In recent years, my country's automobile industry has shown a rapid development momentum. The rapid development of the automobile industry has put forward new requirements for automotive rubber materials and their products, and has also stimulated and driven the development of the rubber industry.
1 Rubber products for automobiles
1.1 Rubber hoses for automobiles
In general, the scale of production enterprises is generally small, the distribution points are scattered, the technical force is weak, the production process and equipment are relatively backward, and the development of new products is slow. From the perspective of production capacity, the supply of ordinary automobile hoses exceeds the demand, while the hoses required for high-end cars are far from meeting the market demand. At present, the localization rate of hoses in joint venture models is less than 40%, and the localization rate of high-end cars is only 5%. Therefore, in the future, the automotive hose industry should keep up with the international trend. Only by accelerating the development of high-performance automobile-specific hose products can the development needs of the automotive industry be met.
1.1.1 Brake hose
Due to the emergence of insurance-free cars, the increase in the working environment temperature of brake fluids and the use of high-boiling-point brake fluids, there is a trend of replacing styrene-butadiene rubber with EPDM rubber in the inner rubber layer of brake hoses. The inner and outer rubber layers of foreign brake hoses are mostly EPDM rubber, and the reinforcement layer uses polyester, polyethanol or rayon fiber. The inner rubber layer can be made of pressure-resistant polyamide, and the outer rubber layer uses chlorosulfonated polyethylene.
1.1.2 Fuel hose
Due to the use of unleaded gasoline and the development towards high oxidation values, the corrosion of fuel to rubber has increased, so the inner layer of the fuel hose must have good fuel resistance. Its inner rubber layer has developed to use fluororubber, chloroether rubber or acrylic rubber instead of nitrile rubber to reduce the permeability of fuel and further improve the heat resistance of rubber.
1.1.3 Power Steering Hose
The development of automobiles has put forward high heat resistance and high durability requirements for hoses. The inner rubber layer should have good oil resistance, and the outer rubber layer should have wear resistance, heat resistance, weather resistance and other characteristics. At present, the inner and outer layers of the hose have been changed from nitrile rubber and chloroprene rubber to hydrogenated nitrile rubber, chlorosulfonated polyethylene rubber, chlorinated polyethylene rubber, and acrylic rubber, and the reinforcement layer is mainly nylon 66.
1.1.4 Radiator Hose
As automobiles develop towards energy saving and low pollution, the temperature of the engine has increased by 15 to 50°C in recent years. Therefore, the radiator hose produced by the sulfur vulcanization system has been gradually replaced by products produced by the peroxide system. The main material used is EPDM rubber.
1.1.5 Turbocharger hose
The main requirement of this hose is good heat resistance. At present, turbocharger hoses abroad use a full rubber structure, that is, the inner rubber layer is composed of fluororubber and heat-resistant silicone rubber, the reinforcement layer is made of high-strength aramid fiber knitting, and the outer rubber layer is made of silicone rubber.
1.1.6 Air conditioning hose
Currently, with the application of new environmentally friendly refrigerant R134a, the structure and material of air conditioning hoses have changed greatly. The inner rubber layer uses resin and chlorobutyl rubber and EPDM rubber, which is the best combination and has a good use effect.
1.2 Automotive Oil Seals
Oil seals are a kind of high-tech precision rubber parts. After nearly a decade of development, the annual demand for oil seals in my country has exceeded 100 billion pieces, of which more than 100 million pieces are used for automotive oil seals for automobile OEMs. There are more than 300 large and small production enterprises, including more than 10 enterprises with an annual production capacity of more than 30 million pieces, more than 3.000 product varieties, and 30% of enterprises have different quantities of exports. The development of the automobile industry has provided a broad market and good opportunities for the development of oil seals. Through the introduction of technology and the adjustment of product structure, my country's oil seal industry has accelerated the application of new technologies and the development of new products. The product performance, quality and variety have been greatly improved, especially the high-tech automotive engine, gearbox, valve oil seals, as well as fluororubber, acrylate rubber, hydrogenated nitrile rubber, polytetrafluoroethylene oil seals and composite special oil seals have made significant progress in manufacturing technology.
It is particularly important that domestic oil seal manufacturers should focus on oil seal fluid dynamics in the future and develop high-performance products with independent intellectual property rights. The future development trend of oil seals is composite oil seals, oil seals made of aluminum skeleton bonded fluororubber using injection vulcanization process, and polytetrafluoroethylene sheets bonded to the lip of the oil seal, and polytetrafluoroethylene oil seals with glass fiber, graphite, molybdenum disulfide, etc. added to polytetrafluoroethylene, which can achieve better use results.
1.3 Automobile sealing strips
At present, my country has more than 60 enterprises producing automobile rubber sealing strips, and has introduced more than 40 advanced automobile rubber sealing strip extrusion production lines from abroad, with an annual production capacity of about 170 million meters and an actual output of about 100 million meters.
The material of rubber sealing strips is basically EPDM rubber. With the rapid development of the automobile industry, more and more new materials are used for automobile sealing strips, especially the superiority of thermoplastic elastomer materials used as automobile sealing strips is recognized by people in the industry. Thermoplastic elastomer materials used in automotive sealing strips are mainly polyolefin thermoplastic elastomers (TPV), which have good wear resistance and low friction coefficient. They can be used not only as extrusion materials for automotive glass guide groove sealing strips, but also as corner materials for automotive sealing strips. In addition, water-foamed sponge-like TPV has been successfully developed abroad and has been widely used in automotive rubber sealing strips, becoming a new trend to replace sponge rubber in the production of automotive sealing strips. In addition, the TPV coloring process is simple and convenient, and is usually used as an external decorative material for automotive rubber sealing strips. At present, the production technology of colored TPV and colored rubber online co-extrusion coated rubber sealing strips has been introduced and applied in several domestic automotive sealing strip manufacturers.
1.4 Automobile transmission belts
Automobile transmission belts are mainly divided into two categories: V-belts and synchronous gear belts. The production of transmission belts for cars in my country, especially synchronous gear belts, started late, and there is still a certain gap in product quality and performance compared with similar foreign products. In 2008. the output of V-belts for automobiles in my country was about 500 million meters, and the output of synchronous belts was about 13 million.
The main materials of foreign automobile V-belts are chloroprene rubber and hydrogenated nitrile rubber, and the skeleton materials are mainly polyester cord and aramid cord; while domestically, chloroprene rubber is mainly used, hydrogenated nitrile rubber is rarely used, and the skeleton materials are mainly rayon and glass fiber. The main materials of domestic automobile synchronous belts are chlorosulfonated polyethylene and hydrogenated nitrile rubber, and the skeleton material is glass fiber, while foreign countries mainly use hydrogenated nitrile rubber/isobutylene acid composite materials, and the skeleton material is aramid cord. Therefore, in the future, the production of domestic transmission belts should be transitioned from traditional chloroprene rubber and chlorosulfonated polyethylene rubber to hydrogenated nitrile rubber as soon as possible, and the skeleton material should be developed and solved based on domestic development, and transition to aramid cord and polyester cord as soon as possible.
1.5 Automobile vibration reduction rubber products
At present, there are hundreds of manufacturers of automobile vibration reduction rubber products in my country, and their products mainly include rubber springs, rubber air springs, frame beams, engine suspension shock absorbers, torsional vibration dampers, etc. It plays an important role in limiting automobile emissions, reducing noise, and improving ride comfort and safety. With the rapid development of the automobile industry, especially the increasing requirements for safety, comfort and easy driving, the amount of automobile vibration reduction products has increased year by year. In addition, the number of high-end cars produced in the future will increase, and the market demand for automobile vibration reduction rubber products will grow faster, so the demand for materials is also diversified. However, it is necessary to choose according to the different parts where the products are used. Considering fatigue resistance and creep performance, natural rubber is often selected; if its heat resistance is to be improved, styrene-butadiene rubber is selected; if the dynamic heat generation is small, butadiene rubber can be selected; if the rubber vibration reduction product is in contact with various oil media during operation, nitrile rubber is selected; due to stricter restrictions on automobile exhaust emission standards, the temperature of the engine and exhaust pipe is increased, and the rubber used in these parts needs to use EPDM with high heat resistance.
The future development direction of my country's automobile vibration reduction products is standardization and serialization, and the focus should be on hydraulic shock absorbers and torsional vibration dampers that have been successfully applied abroad. Improve the level of detection and testing technology, develop new vibration-damping rubber materials, and further improve the heat resistance of rubber vibration-damping materials. Develop new elastomer materials with low dynamic ratio and high damping.
1.6 Other rubber products
In addition to the above-mentioned rubber products for automobiles, other major varieties include brake diaphragms, leather cups and dust covers. The future development focus should be on the use of fluorosilicone rubber and polyester fabric as the skeleton material for the oil supply pressure regulator diaphragm for cars; and the use of chlorinated polyethylene to manufacture automotive diaphragms. As a material for dust covers, the most important requirement is good weather resistance. Constant velocity directional joints generally use chloroprene rubber, but with the improvement of heat resistance, the application of polyolefin thermoplastic elastomers has gradually increased. In Europe and the United States, most cars use polyolefin thermoplastic elastomers to make dust covers. This type of material can not only meet the requirements for weather resistance, oil resistance, and heat resistance, but also achieve lightweight cars.
2 Technical requirements for materials of automotive rubber products
Although some natural rubber and general synthetic rubber are used for automotive rubber products (excluding tires), special rubber with better performance is used in most occasions. Foreign automotive rubber product manufacturers are constantly developing and applying special rubbers with unique performance while using ACM, HNBR, FKM, SI, CHC, chlorosulfonated polyethylene and other special rubbers in large quantities. The fluorosilicone rubbers with the brands of Silastic4-9040. 4-9060 and 4-9080 of Dow Corning Company in the United States have excellent high temperature resistance, fuel resistance and solvent resistance, and are very suitable for the manufacture of automotive hoses and sealing products. Santaprene rubber of AES Company in the United States has been used in sealing products such as automotive sealing strips of Ford, Volkswagen, Toyota and Mercedes-Benz. EPDM/organic silicon modified rubber products developed abroad are superior to silicone rubber in terms of heat resistance, weather resistance, compression permanent deformation performance, etc. They can be vulcanized with sulfur and peroxide, and are suitable for a variety of molding methods. Therefore, they can be used in occasions where silicone rubber or ethylene-propylene rubber cannot adapt (such as automotive vibration reduction materials).
The main materials used in my country's current automotive rubber parts are mostly traditional NR, SBR, CR, NBR and EPDM, while special new rubbers such as ACM, FKM, SI, HNBR (hydrogenated nitrile rubber), TPE (polyurethane elastomer) are only used in small quantities. The main reason is that my country's special rubber products have very little output, and production has not formed scale and serialization. Many varieties need to be imported from abroad, which to some extent restricts and affects the development of my country's automotive rubber products towards high performance and specialization. In the future, with the rapid development of the automotive industry, higher requirements will be put forward for the quality, performance and quantity of automotive rubber products. Therefore, in a sense, it will also stimulate the development of my country's special rubber industry to promote the development of new materials and new products.
