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Injection Molding Material Selection Guide: Avoid Costly Failures for Custom Parts

Created on 05.21

Meta Description: A practical guide to selecting injection molding materials, comparing mainstream plastics (PP, ABS, PC, POM, PA66, TPU) and matching them to application scenarios, helping you avoid material-related failures and cost overruns.

Selecting the right plastic material is critical for custom injection molding parts—choosing the wrong material can lead to costly failures: parts crack during assembly, warp in use, fail to withstand environmental conditions, or exceed raw material budgets. As an OEM manufacturer with years of experience, we’ve compiled this guide to help you select the optimal material for your project, balancing performance, cost, and manufacturability.

Key Factors to Consider When Selecting Injection Molding Materials

Before choosing a material, align your selection with three core requirements: part function, application environment, and manufacturing feasibility.

1. Part Function & Performance Requirements

Define non-negotiable performance metrics (strength, flexibility, heat resistance, chemical resistance) based on how the part will be used. For example, structural parts need high strength, while flexible components need ductility.

2. Application Environment

Consider the environment the part will face: temperature (high/low), moisture, chemicals, UV exposure, and wear. These factors directly determine material selection.

3. Manufacturability & Cost

Some materials are easier to mold than others—complex parts require materials with good flowability. Also, balance material cost with performance: avoid over-specifying high-cost materials when a lower-cost option meets your needs.

Mainstream Injection Molding Materials: Comparison & Applications

• PP (Polypropylene): Low cost (typically $1.00-$1.80/kg), good chemical resistance, and excellent flowability. Ideal for non-structural parts (e.g., containers, covers, automotive interior parts). Limitation: Low impact resistance at low temperatures (below -10℃, impact strength drops significantly; choose impact-modified PP for low-temperature applications).

• ABS (Acrylonitrile Butadiene Styrene): Balances strength, impact resistance, and machinability. Suitable for structural parts (e.g., consumer electronics enclosures, automotive parts). Limitation: Poor UV resistance (needs coating for outdoor use).

• PC (Polycarbonate): High transparency, impact resistance, and heat resistance (up to 120°C). Ideal for parts requiring clarity (e.g., lenses, medical devices, safety shields). Limitation: High cost, prone to scratching.

• POM (Polyoxymethylene): High rigidity, wear resistance, and dimensional stability. Suitable for moving parts (e.g., gears, bearings, fasteners). Limitation: Poor chemical resistance to strong acids/bases.

• PA66 (Nylon 66): High strength, toughness, and wear resistance. Ideal for structural parts exposed to wear (e.g., automotive components, industrial gears). Limitation: Absorbs moisture, which affects dimensional stability.

• TPU (Thermoplastic Polyurethane): Flexible, elastic, and resistant to wear and oil. Suitable for soft components (e.g., gaskets, seals, medical tubing). Limitation: Higher cost than rigid plastics.

Common Material Selection Mistakes to Avoid

• Over-Specifying Materials: Choosing PC (typically $3.50-$5.00/kg) when PP meets your performance needs—unnecessarily increasing material cost by 200%-300%.

• Ignoring Environmental Factors: Using ABS for outdoor parts without UV coating—leading to material degradation and part failure.

• Neglecting Flowability: Choosing a rigid material (e.g., POM) for complex parts with thin walls—causing filling difficulties and short shots.

Our team can help you select the optimal material for your custom part, leveraging our stock of mainstream materials to shorten lead times and reduce costs. Contact us for personalized material recommendation.