There are three kinds of rubber materials for automobile sealing strip: compact rubber, sponge rubber and hard rubber. The hardness of hard rubber can reach Shore A95. The rubber compound of the sealing strip is mostly made of EPDM which is resistant to aging, low temperature, moisture and chemical corrosion, especially ozone-resistant aging. EPDM can be compounded with steel belt, steel wire braided belt, TPE, flannel, flocking, PU coating, silicone coating, etc. Grinding and decorative effects. Under normal circumstances, EPDM sealing strips can be used stably for more than ten years. Neoprene rubber (CR) with good ozone resistance and good aging resistance can also be selected. Considering the technical properties of commonly used rubber compounds, it is sometimes necessary to use a combination of rubber, such as natural rubber (NR), CR and styrene-butadiene rubber (SBR), or polyethylene (PE), EPDM and NR. Improved ozone resistance.

In recent years, with the continuous development and maturity of thermoplastic elastomer (TPE) technology, the application fields continue to expand. Among the raw materials for the manufacture of sealing strips, EPDM, the main raw material used in the past, is also constantly being updated and developed. The new EPDM with excellent physical properties and good processability can control the long chain branching in the molecule, make its vulcanization performance better, and improve the extrusion speed and product output. New thermoplastic elastomers such as TPO and TPV are also used more and more in automotive weather strips. These materials not only have the excellent engineering properties of elastomers, but also have the excellent characteristics of plastics, which are easy to process and can be recycled and reused. These materials are gradually replacing EPDM products.

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The commonly used door sealing strip is composed of a co-extruded solid carrier and a tubular sponge sealing strip, and the sponge part is compressed by the door frame of the vehicle body to provide a sealing function. This is the traditional form of sealing, which has been used for many years and generally has satisfactory sealing performance. However, in some cases, this traditional structure may be difficult to achieve sufficient sealing function. For example, when the vehicle speed is very high, the external air pressure may exceed the maximum sealing force provided by the sponge, resulting in sealing failure. In order to solve this problem, a company designed a new type of sealing profile, which introduced magnetic rubber into the sponge body. The method of realization is to extrude a layer of magnetic coating on the sponge body or add magnetic strips to directly play a role with the metal frame of the car body, thereby increasing the sealing function of the sponge body.

For auxiliary materials, mainly carbon black, skeleton materials, reinforcing agents, plasticizers and vulcanizing agents are also constantly developing new products, which are used in the production of automotive seals. Rubber additives are also developing in the direction of high efficiency, energy saving, low pollution and low toxicity.

The automotive weather strip industry is increasingly developing into an important part of the automotive industry. With the continuous development of China's automobile industry, the automotive rubber sealing strip industry must also continue to innovate, actively apply new materials, new processes, and new equipment, and constantly develop new rubber sealing strip products to meet the needs of different users.

The car body has a very important seal, which is a sealing strip made of synthetic rubber, also known as a protective molding insert. Mainly used in door frames, side windows, front and rear windshields, engine covers and trunk lids, and play a role in sealing, and also play a role in vibration reduction protection.

The sealing strip is mainly made of polyvinyl chloride (PVC), ethylene propylene rubber (EPDM), synthetic rubber modified polypropylene (PP-EPDM), etc., which are made by extrusion molding or injection molding.

The sealing strip of the compartment door mainly refers to the sealing strip of the door frame and the sealing strip of the door headway. The door frame sealing strip, as the name suggests, is the sealing strip inlaid on the door frame. The door frame sealing strip must not only ensure the sealing performance, but also bear the impact force when the door is closed. Therefore, it must have both elasticity and toughness. It is mainly composed of a dense rubber matrix and a sponge rubber foam tube. The compact adhesive contains a metal skeleton, which strengthens the shaping and fixing of the adhesive strip. The sponge rubber foam tube is soft and elastic, and plays the function of deformation under pressure and rebound after pressure relief. In addition, the lip part of some sealing strips is made of colored glue or pasted with fabric, and the color tone is beautiful and decorative.

There are two structures of the door headway sealing strip, one is a full sponge rubber foam tube, and the other is composed of a dense rubber matrix and a sponge rubber. The sealant is pasted or inlaid on the car door, and cooperates with the door frame sealing strip to increase the sealing effect between the car door and the car body. The door headway sealing strip is not used in every car, for example, some economical cars do not have it, which is mainly from the perspective of cost saving.

The sealing strip of the engine cover is composed of pure sponge rubber tube or sponge rubber bubble tube and dense glue, which is used for sealing the engine cover and the front part of the vehicle body. The sealing strip of the trunk lid or the back door is composed of a dense rubber matrix with a skeleton and a sponge rubber foam tube, which can withstand a certain impact force and ensure the sealing when the back cover is closed.

The window sealing strips are divided into front and rear windshield sealing strips, window glass guide groove sealing strips and inner and outer window strips.

The front and rear windshield sealing strips are surrounded by pure rubber strips, which have elasticity and considerable hardness, and play the role of cushioning, fixing and sealing between the windshield and the car body. The window glass guide groove sealing strip is composed of dense glue with different hardness, which is embedded into the body to ensure the accuracy of size matching, and achieve the functions of sealing, leakage prevention and sound insulation. The lip of the sealing strip is also pasted with a flocking surface, which can reduce the sliding friction between the glass and the rubber strip when the glass moves up and down, and can also reduce noise. This form of weatherstrip is also used for sunroof weatherstrips. The inner and outer strips of the window are composed of pure plastic strips or pure plastic strips and plastic parts. It has a flocking surface, which not only reduces the friction with the glass, but also plays a decorative role.

Due to the complex geometry of doors, covers and windows, special-shaped sealing strips are often used at corners. Therefore, vehicle sealing strips have special sealing strips such as corner joint type and variable section type. Conventional sealing strips and special sealing strips are connected at both ends or single-ended by molding, which can meet the requirements of the overall sealing strip at the corners. And the installation needs of special shape parts.

In the past, the production of sealing strips used manual compression molding, the process was simple and backward, and the shape was single, mostly H-shaped. The current sealing strip production adopts computer-controlled extrusion molding or injection molding technology, including compound extrusion, variable diameter extrusion, microwave vulcanization, surface spraying and other technologies. For example, under the control of the computer, the variable-diameter extrusion technology can change the size and shape of the cross-section during the extrusion process of the sealing strip, and the shapes are various and completed in one go. In this way, the sealing strip can be close to the body, and the sealing effect is good.

Rubber seals must have good mechanical strength, elasticity, oil resistance, water resistance and non-deformation characteristics, which is the key to ensuring that the engine, chassis and other parts do not seep oil and water. Now some good quality rubber seals produce durable "rubber elasticity" through cross-linking (vulcanization), and have a service temperature range from -50℃ to 180℃ according to different varieties to adapt to different installation parts.

Over the years, the production of rubber sealing products in China has always kept pace with the automotive industry, but in recent years, China's automotive industry has entered a stage of rapid development, and the rubber sealing product industry has been relatively lagging behind. The service life of foreign rubber oil seal products has been more than 150,000 kilometers, and the operating temperature has reached 150-200 ℃. The service life of domestic oil seal products is only 50,000-80,000 kilometers at a working temperature of 120 ° C, and the oil leakage rate is 3-5 times that of foreign countries. In addition, foreign rubber sealing strips have been made of EPDM rubber, and the service life is also more than 150,000 kilometers. However, the EPDM rubberization of domestic seals has not been fully popularized, and some seals made of chloroprene-natural rubber have a service life of only 30,000-50,000 kilometers.

Intelligent rubber products have been developed abroad. Chinese sealing strip enterprises should pay attention to the development trend of the world's polymer intelligent materials and intelligent rubber products in a timely manner, develop intelligent rubber sealing strips with intellectual property rights, and enhance the competitiveness of enterprises.

Rubber materials for automotive seals

At present, the materials used in rubber sealing products in the automobile manufacturing industry are mainly fluorine rubber, silicone rubber, acrylate rubber, butadiene rubber, EPDM rubber, chlorohydrin rubber and hydrogenated butadiene rubber.

Silicone Rubber

The service life of automotive engine silicone rubber sealing products can meet the harsh requirements of more than 10 years and 150,000 kilometers. In recent years, new varieties of silicone rubber without secondary vulcanization have been successfully developed. A breakthrough has been made in the research on the application of high temperature resistant silicone rubber formulated with nanometer rare earth element oxides, which has increased the heat resistance temperature of the silicone rubber by 50°C and improved the adhesiveness and mechanical strength of the silicone rubber.

Silicone rubber is widely used in sealing products. The main products include automobile engine crankshaft rear seals, fuel pump seals, air conditioner compressor seals, potentiometer insulating bushings and potting materials. According to news in March 2003, a series of high-performance thermoplastic elastomers developed by Dow Corning have the potential to replace hot vulcanized rubbers such as Ding Yueqing rubber and hydrogenated Ding Yueqing rubber in engine compartment seals, gaskets and hoses for automotive applications. The silicone rubber-based material, called TPSiV, is priced at $10-15/kg depending on grade and product. This material is a dispersion of fully vulcanized silicone rubber particles in an engineering thermoplastic phase. The continuous ETP phase can be polyamine or an undisclosed proprietary technology material. This new TPE combines the good high and low temperature properties of silicone rubber with the typical hot melt processability and chemical resistance of ETP, and can be melt repeatedly processed, reducing total material consumption and being recyclable. They do not replace styrenic TPEs and DPDM/PP TPVs, but are used where performance requirements cannot be met by these two types of materials. In addition, TPSiV can replace high-performance organic thermally vulcanizable rubber.

fluororubber

Fluorine rubber has excellent high temperature resistance and resistance to various harsh corrosive media, and is widely used in rubber sealing products. At present, the annual output of fluororubber in the world is about 10,000 tons, of which 70% is used in rubber sealing products, mainly used in automotive products. At present, various special properties of fluororubber have been successfully developed, including phosphorus fluororubber with a fluorine content of 30-40%, fluororubber with low temperature resistance up to -66°C, fluoroether rubber with excellent hydrogen sulfide resistance, and There are fluororubbers that can greatly improve the productivity of products and do not require secondary vulcanization. Fluorine rubber sealing products are mainly used in oil seals, O-rings, gaskets, fuel pump seals, etc. Due to the unsatisfactory mechanical strength and tear resistance of fluororubber, the process performance is not easy to master, which affects the popularization and application of fluororubber in a wider range of fields.