Compared to most of my friends, silicone materials are also known by relative friends. However, you may not know enough about the material characteristics of silicone materials. Actually, it ’s synthetic rubber. Among the materials, silicone can also be divided into a variety of different compound materials. Different silicone products are made of different silicone materials. Their performance and application fields are not consistent. Do you know their classification? ?

Division of types of silicone rubber materials:

One, dimethyl silicone rubber

Dimethyl silicone rubber is one of the earliest commercially available silicone rubbers. It can maintain good elasticity in the range of -60 to 200 ° C, has good aging resistance, has excellent electrical insulation properties, and is resistant to moisture, shock and Physiological inertia and other characteristics.

Dimethyl silicone rubber is mainly used for coating strong materials. It can also be made into various extruded silicone products and rolled silicone rubber products for mechanical and electrical, aviation, automotive and medical industries. However, due to the low vulcanization activity of dimethyl silicone rubber, it is difficult to vulcanize when used to make thicker and larger silicone products. The inner layer is easy to foam and the high-temperature compression permanent deformation is large. .

Dimethyl vinyl silicone rubber

Since the introduction of a small amount of vinyl in the macromolecular structure of silicone rubber can greatly improve the vulcanization processability of silicone rubber, most of the currently used silicone rubbers contain vinyl. Methyl vinyl silicone rubber is the most common type of silicone rubber, and currently dominates the production of silicone rubber at home and abroad.

Because it introduces partially unsaturated vinyl on the side chain, its processing performance and physical and mechanical properties are better than two base silicone rubbers. In addition to the general characteristics of dimethyl silicone rubber, it also has a wide operating temperature range, which can maintain good elasticity in the range of 60 ~ 260 ℃, it is easier to vulcanize than dimethyl silicone rubber, and has less compression and permanent Deformation, good resistance to solvent expansion and high pressure steam stability, and excellent cold resistance, etc., and because less active peroxides are used for vulcanization, which reduces the occurrence of bubbles and poor rubber stability during vulcanization. weakness.

Methyl vinyl silicone rubber can be used to make thick products. Methyl vinyl silicone rubber products are the most widely used varieties of silicone rubber. In recent years, various high-performance and special-purpose silicone rubbers have emerged. Most are based on vinyl silicone rubber, such as high-strength silicone rubber, Low compression permanent deformation silicone rubber, high temperature vulcanized silicone rubber, heat-resistant conductive silicone rubber and medical silicone rubber and other materials.

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

Three, methylphenyl vinyl silicone rubber

Methylphenyl vinyl silicone rubber is a product obtained by introducing methylphenylsilicone or diphenylsilicone into the molecular chain of methylvinylsilicone rubber.

Introducing a phenyl group on the side group of polysiloxane, because the regularity of the dimethylsiloxane structure is destroyed, the crystallization temperature of the polymer is greatly reduced, and the low-temperature application range of the polymer material is expanded. Therefore, methylphenylvinyl silicone rubber has all the advantages of small compression set, wide temperature range, oxidation resistance, weather resistance, shock resistance, moisture resistance, and good electrical insulation properties. Low temperature resistance, ablation resistance and radiation resistance.

These properties vary with the content of phenyl in the molecular chain. Generally speaking, when the phenyl content (ratio of phenyl to silicon atom) is 5-10%, it is called low phenyl silicone rubber. It has Unique cold resistance, can still maintain the elasticity of the rubber at -70 ~ -100 ℃, is the best low temperature performance of all silicone rubbers, plus it has the advantages of methyl vinyl silicone rubber and the cost is not high, so There is a strong tendency to replace methyl vinyl silicone rubber. When the phenyl content is 20 to 40%, it is said that the medium phenyl silicone rubber has the advantages of methyl vinyl silicone rubber and the cost is not high, so there is a great tendency to replace methyl vinyl silicone rubber.

Medium phenyl silicone rubber is called when the phenyl content is 20 to 40%. It has excellent flame resistance and can be self-extinguished if it catches fire. When the phenyl content is 40-50%, it is called high phenyl silicone rubber. It has excellent radiation resistance and γ-ray resistance is 1xI08 Roentgen. Generally speaking, with the increase of the phenyl content, the rigidity of the silicone rubber molecular chain gradually increases, and the low temperature resistance of the silicone rubber gradually decreases, but with the increase of the phenyl content, the flame resistance and radiation resistance of the vulcanizate are improved.照 性。 According to sex.

Methylphenyl 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. Seals, gaskets, pipes and rods in ablation, heat aging or radiation resistant areas.

Four, fluorine silicone rubber

Fluorosilicone rubber means γ-trifluoropropylmethylpolysiloxane. Fluorosilicone rubber has excellent resistance to chemicals, solvents and lubricants. This silicone rubber has a small expansion rate in non-polar solvents, good cold resistance and thermal stability, and good fire resistance. , Rockets, missiles, spaceflight, petrochemicals used as hoses, gaskets, seals, fuel tanks, etc. in contact with fuel oil and lubricants, and can also be used to make corrosion-resistant clothes, gloves, coatings, adhesives, etc. .

Five, nitrile silicone rubber

Because the polymer side chains contain β-nitrileethyl or γ-nitrilepropyl 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 also greatly improved. The type and content of nitrile alkyl groups have a great impact on performance. For example, silicone rubber containing 7.5 mol% γ-nitrilepropyl has similar low temperature performance to low phenyl silicone rubber (its glass transition temperature is -114.5 ° C). Oil resistance is better than phenyl silicone rubber.

As the content of γ-nitrilepropyl increases to 33-50 mol%, the cold resistance decreases and the oil resistance improves. Using β-nitrileethyl instead of γ-nitrilepropyl 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 resistance. It can maintain elasticity in the range of -60 to 180 ° C. Therefore, it can be made into oil resistant rubber products for aviation industry, automobile industry and petroleum industry. It can also be used as the environmental sealant and fuel tank sealant of high-performance aircraft, which can keep the seal at -54 ℃ to 200 ℃ or more. Nitrile silicone rubber can be processed with ordinary equipment.

Six, phenylene silicone rubber

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

Seven, ethyl silicone rubber

Diethyl silicone rubber made by introducing ethyl group on the side chain of polysiloxane. Its outstanding performance is particularly good cold resistance. Cold resistance 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 the ethyl group is greater than that of the methyl group. Therefore, as the ethyl group content increases, the heat resistance decreases. As the ethyl silicone rubber used at a low temperature, it is preferable that the polymer contains diethylsiloxane chain links at 8 mol%. The operating temperature of ethyl silicone rubber is generally -70--200 ° C.

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 silicone rubber is the poor hydrolytic stability, which was once considered to have no future development. Later, it was found that polymers introduced with cyclodisilazane in the main chain had good thermal stability. Cyclic disilazane-containing elastomers modified with silarylene do not lose weight when heated to 425 ° C in air, and the weight loss is only 10% at 570 ° C, and has good hydrolysis stability.