Among general-purpose engineering plastics, five materials are most widely used ??collectively known as the five major engineering plastics: Polyamide (PA), Polyoxymethylene (POM), Polyphenylene Oxide (PPO), Polycarbonate (PC), and Polybutylene Terephthalate / Polyethylene Terephthalate (PBT/PET). Each material serves different applications based on price and performance characteristics.
Polyamide (PA) ??Nylon
Polyamide, commonly known as nylon, was the earliest developed and remains the highest-volume engineering plastic. The name “nylon” originated as DuPont’s trade name when they invented polyamide. Based on monomer type and production method, polyamides are divided into multiple grades. Nylon 66 and Nylon 6 are the most common, accounting for over 90% of all polyamide consumption.
- Nylon 6: Good elasticity, high impact strength, relatively high water absorption
- Nylon 66: Superior to Nylon 6 ??higher strength, excellent wear resistance
- Nylon 610: Similar to Nylon 66 but lower water absorption and stiffness
- Nylon 1010: Translucent, low water absorption, good cold resistance ??suitable for general mechanical parts, wear-resistant components, transmission parts, and chemical/electrical/instrument components
Polycarbonate (PC)
Polycarbonate combines non-ferrous metal-like strength with excellent ductility and toughness. Its impact strength is extraordinarily high ??a hammer strike cannot shatter it, and it can withstand the implosion of television picture tubes. Polycarbonate offers exceptional transparency and can be tinted in any color. Due to these properties, it is widely used in safety lamp covers, signal lights, transparent protective panels for stadiums, daylighting glass, high-rise building glazing, automotive reflectors, windshields, aircraft cockpit windows, and motorcycle safety helmets. The largest markets include computers, office equipment, automotive applications, glass replacement and sheet materials, with CD and DVD discs representing one of the most promising market segments.
Polyoxymethylene (POM) ??Acetal
Polyoxymethylene is a high-density, highly crystalline thermoplastic engineering plastic with excellent physical, mechanical, and chemical properties ??particularly outstanding friction and wear resistance. Its combination of properties rivals steel while weighing significantly less, earning it the nickname “synthetic steel.” POM offers high strength and stiffness, excellent wear resistance, low water absorption, and good dimensional stability. However, it has poor thermal stability, is flammable, and degrades under prolonged outdoor exposure. It is ideal for wear-resistant components, transmission parts, and chemical/instrument components.
Polyphenylene Oxide (PPO)
PPO has the lowest density among the five major engineering plastics. It offers excellent electrical insulation and dimensional stability, resistance to water and steam, good mechanical strength, and tensile and creep resistance. It maintains high impact strength at low temperatures and absorbs little water. However, PPO is difficult to process, relatively expensive, and susceptible to chemical corrosion. Applications include camera components, automotive instrument panels, electrical housings, switches, and engine covers.
PBT and PET ??Thermoplastic Polyesters
Both PBT and PET are thermoplastic polyesters. PBT offers good processing characteristics and electrical properties, a low glass transition temperature, rapid crystallization at mold temperatures as low as 50?C, and short processing cycles. PBT is widely used in electronics, electrical, and automotive industries. Thanks to its high insulation and temperature resistance, PBT is used in television flyback transformers, automotive distributors and ignition coils, office equipment housings and bases, various automotive exterior components, air conditioner fans, and electric stove bases.
Modified Engineering Plastics
Beyond direct use of the five major engineering plastics, modification technologies have been developed to further enhance performance, expanding the application range of engineering plastics. Glass fiber reinforcement significantly improves plastic strength and toughness. Other modification techniques such as copolymerization have produced numerous new products with excellent properties across multiple performance dimensions.
References
- Wikipedia: Engineering Plastics: Overview of engineering plastics classification, properties, and applications
- Wikipedia: Nylon (Polyamide): Comprehensive reference on nylon types, properties, and manufacturing
- Wikipedia: Polycarbonate: Properties, processing, and applications of polycarbonate
- ASTM D4000 ??Classification System for Plastic Materials: Standard classification system for specifying plastic materials
- ISO 1043 ??Plastics Symbols: International standard for plastic material symbols and abbreviated terms