Engineering plastics can be used as engineering materials and as plastics to replace metals in the manufacture of machine parts, etc. Engineering plastics have excellent comprehensive properties, including high rigidity, low creep, high mechanical strength, good heat resistance, and good electrical insulation. They can be used for a long time in harsh chemical and physical environments and can replace metals as engineering structural materials, but they are more expensive and have a smaller output.
Classification
Engineering plastics can be divided into two categories: general engineering plastics and special engineering plastics. The former mainly includes five general engineering plastics: polyamide, polycarbonate, polyoxymethylene, modified polyphenylene ether and thermoplastic polyester; the latter mainly refers to engineering plastics with heat resistance of more than 150°C, and the main varieties include polyimide, polyphenylene sulfide, polysulfone, aromatic polyamide, polyarylate, polyphenylene ester, polyaryletherketone, liquid crystal polymer and fluororesin.
Main performance
The performance characteristics of engineering plastics are mainly:
- Compared with general-purpose plastics, it has excellent heat and cold resistance, excellent mechanical properties in a wide temperature range, and is suitable for use as a structural material;
- Good corrosion resistance, less affected by the environment, and good durability;
- Compared with metal materials, it is easy to process, has high production efficiency, simplifies procedures and saves costs;
- Good dimensional stability and electrical insulation;
- Light weight, high specific strength, and outstanding friction reduction and wear resistance.
History
Engineering plastics developed rapidly in the 1950s. Although nylon 66 resin was successfully developed and put into production as early as 1939, it was mainly used to make synthetic fibers at that time. It was not until the 1950s that it broke through the traditional use of pure fibers and was molded to make plastics. Engineering plastics really developed rapidly after the successful development of polyoxymethylene and polycarbonate in the late 1950s. Their emergence was of great significance. Due to the high crystallinity of polyoxymethylene, it has excellent mechanical properties, making plastics a material that can replace metals and join the ranks of structural materials for the first time. Later, with the successful development of copolymer formaldehyde and the popularization of screw injection molding machines, the important position of engineering plastics in the field of materials was further established. Polycarbonate is a transparent engineering plastic with excellent comprehensive properties. It is widely used and is one of the fastest-growing engineering plastics. In the field of engineering plastics, its output and consumption are second only to polyamide.
In 1961, DuPont successfully developed polyimide, opening the way to the development of special engineering plastics. The emergence of polyimide also promoted the development of many heat-resistant engineering plastics such as polysulfone, polyphenylene sulfide and polybenzimidazole, which had a profound impact on the development of the plastics industry.
In 1964, General Motors of the United States put the polyphenylene ether resin it developed into industrial production.
In 1980, the British ICI company successfully developed polyetheretherketone (PEEK), a special engineering plastic with a melting point of up to 336°C. PEEK has excellent heat resistance, radiation resistance and chemical resistance, and can be injection molded, which has attracted widespread attention. Composite materials made of PEEK as a matrix and reinforced with glass fiber or carbon fiber have been used in the fields of aviation and aerospace.
The successful development of thermotropic liquid crystal polymers in the mid-1980s was another major event in the history of the development of special engineering plastics. Liquid crystal polymers have excellent heat resistance and can be used at temperatures above 200°C. They have the characteristics of self-reinforcement, high strength, high modulus, and chemical resistance. They have low melt viscosity and are easy to mold. They have very broad application prospects in the electronics industry.
Applications
Compared with general-purpose plastics, engineering plastics can meet higher requirements in terms of mechanical properties, durability, corrosion resistance
Engineering plastics are increasingly used in automobiles, mainly as bumpers, fuel tanks, dashboards, body panels, doors, headlight covers, fuel pipes, radiators and engine-related parts.
In machinery, engineering plastics can be used in mechanical parts such as bearings, gears, screw nuts, seals, and mechanical structural parts such as housings, covers, handwheels, handles, fasteners, and pipe joints.
In electronic appliances, engineering plastics can be used for wire and cable covering, printed circuit boards, insulating films and other insulating materials and electrical equipment structural parts.
In household appliances, engineering plastics can be used in refrigerators, washing machines, air conditioners, televisions, electric fans, vacuum cleaners, electric irons, microwave ovens, rice cookers, radios, stereo equipment and lighting fixtures.
In the chemical industry, engineering plastics can be used in chemical equipment such as heat exchangers, chemical equipment linings, and in chemical pipelines such as pipes and pipe fittings, valves, and pumps.
Due to the rapid development of chinese automobile, electronics and construction industries, china has become the country with the fastest growth in demand for engineering plastics in the world. According to analysis, with the continuous development of the chinese economy, the demand for engineering plastics will further increase, and the development prospects of chinese engineering plastics industry are very broad. In the home appliance industry, the annual demand for engineering plastics for refrigerators, freezers, washing machines, air conditioners and various small household appliances will reach about 600,000 tons. The amount of engineering plastics used in communication infrastructure construction, railway and highway construction is even more amazing, and it is expected that the total demand will reach more than 4.5 million tons in the next few years.
In 2010, the chinese engineering plastics consumption reached 2.443 million tons, up 11% year-on-year, making it the country with the fastest demand growth in the world; in 2011, chinese engineering plastics consumption was 2.72 million tons, up 11.34% year-on-year. It is expected that chinese engineering plastics consumption will reach 3.37 million tons in 2013 and 4.17 million tons in 2015.
Development prospects
According to a research report by Markets and Markets, the global engineering plastics market value was approximately US$53.58 billion in 2013 and is expected to reach US$79.03 billion by 2018, with a compound annual growth rate of 8%.
Engineering plastics have a wide range of applications due to their excellent stability, good heat and chemical resistance, and high strength, and their demand continues to grow rapidly. One of the main uses of engineering plastics is to replace metals in various terminal industries. In particular, increasingly stringent environmental regulations require automobiles to reduce emissions and improve fuel economy, and engineering plastics are being widely used in the automotive and transportation industries. In addition, engineering plastics are also widely used in consumer and home appliances, electrical and electronic products, industrial machinery, packaging, as well as medical, construction and other industries.
In 2014, the Asia-Pacific region occupied the majority of the global engineering plastics market. According to statistics, the Asia-Pacific region accounted for 47.9% of the global engineering plastics market demand in 2013. It is expected that the Asia-Pacific region will continue to maintain its position as the world’s largest engineering plastics market in 2018, followed by the Western European market. In the next five years, its engineering plastics market demand is expected to grow at an average annual rate of 7.8%.
Main types
Engineering plastics mainly include polycarbonate (PC), polyamide (PA), polyacetal (POM), polyphenylene oxide (PPO), polyester (PET, PBT), polyphenylene sulfide (PPS), polyarylate, etc.
Polyamide
Polyamide (PA, commonly known as nylon) has won people’s attention due to its unique low specific gravity, high tensile strength, wear resistance, good self-lubrication, excellent impact toughness, and both rigid and flexible performance. In addition, it is easy to process, highly efficient, light in specific gravity (only 1/7 of metal), and can be processed into various products to replace metal. It is widely used in the automobile and transportation industries. Typical products include pump impellers, fan blades, valve seats, bushings, bearings, various instrument panels, automotive electrical instruments, hot and cold air control valves and other parts. About 3.6 to 4 kilograms of nylon products are consumed per car. The consumption proportion of polyamide in the automotive industry is the largest, followed by electronics and electrical.
According to the different purposes of polyamide modification, polyamide modification can be divided into reinforcement, toughening, flame retardant, filling and alloying types. Research on polyamide nanocomposites has also made great progress.
In order to obtain polyamide materials with higher strength and heat deformation temperature, inorganic or organic fibers or fillers are added to the polyamide matrix, and high-strength polyamide composite materials are obtained by blending and extrusion. There are many varieties of reinforced PA, and almost all polyamide materials can be made into reinforced varieties.
The main commercial varieties are: reinforced PA6, reinforced PA66, reinforced PA46, reinforced PA1010, reinforced PA610, etc. Among them, the largest output is reinforced PA6 and PA66. Commonly used polyamide reinforcement materials are glass fiber, carbon fiber, aramid fiber, and inorganic whiskers are also used to reinforce polyamide.
Polyphenylene sulfide
Abbreviated as PPS.
The outstanding properties of PPS are: ① good heat resistance, can be used in the temperature range of 180 ~ 220 ℃; ② corrosion resistance close to polytetrafluoroethylene; ③ excellent electrical properties; ④ excellent mechanical properties; ⑤ good flame retardant properties.
The disadvantages of PPS are: ① The price is too high. It is low-priced among high-temperature resistant plastics, but much higher than general engineering plastics; ② Poor toughness and brittleness; ③ Unstable viscosity during processing. Pure PPS is rarely used alone due to its brittleness. The PPS used is its performance-modified varieties. Specifically: 40% glass fiber reinforced PPS (R4), inorganic filled PPS (R8), carbon fiber reinforced PPS (G6), etc. PPS is used in automobiles accounting for 45%, in electronics and electrical appliances accounting for 30%, and in other fields accounting for 25%. PPS is developing rapidly and is expected to become the sixth largest engineering plastic.
Polycarbonate
Polycarbonate (PC) has similar strength to nonferrous metals, and at the same time has ductility and toughness. It has extremely high impact strength and cannot be damaged by hammering. It can withstand the explosion of TV screens. Polycarbonate has excellent transparency and can be colored in any way. Due to the above excellent properties of polycarbonate, it has been widely used in various safety lampshades, signal lights, transparent protective plates for gymnasiums and stadiums, lighting glass, high-rise building glass, automobile reflectors, windshield panels, aircraft cockpit glass, and motorcycle driving helmets. The largest market is computers, office equipment, automobiles, and replacement glass and sheets. CDs and DVDs are one of the most potential markets.
Polyoxymethylene
Polyoxymethylene (POM) is an engineering plastic with excellent performance, known as “steel” and “super steel” abroad. POM has the hardness, strength and rigidity similar to metals, and has good self-lubrication, good fatigue resistance and elasticity in a wide range of temperature and humidity. In addition, it has good chemical resistance. With a lower cost than many other engineering plastics, POM is replacing some markets traditionally occupied by metals, such as replacing zinc, brass, aluminum and steel to make many parts. Since its introduction, POM has been widely used in electronics, machinery, instrumentation, daily light industry, automobiles, building materials, agriculture and other fields. In many new fields of application, such as medical technology and sports equipment, POM also shows a good growth trend.
PBT
Polybutylene terephthalate (PBT) is a thermoplastic polyester. Compared with other thermoplastic engineering plastics, non-reinforced PBT has better processing performance and electrical properties. PBT has a low glass transition temperature, can quickly crystallize at a mold temperature of 50°C, and has a short processing cycle. Polybutylene terephthalate (PBT) is widely used in the electronics, electrical and automotive industries. Due to its high insulation and temperature resistance, PBT can be used as flyback transformers for televisions, automotive distributors and ignition coils, office equipment housings and bases, various automotive exterior parts, air conditioner fans, electronic stove bases, and office equipment shells.
Polyphenylene oxide
PPO for short. It has excellent comprehensive properties. Its biggest feature is that it has excellent dimensional stability and outstanding electrical insulation under long-term load. It has a wide operating temperature range and can be used for a long time in the range of -127 to 121°C. It has excellent water resistance and steam resistance. The products have high tensile strength and impact strength, and good creep resistance. In addition, it has good wear resistance and electrical properties. It is mainly used to replace stainless steel in the manufacture of surgical medical equipment. In the electromechanical industry, it can be used to make gears, blower blades, pipes, valves, screws and other fasteners and connectors, etc. It is also used to make parts in the electronics and electrical industries, such as coil skeletons and printed circuit boards.
