability.

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