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Overview of the development of fluorine rubber and silicone rubber


Both fluorine rubber and silicone rubber are special synthetic rubbers. Compared with general synthetic rubbers used to manufacture general rubber products, special synthetic rubbers are mostly used in special environments and high-tech fields because of their high temperature resistance, low temperature resistance, acid and alkali resistance, and radiation resistance. At the beginning of their development and application, they were used as supporting equipment for the military industry. Later, due to their excellent performance, they were promoted to the civilian field, and quickly penetrated into all aspects of people's production and life, greatly improving the production process and people's living environment, and showing broad development. prospect.

Simply put, fluorine rubber is resistant to high and low temperatures, is not afraid of acid and alkali, and has the best oil resistance among oil resistant rubbers. It has good radiation resistance and high vacuum performance and comprehensive performance. The disadvantages are poor processability, high price, poor cold resistance, low elasticity and air permeability.

Silicone rubber is currently the best high and low temperature resistant rubber, with good electrical insulation, good resistance to thermal oxidation and ozone, chemical inertness and biocompatibility. The disadvantage is low strength, poor solvent resistance and acid and alkali resistance.

1 Fluorine rubber

1.1 The main performance and application of fluorine rubber

From the perspective of the main chain structure, fluoroelastomers can be divided into three basic types: fluorocarbon rubber, fluorosilicone rubber, and fluorophosphazene rubber. Among them, fluorocarbon rubber is the main one, and among them, the copolymer of vinylidene fluoride and chlorotrifluoroethylene (type 23), the copolymerization of vinylidene fluoride and hexafluoropropylene (type 26), vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene Mainly ternary copolymerization (type 246).

Type 23 fluororubber is mainly used to prepare heat-resistant and strong acid-resistant rubber products, such as seals, hoses, rubber pads, tapes, tapes, films, fuel tanks and impregnated products, etc. It can also be used as the outer sheath of wires and equipment anti-corrosion. Lining, etc., are widely used in aviation, petroleum, automotive and chemical industries.

Type 26 fluororubber is the most used fluororubber variety, mainly used for heat-resistant, oil-resistant, and acid-resistant rubber products. The product can be used for a long time at 200°C and for a short time at 300°C, and its oil resistance is better than other types of fluorine rubber. It can be used for O-rings, V-rings, oil seals with metal skeletons, valve gaskets, etc. that work for a long time at 200~250℃; in drilling machinery, oil refining equipment, natural gas desulfurization equipment, it is used to withstand high temperature, high pressure, Seals for oils and strong corrosive media; used as seals for pumps, pipe joints, equipment containers, and seals chemical substances such as inorganic acids and organics.

Type 246 fluorine rubber is widely used in aerospace, automobile, machinery, petrochemical and other fields. For example, it can be used as the static and dynamic sealing material of the hydraulic system and lubrication system of the aircraft; used as the sealing material on the cable transmission pipeline of the oil field and the lead well equipment; used as the lining of the chemical equipment, the flexible connection of the pipeline, the pump or the corrosion-resistant seal Materials, made into pipelines to transport organic solvents or other corrosive media, etc.

At present, the fluororubber varieties produced by several domestic manufacturers are still dominated by the traditional 23, 26, and 246 fluororubbers. Among them, a chemical research institute started to produce a variety of fluorine-containing monomers from fluorite, and then obtained different varieties and different grades of fluorine rubber through binary and multi-component copolymerization. The domestic production technology is synchronized with the international one. The used Freon dilution and cracking monomers, continuous polymerization to produce fluorine rubber with different fluorine content, wide molecular mass distribution and control technology, low Mooney rubber production and other processes have reached or approached the international Advanced level.

2 silicone rubber

Silicone rubber is the largest and most widely used category of silicone products. It is a linear polysiloxane with high molar mass before vulcanization. Since the Si-O-Si bond is the basic bond type, the intermolecular force is small, the molecules are in a helical structure, and the methyl groups are arranged outwards and can rotate freely. After vulcanization, the silicone rubber has excellent resistance to high and low temperatures, weather resistance, and Hydrophobicity, arc resistance, electrical insulation, physiological inertia, etc., are widely used in national defense industry, medical and health, industrial and agricultural production and people's daily life.

There are many ways to classify silicone rubber. Usually, it is divided into solid silicone rubber and liquid silicone rubber according to the form before curing; it is divided into room temperature vulcanized silicone rubber and high temperature vulcanized silicone rubber according to the vulcanization temperature; according to the different monomers used, it can be divided into methyl Vinyl silicone rubber, methyl phenyl vinyl silicone rubber, fluorosilicone, nitrile silicone rubber, etc.; can be divided into general type, ultra low temperature resistant type, ultra high temperature resistant type, high strength type, and oil resistant according to different properties and uses. Type, medical type, etc.

2.1 Main properties and applications of silicone rubber

According to the vulcanization temperature, silicone rubber can be divided into high temperature (heating) vulcanization type and room temperature vulcanization type. High temperature rubber is mainly used to manufacture various silicone rubber products, while room temperature rubber is mainly used as an adhesive, potting material or Mold use.

Thermally vulcanized silicone rubber (HTV) is the most important category of silicone products, and methyl vinyl silicone rubber (VMQ) is the most important category in HTV, commonly known as high temperature rubber. Methyl vinyl silicone rubber (raw rubber) is a colorless, odorless, non-toxic, and no mechanical impurities. The raw rubber is mixed with appropriate reinforcing agents, structure control agents, vulcanizing agents and other additives as needed. Refining, then heating and compression molding or extrusion molding, and then two-stage vulcanization into various products. Its products are mainly used in aviation, instrumentation, electronic appliances, navigation, metallurgy, machinery, automobiles, medical and health and other industries. It can be used to make various shapes of sealing rings, gaskets, tubes, cables, and can also be used for human organs, blood vessels, and ventilation. Film and rubber molds, mold release agents for precision casting, etc.

Room temperature vulcanized silicone rubber (RTV) generally includes two categories: condensation type and addition type.

Addition type room temperature glue is based on a linear polysiloxane with vinyl groups, and hydrogen-containing siloxane is used as a crosslinking agent. In the presence of a catalyst, a crosslinking reaction occurs at room temperature to medium temperature to become an elastomer. It has good heat resistance, water repellency, and electrical insulation. Because of its high conversion rate, easy control of cross-linking density and cross-linking speed, its overall performance is better. It is suitable for a variety of vulcanization methods, such as radiation vulcanization, peroxide vulcanization, and addition molding vulcanization. It is widely used in heat resistance, moisture resistance, electrical insulation, and high-strength silicone rubber products.

Condensation-type room temperature vulcanized silicone rubber is characterized by the condensation reaction between silicone hydroxyl and other active substances, which can be cross-linked to become elastomers at room temperature. The products are divided into one-component packaging and two-component packaging. form. One-component room temperature vulcanized silicone rubber (RTV-1 rubber for short) is one of the main products in condensed liquid silicone rubber, which is usually formulated from basic polymers, crosslinking agents, catalysts, fillers and additives. The product is packaged in a sealed hose, squeezed out during use, and can be vulcanized into an elastomer after being exposed to air, which is extremely convenient to use. Vulcanized rubber can be used for a long time at -60~200℃, has excellent electrical insulation properties and chemical stability, is resistant to water, ozone, and weathering, and has good adhesion to a variety of metal and non-metal materials. It is mainly used for coating various electronic components and electrical equipment. The encapsulating material has the functions of insulation, moisture-proof and shock-proof; it can be used as a surface protection material for semiconductor devices, and can also be used as a sealing filler and elastic adhesive.

Two-component room temperature vulcanized silicone rubber (RTV-2 rubber for short) is not as convenient as RTV-1 rubber, but its component ratio is rich in changes. One variety can obtain vulcanized products with multiple specifications and properties, and it can also be deeply vulcanized. Therefore, it is widely used in electronics, automobiles, machinery, construction, textile, chemical, light industry, printing and other industries for insulation, encapsulation, caulking, sealing, moisture-proof, anti-vibration and making rollers. In addition, because RTV-2 glue has excellent mold release properties, it is widely used in the reproduction and manufacture of cultural relics, handicrafts, toys, electronic appliances, and mechanical parts.

One of the typical applications of silicone sealants is glass curtain walls. The glass and aluminum alloy frame are bonded with organic silicon structural adhesive as the exterior wall material, and the expansion joint is waterproof and sealed with organic silicon weather-resistant adhesive. Other applications include the peripheral sealing of aluminum alloy doors and windows and plastic steel doors and windows, the joints of glass installation and moving grooves, the sealing of rivets and fixing screws, the sanitary ware and countertops, walls, and furniture of kitchens, bathrooms, and toilets. Waterproof sealing between aquariums, ceilings, metal roofs, showcases, counters, wall panels, color steel plates, and waterproof caulking sealing between high-grade highway plates, etc.

RTV, in addition to sealants for construction, also includes sealing materials used in aerospace, nuclear power plants, electronics, machinery, automobiles and other industries, silicone potting materials used for potting electronic components, and organic materials used as soft mold materials. Silicone mold glue, etc. The demand for these varieties is relatively small, but they are indispensable on many occasions.

2.2 The development status of my country's silicone rubber industry

Since Dow Corning first realized the industrial production of organochlorosilane in 1943, after years of development, Dow Corning, GE, RP, Wacker, ShinEtsu, etc. have been formed in the current international silicone market. A situation of multiple competitions. There are more than 10 large-scale organic silicon companies in the world, and the production scale of methylchlorosilane is increasing. Various silicone oils and secondary processed products, silicone rubber, silicone resin, silane coupling agent, silane surfactant, etc. Widely used in various industrial sectors, there are more than 5,000 varieties and specifications of organic silicon products, and the output and sales are increasing day by day. In the past 30 years, the growth rate of organic silicon industrial products has remained at 8% to 15%, far exceeding the growth rate of the national economy of general countries. At present, organic silicon has been widely used in my country, with continuous growth in quantity and variety, and continuous expansion of application fields. my country has become the most potential market for organic silicon products.

2.2.1 Heat vulcanized silicone rubber

Due to the different industrial structures in various countries and regions, the market structure of silicones is also different. For example, silicone rubber in the United States accounts for 25%-30% of the silicone market, 40% in Europe, and more than 50% in Japan. Nearly half of them are hot Vulcanized silicone rubber, my country's silicone rubber accounts for a larger proportion, about 60%. In my country, thermally vulcanized silicone rubber is mainly used in office automation equipment, electrical and electronic industries and automobile industries. With the development of the national economy, the demand for thermally vulcanized silicone rubber is increasing at a rate of not less than 20% per year.

The production technology of thermally vulcanized silicone rubber is complex and the added value of the product is high. In the world silicone market, its sales share is about 10%. The use of thermally vulcanized silicone rubber can be roughly divided into: extrusion molding products accounted for 35%, molded products accounted for 30%, wire and cable accounted for 30%, coating materials accounted for 5%, consumption growth rate of 4% to 6%.

For civilian use, milk bottle pacifiers, thermos bottle stoppers, pressure cooker gaskets, and hoses for food vending machines made of thermally vulcanized silicone rubber have been widely used, and some raw rubber and rubber compounds have been exported abroad.

In the field of modern medicine, silicone rubber has obtained a very wide range of important uses. It can be used as a drug release carrier attached to the skin or implanted in the human body, and used to make silicone rubber anti-noise earplugs, silicone rubber fetal head suction devices, artificial blood vessels, Tympanic membrane repair patch, artificial trachea, artificial lung, artificial bone, silicone rubber duodenal tube, etc., are very effective.

2.2.2  RTV Silicone Rubber

Room temperature vulcanized silicone rubber is mainly used as adhesive sealant, potting material and mold. The largest amount is the sealant (commonly known as "glass glue") in the construction and decoration market, which is mainly used in new building forms such as glass curtain walls and high-rise buildings. The adhesive seal. In developed countries, the consumption of silicone sealants has mostly maintained an annual growth rate of more than 10% in recent years. According to statistics, the consumption of silicone sealants in my country in 2000 reached more than 50,000 tons, and the annual growth rate was 20% to 30%.

In recent years, with the improvement of technology and the expansion of market demand, the production of silicone sealants has developed rapidly, and two major silicone sealant production bases have been formed in Zhejiang and Guangdong. With the technological advancement of the silicone industry, the quality of domestic silicone structural adhesives has been greatly improved, and the price of domestic structural adhesives is much lower than that of imported adhesives, making domestic adhesives an absolute advantage in terms of performance and price ratio. On the other hand, domestic manufacturers provide timely delivery and can provide users with fast and thoughtful services. Domestic brands have used them well in the past few years and have won more and more users. The market share of domestic structural adhesives is increasing year by year.

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