Most Common Plastic Resins for Injection Molding
Designing plastic parts is a complex task with many factors addressing numerous application requirements. “How will the part be used?” “How will it fit with other parts in the assembly?” “What will be the load during use?” In addition to functional and structural challenges, injection molded plastic parts Problem solving plays a big role in the design of . How the molten plastic is injected, filled and cooled into the cavities to form the part has a large impact on the shape that the features of the part should take. Following the basic rules of injection molded part design not only makes the part easier to manufacture and assemble, it also typically makes it much more durable in use. Many types of plastic resin like Polypropylene, Polyethylene, ABS resin, pvc resin etc.
Injection molding applications:
Plastic injection molding is recommended for manufacturing plastic parts. Injection molding is used to make most of the plastic products available today, including electronic housings, containers, bottle caps, automotive interiors, and combs. Multiple parts can be produced in one cycle using multi-cavity injection molding, making it ideal for high-volume production of plastic parts. Advantages of injection molding include high tolerance precision, repeatability, wide selection of materials, low labor costs, minimal scrap loss, and virtually no finishing required for molded parts. Disadvantages include a large upfront investment in tooling and process limitations.
There are two types of plastic
Thermosetting resins
First, let’s take a look at thermoplastic resins, which account for 90% of the plastics in circulation.
Main properties of thermoplastics:
It softens when heated and solidifies when cooled. This can be repeated. “Thermoplastic resin” is classified into three types according to strength and heat resistance. 1. general-purpose plastics
2. general-purpose engineering plastics
3. and super engineering plastics
General-purpose plastic
Heat resistance: less than 100°C
Strength: less than 49MPa
Flexural modulus: less than 2.4GPa
Main general-purpose resins
Polypropylene
[Regular heat resistance temperature] 100-140℃
[Features] Lowest specific gravity (0.9-0.91). Relatively high heat resistance. Excellent mechanical strength.
[Main applications] Automotive parts, home appliance parts, packaging films, food containers, medical equipment, etc.
Polyethylene
[Normal heat resistance temperature] 90 to 110°C
[Features] Excellent electrical insulation, water resistance, and chemical resistance. Whitish and opaque. [Main applications] Packaging materials (film, food containers), shampoo and conditioner containers, kerosene, gasoline tanks, plastic bags, wash basins, etc.
ABS resin
[Regular heat resistance temperature] 70 to 100°C
[Features] Excellent balance of mechanical properties such as rigidity, hardness, workability, impact resistance, and bending fatigue resistance
[Main applications] OA equipment, automobile parts (interior and exterior), Stationery , miscellaneous goods, game consoles, building materials (for indoor use), electrical appliances (air conditioners, refrigerators), etc.
Polyvinyl chloride
[Regular heat resistance temperature] 60 to 80°C
[Features] Depending on the amount of plasticizer added, it can be hard or soft, and has excellent water resistance, acid resistance, alkali resistance, and solvent resistance. and sewage pipes, flooring, wallpaper, vinyl leather, hoses, agricultural films, etc.
Methacrylic resin
[Regular heat resistance temperature] 70 to 90°C
[Features] Excellent transparency, weather resistance, surface gloss, and scratch resistance. [Main applications] Vehicle parts (tail lamp covers, door visors, meter covers), lighting plates, water tank plates, contact lenses, etc.
General-purpose engineering resin
Heat resistance: above 100℃
Strength: above 49MPa
Flexural modulus: 2.4GPa or more
Nylon/Polyamide
[Regular heat resistance temperature] 80 to 140°C
[Features] Excellent abrasion resistance, heat resistance, toughness, durability, and chemical resistance [Main applications] Automobiles, vehicles, electric/electronic equipment, industrial machinery, food film, fishing line, etc.
Main molding methods : injection molding, extrusion molding, blow molding, vacuum casting , various secondary processing
Polyacetal
[Regular heat resistance temperature] 80-120℃
[Features] Excellent mechanical strength, elasticity, impact resistance, abrasion resistance, and electrical insulation
[Main applications] Various gears, automobile parts, various fasteners, clips, etc. Main molding methods : injection molding, extrusion molding, blow molding, various secondary processing
Polycarbonate
[Regular heat resistance temperature] 120 to 130°C
[Features] Excellent transparency, impact resistance, heat resistance, flame resistance, and dimensional stability
[Main applications] Camera lenses, partitions, translucent plates for highways, cars headlamps, housings for electronic components , etc.
Main molding method : Molding methods for most thermoplastic resins are possible Polybutylene terephthalate
[Regular heat resistance temperature] 60 to 140°C
[Features] Excellent electrical properties, oil resistance, chemical resistance, friction and heat resistance, etc.
[Main applications] Electrical parts, automotive electronic parts, etc.
Main molding method : Injection molding, extrusion molding
Modified polyphenylene ether
[Continuous use temperature] –
[Features] Excellent flame resistance, oil resistance, abrasion resistance, and dimensional stability. [Main applications] OA equipment, electric/electronic parts, automotive parts, water-related parts, etc. Main molding methods : injection molding, extrusion molding, blow molding
Super engineering resin
Superior strength, heat resistance, chemical resistance, etc., compared to general-purpose engineering resins . and are mainly used as substitutes for metal parts.
Polysulfone
[Continuous use temperature] 160°C
[Features] Excellent heat resistance, hydrolysis resistance, mechanical strength, dimensional stability, transparency, chemical resistance, electrical properties, etc.
[Main applications] Electrical and electronic parts, Electronic circuit boards, automobile parts, aircraft parts (fuses, battery cases, ignition parts, etc.), precision machinery parts (clocks, cameras), microwave oven parts, coffee makers, respirators, nursing devices, contact lens sterilization cases Main molding methods : injection molding, extrusion molding, blow molding, compression molding, thermoforming
Polyether sulfone
[Continuous use temperature] 180 to 190°C
[Features] Excellent heat resistance, mechanical properties, flame resistance, chemical resistance, hot water resistance, etc.
[Main applications] Electricity, electronic parts, precision parts, automobile parts, heat resistant paint etc. Main molding method : Injection molding, extrusion molding
Polyphenylene sulfide
[Continuous use temperature] 200 to 220°C
[Features] Heat resistance, mechanical strength, flame resistance, dimensional stability, chemical resistance, electrical insulation, dielectric properties, etc.
[Main applications] Home appliances, electricity, electronic parts, Automotive parts, precision equipment parts, corrosion-resistant paints, non-adhesive paints, etc.
Main molding method : injection molding, compression molding
Polyarylate
[Continuous use temperature] 140°C
[Features] Excellent heat resistance, dimensional stability, flame resistance, mechanical properties, transparency, and weather resistance
[Main applications] Electrical and electronic products, automobile parts, precision machinery parts, Combined heat-resistant bottles for fruit juices and carbonated drinks, eye drop containers, etc. Main molding methods : injection molding, extrusion molding, blow molding
Thermosetting resin
It hardens when heated and does not soften again when cooled or reheated. (Same principle as cookies, eggs, pancakes, etc.)
Features
When the thermosetting resin is heated alone or mixed with a curing agent, a curing reaction occurs and a cured product is obtained.
Use
It has excellent heat resistance, corrosion resistance, and impregnation properties, and is used in a wide range of applications such as base materials for molding materials, adhesives, paints, electrical and electronic materials, heat-resistant materials, and laminated materials .
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