I, the conventional varieties of plastics and classification in our daily lives, we can directly contact or perceived plastics, most of the conventional general-purpose plastics, including five categories: PE, PP, ABS, PVC, PS, these five categories of plastics account for the majority of plastic raw materials used, the rest of the basic can be categorized as a special variety of plastics, such as: PPS, PPO, PA, PC, POM, etc., which are rarely used in daily life products, and are mainly used in the engineering industry, national defense science and technology and other high-end fields, such as automotive, aerospace, construction, communications and other fields. Plastics can be categorized into thermoplastics and thermosets according to their plasticity. Usually, thermoplastic products can be recycled, while thermosetting plastics can not, according to the optical properties of plastics can be divided into transparent, semi-transparent and opaque raw materials, such as PS, PMMA, AS, PC, etc. belong to the transparent plastics, while most of the other plastics are opaque plastics.
Second, the performance and use of commonly used plastic varieties
1, polyethylene: commonly used polyethylene can be divided into low-pressure polyethylene (HDPE), high-pressure polyethylene (LDPE) and linear high-pressure polyethylene (LLDPE). Among the three, HDPE has better thermal, electrical and mechanical properties, while LDPE and LLDPE have better flexibility, impact properties, film-forming properties, etc. LDPE and LLDPE are mainly used for packaging film, agricultural film, plastic modification, etc., while the use of HDPE is more widely used, film, tubing, injection of daily necessities in many areas.
2, polypropylene: relatively speaking, more varieties of polypropylene, the use of more complex, a wide range of areas, varieties are mainly homopolymer polypropylene (homopp), block *** polypropylene (copp) and random *** polypropylene (rapp), according to the use of the different homopolymer is mainly used in the field of wire drawing, fibers, injections, BOPP film, etc., *** polypropylene Mainly used in household appliances injection parts, modified raw materials, daily injection products, tubes, etc., atactic polypropylene is mainly used for transparent products, high-performance products, high-performance tubes and so on.
3, polyvinyl chloride: due to its low cost, the product has the characteristics of self-flame retardant, it is widely used in the field of construction, especially in the sewer pipe, plastic doors and windows, panels, artificial leather and other most widely used.
4, polystyrene: as a transparent raw material, in the case of transparent demand, a wide range of uses, such as automotive lampshades, daily transparent parts, transparent cups, cans and so on.
5, ABS: a wide range of engineering plastics, with outstanding physical and mechanical and thermal properties, widely used in household appliances, panels, masks, combinations, accessories, etc., especially household appliances, such as washing machines, air conditioners, refrigerators, fans, etc., the dosage is very large, and in addition in the modification of plastics, the use of a wide range of applications.
Three, commonly used plastics identification
1, density method: examining the density of various plastics, liquid as a medium, to test the plastic in the liquid medium of the sinking and floating to roughly identify the plastic categories, such as a piece of plastic in the water, floating on the surface of the water can be concluded that the raw material is not PVC (due to the density of PVC>1).
2, combustion method: the main examination of the color of the flame and combustion odor and smoke, in general, polyolefin raw materials combustion flame is blue or light blue, the smell is relatively mild and light, smoke was white, and most of the raw materials with benzene or chlorine combustion is prone to black smoke, strong odor. In addition, such as PE, PP, drip burning phenomenon, while PVC and other non-drip burning, but there is a self-extinguishing phenomenon.
3, optical method: the main examination of the transparency of the raw materials, generally used transparent raw materials: PS, PC, PMMA, AS; semi-transparent raw materials: PE, random **** poly PP, homopolymerization of PP, soft PVC, transparent ABS, etc., the other raw materials are basically opaque.
4, color identification method: in general, without additives raw materials, if itself contains a double bond, the color will be slightly yellow, such as ABS, due to butadiene **** polymerization, polymerization of polymers still contain a double bond, so it will be slightly yellow. Most of the other methods of identification with the help of various instruments, such as infrared spectroscopy, mass spectrometry, nuclear magnetic **** vibration, differential thermal scanning, thermal analysis.
Polyvinyl chloride (PVC) performance: polyvinyl chloride is divided into soft, hard two kinds: hard polyvinyl chloride, high mechanical strength, electrical performance is excellent, acid and alkali resistance is very strong, chemical stability is very good; shortcomings: softening point is low. Soft polyvinyl chloride tensile strength, flexural strength, impact strength, impact toughness, etc. are hard polyhard vinyl for the low, while the elongation of the break is higher. Uses: hard PVC products are pipes and rods, plates, welding rods, centrifugal pumps, ventilators, wheel oil pipes, acid and alkali pumps, valves and containers. Soft PVC products are storage tanks, sheet, film, wire insulation, window cover, acid and alkali resistant hose.
Polyethylene (PE) performance: divided into high-pressure, medium-pressure and low-pressure polyethylene three. High-pressure polyethylene texture flexible; low-pressure polyethylene texture hard, good cold resistance, in -70 ℃ also remain soft. It has high chemical stability and is resistant to acids, alkalis and organic melts. It has outstanding electrical properties and good radiation resistance. Coated on metal surface by flame spraying method or electrostatic spraying method, it can achieve the purpose of friction reduction and corrosion prevention. The disadvantage is that the mechanical strength is not high, the heat distortion temperature is very low, so it can not withstand higher loads. Uses: corrosion-resistant lining of chemical equipment and storage tanks, chemical corrosion-resistant pipes, valve parts, bushings, roller frames, to replace copper and stainless steel. Insulation for high frequency underwater cables or general cables. Transistor radio magnet bar antenna clamp frame.
Polystyrene (PS) performance: a certain degree of mechanical strength, chemical stability and electrical properties are better, good light transmission, good coloring, and easy to form, it is characterized by almost completely water-resistant, the lack of heat resistance is low, brittle, and its products due to the internal stress of the easy to crack, can only be used at low loads and low temperatures (60 ~ 75 ℃). Uses: all kinds of instrument shell, skeleton, instrument indicator, lampshade, automobile lampshade, chemical acid storage tank, acid transport tank (especially such as hydrofluoric acid), chemical instrument parts, telecommunication parts, due to good transparency, can be used as optical instrument parts and lenses.
High impact polystyrene (HIPS) performance: compared with polystyrene, has a higher toughness and impact strength, the rest of the performance is basically similar to the molding process is good. Uses: a variety of instruments, transistor radio shell, coil skeleton, textile yarn tube, television structural parts, agricultural waterboard accessories and small plastic pipe, plate, etc.. Polystyrene modified plexiglass performance: good transparency. Mechanical strength is also high, a certain degree of heat resistance, cold resistance and weather resistance, corrosion resistance, good insulation. Product size stability, easy to form. Disadvantages are brittle, soluble in organic solvents, as a light-transmitting materials, surface hardness is not enough, easy to rub hair, in terms of its comprehensive performance, more than polystyrene and other general plastics. Uses: used to manufacture a certain degree of transparency and strength of the parts, such as oil markers, oil cups, optical lenses, lenses, equipment signage, transparent pipes, automobile lights and transistor radio dials and electrical insulation parts.
Styrene acrylonitrile **** polymer (AS or SAN) performance: than polystyrene has a higher impact strength and excellent heat resistance, oil resistance, chemical resistance. Such as it can be very good resistance to certain hydrocarbons that make polystyrene stress cracking. And the modulus of elasticity is one of the higher existing thermoplastics. Uses: Widely used in the production of oil-resistant, heat-resistant, chemical-resistant industrial products, as well as instrument panels, instrument frames, covers, battery boxes, junction boxes, a variety of switches and press gauges.
Styrene-butadiene-acrylonitrile*** polymer (ABS) performance: ABS is a "tough, hard, rigid" material. With high impact toughness and mechanical strength, dimensional stability, chemical resistance and good electrical properties, easy to form and mechanical processing and other characteristics. In addition, the surface can also be chromium-plated, becoming a common material for plastic coated metal. In addition, ABS and # 372 plexiglass with good connectivity, can be used for two-color molding plastic parts. Uses: in the mechanical industry system used to manufacture cams, gears, pump impellers, bearings, motor housing, instrument cases, battery tank, water tank shell, handle, refrigerator lining, etc., the automotive industry used to manufacture the driving plate, hot air conditioning, tube heaters, etc., but also available for the manufacture of TV transistor radio shell.
Polypropylene (PP) performance: the main feature of polypropylene is the density of small, its mechanical properties are better than low-pressure polyethylene, and has outstanding rigidity, heat resistance is better. Can be used above 100 ℃. Basically does not absorb water, and has good chemical stability, except for concentrated sulfuric acid, concentrated nitric acid, almost all very stable. Excellent high-frequency electrical properties, and is not affected by temperature, easy to form. Disadvantage is not high enough wear resistance, molding shrinkage, low temperature is brittle, heat distortion temperature is also low. Uses: It can be used to make various mechanical parts, such as flanges, gears, joints, pump impellers, automobile parts. Chemical pipeline and container equipment. And can be used as lining, surface coating, recording tape, medical instruments and surgical instruments.
Polycarbonate (PC) performance: impact strength is particularly outstanding. In general thermoplastic resin is better. Higher modulus of elasticity, very little affected by temperature, heat-resistant temperature of 120 ℃. Cold-resistant up to -100 ℃ pick embrittlement. High dimensional stability. Corrosion resistance, wear resistance are good. But there is a high temperature sensitivity to water. Uses: used to manufacture gears, worm gears, racks, cams, mandrels, bearings, gaskets, rivets, pump impellers, automobile carburetor parts, lamp shades, flash lamp shades, throttle valves, lubricating oil pipelines, a variety of shells, containers, refrigeration and cooling device parts, electrical wiring boards, coil bobbins, acidic battery tanks and high-temperature lenses and so on.