Development Status and Prospects of Adhesives for Automobiles

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The history of automotive adhesives is almost as long as the automotive industry itself. With the improvement of the performance of automotive adhesives and their manufacturing and application technologies, the automotive industry has become the largest adhesive application field after construction and light industry. Almost all types of adhesives are covered, and the application range is getting wider and wider, and the proportion of the whole vehicle is also getting higher and higher.

Automotive adhesives must meet the life requirements of automobiles under harsh conditions, and need to be resistant to temperature gelation, salt water, fuel, oil, high temperature, vibration, impact, detergent and dust. The application of adhesives can improve driving comfort, noise reduction, vibration reduction, weight reduction, energy consumption reduction, process simplification, and product quality improvement, achieving results that are difficult to achieve with other connection methods.

1. Development background and status quo of automotive adhesives

In 1979, the automobile industry invited Japanese companies to China for the first time to discuss the technology of automotive adhesives. Some special adhesives for automobiles, such as epoxy adhesive, liquid sealant, PVC melt adhesive, and polyurethane adhesive, were all developed during this period. .

After the 1980s, due to the introduction of automotive technology, the bonding and sealing industry has brought greater development, and a number of new and more specialized adhesives have been developed in the process of localization of automotive materials. Such as anaerobic adhesive series products, shock-proof thermal insulation film, wear-resistant silicone adhesive, automotive special ceiling adhesive, carpet adhesive, weld adhesive, double-sided tape, potting adhesive, etc. all belong to this category. At the same time, some larger-scale and more specialized professional adhesive factories have also been built, such as Loctite (China) Company, Henkel Surface Technology Changchun Company, Shandong Kaien New Material Technology Co., Ltd., etc. Except for a very small number of adhesives, a considerable part has been domestically produced.

Second, the application classification of automotive adhesives

1. Adhesive for automobile body

The bonding parts of the automobile body structure include the bonding and sealing of the body, roof, doors and seats.

1.1 Adhesives for Auto Body

(1) Acrylate pressure-sensitive adhesive: pressure-sensitive adhesive refers to an adhesive that can generate adhesive force by appropriate pressure. This adhesive has a certain adhesive force to various materials and has High peel strength, can even be reused. Acrylic pressure-sensitive adhesive is a copolymer of acrylic acid. This adhesive has a simple formula, does not require thickeners, softeners and antioxidants, is non-toxic or low-toxic, and has little degradation in long-term outdoor performance. Therefore, it has become the largest variety in the field of pressure-sensitive adhesives.

(2) SBS type pressure-sensitive adhesive: The main raw materials are SBS and SIS, which are used less.

1.2 Adhesives for Automotive Interiors

(1) Neoprene decorative adhesive

Neoprene rubber is the earliest developed synthetic rubber, with reversible crystallinity, high bonding strength, high tensile strength and elongation, excellent weather resistance and heat resistance, and the prepared adhesive can be cold-cured at room temperature. It has the characteristics of high bonding strength, large initial adhesion, good medium resistance and wide bonding range. However, long-term storage of neoprene rubber will release hydrogen chloride, which will promote its hydrolysis and corrode metals. Therefore, magnesium oxide and light zinc chloride should be added. In order to prevent the aging of the adhesive, an anti-aging agent can also be added.

(2) SBS type decorative adhesive

It has the characteristics of high strength, good toughness, fast curing and low temperature resistance.

(3) Water-based decorative adhesives

High solids content and good bond strength.

There are also polyurethane adhesives.

1.3 Adhesives for Automotive Ceiling Lamps

(1) EVA hot melt adhesive

Currently the largest amount of hot melt adhesive. Taking EVA resin as the base material, the tackifier is glycerol rosin, polymerized rosin, etc., and the plasticizer is polymer paraffin.

(2) SBS hot melt adhesive

The composition is similar to EVA hot melt adhesive, but SBS is used instead of EVA to obtain hot melt adhesive with different properties.

There are also polyamide hotmelts and polyester hotmelts.

1.4 Sealing adhesive for automobile body structure

PU adhesive is an adhesive containing urethane group (NHCOO) and/or isocyanate group (NCO) in the base material molecule. It is the most commonly used sealant, with good wear resistance, adjustable performance, wide application range, high mechanical strength, Low temperature flexibility, excellent recovery, can be used for dynamic seam sealing. However, there are also disadvantages, such as not being able to withstand heat for a long time, and being susceptible to ultraviolet light aging, and primer coating is required in many occasions. The application of polyurethane sealant in automobiles includes the assembly and sealing of windows (windshields), the assembly of body and other parts, etc. In recent years, the annual demand for polyurethane adhesives in my country has grown at an average rate of 30%. In addition, there are rubber-type sealing adhesives and polysulfide sealing adhesives.

1.5 Electric welding sealant

It is pre-coated on the lap joint of steel plate welding, and the gap is filled after spot welding to ensure sealing and prevent rust. Spot weld sealant is even more indispensable for those parts that are masked after assembly and difficult to apply weld sealant. This type of adhesive mainly includes resin-based sealants based on PVC weld sealants and rubber-based electric welding sealants based on styrene-butadiene and butyl rubber.

2. Adhesives for automotive operating systems

The bonding of automobile operating systems mainly includes the bonding of friction plates and clutch plates. This type of adhesive requires high bonding strength, excellent heat resistance, certain toughness, low cost and good process performance.

The adhesives used in the automobile running system are mainly modified phenolic resin adhesives for the bonding of brake pads. Drum brake pad adhesive is to bond the manufactured brake pad and steel back together, generally using nitrile rubber modified phenolic resin adhesive. The disc brake pad adhesive is to press the brake pad powder into a cold embryo and apply glue, and then position it with the glued steel back at a high temperature for a short time, and then perform post-processing at high temperature and no pressure. At present, calcium oxide is used as a catalyst in China. Prepared disc brake pad adhesive. In addition to the above adhesives, the adhesive for clutch can also be bonded with silicone-modified phenolic resin.

3. Adhesives for automotive power systems

The bonding parts of the automobile power system mainly include the tightening and sealing of screws and bolts, and the sealing of cylinder gaskets. In the automobile manufacturing industry, anaerobic adhesives are more often used, which are used for thread tightening and locking, and the fixing of matching parts. , plane bonding, sealing of pipes and flanges and pinhole sealing, which can solve the problems of anti-loosening, anti-leakage, etc., and simplify the assembly process.

Various types of anaerobic adhesives are mainly used in the trachoma produced by the engine casting in the automobile power system, the fastening of various bolts, the sealing of pipelines and the plane sealing . The trachoma generated when the engine is cast is infiltrated with water glass, and the sealing effect is poor, while the infiltration of high temperature anaerobic glue can obtain a good sealing effect. High-strength anaerobic adhesive can be used for engine cylinder head and gearbox stud bolts, as well as bolts that are not often disassembled, collective process body, cylindrical bowl plug drive axle differential case connecting bolts, round shaft gears and differential Fastener fixing bolts, etc. to hold and seal. In addition, automotive gaskets cannot guarantee the sealing performance and the geometric accuracy of the connecting parts, and the use of anaerobic adhesive for plane sealing can solve these problems. Easy-to-remove parts can use low-strength anaerobic adhesives.

4. Adhesives for auto repair

In automobile maintenance, various new adhesives are widely used in automobile corrosion, wear, abrasion, defect repair and thread locking, plane sealing, pipeline thread sealing, cylindrical parts retention, etc., thus prolonging the service life of automobiles , to ensure the normal operation of the car, reduce the consumption of accessories and maintenance costs.

Epoxy glue, phenolic-nitrile glue, etc. can be used for the stressed structural parts such as sheets and bars; for sheet metal and the film is required to be elastic, neoprene glue can be used; screws and nuts are fastened, sealed, and protected. If there is no leakage, anaerobic adhesive can be used; when a small area needs to be quickly bonded, cyanopropionate adhesive can be used. According to the different properties of the non-metallic materials to be bonded, such as elasticity, coefficient of linear expansion and shrinkage, rubber, epoxy, acrylate and polyurethane adhesives can be selected. When bonding plastics, it should be divided into thermosetting or thermoplastic. , Thermosetting plastics can be bonded with epoxy, polyurethane and other adhesives; amorphous plastics in thermoplastics can be bonded with solvents, and crystalline plastics can be bonded with epoxy, polyurethane and other adhesives.

5. Search for the development prospects of automotive adhesives

The continuous application of new materials and new processes in my country's automotive industry has promoted the continuous improvement and specialization of automotive adhesives. The application of adhesives in vehicle manufacturing is in a very important position, the scope of application is also expanding, and the amount is also increasing. With the development of automobiles in the direction of environmental protection, energy saving, safety and comfort, light weight, low cost, long life and pollution-free, the development and application of new high-quality automotive adhesives will become more and more important.

Due to the early start of foreign adhesive brands, they have strong advantages in market share and product technology. In the mid-to-high-end adhesive market, foreign brands currently have a greater degree of competitive advantage upstream. With the strong support of the national industrial policy, the research and development level of domestic adhesive enterprises has been significantly improved in recent years, and the import substitution effect of domestic brand adhesive products will become more apparent.