7 Common Plastic Resins Used in Injection Molding

Injection molding is a widely used process for producing plastic parts in large volumes. The type of plastic resin selected significantly influences the properties of the final product, such as its strength, flexibility, heat resistance, and chemical durability. Below, we’ve outlined seven commonly used plastic resins in injection molding, highlighting their key properties and typical applications:

Summary Table: Common Plastic Resins in Injection Molding

1. Acrylonitrile Butadiene Styrene (ABS)

Properties:

• Impact Resistance: ABS is well known for its toughness and ability to resist impacts, making it perfect for products that need to endure physical stress.
• Dimensional Stability: It maintains its shape well, even when exposed to heat.
• Easy to Process: ABS is easy to mold and can achieve a smooth surface finish.
• Moderate Heat Resistance: Although not the most heat-resistant plastic, it performs well under moderate temperatures.

Applications:

• Consumer Electronics: Frequently used in TV housings, remote controls, and keyboard keycaps.
• Automotive Parts: Used for bumpers, interior panels, and dashboard components.
• Toys: Common in durable toys like Lego bricks.

2. Polyethylene (PE)

Properties:

• Affordable and Versatile: PE is a cost-effective resin that’s easy to process, making it one of the most common choices.
• Chemical Resistance: It’s resistant to acids, bases, and solvents, which makes it ideal for challenging environments.
• Low Moisture Absorption: PE doesn’t absorb moisture easily, helping it maintain its strength and rigidity.
• Flexibility: PE is quite flexible, especially in its low-density form (LDPE).

Applications:

• Packaging: Used for plastic bags, bottles, containers, and films.
• Medical: Found in syringes, tubing, and implants.
• Toys: Used in plastic playsets and action figures.

3. Polypropylene (PP)

Properties:

• High Chemical Resistance: PP is resistant to a wide range of chemicals, making it suitable for tough, chemically demanding applications.
• Fatigue Resistance: It can withstand repeated bending, which makes it perfect for applications like living hinges.
• Lightweight: PP is lighter than many other resins, ideal for applications where weight matters.
• Moderate Heat Resistance: PP can withstand temperatures up to about 100°C (212°F), though it’s not as heat-resistant as some other materials.

Applications:

• Packaging: Widely used in food containers, bottles, and caps.
• Automotive: Found in interior panels, dashboards, and trays.
• Textiles: Used in nonwoven fabrics, filters, and carpet fibers.

4. Polystyrene (PS)

Properties:

• Brittle: While PS is rigid, it tends to be more brittle compared to other resins, making it less impact-resistant.
• Low Cost: Its affordability makes it a popular choice for disposable products.
• Good Surface Finish: PS can achieve a glossy, smooth finish, which is ideal for aesthetic products.
• Electrical Insulation: It has excellent insulating properties, which make it suitable for electrical components.

Applications:

• Consumer Goods: Used in disposable cutlery, food containers, and cups.
• Packaging: Common in clamshell packaging and plastic trays.
• Electronics: Utilized in enclosures and electrical components.

5. Polyvinyl Chloride (PVC)

Properties:

• Chemical and Weather Resistance: PVC is highly resistant to acids, alkalis, and outdoor weather conditions.
• Rigid and Strong: When in its rigid form, PVC offers excellent strength and structural integrity.
• Versatile: It can be made flexible or rigid by adding plasticizers.
• Electrical Insulation: Often used for electrical cables and insulation.

Applications:

• Building Materials: Used in pipes, window frames, and flooring.
• Medical: Found in blood bags, medical tubing, and surgical gloves.
• Packaging: Used in blister packs and bottles.

6. Nylon (Polyamide, PA)

Properties:

• High Strength and Durability: Nylon is known for its excellent tensile strength and resistance to wear, making it ideal for high-stress applications.
• Abrasion Resistance: It performs well in moving parts and machinery, resisting wear and tear.
• Heat Resistance: Nylon can handle temperatures up to around 150°C (302°F).
• Moisture Absorption: Nylon can absorb moisture, which may affect its mechanical properties unless treated properly.

Applications:

• Automotive: Used in gears, bearings, and fuel lines.
• Consumer Goods: Common in textiles, towels, and bags.
• Industrial: Found in conveyor belts, brushes, and wires.

7. Polycarbonate (PC)

Properties:

• Impact Resistance: Polycarbonate is a tough material that performs well under high-impact conditions.
• Optical Clarity: It’s transparent, which makes it ideal for applications requiring clear components.
• Heat Resistance: PC can withstand temperatures up to 135°C (275°F) without significant degradation.
• UV Resistance: It can be treated to resist UV damage, making it perfect for outdoor applications.

Applications:

• Automotive: Used in headlamp lenses, sunroofs, and interior components.
• Electronics: Found in casings for smartphones, TV screens, and computers.
• Medical: Used in medical devices, surgical instruments, and protective eyewear.

Conclusion:

Choosing the right resin for injection molding depends on your product’s requirements—whether it’s strength, durability, heat resistance, flexibility, or transparency. Each of these seven resins—ABS, PE, PP, PS, PVC, Nylon, and Polycarbonate—has its own unique advantages, making it suitable for a variety of applications across industries such as consumer goods, automotive, and medical devices. Understanding the properties of each resin will help you make the most informed decision for your injection molding projects.