In recent years, China's automotive industry has shown a rapid development momentum, and the rapid development of the automotive industry has put forward new requirements for automotive rubber materials and products, while also stimulating and driving the development of the rubber industry.

1 Rubber products for automobiles

1.1 Automotive hose

Overall, the scale of production enterprises is generally small, with scattered distribution points, weak technical strength, outdated production processes and equipment, and slow development of new products. From the perspective of production capacity, the supply of rubber hoses for ordinary cars exceeds the demand, while the rubber hoses required for high-end cars are far from meeting the market demand. At present, the localization rate of rubber hoses is less than 40% in the joint venture introduced models, and the localization matching rate of high-end sedans is only 5%. Therefore, in the future, the automotive hose industry should keep up with international trends, and only by accelerating the development of high-performance automotive hose products can we meet the development needs of the automotive industry.

1.1.1 Brake hose

Due to the emergence of warranty free cars, the increase in working environment temperature of brake fluid, and the use of high boiling point brake fluid, there is a trend to use EPDM rubber instead of styrene butadiene rubber in the inner rubber layer of brake hose. In foreign countries, the inner and outer rubber layers of brake hose are mostly EPDM rubber, and the reinforcing layer is made of polyester, polyethylene glycol, or rayon fibers. The inner adhesive layer can be made of pressure resistant polyamide, while the outer adhesive layer can be made of chlorosulfonated polyethylene.

1.1.2 Fuel hose

Due to the use of unleaded gasoline and its development towards high oxidation value, the corrosiveness of fuel to rubber increases. Therefore, the inner layer of the fuel hose must have good fuel resistance. The inner rubber layer has developed to use fluororubber, chloroether rubber, or acrylic rubber instead of nitrile rubber to reduce fuel permeability and further improve the heat resistance of the rubber.

1.1.3 Power steering hose

The development of automobiles has put forward requirements for high heat resistance and durability of rubber hoses. The inner rubber layer should have good oil resistance, while the outer rubber layer should have characteristics such as wear resistance, heat resistance, and weather resistance. At present, the inner and outer layers of the rubber hose have shifted from nitrile rubber and chloroprene rubber to hydrogenated nitrile rubber, chlorosulfonated polyethylene rubber, chlorinated polyethylene rubber, and acrylic rubber, with nylon 66 as the main reinforcement layer.

1.1.4 Radiator hose

With the development of automobiles towards energy conservation and low pollution, the temperature of engines has increased by 15-50 ℃ in recent years. Therefore, the heat dissipation hose produced using sulfur vulcanization system has gradually been replaced by products produced using peroxide system, mainly using EPDM rubber as the material.

1.1.5 Turbocharger hose

The main requirement of this hose is to have good heat resistance. Currently, turbocharged hose in foreign countries adopts a full rubber structure, which means that the inner rubber layer is composed of fluororubber and silicone rubber with good heat resistance, the reinforcing layer is composed of high-strength aramid fiber knitting, and the outer rubber layer is made of silicone rubber.

1.1.6 Air conditioning hose

At present, with the application of the new environmentally friendly refrigerant R134a, the structure and materials of air conditioning hoses have undergone significant changes. The best combination of resin, chlorinated butyl rubber, and ethylene propylene diene monomer rubber is used as the inner rubber layer, and its use effect is good.

1.2 Automotive oil seals

Oil seal is a high-tech precision rubber component. After nearly a decade of development, the annual demand for oil seals in China has exceeded 100 billion pieces. Among them, more than 100 million pieces of automotive oil seals have been supplied to automotive OEMs, and there are more than 300 production enterprises of different sizes. Among them, there are more than 10 enterprises with an annual production capacity of over 30 million pieces, and more than 3000 product varieties, 30% of enterprises have different quantities of exports. The development of the automotive industry has provided a vast market and good opportunities for the development of oil seals. Through the introduction of technology and the adjustment of product structure, China's oil seal industry has accelerated the application of new technologies and the development of new products. The performance, quality, and variety of products have been greatly improved, especially for automotive engines, transmissions, valve oil seals with high technological content, as well as fluorine rubber, acrylic rubber, hydrogenated nitrile rubber PTFE oil seals and composite special oil seals have made significant progress in manufacturing technology.

It is particularly crucial for domestic oil seal production enterprises in the future to focus on oil seal fluid dynamics and develop high-performance products with independent intellectual property rights. The development trend of oil seals in the future is composite oil seals, oil seals made of aluminum skeleton bonded fluororubber using injection vulcanization technology, PTFE sheets attached to the oil seal lip, and glass fiber, graphite Molybdenum disulfide and other PTFE oil seals can achieve better performance.

1.3 Sealing strips for automobiles

At present, China has more than 60 enterprises producing automotive rubber sealing strips, and has introduced more than 40 advanced extrusion production lines for automotive rubber sealing strips from abroad. The annual production capacity is about 170 million meters, and the actual output is about 100 million meters.

The rubber sealing strip material is basically EPDM rubber. With the rapid development of the automotive industry, there are more and more new materials used for automotive sealing strips, especially the superiority of thermoplastic elastomer materials used for automotive sealing strips is recognized by industry insiders. The main thermoplastic elastomer materials used in automotive sealing strips are polyolefin thermoplastic elastomer (TPV), which has good wear resistance and low friction coefficient. It can be used not only as an extrusion material for automotive glass guide groove sealing strips, but also as a corner material for automotive sealing strips. In addition, water-based foam like TPV has been successfully developed abroad and widely used in automotive rubber sealing strips, becoming a new trend to replace sponge rubber in making 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. Currently, the production technology of color TPV and color rubber online co extrusion coating rubber sealing strips has been introduced and applied in several domestic automotive sealing strip production enterprises.

1.4 Automotive transmission belt

There are two main types of automotive transmission belts: V-belts and synchronous gear belts. The production of transmission belts, especially synchronous gear belts, for sedans in China started relatively late, and there is still a certain gap in product quality and performance compared to similar foreign products. In 2008, the production of V-belts for automobiles in China was about 500 million meters, and the production of synchronous belts was about 13 million pieces.

The main materials used for the V-belt of foreign cars are chloroprene rubber and hydrogenated nitrile rubber, while the main skeleton materials are polyester cord and aramid cord; In China, chloroprene rubber is mainly used, and hydrogenated nitrile rubber is rarely used. The skeleton materials are mainly made of artificial silk and glass fiber. The main materials for automotive synchronous belts in China are chlorosulfonated polyethylene and hydrogenated nitrile rubber, with a skeleton material of glass fiber. However, in foreign countries, hydrogenated nitrile rubber/isobutyric acid composite materials are mainly used, with a skeleton material of aramid cord. Therefore, in the future, the production of domestic transmission belts should transition from traditional chloroprene rubber and chlorosulfonated polyethylene rubber to hydrogenated nitrile rubber as soon as possible. At the same time, 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 Automotive damping rubber products

At present, there are hundreds of manufacturers of rubber products for automotive vibration reduction in China, mainly including rubber springs, rubber air springs, frame crossbeams, engine suspension shock absorbers, torsional vibration dampers, etc. It plays an important role in limiting car emissions, reducing noise, improving ride comfort and safety. With the rapid development of the automotive industry, especially the increasing requirements for safety, comfort, and ease of operation, the consumption of automotive damping products has been increasing year by year. In addition, the production quantity of high-end sedans will increase in the future, and the market demand for rubber products for automotive damping will grow faster. Therefore, the demand for materials is also diversified. However, it is necessary to choose according to the different parts of the product used, and from the perspective of fatigue resistance and creep performance, natural rubber should be preferred; If you want to improve its heat resistance, choose styrene butadiene rubber; If in situations with low dynamic heat generation, polybutadiene rubber can be used; If rubber damping products come into contact with various oil media during operation, nitrile rubber should be selected; Due to stricter restrictions on automobile exhaust emission standards, the temperature of the engine and exhaust pipes has increased. Rubber used in these areas requires the use of highly heat-resistant EPDM rubber.

The future development direction of shock absorption products for automobiles in China is standardization and serialization, with a focus on hydraulic and torsional shock absorbers that have been successfully applied abroad. Improve the level of detection and testing technology, develop new damping rubber materials, and further improve the heat resistance of rubber damping materials. Develop new elastic materials with low dynamic magnification and high damping.

1.6 Other rubber products

In addition to the rubber products used in automobiles mentioned above, other main varieties include brake films, leather cups, and dust covers. The future development focus should be on using the fuel supply pressure regulator diaphragm for passenger cars made of fluorosilicone rubber and polyester fabric as the skeleton materials; Using chlorinated polyethylene to manufacture automotive membranes. As a material for dust covers, the most important requirement is good weather resistance. Isokinetic directional joints generally use chloroprene rubber, but with the improvement of heat resistance, the application of polyolefin thermoplastic elastomers gradually increases. In Europe and America, most cars use polyolefin thermoplastic elastomers to make dust covers, which not only meet the requirements for weather resistance, oil resistance, and heat resistance, but also achieve lightweight of the car.

2. Technical requirements for materials of rubber products used in automobiles

Automotive rubber products (excluding tires), although some natural rubber and general synthetic rubber are used, most situations use special rubber with better performance. Foreign automobile rubber production enterprises are not only extensively using special rubbers such as ACM, HNBR, FKM, SI, CHC, and chlorosulfonated polyethylene, but also continuously developing and applying special rubber varieties with unique performance. Fluorosilicone rubber with grades Silastic4-9040, 4-9060, and 4-9080 from Dow Corning in the United States has excellent heat resistance, fuel resistance, and solvent resistance, making it very suitable for the manufacturing of automotive hose and sealing products. The Santaprene rubber from AES in the United States has been used in sealing products such as automotive seals from Ford, Volkswagen, Toyota, and Mercedes Benz. The EPDM/silicone modified rubber products developed abroad are superior to silicone rubber in terms of heat resistance, weather resistance, and compression permanent deformation performance. They can be vulcanized with sulfur or peroxide, and are suitable for various molding methods. Therefore, they can be used in situations where silicone rubber or ethylene propylene rubber cannot adapt (such as automotive damping materials).

At present, the main materials used in automotive rubber parts in China are mostly traditional NR, SBR, CR, NBR, EPDM, etc., while special new types of rubber such as ACM, FKM, SI, HNBR (hydrogenated nitrile rubber), TPE (polyurethane elastomer), etc., have only a small number of applications. The main reason is that the production of special rubber products in China is very small, and the production has not formed a scale or series, and many varieties need to be imported from abroad, To some extent, it restricts and affects the development of rubber products for automobiles in China towards high-performance and specialized fields. In the future, with the rapid development of the automotive industry, higher requirements have been put forward for the quality, performance, and quantity of rubber products used in automobiles. Therefore, in a sense, it will also stimulate the development of China's special rubber industry to promote the development of new materials and products.