Engineering plastics - refers to a class of high-performance polymer materials that can be used as structural materials to withstand mechanical stress in a wide temperature range, used in harsh chemical and physical environments.

 

1. Can withstand a certain external force;
2. Good mechanical properties and dimensional stability,
3. It can still maintain its excellent performance at high and low temperature, and can be used as engineering structural parts.

Thermal properties: glass transition temperature (Tg) and melting point (Tm); high heat distortion temperature (HDT); high long-term use temperature (UL-746B); large operating temperature range; small thermal expansion coefficient.
Mechanical properties: high strength, high mechanical modulus, low latent, strong wear and fatigue resistance.
Others: chemical resistance, electricity resistance, flame resistance, weather resistance, good dimensional stability.

Nylon, polyoxymethylene, polycarbonate, polysulfone, etc.

1. Polyamide (PA): Carothers (W.H.Carothers American chemist) developed polyamide research and applied for a patent in 1931. It was organized and industrialized by DuPont in 1939.
2. Homopolyoxymethylene (POM): DuPont successfully developed it in 1956, and realized industrial production in 1959.
Copolymer: It was developed and commercialized by Celanese Corporation of United States in 1962.
3. Polycarbonate (PC): In 1958 and 1960, Bayer of Germany and General Electric of United States developed and produced polycarbonate by transesterification and phosgenation respectively.
4. Polyphenylene ether (PPO): It was developed by General Electric Company in 1964, and modified polyphenylene ether was launched two years later.
5. Polybutylene terephthalate (PBT): In 1970, American Celanese Company developed thermoplastic polyesters into engineering plastics, which became last successful development of five general engineering plastics with extremely high output growth rate.

 

Since emergence of engineering plastics in the 1950s, development of half a century has grown and grown in market competition. In 2000, output of engineering plastics in the world has exceeded 5 million tons, and annual growth rate is 7~9%. Although it only accounts for 2~3% of all plastics, its excellent performance is unmatched by other materials.

1. Light weight and low relative density
Relative density of engineering plastics is generally between 1.0 and 2.0, which is much lower than that of metals. It is light in weight and can replace some traditional metal materials for use in aerospace vehicles, vehicles and other fields.
2. Higher specific strength
Reinforced with glass fiber, carbon fiber and other fibers, tensile strength can be greatly improved. Ratio of maximum tensile strength to relative density is generally 1500-1700, even as high as 4000 (steel 1600, aluminum 1500)
* Tensile strength (tensilestrength): refers to stress of material to produce maximum uniform plastic deformation. In tensile test, tensile strength is maximum tensile stress that sample receives until it breaks, and result is expressed in MPa.
3. Outstanding wear resistance and self-lubricating properties
Use engineering plastics as friction parts. Compared with wear-resistant metal alloys, wear rate is lower than 1:5, and fluorine plastics are better.
4. Excellent mechanical properties
In a wide temperature range, many engineering plastics, especially reinforced engineering plastics, have excellent impact resistance and fatigue resistance.
5. Excellent electrical insulation
Almost all engineering plastics have excellent electrical insulation and arc resistance properties, can be among ranks of excellent insulating materials
6. Chemical stability
It has good corrosion resistance to acids, alkalis and general organic solvents.
7. Good dimensional stability of parts
8. High heat resistance
When general engineering plastics are reinforced with different glass fibers, long-term continuous use temperature of UL exceeds 100 ℃, and index of special engineering plastics generally exceeds 150 ℃.
9. Excellent shock absorption, noise reduction and burial performance for foreign bodies
When engineering plastics are used as moving parts, there is no metal impact noise, they have excellent shock absorption and noise reduction performance. For presence of abrasive particles, foreign objects can be buried, unlike metal that may be bitten or scratched before.