about Plastic Materials
Plastic is made of resin (natural or synthetic) as the main component, adding some additives to improve the performance of the service and process performance. Because it is usually molded under heating and pressure conditions, it is called plastic.
General guidelines for the selection of plastic materials for injection molding.
Selecting the right material for each application is a difficult task that requires in-depth knowledge and recommending the correct resin type and grade depends on a thorough understanding of the product application; All application characteristics need to be carefully weighed before determining the various injection molded resins available. We are happy to work with you to complete satisfactory products.
Classification of plastics
1. Classify according to the properties of resin
Thermoplastics: Plastics that can be repeatedly softened and cooled over a specified temperature range. Such as polyethylene plastic, polyvinyl chloride plastic.
Thermosetting plastics: Plastics that can be cured into insoluble materials by exposure to heat or other conditions. For example, phenolic and epoxy plastics. 2. Classify plastics according to their application range.
General plastics: refers to large output, wide use, good formability, cheap plastics. Such as polyethylene, polypropylene, PVC and so on. Engineering plastics: can withstand a certain external force, and has good mechanical properties and dimensional stability, at high and low temperature can still maintain its excellent performance, can be used as engineering structural parts of the plastic. Such as ABS, nylon, alum and so on.
Special plastics: generally refers to the plastic with special functions (such as heat resistance, self lubrication, etc.), applied to special requirements. Such as fluorine plastics, silicone and so on.
Basic properties of plastics
1.Hight weight, high specific strength. Plastic light, general plastic density in 0.92.3 g/cm 3, only 1/8~1/4 of steel, aluminum 1/2, and a variety of foam plastic density is lower, about 0.010.5 g/cm 3 between. Strength per unit mass is called specific strength, and some reinforced plastics have specific strength that approaches or even exceeds that of steel. Alloy steel, for example, has a tensile strength of 160 mpa per unit mass, while fiberglass reinforced plastics can reach 170 to 400 mpa.
2. Excellent electrical insulation performance. Almost all plastics have excellent electrical insulation properties, such as minimal dielectric loss and excellent arc resistance, which are comparable to ceramics.
3.Excellent chemical stability. General plastics have good corrosion resistance to acid and alkali and other chemicals, especially polytetrafluoroethylene chemical corrosion resistance is better than gold, and even the ability of “king water” and other corrosive electrolyte corrosion, known as “plastic king”.
4.Good friction reduction and wear resistance. Most plastics have excellent anti-friction, wear resistance and self-lubrication properties. Many engineering plastics make use of these characteristics of friction resistant parts, adding some solid lubricants and fillers in wear-resistant plastics, can reduce its friction coefficient or further improve its wear resistance.
5. Light transmission and protection performance. Most plastics can be made as transparent or translucent products, but polystyrene and acrylic cool plastics are as transparent as glass. Organic glass chemical name for polymethacrylate methyl vinegar, can be used as aviation glass materials. Polyvinyl chloride, polyethylene, polypropylene and other plastic films have good light transmission and thermal properties, and are widely used as agricultural films. Plastic has a variety of protective properties, so commonly used as protective equipment, such as plastic film, boxes, barrels, bottles, etc.
Common engineering plastics names, properties and uses:
thermoplastic：
1.Polyvinyl（PE):
Main characteristics: high pressure polyethylene soft, transparent, non-toxic: low pressure polyethylene rigid, wear resistance, corrosion resistance, good electrical insulation.
Use examples: high pressure polyethylene: film, hose, plastic bottles: low pressure polyethylene: chemical equipment, pipes, low bearing gear, bearings, etc.
2.polypropylene（PP)
Main characteristics: Strength, hardness, elasticity are higher than polyethylene, low density, good heat resistance, electrical insulation and corrosion resistance, poor toughness, no wear resistance, easy aging use Examples: flange, gear, fan impeller, pump impeller, handle, TV (radio recorder) shell and chemical pipeline, container, medical equipment, etc.
3.Polyvinyl chloride (PVC)
Main characteristics: high strength and good corrosion resistance. Soft polyvinyl chloride, its high elongation, soft products, corrosion resistance and good electrical insulation.
Application examples: exhaust gas sewage detoxification tower, gas liquid conveying pipe, centrifugal pump, fan, joint; Soft PVC: film, raincoat, acid and alkali resistant hose, cable cover, insulation, etc.
4.Polyethylene (PS)
Main characteristics: corrosion resistance, electrical insulation, transparency, strength, stiffness, heat resistance, wear resistance is not high, impact resistance is poor, flammable, easy to crack.
Application examples: yarn tube, yarn split, spool; Instrument parts and equipment enclosures; Storage tank, pipe, elbow; Lampshade, transparent window: electrical insulation materials, etc.
5.ABS plastic
Main characteristics: high strength and impact toughness, good wear resistance and heat resistance, high chemical stability and insulation, easy to form, good machinability, poor high and low temperature resistance, flammable, opaque.
Application examples: gear, bearing, instrument panel shell, refrigerator lining and various containers, pipes, aircraft cabin decoration board, window frame, sound insulation board, etc., can also make car body and file mud board, handrail, hot air conditioning duct and other automotive parts.
6.Polycoolamine (PA)(nylon or brocade)
Main characteristics: strength, toughness, wear resistance, corrosion resistance, vibration absorption, good formability, non-toxic, tasteless. The creep value is large, the thermal conductivity is poor, the water absorption is high, the forming shrinkage rate is large.
Examples of uses: Nylon 610, 66, 6, etc.Manufacture of small parts (gear, worm gear, etc.): aromatic nylon to make high temperature wear-resistant parts, insulation materials and cosmological clothing, etc. It should be noted that the properties and dimensions of nylon change greatly after absorbing water.
7.Polycarbonate (PC)
Main characteristics: high tensile and bending strength, good impact toughness and creep resistance, high heat resistance, cold resistance and dimensional stability, high transparency, low water absorption, good insulation and formability, poor chemical stability
Application examples: gaskets, gaskets, bushings, capacitors and other insulation parts: instrument shell, guard. Manufacturing of signal lights, windshields, cockpit covers, helmets, etc., in the aviation and aeronautical industries.
8.Teflon (Plastic king)(PTFE)
Main features: excellent chemical corrosion resistance, excellent high and low temperature resistance, small friction coefficient, small water absorption, low hardness, strength, compressive strength is not high, high cost use examples: anti-friction sealing parts, chemical corrosion resistant parts and heat exchangers and insulation materials under high frequency or wet conditions, such as chemical pipes, electrical equipment, corrosive media filters, etc.
9.Polymethacrylate (Plexiglass)(PMMA)
Main characteristics: transmittance 92%, relative density is half of glass, high strength, toughness, UV resistance, anti-aging atmosphere, easy to form, hardness is not high, not wear-resistant, easy to dissolve in organic solvents, heat resistance, poor thermal conductivity, large expansion coefficient.
Application examples: aircraft seat cover, turret observation hole cover, instrument lampshade and optical lens, bullet-proof glass, TV and radar plotting screen, automobile windshield, instrument equipment protective cover, etc.
Thermosetting plastics：
1.Phenolic plastic (PE)
Main characteristics: certain strength and hardness, high wear resistance, heat resistance, good insulation and corrosion resistance, high stiffness, low moisture absorption, small deformation, simple forming process, low price. The disadvantage is the quality brittle, not alkali resistant.
Application examples: plug, switch, telephone, instrument box, automobile brake pad, internal combustion engine crankshaft, pulley, textile machine and instrument silent gear, chemical acid pump, daily use, etc.
2.Epoxy (EP)
Main characteristics: high specific strength, good toughness, heat resistance, cold resistance, corrosion resistance, insulation, waterproof, moisture-proof, mildew proof, good forming process and dimensional stability. Examples of toxic, high cost.
Uses: plastic mold, precision measuring tools, potting appliances, preparation aircraft paint, tanker paint can paint, printing lines, etc.
