Technical Guide: Strategic Material Selection in Injection Molding -- How to choice proper plastic?

How to choice proper plastic? As the senior mold designers specializing in export tooling, we recognize that Material Selection is the cornerstone of Design for Manufacturing (DFM). When working wi

How to choice proper plastic?

As the senior mold designers specializing in export tooling, we recognize that Material Selection is the cornerstone of Design for Manufacturing (DFM). When working with international clients, we don't just "pick a plastic"—我们执行的是 "Material Engineering Validation."

Technical Guide: Strategic Material Selection in Injection Molding

Section I: Critical Factors in Material Selection

Choosing the right polymer is a balance of maximizing inherent advantages while mitigating physical limitations. For export-grade tooling, this selection dictates the mold's cooling layout, shrinkage compensation, and steel choice.

1. Ideal Scenarios for Plastic Application

Plastic is the preferred medium when the project requires:

Mass Reduction: Where light weighting is critical, and traditional materials like timber or metal are impractical.

Complex Geometries: Parts with intricate undercuts or fine details that demand high-efficiency, high-precision molding.

Structural Efficiency: Components requiring high strength-to-weight ratios under low-to-medium loads.

Functional Integration: Applications requiring self-lubrication, vibration damping, thermal insulation, or chemical resistance.

Multi-Attribute Synergy: Parts that must simultaneously be lightweight, rigid, heat-resistant, and electrically insulating.

2. Constraints and Non-Suitable Scenarios

Plastics should be avoided or heavily reinforced in the following cases:

Ultra-High Loads: Applications requiring tensile strength exceeding 300MPa or extreme structural stiffness.

Extreme Thermal Environments: Long-term exposure to temperatures exceeding 300°C–350°C.

Ultra-High Voltage: Insulation requirements exceeding 550kV.

Section II: Performance Requirements and Environmental Adaptation

The goal of professional selection is to maximize performance while minimizing the Total Cost of Ownership (TCO).

1. Environmental Survivability

A part is only as good as its resistance to its working environment. We evaluate:

Thermal Fluctuations: Ambient vs. peak operating temperatures.

Humidity & Hydrolysis: Critical for materials like PA (Nylon), which are hygroscopic and may undergo dimensional or degradative changes.

Chemical Exposure: Resistance to oils, solvents, and cleaning agents to prevent Environmental Stress Cracking (ESC).

2. Manufacturing Compatibility

We assess the resin's "Processability" to ensure stable mass production:

Thermal Stability: Resistance to degradation during the residence time in the barrel.

Melt Rheology: High-viscosity resins may require specialized gating and high-pressure machines.

Section III: Selecting Materials Based on Functional Application

1. Mechanical Performance Categories

General Structural Parts: (Bolts, brackets, handles). Low-to-medium fixed loads. Common choices: UPVC, HDPE, PP, HIPS. For higher performance: PA, POM, PC or GF (Glass Fiber) reinforced grades.

Dynamic/Kinematic Parts: (Gears, cams, bushings). These require fatigue resistance, impact strength, and self-lubrication. Standard engineering plastics include POM, PPO, PEEK, PI, and UHMWPE.

2. Thermal Management

Thermal performance is typically measured by Heat Deflection Temperature (HDT) and Vicat Softening Point.

Pro Tip: Adding Glass Fiber (GF) or mineral fillers can significantly elevate a material's HDT, allowing lower-cost resins to perform in higher-heat environments.

3. Optical, Barrier, and Electrical Properties

Optics: Amorphous plastics (PC, PMMA, PS) offer superior clarity. Crystalline plastics (PP, PE) require nucleating agents or specific processing to achieve transparency.

Barrier Properties: Critical for packaging. Multi-layer co-injection or specialized coatings (e.g., EVOH) are used to block oxygen or moisture.

Electrics: While PVC is standard for low-voltage, high-frequency/high-voltage applications require PTFE, PI, or PPS due to their superior dielectric strength and arc resistance.

Section IV: Economic Viability and Value Engineering

In the export market, Cost-Competitiveness is non-negotiable. Material costs typically represent 60%–80% of the final part cost.

Raw Material Optimization: Choosing the right grade to prevent "Over-Engineering" (e.g., using an expensive PEEK where a reinforced PPS would suffice).

Cycle Time Efficiency: Selecting materials with faster crystallization rates to reduce cooling time and lower per-part processing costs.

Tooling Longevity: Abrasive materials (like 50% GF reinforced) require hardened tool steels (H13, S136, or D2), which impacts initial investment.

Summary: The "Logic" of Professional Selection

Modern selection methods have evolved from "trial and error" to scientific models, including:

Computer-Aided Selection (CAE/MoldFlow)

Star-Profile Modeling (Visualizing trade-offs between cost, strength, and heat)

Value Analysis (VA) / Value Engineering (VE)

Why Choose JST Mould Limited for Your Next Project?

Material selection is the first step in our Zero-Defect Strategy. As a professional overseas injection mold maker, we provide:

Material Validation Reports: We cross-reference your requirements with our extensive resin database.

Equivalent Grade Sourcing: Helping you find local equivalents to high-cost brand-name resins to save costs without sacrificing quality.

Expert DFM: We analyze how your material choice affects shrinkage, warpage, and mold life.

[CTA] Contact our Engineering Team (JST Mould Limited www.jstmould.com) today for a professional Material & MoldFlow Consultation.