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The properties of some commonly used plastic materials
2024.10.09
The following are the properties of some commonly used plastic materials:
1.ABS plastic (Acrylonitrile Butadiene Styrene):
Physical Properties:
  • Specific gravity is 1.05 g/cm3, relatively moderate density.
  • The molding shrinkage is between 0.4% and 0.7%, which is relatively small and helps to ensure the dimensional stability of the product.
Mechanical properties:
  • Comprehensive performance is relatively good, with high impact strength, can withstand a certain degree of external impact without easy rupture.
  • Good chemical stability and electrical properties, suitable for use in a variety of environmental conditions.
Processing performance:
  • Flow better than PC (polycarbonate) and other materials, but slightly inferior to HIPS (high impact polystyrene), which makes it easy to fill the mold cavity in injection molding, able to manufacture products with more complex shapes.
  • Molding temperature is 200-240 ℃, injection molding before the need for drying treatment, drying conditions for 80-90 ℃ under the drying of 2 hours.
  • Scope of application: Wide range of uses, commonly used in the production of general product shells, such as electrical appliances shells, toy shells, etc., but also suitable for the surface needs to be high-gloss, brushed and other processing products.
2.PS plastic (polystyrene):
Physical properties:
  • Specific gravity is 1.05 g/cm3, similar to ABS plastic.
  • The molding shrinkage is between 0.6% and 0.8%, and the shrinkage is relatively stable.
Mechanical properties:
  • Electrical insulation, especially high-frequency insulation is excellent, colorless and transparent, light transmittance is second only to Plexiglas.
  • Strength in general, but the texture is brittle, easy to produce stress cracking, so it is not suitable for withstand large external forces or impact occasions.
  • Poor resistance to organic solvents such as benzene and gasoline.
Processing performance:
  • The molding temperature range is wide, 170-250°C. However, the injection temperature and pressure need to be adjusted accordingly to the molecular weight of the raw material and the shape and size of the product.
  • The molding cycle depends on the wall thickness of the product and the injection volume, and the cooling time is based on the principle of not causing deformation of the product during demolding.
  • Scope of application: It can be used for the manufacture of large lampshades, protective glass, left and right eyepiece barrels of optical instruments, and other products that require transparency and insulation, but do not require high strength.
3.PMMA plastic (polymethyl methacrylate, also known as plexiglass):
Physical Properties:
  • Specific gravity is 1.18 g/cm3, slightly denser than ABS and PS plastics.
  • The molding shrinkage rate is 0.5%-0.7%, the shrinkage rate is relatively small, which is conducive to the precise control of product size.
Optical properties:
  • It has extremely excellent transparency, with a light transmittance of 90%-92%, which is one of the best polymer transparent materials at present, and has a higher light transmittance than ordinary glass.
  • The filtering effect on ultraviolet rays varies according to the wavelength, it can effectively filter out ultraviolet rays with a wavelength of less than 300nm, but the filtering effect on ultraviolet rays between 300nm and 400nm is poor.
Mechanical properties:
  • Higher strength, with a certain degree of heat and cold resistance and insulation, but the texture is brittle, easy to melt in organic solvents, the surface hardness is slightly lower, easy to be scratched.
Processing properties:
  • Molding temperature is 160-230℃, need to dry at 70-90℃ for 4 hours before processing.
  • Scope of application: Suitable for making transparent insulated parts, such as lamp fittings, optical lenses, display racks, etc. It can also be used to make parts of general strength with high requirements for appearance.
4.POM plastic (polyoxymethylene):
Physical properties:
  • Specific gravity is between 1.41-1.43 g/cm3 with relatively high density.
  • Molding shrinkage is 1.2%-3.0%, relatively large shrinkage, the effect of shrinkage on the size of the product needs to be taken into account in design and processing.
Mechanical properties:
  • Comprehensive performance is relatively good, with high strength, stiffness and wear reduction and abrasion resistance, small water absorption and good dimensional stability.
  • High fatigue strength and good recovery, in the case of repeated stress can still maintain good performance.
Processing performance:
  • Processing temperature is narrower, 170-200 ℃, in the barrel stay a little longer or the temperature exceeds 220 ℃ will decompose, producing irritating formaldehyde gas.
  • The holding pressure during injection molding should be larger to reduce the pressure drop, and the screw speed should not be too high, and the residual amount should be less.
  • Scope of application: often used in the production of wear-reducing and wear-resistant parts, such as automobiles, machine tools, instrumentation within the parts, bearings, fasteners, gears, spring plates, pipelines, transportation belt fittings and so on.
5.PP plastic (polypropylene):
Physical Properties:
  • Specific gravity is 0.9-0.91 g/cm3, one of the lighter varieties of plastics, which makes the products lighter in weight and easier to transport and use.
  • The molding shrinkage is 1.0%-2.5%, which is relatively moderate.
Mechanical Properties:
  • It has good heat resistance, with a melting point of about 165°C, and a service temperature range of -30°C to 140°C. It can withstand a certain amount of pressure and bending at room temperature.
  • Flammable, but no harmful substances are produced during combustion, and the products of combustion are mainly carbon dioxide and water.
Processing performance:
  • Department of crystalline material, hygroscopicity is small, but prone to melt rupture, long-term contact with hot metal is easy to decompose.
  • Good mobility, but the shrinkage range and shrinkage value is large, easy to occur shrinkage holes, dents, deformation and other defects, so in the mold design and processing technology needs to be adjusted accordingly.
  • Scope of application: widely used in clothing, blankets and other fiber products, medical equipment, automobiles, bicycle parts, conveying pipes, chemical containers, food and drug packaging and other fields.
6.PE plastic (polyethylene)
Physical properties:
  • Specific gravity is 0.94-0.96 g/cm3, less dense.
  • Molding shrinkage is 1.5%-3.6%, relatively large shrinkage rate, which needs to be taken into account in product design and processing.
Mechanical properties:
  • Mechanical properties in general, relatively soft and good toughness, in addition to high impact strength, other mechanical properties in the plastic is relatively low.
  • Good chemical stability, generally insoluble in solvents below 60 ℃, but not resistant to strong oxidizers.
Processing properties:
  • Processing is mainly carried out in the molten state, such as injection molding, extrusion, blow molding, pressing and so on. The raw material can be dried without drying before processing, because its hygroscopicity is very low.
  • Scope of application: mainly used as agricultural film, industrial packaging film, pharmaceutical and food packaging film, machinery parts, daily necessities, construction materials, wire, cable insulation, coating and synthetic paper. According to the different polymerization process, can be divided into high-density polyethylene (HDPE), low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), etc., each with different performance characteristics and application areas.
7.PVC plastic (polyvinyl chloride):
Physical Properties:
  • The color is slightly yellow translucent, glossy, transparency is better than polyethylene, polypropylene, but worse than polystyrene.
  • Relative density of 1.35-1.45 g/cm3, higher density.
Mechanical properties:
  • The hardness of hard products is higher than that of low-density polyethylene and lower than that of polypropylene, and there will be whitening at the flexure.
  • It has good tensile, bending, compression and impact resistance.
Processing properties:
  • Heat stabilizers need to be added during processing to ensure the performance of the product, because of its poor heat stability, 140 ℃ that is the beginning of decomposition, melting temperature of 160 ℃.
  • Scope of application: Common products are plates, tubes, shoe soles, toys, doors and windows, wire outer skin, stationery, etc. It is widely used in chemical industry, fertilizer, construction, electroplating and other fields.
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