The world's top five engineering plastics are polyamide (PA), polycarbonate (PC), polyoxymethylene (POM), polyphenylene ether (PPO) and thermoplastic polyester (PBT). Engineering plastics can be divided into two categories: general engineering plastics and special engineering plastics.
The former main varieties of polyamide, polycarbonate, polyformaldehyde, modified polyphenylene ether and thermoplastic polyester five general-purpose engineering plastics; the latter mainly refers to heat-resistant up to 150 ℃ above the engineering plastics, the main varieties of polyimide, polyphenylene sulfide, polysulfone, aromatic polyamides, polyaromatic esters, polyphenylene esters, polyarylene ether ketone, liquid crystal polymers and fluorine resins.
1 Polyamide (PA)
Advantages: low specific gravity, high tensile strength, abrasion resistance, self-lubricating, excellent impact toughness, with both rigid and flexible performance, and its processing ease, high efficiency, light weight.
Disadvantages: insufficient filling, no surface luster, easy to discolor, heat shrinkage, products cooled too quickly, poor exhaust, mold release difficulties, difficult to get off the material, and so on.
Main use: processed into a variety of products to replace the metal, widely used in automotive and transportation industry. Typical products include pump impellers, fan blades, valve seats, bushings, bearings, various instrument panels, automotive electrical instruments, hot and cold air conditioning valves and other parts.
2 Polycarbonate (PC)
Advantages: both the strength of similar non-ferrous metals, while both ductility and toughness, its impact strength is extremely high, with a hammer can not be destroyed, can withstand the explosion of the TV screen. Polycarbonate transparency and excellent, and can be applied to any coloring.
Disadvantages: silver filaments, bubbles, easy discoloration of the resin, reduced transparency, possible fusion marks, products are prone to cracking, mold release difficulties.
Main applications: widely used in various safety lampshades, signal lamps, gymnasiums, stadiums, transparent protective panels, lighting glass, high-rise building glass, automobile mirrors, windshield panels, aircraft cabin glass, motorcycle driving helmets. The markets with the highest usage are computers, office equipment, automobiles, replacement glass and sheets, and CD and DVD disks are one of the most promising markets.
3 Polyoxymethylene (POM)
Advantages: similar to the hardness, strength and steel of the metal, in a wide range of temperatures and humidity have good self-lubrication, good fatigue resistance, and rich in elasticity, in addition to its good resistance to chemicals, low cost.
Disadvantages: poor thermal stability and thermal oxygen stability.
Main use: widely used in electrical and electronic, machinery, instrumentation, daily light industry, automotive, building materials, agriculture and other fields. In many new areas of application, such as medical technology, sports equipment, etc., POM also showed good growth.
4 Polyphenylene ether (PPO)
Advantages: excellent overall performance, the most important feature is the long-term load, excellent dimensional stability and outstanding electrical insulation, the use of a wide range of temperatures, can be used for a long time in the range of -127 ~ 121 ℃. With excellent water resistance, steam resistance, products with high tensile strength and impact strength, creep resistance is also good. In addition, there are good abrasion resistance and electrical properties.
Disadvantages: poor melt fluidity, processing and molding difficulties, poor light resistance, long time in the sun will change color, resistance to inorganic acids, alkalis, aromatic hydrocarbons, halogenated hydrocarbons, oils and other properties are poor, easy to dissolve or stress cracking.
Main application: mainly used in place of stainless steel to manufacture surgical medical equipment. In the electromechanical industry can make gears, blower blades, pipes, valves, screws and other fasteners and connectors, etc., but also for the production of electronic and electrical industry parts, such as coil skeleton and printed circuit boards.
5 thermoplastic polyester (PBT)
Advantages: better processing and electrical properties, PBT glass transition temperature is low, the mold temperature at 50 ℃ can be quickly crystallized, short processing cycle.
Disadvantages: not easy to get.
Main uses: widely used in electronics, electrical and automotive industries. Because of the high insulation and temperature resistance of PBT can be used as a television set back to the scanning transformer, car distributor and ignition coil, office equipment shell and base, a variety of automotive exterior parts, air conditioning fan, electronic stove base, office equipment shell parts.
Expanded Information:
The performance characteristics of engineering plastics are mainly:
(1) Compared with general-purpose plastics, they have excellent heat- and cold-resistant properties, excellent mechanical properties over a wide range of temperatures, and are suitable for use as structural materials;
(2) Good corrosion resistance, less affected by the environment, and good durability ;
(3) Compared with metal materials, it is easy to be processed, has high productivity, and can simplify procedures and save costs;
(4) It has good dimensional stability and electrical insulation;
(5) It is light in weight, has a high specific strength, and outstanding friction reduction and wear resistance.
Compared with general-purpose plastics, engineering plastics can meet higher requirements in terms of mechanical properties, durability, corrosion resistance, heat resistance, etc., and the processing is more convenient and can replace metal materials. Engineering plastics are widely used in electrical and electronic, automotive, construction, office equipment, machinery, aerospace and other industries, plastic instead of steel, plastic instead of wood has become an international trend.
Engineering plastics has become the world's fastest-growing plastics industry in the field of its development not only on the national pillar industries and modern high-tech industries play a supporting role, but also to promote the transformation of traditional industries and the adjustment of product structure.
Engineering plastics are increasingly used in automobiles, mainly used as bumpers, fuel tanks, instrument panels, body panels, doors, lampshades, fuel pipes, radiators, and engine-related parts.
In machinery, engineering plastics can be used for bearings, gears, screw nuts, seals and other mechanical parts and shells, covers, handwheels, handles, fasteners and pipe fittings and other mechanical structures.
In electronic and electrical appliances, engineering plastics can be used in 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, fans, vacuum cleaners, irons, microwave ovens, rice cookers, radios, combined audio equipment and lighting appliances.
In the chemical industry, engineering plastics can be used in heat exchangers, chemical equipment lining and other chemical equipment and pipe and pipe fittings, valves, pumps and other chemical pipelines.
Due to the rapid development of China's automotive, electronics and construction industries, at present, China has become the world's fastest growing demand for engineering plastics. According to analysis, with the continuous development of the domestic economy, the demand for engineering plastics will be further growth, China's engineering plastics industry has a very broad development prospects.
To the home appliance industry, only to the refrigerator, freezer, washing machine, air conditioning and various types of small household appliances will reach 600,000 tons of engineering plastics demand each year. For communications infrastructure construction and railroad, highway construction and other aspects of engineering plastics is even more amazing, is expected in the next few years the total demand will reach more than 4.5 million tons.
The main varieties of polyamide are nylon 6, nylon 66, nylon 11, nylon 12, nylon 610, nylon 612, nylon 46, nylon 1010 and so on. Among them, nylon 6, nylon 66 production is the largest, accounting for about 90% of nylon production. Nylon 11, nylon 12 has outstanding low-temperature toughness; nylon 46 has excellent heat resistance and rapid development, nylon 1010 is produced from castor oil as the raw material of our unique varieties.
Because of the different chemical structures of various nylon, its performance also varies, but they have *** the same characteristics: nylon molecules can form hydrogen bonds between the structure of easy, crystallization occurs Moreover, the molecules interact with each other with a greater force, giving nylon a high melting point and mechanical properties; due to amide groups are hydrophilic groups, greater water absorption.
In the chemical structure of nylon there are also methylene and aryl groups, so that nylon has a certain flexibility or rigidity. The greater the proportion of methylene-amino groups in nylon, the fewer the number of hydrogen bonds in the molecule, the smaller the intermolecular forces, the greater the flexibility and the smaller the water absorption.
So, nylon engineering plastics generally have good mechanical properties, electrical properties, heat resistance and toughness, but also has excellent oil resistance, abrasion resistance, self-lubricating, chemical resistance and molding processability.
Polycarbonate (PC) is a polyester class of carbonic acid, carbonic acid itself is not stable, but its derivatives (such as phosgene, urea, carbonate, carbonate) have a certain stability.
Polycarbonate can be divided into two categories, aliphatic and aromatic, according to the different alcohol structures.
Aliphatic polycarbonate. Such as polyethylene carbonate, polytrimethylene carbonate and its **** polymer, low melting point and glass transition temperature, poor strength, can not be used as a structural material; but the use of its biocompatibility and biodegradable properties, can be in the slow-release carriers for drugs, surgical sutures, bone support materials and so on to obtain applications.
Polycarbonate is resistant to weak acids, weak bases and neutral oils.
Polycarbonate is not resistant to ultraviolet light and strong alkali.
PC is a linear carbonate polyester with a molecule in which carbonate groups alternate with other groups that can be aromatic, aliphatic, or both. Bisphenol A-based PC is the most important industrial product.
PC is an almost colorless glassy amorphous polymer with good optical properties. pc high molecular weight resins have high toughness, cantilever beam notched impact strength of 600~900J/m, unfilled grades of heat distortion temperature of about 130°C, glass fiber reinforced can increase this value by 10°C.
PC's flexural modulus can be up to 2400MPa or more, the resin can be processed into large rigid products. The creep rate under load is very low at temperatures below 100°C. PC has poor hydrolysis resistance and cannot be used for products that are repeatedly subjected to high pressure steam.
PC main performance defects are hydrolysis stability is not high enough, sensitive to the gap, resistance to organic chemicals, scratch resistance is poor, long-term exposure to ultraviolet light will be yellowing. Like other resins, PC is susceptible to the erosion of certain organic solvents.
PC materials are flame retardant, wear-resistant. Resistant to oxidation.
Polyformaldehyde is a linear polymer with no side chains, high density, and high crystallinity, and has excellent overall properties.
Polyformaldehyde is a hard, dense material with a smooth, glossy surface, yellowish or white in color, and can be used for long periods of time at temperatures ranging from -40 to 100°C. It has a high resistance to abrasion and self-lubrication. Its abrasion resistance and self-lubricating properties are also superior to most engineering plastics, and has good resistance to oil, peroxide resistance. It is not resistant to acid, strong alkali and ultraviolet radiation from the sun.
Polyformaldehyde tensile strength of 70MPa, small water absorption, dimensional stability, glossy, these properties are better than nylon, polyformaldehyde is highly crystalline resin, thermoplastic resins in the toughest. With thermal strength, bending strength, fatigue strength are high, wear resistance and excellent electrical properties.
References: