Features and Uses of Common Injection Molding raw Materials

Posted on : Aug 15, 2022 By  GREFEE

Common raw materials for injection molding include the thermal-plastic injection modeling materials, injection molding materials, etc. Each kind of material and its characteristic have a wide product range. The following is the injection molding material selection guide according to the properties and use of different varieties of materials.  

Polyvinyl Chloride (PVC)

Features: Rigid PVC has high strength, excellent insulation, good chemical stability, and strong resistance to acid and alkali, which can be used at -15℃~+60℃, with good thermoforming properties and low density. Soft PVC is not as strong as hard PVC, but it has a large elongation rate and good electrical insulation, which can be used at -15℃~+60℃. The foamed polyvinyl chloride is light in weight, and also has other features, like thermal insulation, sound insulation and vibration resistance.

Use: As a corrosion-resistant structural material, PVC is widely applied in the chemical industry, such as oil pipelines, containers, centrifugal pumps, valve fittings, insulation sheathing of wires and cables, agricultural films, industrial packaging. However, due to its toxicity, it is not suitable for food packaging. The foamed polyvinyl chloride gasket is a common packaging materials.

Polyethylene (PE)

Features: Low-pressure polyethylene is hard in texture with good wear resistance, corrosion resistance and electrical insulation properties, but poor heat resistance, which will become soft in boiling water. The high-pressure polyethylene is a lighter type of polyethylene, with high chemical stability and greater performance, good high-frequency insulation, flexibility, impact resistance and transparency. The UHMWPE has high impact strength, fatigue resistance, wear resistance, which needs to be cold-pressed.

Use: Low-pressure polyethylene is utilized to manufacture plastic plates, plastic ropes, gears and bearings that bear small loads, etc. While, the molecular weight polyethylene is used as anti-friction, anti-wear parts and transmission parts, as well as wire and cable sheathing.

Polypropylene (PP)

Features: the density of polypropylene is low and it is light in weight, which is one of the commonly used plastics. The strength, hardness, stiffness and heat resistance of PP are higher than low pressure polyethylene, which can be used for a long time at 100 ~ 120 ℃ with almost no water absorption. Its chemical stability and high frequency insulation also stand out, so it isn’t  affected by temperature . However, it is brittle at low temperature, not wear-resistant, and easy to age.

Uses: PP is used to manufacture the general mechanical parts, such as gears, pipes, joints, etc.; make corrosion-resistant parts, such as pump impellers, chemical pipelines, containers, insulating parts; make covers for televisions, radios, fans, motors, etc.

Polyamide (commonly known as nylon) (PA)

Features: Polyamide is odorless, non-toxic with high strength, good toughness, and certain heat resistance, which can be used at 100 ℃. Its is known for its excellent wear resistance and self-lubrication, small friction coefficient, good noise reduction and oil resistance, water, oil and general solvent resistance, good corrosion resistance; antibacterial mildew, and good formability. The disadvantages of PA are that a large creep, poor thermal conductivity, high water absorption, and the molding shrinkage rate is large.

Uses: the commonly used types include nylon 6, nylon 66, nylon 610, and nylon 1010,  etc. PA is used to manufacture some load-bearing and transmission parts that require wear resistance and corrosion resistance, such as bearings, gears, pulleys, screws, nuts and some small parts. Besides, it can also be used as high-pressure oil-resistant sealing rings, and anti-corrosion and wear-resistant coatings on metal surfaces.

Polymethyl methacrylate (commonly known as plexiglass) (PMMA)

Features: PMMA has good transparency, and can transmit more than 99% of sunlight. Its good colorability, certain strength, UV resistance and atmospheric aging, very corrosion resistance, excellent electrical insulation properties make it a popular material in different industries. PMMA can be used at -60~+100 ℃. However, its quality is brittle, and is soluble in organic solvents. Meanwhile, since the surface hardness is not high, easy to scratch

Use: as a material to manufacture aviation, transparent parts in the instrumentation, automotive and radio industries, such as aircraft seat windows, lamp shades, televisions, radar screens, oil markers, oil cups, equipment signs, instrument parts, etc.

Styrene-dibutylene-acrylonitrile copolymer (ABS)

Features: Its properties can be adjusted by changing the amount of the three monomers. ABS has high impact toughness and strength, excellent oil resistance, water resistance and chemical stability, high electrical insulation and cold resistance, high dimensional stability and certain wear resistance. The surface can be coated with metal, which is easy to be processed and formed, but it is easy to layer after long-term use.

Uses: manufacturing telephones, amplifiers, televisions, instruments, motor casings, gears, pump impellers, bearings, handles, pipes, tank linings, instrument panels, car bodies, car armrests, etc.

Polyoxymethylene (POM)

Features: Excellent comprehensive mechanical properties, good wear resistance, low water absorption, high dimensional stability, good colorability, good anti-friction and anti-aging properties, great electrical insulation and chemical stability, which can be used in the range of 40 ~+100℃. However, it is easy to decompose when heated, and the molding shrinkage rate is large.

Uses: manufacturing anti-friction and wear-resistant transmission parts, like bearings, rollers, gears, electrical insulating parts, corrosion-resistant parts and chemical containers, etc.

Teflon (also known as King of Plastics) (F-4)

Features: Teflon is corrosion resistant to almost all chemicals with good aging resistance and electrical insulation, as well as no water absorption. Its excellent high and low temperature resistance allow it to be used under long-condition of -195~250 ℃ for a long term. Besides, its small friction factor and self-lubricating are also remarkable. However, it cannot be thermoformed, but can only be sintered to form, which decomposes harmful gases at high temperatures, and is also expensive.

Uses: used to manufacture corrosion-resistant, anti-friction and wear-resistant parts, seals, insulating parts, such as high-frequency cables, capacitor coil formers, chemical reactors, pipelines, etc.

Polysulfone (PSF)

Features: Bisphenol A type: PSF has excellent heat resistance, cold resistance, weather resistance, creep resistance and dimensional stability, high strength, excellent electrical insulation, high chemical stability, which can be used at -100~+150℃ for a long term . Non-bisphenol A type: heat-resistant, cold-resistant, can work at -240~+260 ℃ for a long time, high hardness, self-extinguishing, aging resistance, radiation resistance, good mechanical properties and electrical insulation, and high chemical stability. However, PSF is not resistant to polar solvents.

Uses: PSF is used to manufacture high-strength, heat-resistant parts, anti-friction and wear-resistant parts, transmission parts, like precision gears, cams, vacuum pump blades, instrument shells but with poor UV resistance, high molding temperature and cover, heat-resistant or insulating instrument parts, automotive trims, dashboards, gaskets, computer parts, plated metal made of integrated electronic printed circuit boards.

Chlorinated polyether (or polychloroether)

Features: Chlorinated polyether has extremely high chemical resistance, and is easy to process and work at 120 °C for a long period of time. In addition, it also owns good mechanical properties and electrical insulation, low water absorption, and dimensional stability. However, its low temperature resistance is poor.

Uses: Chlorinated polyether is utilized to manufacture anti-friction and wear-resistant transmission parts in corrosive media, precision mechanical parts, lining and coating of chemical equipment, etc.

Polycarbonate (PC)

Features: the transparency of PC is up to 86%~92 which can be used under the condition of -100~+130℃ with good stability. In addition, PC has good toughness, impact resistance, high hardness, creep resistance, heat resistance, cold resistance, fatigue resistance, and good water absorption. However, there is a tendency for stress cracking.

Uses: airplane window covers, protective face helmets, bulletproof glass and parts of mechatronics and instruments.

Polyurethane Plastic (PUR)

Features: PUR is known for its excellent wear resistance, good toughness, high bearing capacity. It is hard but not brittle at low temperature. It is also resistant to ozone, weather, oils, radiation, and many chemicals. It is flammable. The flexible foam has excellent high and low temperature thermal insulation properties.

Uses: manufacturing seals, transmission belts, heat insulation, sound insulation and anti-vibration materials, gears, electrical insulation parts, solid tires, wire and cable sheaths, auto parts.

Bakelite (commonly known as bakelite) (PF)

Features: PF has high strength, hardness and heat resistance with the working temperature be above 100 ℃. There is extremely small friction coefficient under water lubrication conditions. The electrical insulation and corrosion resistance (except strong alkali) are good, and mold resistant and dimensionally stable. However, the quality is relatively brittle, the light resistance is poor, the color is dark, and the molding processability is poor, so it can only be molded.

Uses: manufacturing the general mechanical parts, water-lubricated bearings, electrical insulating parts, structural materials and lining materials resistant to chemical corrosion, such as instrument housings, electrical insulating boards, insulating gears, fairings, acid-resistant pumps, brake pads, etc.

Epoxy Plastic (EP)

Features: PE has high strength, good toughness, excellent point insulation, waterproof, moisture-proof, mildew-proof, heat-resistant, and cold-resistant, which can be used for a long time in the range of -80~+200℃. The  chemical stability of EP is good, and the shrinkage after curing and molding is low. It is strongly adhesive to many materials.

Uses: plastic molds, precision measuring tools, structural parts of mechanical instruments, perfusion, coating and encapsulation of electrical, electronic components and coils, repairing parts, etc.

Silicone plastic

Features: Silicone plastic has high heat resistance, which can be used for a long time at 180~200℃. In addition, silicone plastic has excellent electrical insulation, good insulation for high-voltage arcs and high frequency, good moisture resistance, certain chemical resistance, radiation resistance, ozone resistance, and low temperature resistance, but is expensive.

Use: For high-frequency insulating parts, electrical and electrical insulating parts in humid tropical areas, perfusion and fixing of electrical and electronic components and coils, heat-resistant parts, etc.

Polypara-carboxybenzoate plastic

Features: Polypara-carboxybenzoate plastic is a new heat-resistant thermosetting plastic, of which the long-term use temperature is at 315°C, and the short-term use temperature range is 371-427°C. Its thermal conductivity is extremely high, which is 3-5 times higher than that of ordinary plastics. It has good wear resistance and self-lubrication, and excellent electrical insulation. , abrasion resistance and self-extinguishing.

Uses: used to produce the self-lubricating bearings with wear resistance, corrosion resistance, and dimensional stability. It also can be used to manufacture high pressure sealing rings, automotive engine parts, electronic and electrical components, and fibers and films for special purposes.

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