What plastics can be injection-molded?

Injection molding can utilize a wide variety of plastics. Here are some commonly used types:

1. Polyethylene (PE)

  • Types:
    • Low-Density Polyethylene (LDPE):
      • Applications: Plastic bags, squeeze bottles, tubing, and toys.
      • Properties: Flexible, impact-resistant, low cost.
      • Data: Density around 0.91–0.93 g/cm³; melting point approximately 110–115°C.
    • High-Density Polyethylene (HDPE):
      • Applications: Milk jugs, detergent bottles, pipes, and playground equipment.
      • Properties: Stiff, strong, excellent chemical resistance.
      • Data: Density around 0.94–0.97 g/cm³; melting point approximately 120–130°C.

2. Polypropylene (PP)

  • Applications: Automotive parts, food containers, textiles, medical devices.
  • Properties: Lightweight, fatigue-resistant, resistant to chemicals and moisture.
  • Data: Density around 0.90–0.91 g/cm³; melting point approximately 160–170°C.
  • Market: One of the most produced plastics globally, with a market size of over 70 million metric tons annually.

3. Acrylonitrile Butadiene Styrene (ABS)

  • Applications: Electronic housings, automotive trim components, toys (e.g., LEGO), helmets.
  • Properties: Tough, impact-resistant, good machinability.
  • Data: Density around 1.04 g/cm³; melting point approximately 105–125°C.
  • Advantages: High strength-to-weight ratio, easily colored and finished.

4. Polystyrene (PS)

  • Types:
    • General Purpose Polystyrene (GPPS):
      • Applications: CD cases, clear plastic cups, models.
      • Properties: Clear, rigid, brittle.
    • High Impact Polystyrene (HIPS):
      • Applications: Refrigerator liners, packaging trays, food service items.
      • Properties: Tough, impact-resistant, opaque.
  • Data: Density around 1.04–1.06 g/cm³; melting point approximately 100–105°C.

5. Polyvinyl Chloride (PVC)

  • Applications: Pipes, fittings, medical tubing, window frames, credit cards.
  • Properties: Durable, weather-resistant, good electrical insulation.
  • Data: Density around 1.3–1.45 g/cm³; melting point approximately 100–260°C (decomposes before melting).
  • Note: Can be rigid (uPVC) or flexible (with plasticizers).

6. Polycarbonate (PC)

  • Applications: Eyewear lenses, optical discs (CDs, DVDs), safety helmets, bulletproof glass.
  • Properties: High impact resistance, clarity, temperature resistance.
  • Data: Density around 1.20 g/cm³; melting point approximately 267°C.
  • Strength: Tensile strength about 60–70 MPa, making it suitable for protective applications.

7. Nylon (Polyamide)

  • Applications: Gears, bearings, bushings, cable ties, automotive components.
  • Properties: Strong, wear-resistant, low friction.
  • Data: Density around 1.15 g/cm³; melting point approximately 190–350°C, depending on type.
  • Moisture Absorption: Can absorb moisture, affecting dimensional stability.

8. Thermoplastic Elastomers (TPE)

  • Applications: Soft grips, flexible hoses, gaskets, overmolded components.
  • Properties: Combines rubber-like elasticity with thermoplastic processing ease.
  • Data: Hardness range from 20 Shore A to 85 Shore D.
  • Advantages: Can be recycled, overmolded onto other plastics.

9. Polyethylene Terephthalate (PET)

  • Applications: Beverage bottles, food containers, fibers for clothing, and packaging.
  • Properties: Strong, lightweight, good gas barrier.
  • Data: Density around 1.38 g/cm³; melting point approximately 250°C.
  • Recyclability: Widely recycled, with a significant role in the circular economy.

10. Polyoxymethylene (POM)

  • Applications: Precision gears, bearings, fasteners, and automotive parts.
  • Properties: High stiffness, low friction, good dimensional stability.
  • Data: Density around 1.41 g/cm³; melting point approximately 175°C.
  • Mechanical Strength: Tensile strength about 60–70 MPa, suitable for mechanical applications.

Conclusion

Each type of plastic offers unique properties that make it suitable for specific applications in injection molding. Selection depends on factors such as mechanical requirements, environmental conditions, and cost-effectiveness. The broad range of materials available makes injection molding a versatile solution for various industries, from automotive to consumer products and beyond. As technology advances, new materials and techniques continue to expand the capabilities and applications of plastic injection molding.