1 General situation of application of automobile adhesives and sealants

 

From the point of view of the working parts and functions involved in the whole manufacturing process of automobiles, automotive adhesives can be roughly divided into five categories: welding adhesives, coating adhesives, interior adhesives, assembly adhesives and special process adhesives. This paper briefly introduces the application of various adhesives in the automotive manufacturing industry based on the specific situation of Dongfeng Automobile Company.

 

Welding technology

 

Sealing adhesives such as adhesives are used to replace spot welding or reduce welding joints in welding process. They play an important role in strengthening structure, sealing rust prevention, vibration and noise reduction. Generally, they are required to have good adhesion with oil surface steel plate. Because there is no special heating and curing equipment in each work station, it needs to be cured under the condition of automobile body paint technology. Therefore, it is not required to be affected by cleaning solution and phosphating solution, nor the quality of electrophoretic paint. Its main varieties are:

 

(1) Flanging glue: It is used in the curling structure of doors, engine hood cover, luggage case cover and so on. Its bonding strength is high and it has completely replaced spot welding structure. At present, one-component epoxy resin is widely used in this kind of adhesive, and the bicycle consumption is about 200 g.

 

(2) Spot welding sealant: pre-coated on the overlap of steel plate welding, filling the gap after spot welding, ensuring sealing and preventing rust. Spot welding sealant is indispensable for those parts which are covered after assembly and are difficult to coat sealant.

 

(3) Expansive shock absorber: This kind of adhesive is often used between the inner and outer panels of the door and between the outer panels of the body and the reinforcing ribs. It is generally made of synthetic rubber or resin with foaming agent. After curing and expansion, it can combine the panel with reinforcing bars and reduce vibration and noise. The rubber content of Dongfeng EQ1030 bicycle is about 400 G.

 

 

 

 

1.2 Coating Process

 

Although there are not many kinds of glue used in the glue coating process, it is the largest type of glue used in automobiles. Bicycle usage: about 2 kg for trucks and more than 5 kg for cars. There are mainly weld sealants and stone-resistant coatings, whose base material is PVC plastic sol. Although the performance of the two coatings has different emphasis, the process requires that mechanical coating or spraying can be carried out through high-pressure glue-coating equipment. Comparatively speaking:

 

(1) Weld sealant has more prominent thixotropy. It can keep edges and corners when it is stacked with a certain thickness, and does not produce flow. After heating and plasticizing, the adhesive layer is elastic, non-cracking, smooth in appearance, and can not produce discoloration phenomenon in the middle coating and finish paint. Weld sealant plays an important role in automobile sealing, leak-proof and rust-proof.

 

(2) The anti-Stone coating is sprayed on the chassis of automobiles to buffer the impact of sand, stone and other objects on the chassis during high-speed driving, improve the anti-corrosion ability of the chassis, prolong the service life, and help to reduce the noise in the car and improve the comfort of the passengers.

 

1.3 Glue for Internal Decoration

 

There are many kinds of materials, different properties and different application occasions for automotive interior decorations, so it is difficult to generalize the different types of rubber. Some of the important varieties are introduced.

 

(1) Body roof glue: used to paste soft roof material onto the body roof to increase the beauty of the car interior. At present, most of the adhesives for this purpose in China are solvent-based neoprene, which requires high initial adhesion in technology and performance to meet the needs of fast-paced production line of automobile body interior decoration, and do not cause discoloration and exfoliation of interior materials.

 

(2) Butyl sealant tape: It is made of butyl rubber with tackifying resin and extruded into strip type. Its characteristics are: easy finger pressing, good adhesion with steel plate and waterproof film, long-term viscoelasticity and sealability can be maintained. It is mainly used for the bonding and sealing of waterproof film on the inner panel of the door to prevent rainwater from infiltrating into the interior of the door. The amount of single door tape used on automobiles is about 2m.

 

(3) high frequency heating adhesive: Fukang car uses high frequency heat glue as modified acrylic emulsion. When molding the door guard, the fiberboard processed by dipping (about 30g) is melted in a short time under high frequency electric field, and is firmly bonded with PVC foam under the specified pressure.

 

(4) Windshield adhesives: These adhesives are usually polyurethane-based, used together with cleaning agents, paint/glass primers, with high shear strength and outstanding elasticity. They can tightly integrate glass and body into a whole, enhance body rigidity, ensure sealing effect and improve vehicle safety. Taking Fukang as an example, the bicycle consumption is about 1.2 kg.

 

1.4 Adhesive for Assembly

 

Adhesives and sealants for assembling automobile engines, gearboxes and chassis are mainly applied in various plane joints. Sealing of the hole-cap pipe joints and bolt locking can prevent oil, water and gas leakage and bolt loosening, which directly affect the normal operation of automobiles. The main varieties of this kind of adhesives are anaerobic adhesives, silicone sealants and so on.

 

(1) Anaerobic Adhesive: Its characteristics are simple coating process, fast curing speed and good locking and sealing performance. According to different requirements, three process methods can be adopted: on-site coating, pre-coating and infiltration. Among them, microencapsulated anaerobic adhesive with high strength can be coated, which is especially suitable for the fast rhythm requirement of mechanical coating of a large number of threaded connectors on automobiles. According to our company's annual automobile production estimates, the annual rubber consumption is close to 2 tons.

 

(2) Silicone sealant: It is used for flat seals with unique characteristics, good elasticity, oil resistance, heat resistance, aging resistance, simple gluing process, strong peelability, easy disassembly, can replace gaskets used alone, good sealing effect.

 

1.5 Adhesive for Special Process

 

In the process of automobile manufacture, various adhesives with different uses are also used, such as brake shoe glue for bonding brake shoe and friction disc. It is mainly a modified phenolic resin adhesive, instead of riveting, which has reliable bonding strength, can reduce noise and prolong the service life of friction disc.