Nowadays, in automotive industry, it has become an inevitable trend for plastics to replace expensive metal materials. High-strength engineering plastics not only reduce cost of parts processing, assembly and maintenance, but also make cars lighter, energy-saving and environmentally friendly. According to data, plastics and their composites are the most important automotive lightweight materials. It can not only reduce quality of parts by about 40%, but also reduce procurement cost by about 40%. Therefore, its usage in automobiles has also risen rapidly in recent years, becoming "new darling" of automobile manufacturing.

 

At present, the most widely used general-purpose plastics in automotive plastics are polypropylene (PP), ABS resin, polyvinyl chloride (PVC) and polyethylene (PE). Polyolefin materials constitute main plastic parts of automobiles, and several mainstream automotive engineering plastics will be listed below.

PP can be used as a variety of auto parts, and now in a typical passenger car, PP plastic parts account for more than 60. Main varieties of PP auto parts are: bumpers, instrument panels, door trim panels, air conditioner parts, battery shells, cooling fans, and steering wheels, of which the first five account for more than half of PP consumption in the entire vehicle.

A series of modified PE alloy materials with good flexibility, weather resistance and coating performance were obtained through graft modification, filling and toughening modification of high-density PE and low-density PE resins. PE mainly uses blow molding to produce fuel tanks, ventilation pipes, deflectors and various storage tanks.
In recent years, amount of PE in automobiles has basically not increased. It is worth noting that development trend of lightweight automobiles has promoted plasticization of fuel tanks. Plastic fuel tanks are officially used in European cars, and their main material is high molecular weight high density polyethylene (HMWHDPE).

It has excellent friction and wear resistance properties, long-term sliding properties, molding fluidity, surface beauty and gloss properties, and is also suitable for insert molding. Automobile chassis bushings, such as steering knuckle bushings, various bracket bushings, front and rear leaf spring bushings, brake bushings, etc., are widely used POM type three-layer composite materials. It is a three-layer composite material with cold-rolled steel plate as matrix, sintered porous bronze powder as intermediate layer, and modified polyoxymethylene coated on the surface as friction-reducing layer. And rolling out a certain regular oil storage pit, its structure determines its special properties: not only has mechanical strength and rigidity of steel, but also has excellent anti-friction and anti-wear properties under condition of boundary lubrication. Other applications include door handles, seat belt mechanics, combination switches and mirrors.

 

ABS resin is a terpolymer of three monomers of acrylonitrile, butadiene and styrene, which can be used to make exterior or interior parts of automobiles such as instrument housings, refrigeration and heating systems, tool boxes, armrests, radiator grilles panels, etc.; it can also be used to make dashboard skins, trunks, glove box covers, etc.
In recent years, increase in amount of ABS resin used in automobiles is not very large. This is mainly because competition between ABS resin and PP resin is very fierce, and ABS itself also has defects such as poor weather resistance, discoloration and flammability, so it is used in automobiles. Applications in major components such as car dashboards, grilles, etc. are also limited.

Polyamide, commonly known as nylon, has high impact strength, friction and wear resistance, heat resistance, chemical resistance, lubricity and dyeing properties. As automotive structural parts, amount of PA is increasing and can be used in harsh environment around engine.