Since then, a new kind of plastic has appeared, which is called "engineering plastic". After more than 20 years' efforts, a huge series of engineering plastics with metal as the challenge object appeared in the 1980s.
The characteristics of engineering plastics are that they can act as stress-bearing structural members, and they can keep their dimensions stable and their properties unchanged for a long time. The tensile strength is greater than 40MPa, and it has excellent comprehensive mechanical properties, corrosion resistance and good electrical insulation. Some engineering plastics can even withstand temperatures above 200℃. After being reinforced with glass fiber, they can be used to manufacture external parts of airplanes and pistons and valves of automobiles. Nylon and kevlar belong to engineering plastics.
Represented by General Electric Company and Dupont Company, the world's largest manufacturers of engineering plastics, a large number of companies mainly "capture" automobile parts and study the replacement of various metal parts with engineering plastics. In the 1970s, Boli Engine Research Institute in New Jersey, USA, once manufactured an automobile engine, which used 90% engineering plastics, that is, except for high-temperature components such as piston and air intake, almost all of them were made of glass fiber and carbon fiber reinforced resin matrix. In this way, the weight of the whole engine is only half of that of the previous metal parts, reducing by about 90 kilograms. It can be seen how high the "engineering plastic fever" was at that time.
At 198 1, the portable home video recorder "Ma starks VT-6500" produced by Hitachi, Japan, in which the bracket for mounting the magnetic head and motor was changed from the original aluminum die-casting bracket to glass fiber reinforced acrylonitrile and styrene polymer resin, the shell was also made of heat-resistant resin and isobutylene resin with good transparency, the internal rotating part was made of polyacetal, and the other parts were made of modified polypropylene oxide. In this way, the weight of the whole machine is reduced from 10 kg to 4.9 kg.
At present, the main varieties of engineering plastics are polyamide, polycarbonate, polyoxymethylene, polyphenylene ether and polyester; Followed by polyphenylene sulfide, alum, polyaryletherketone, polyimide and other polyaryletherheterocyclic resins. When they are compounded with glass fiber, carbon fiber, boron fiber, whisker and other reinforcing materials to form nonmetallic composite materials, their properties are greatly improved, which is really "adding wings to the tiger".
In a word, engineering plastics, as various structural parts, transmission parts, insulation parts, corrosion-resistant parts and sealing parts, have been widely used in automobile, aerospace, household appliances, mechanical construction and chemical industry. Under the condition of ensuring sufficient strength and other properties, the weight of the product is greatly reduced.