Main function of engineering plastics used in automobiles is to lighten weight of automobiles, so as to achieve purpose of fuel saving and high speed. Developed countries regard amount of plastic used in automobiles as an important indicator to measure level of automobile design and manufacturing. Germany has the largest single consumption of automobile plastics in the world, and amount of plastics accounts for 15% of the overall material.

 

In recent years, my country's automobile industry has developed rapidly. At present, annual output of automobiles exceeds 4 million. According to forecast of foreign plastic consumption, annual use of modified plastics in automobile industry is more than 500,000 tons, of which engineering plastics account for a large proportion. Performance characteristics of five major engineering plastics are different, and their uses in automobiles are also different.

Nylon is mainly used in automobile engines and engine peripheral parts, main varieties are GFPA6, GFPA66, enhanced flame retardant PA6 and other products.
(1) Application in peripheral parts of automobile engine. Since peripheral parts of engine are mainly heating and vibrating parts, most of materials used in parts are glass fiber reinforced nylon. This is because nylon has better comprehensive properties. Main properties of nylon modified with glass fiber are greatly improved, such as strength, product accuracy, and dimensional stability.
In addition, nylon has many varieties, it is easier to recycle and reuse, and price is relatively cheap. These factors make nylon an ideal material for engine peripheral parts. Intake manifold is the most typical application of modified nylon in automobiles. In 1990, BMW Motor Company of Germany first applied intake manifold made of glass fiber reinforced nylon to six-cylinder engine; later, Ford of United States cooperated with DuPont to jointly use intake manifold made of glass fiber reinforced PA66 to apply to V6 engine. In the future, major automobile companies in the world have followed suit, and modified nylon intake manifold has been widely used.
(2) Application in automobile engine parts. Engine cover, engine decorative cover, cylinder head cover and other components are generally made of modified nylon as preferred material. Compared with metal materials, cylinder head cover as an example reduces quality by 50% and cost by 30%. In addition to engine parts, reinforced nylon can also be used in other stressed parts of car, such as oil filters, wipers, radiator grilles, etc.

In the field of automobile manufacturing, PBT is widely used in production of bumpers, carburetor components, fenders, spoilers, spark plug terminal boards, fuel supply system parts, instrument panels, automotive ignitions, accelerators and clutch pedals. Competition between PBT and enhanced PA, PC, and POM in automobile manufacturing industry is very fierce. PA is easy to absorb water, heat resistance and drug resistance of PC is not as good as that of PBT. In terms of automobile use, PBT will gradually replace PA because its water absorption resistance is better than that of PA.
In the case of high relative humidity and very humid conditions, plasticity is easily reduced due to humidity, and electrical nodes are prone to corrosion. Modified PBT can often be used. At 80℃ and 90% relative humidity, PBT can still be used normally, and effect is very good.
GE's PBT/PC alloy, trade name Xenoy1731, is the most widely used in luxury cars; it has good heat resistance, stress crack resistance, excellent wear resistance, chemical corrosion resistance, high low temperature impact strength, and easy processing. It has good paintability and is mainly used in high-end car bumpers, car floor, panels and motorcycle guards.

Automotive industry is the largest potential market for POM. POM is light in weight, simple in processing and molding, low in production cost, and similar in material properties to metals. Modified POM has a very low wear coefficient and strong rigidity; it is very suitable for manufacture of automobile pumps, carburetor parts, fuel pipes, power valves, Wanshang joint bearings, motor gears, cranks, handles, dashboards, window lifters, electrical switches, seat belt buckles, etc. Manufacture of wear-resistant parts such as bushings, gears, and sliders is strength of modified POM. These parts have less metal wear, reduce amount of lubricating oil, and enhance service life of parts.
Therefore, it can widely replace copper, zinc and other metals to produce bearings, gears, tie rods, etc. Automotive parts produced by POM are light in weight, low in noise, easy to form and assemble, so they are more and more widely used in automotive manufacturing industry.

Due to its high mechanical properties and good appearance, modified PC is mainly used for exterior parts and interior parts in automobiles. The most widely used are PC/ABS alloys and PC/PBT alloys.
(1) Automotive interior parts. PC/ABS alloy is the most suitable material for automotive interior parts. This is because PC/ABS alloy has excellent heat resistance, impact resistance and rigidity, and good processing fluidity. It is also an ideal material for making car dashboards. Thermal deformation temperature of PC/ABS alloy is 110℃～135℃, which can fully meet heating requirements of cars parked outdoors at noon in hot summer in tropical countries.
PC/ABS alloy has good paintability and adhesion to cover film, so instrument panel made of PC/ABS alloy does not need surface pretreatment, and can be directly sprayed with soft topcoat or coated with PVC film. PC/ABS alloys are also used to manufacture automotive parts such as parts around dashboard, antifreeze panels, door handles, drain panels, brackets, steering column sheaths, trim panels, and air conditioning system accessories.
(2) Automotive exterior parts. PC/PBT alloy and PC/PET alloy not only have high heat resistance and high impact resistance of PC, but also have chemical resistance, wear resistance and molding processability of PBT and PET, so they are ideal materials for manufacturing automotive exterior parts .
PC/PBT car bumpers can withstand low temperature impact below -30 ℃, and when bumper breaks, it is ductile fracture without fragmentation. Elastomer toughened PC/PBT alloys and PC/PET alloys are more suitable for making auto body panels, auto side guards, fenders, auto door frames, etc. Injection-molded exterior parts of high heat-resistant PC/PBT alloy and PC/PET alloy may not be painted.
PC/PET alloy can be used to make car exhaust vents and license plate covers. PC/ABS alloys can also be used to make car exterior parts, such as car wheel covers, mirror housings, taillight covers, etc. PC/ABS has good formability and can process large automobile parts, such as automobile fenders.

Modified PPO is mainly used in automobiles as parts with high requirements for heat resistance, flame retardancy, electrical properties, impact properties, dimensional stability and mechanical strength. For example, PPO/PS alloy is suitable for wet, loaded and high requirements for electrical insulation, good dimensional stability, suitable for manufacturing automotive wheel covers, headlight glass grooves, tail light housings and other parts, and also suitable for manufacturing junction boxes, fuses boxes, circuit breaker housings and other automotive electrical components.
PPO/PA alloys have excellent mechanical properties, dimensional stability, oil resistance, electrical insulation, and impact resistance. It can be used to make car exterior parts, such as large baffles, bumpers, rear spoilers, etc. Engine covers with higher glass transition temperature requirements are future application directions of PPO/PA alloys.
PPO/PBT alloy has high heat distortion temperature and low sensitivity to moisture, and is an ideal material for manufacturing automobile outer panels.
Development direction of automobile industry is high-grade, miniaturization, light weight and diversification, and research on replacing steel with plastic in automobile applications has also become very active. At present, domestic automotive plastics account for 7% of the total materials on average, and proportion in Germany is 15%; we need to increase research and development work, so that design of parts structure, selection of plastic materials and development of industry are synchronized.