Material Recommendations and Injection Molding Process for Outdoor Overmolded Products

Material Recommendations

Base Materials (Hard Substrate)

1. Polycarbonate (PC)

• High impact resistance & excellent weather resistance

• Ideal for transparent or high-strength components

2. ABS (Acrylonitrile Butadiene Styrene)

• Cost-effective with good processability

• Suitable for general outdoor applications

3. Nylon (PA)

• Superior abrasion resistance & mechanical strength

• Best for wear-resistant parts

Overmolding Materials (Soft Layer)

1. Thermoplastic Polyurethane (TPU)

• Excellent abrasion & tear resistance

• Wide hardness range (60A-80D)

• UV and weather-resistant grades available

2. Thermoplastic Elastomers (TPE/TPR)

• Soft touch with good shock absorption

• More economical than TPU

• Must use UV-stabilized formulations

3. Silicone Rubber

• Extreme temperature resistance (-60°C to 250°C)

• Outstanding long-term weather resistance

• Higher mold costs due to specialized tooling

Injection Molding Process Requirements

Mold Design Considerations

1. Two-Shot or Overmolding Structure

• Precision alignment systems to prevent misplacement

• Account for different shrinkage rates between materials

• Runner design must avoid material cross-contamination

2. Surface Treatment

• Mirror polishing for smooth finishes

• Chrome plating recommended for wear resistance

3. Cooling System

• Optimized cooling channels for uniform heat dissipation

• Prevents warping and ensures dimensional stability

Key Process Parameters

1. Temperature Control

• Precise melt temperatures for both substrate and overmold

• Mold temperature significantly affects bonding strength

2. Injection Pressure

• Sufficient pressure for strong material adhesion

• Excessive pressure may cause flash (unwanted material seepage)

3. Cycle Time

• Proper cooling time for the substrate before overmolding

• Avoid excessive cooling, which weakens bonding

Critical Considerations

✅ Material Compatibility Testing

• Verify adhesion between substrate and overmold

• Use adhesion promoters if necessary

✅ UV & Weather Resistance

• Add UV stabilizers and antioxidants

• Test color fading under prolonged sun exposure

✅ Mold Maintenance

• Regular cleaning to prevent residue buildup

• Inspect alignment systems for accuracy

✅ Product Testing

• Accelerated aging tests (QUV, salt spray, thermal cycling)

• Evaluate mechanical performance after exposure

✅ Ejection Design

• Account for overmold elasticity during demolding

• Proper draft angles and ejection mechanisms

Conclusion

Successful outdoor overmolding requires the right material combination, optimized mold design, and strict process control. TPU and TPE are excellent choices for soft layers, while PC, ABS, or PA provide strong substrates. Proper mold maintenance and thorough testing ensure durable, high-quality products that withstand harsh outdoor conditions.