Plastic Material Selection Guide

Before evaluating any materials, clearly define what your product must do. Requirements typically fall into these categories:

Functional Requirements: - Mechanical: Tensile strength, impact resistance, stiffness, fatigue life - Thermal: Service temperature range (min/max), heat deflection temperature, flammability - Environmental: UV exposure, chemical contact, moisture, outdoor weathering - Electrical: Dielectric strength, surface resistivity, flame class (UL94) - Aesthetic: Color, gloss, surface finish, transparency

Regulatory Requirements: - Food contact compliance (FDA, EU 10/2011, GB 9685) - Flame retardancy (UL94, IEC 60695) - RoHS and REACH compliance - Automotive specifications (IATF 16949, OEM-specific) - Medical device classification (ISO 10993)

Economic Requirements: - Target part cost (material + processing) - Annual production volume - Tooling investment budget - Expected product lifetime

Document these requirements in a specification matrix ranked by importance (must-have vs. nice-to-have) before beginning material evaluation.

Once requirements are defined, evaluate candidate materials against these key properties:

Mechanical Properties: - Tensile Strength: Resistance to pulling forces. PP: 25-35 MPa, ABS: 40-50 MPa, PA6 GF30: 180 MPa - Impact Strength: Resistance to sudden forces. Measured by Izod or Charpy at 23°C and -20°C - Flexural Modulus: Stiffness indicator. PP: 1000-1500 MPa, ABS: 2000-2700 MPa, PA6 GF30: 8000+ MPa - Elongation at Break: Ductility. PP: 100-600%, ABS: 10-50%, PA6 GF30: 3-5%

Thermal Properties: - Heat Deflection Temperature (HDT): Temperature at which material deforms under load. PP: 100-155°C, ABS: 90-105°C, PA6 GF30: 210°C - Vicat Softening Point: Upper service temperature indicator - Coefficient of Thermal Expansion (CTE): Dimensional change with temperature. Critical for assemblies - Continuous Use Temperature: Maximum long-term service temperature

Environmental Resistance: - Chemical Resistance: Check against all chemicals in service environment - UV Resistance: Required for outdoor applications (ASA, UV-stabilized PP) - Moisture Absorption: PA6 absorbs 2.5-3.0% moisture vs PP at <0.01%

Processing Properties: - Melt Flow Index (MFI): Affects injection molding fill behavior - Shrinkage: Determines mold design and dimensional accuracy - Drying Requirements: Hygroscopic materials (PA6, ABS) require pre-drying

The intended processing method significantly influences material selection.

Injection Molding (most common): - Best for complex geometries and high-volume production - Materials need good melt flow (MFI 5-30 g/10min typical) - Wall thickness uniformity important for dimensional control - PP and ABS are excellent injection molding materials

Extrusion (films, profiles, sheets): - Requires materials with stable melt strength - LDPE/LLDPE dominate film applications - PP for sheets and thermoformed containers - Higher MFI grades preferred for thin films

Blow Molding (bottles, containers): - Requires materials with high melt strength and ESCR (Environmental Stress Crack Resistance) - HDPE is the dominant blow molding material - PP used for automotive ducts and containers

Impact on Material Selection: - If processing method is fixed, narrow your material choices first - Some materials are processing-method specific (e.g., film grades have very different MFI than injection grades) - Cycle time affects unit cost — faster-crystallizing materials (PP, PA6) offer shorter cycles than amorphous materials (ABS, PC)

Material cost is never just the price per kilogram. Consider the total cost of ownership.

Direct Material Cost: - Commodity plastics (PP, PE): $1.0-1.5/kg - Engineering plastics (ABS, PA6): $2.0-4.0/kg - High-performance (PC, PPS, PEEK): $5.0-50.0/kg - Masterbatch addition: adds $0.5-2.0/kg depending on loading - Glass fiber reinforcement: adds $0.3-0.8/kg

Processing Cost Factors: - Faster cycle times reduce per-part cost - Lower processing temperature saves energy - No drying required (PP, PE) reduces equipment and labor - Recyclable runners and scrap reduce material waste

**Lifecycle Cost Considerations: - Longer product life reduces replacement cost - Fewer warranty claims reduce service cost - Lighter materials reduce shipping cost - Single material design enables easier recycling

Cost Optimization Tips: - Don't overspecify — match properties to actual requirements - Consider filler/reinforcement instead of upgrading base polymer - Evaluate total system cost, not just material price - Negotiate volume pricing with your material supplier

Follow this systematic workflow for optimal material selection:

Step 1: Requirements Matrix List all functional, regulatory, and economic requirements. Rank by criticality (A = must-have, B = important, C = nice-to-have).

Step 2: Initial Screening Eliminate materials that clearly cannot meet A-level requirements (e.g., eliminate PP if HDT > 150°C required).

Step 3: Detailed Comparison Compare remaining candidates across all B and C requirements using datasheets and supplier technical data.

Step 4: Prototype Testing Produce sample parts in 2-3 candidate materials. Test under real-world conditions including temperature cycling, chemical exposure, and mechanical loading.

Step 5: Long-Term Validation For critical applications, conduct accelerated aging tests (1000h thermal aging, QUV weathering, humidity cycling).

Step 6: Production Qualification Validate processing parameters, dimensional stability, and quality consistency in production-scale trials.

Working with YicaiPlas: Our application engineers can assist at every stage of material selection. We provide datasheets, sample materials, and technical consultation to help you find the optimal material for your application. Contact us with your requirements to get started.