Plastic Materials in Injection Molding: Key Properties And Applications

1. General-Purpose Plastics

(1) ABS (Acrylonitrile Butadiene Styrene)

• Key Properties:

• Good balance of strength, toughness, and rigidity.

• Excellent surface finish (paintable and electroplatable).

• Limited heat resistance (80–100°C).

• Applications: Automotive interiors, electronic housings, toys.

(2) PP (Polypropylene)

• Key Properties:

• Lightweight, chemically resistant (to acids and bases).

• Poor UV resistance, prone to warping (high shrinkage).

• Food-safe grades available.

• Applications: Food containers, medical devices, household products.

(3) PS (Polystyrene)

• Key Properties:

• High clarity, easy to process, low cost.

• Brittle, poor impact resistance.

• Applications: Disposable cutlery, CD cases, optical components.

2. Engineering Plastics

(4) PC (Polycarbonate)

• Key Properties:

• High impact strength and transparency.

• Resistant to high temperatures (up to 120°C).

• Prone to stress cracking (requires careful mold design).

• Applications: Safety goggles, smartphone cases, automotive headlights.

(5) PA (Nylon, Polyamide)

• Key Properties:

• Excellent wear resistance and self-lubrication.

• Absorbs moisture (must be dried before molding).

• PA66 has higher heat resistance than PA6.

• Applications: Gears, bearings, industrial tubing.

(6) POM (Polyoxymethylene, Acetal)

• Key Properties:

• High stiffness and fatigue resistance.

• Releases formaldehyde during processing (good ventilation needed).

• Applications: Precision gears, zippers, pump components.

3. High-Performance Plastics

(7) PEEK (Polyether Ether Ketone)

• Key Properties:

• Extremely high heat resistance (up to 260°C).

• Expensive and difficult to process (high melting point).

• Applications: Aerospace components, medical implants.

(8) PTFE (Polytetrafluoroethylene, Teflon®)

• Key Properties:

• Chemically inert (resists even strong acids).

• Poor flow properties (usually compression-molded, not injection-molded).

• Applications: Non-stick coatings, chemical seals.

4. Thermoplastic Elastomers (TPEs)

(9) TPE/TPR (Thermoplastic Elastomer/Rubber)

• Key Properties:

• Soft, flexible, and recyclable.

• Wide hardness range (Shore A 10–90).

• Applications: Grips, medical tubing, soft-touch handles.

(10) TPU (Thermoplastic Polyurethane)

• Key Properties:

• Superior abrasion resistance compared to TPE.

• Sensitive to hydrolysis (avoid in humid environments).

• Applications: Shoe soles, protective cases, industrial belts.

Material Selection Guide

Injection Molding Tips

1. Pre-Drying: Nylon (PA) and PC must be dried to avoid defects.

2. Mold Temperature:

• POM requires high mold temps (80°C+) to reduce shrinkage.

• TPU needs cooler molds (20–40°C) to prevent sticking.

3. Shrinkage Compensation: PP shrinks the most (1.5–2.5%), while ABS and PC shrink less (~0.5–0.7%).

Final Thoughts

Choosing the right plastic depends on the application’s mechanical, thermal, and cost requirements. For example:

• Low-cost housings: ABS or PP.

• High-strength parts: PC or glass-filled nylon (PA+GF).

• Flexible components: TPE or TPU.