High-Temperature Plastic Injection Molding

Key Takeaways

• Tooling Must Withstand Extreme Heat – High-temperature resins require molds capable of handling temperatures up to 400°F (205°C) or more, with careful attention to tooling material, heating systems, cooling systems, and venting to prevent defects and maintain part quality.

• Resin Selection Depends on Application Needs – Materials like PEEK, Torlon, PPS, and Ultem offer varying balances of heat tolerance, chemical resistance, processability, and cost, making it essential to match resin properties to the part’s performance requirements.

• Processing Demands Are Higher for High-Temp Resins – These resins are hygroscopic, abrasive, and require specialized drying, purging, and high-temperature-capable equipment, which can increase wear on tooling and machinery.

 

When working with high-temperature plastic injection molding, both the tooling and resin selection are critical due to the extreme temperatures involved. High-temperature resins can be a less expensive option for metal-to-plastic conversions in high-heat applications. The following overview outlines key considerations and compares popular high-performance resins:

Tooling Considerations

1. Tooling Material
   High-temp resins require tooling that can withstand mold temperatures up to 400°F (205°C) or more:

• • H13 Tool Steel: Common choice due to high strength and thermal fatigue resistance.
  • Stainless Steel (e.g., 420 SS): Useful when corrosion resistance is needed.
  • Beryllium-Copper Inserts: For improved thermal conductivity in specific mold areas.

2. Heater Systems

• • Use oil or electric cartridge heaters to maintain high mold temps (350°F–400°F / 177°C–205°C).
  • Thermal insulation is critical to reduce energy loss and protect operators.

3. Cooling System

• • Cooling must be controlled and uniform.
  • High-temp molds may need pressurized water or oil systems.

4. Ventilation

• • High-temp resins outgas more—proper venting prevents short shots and burning.

5. Surface Finish & Mold Design

• • Polished cavities reduce resin sticking.
  • Mold must account for high shrinkage or warping behavior.
  • Highly recommend MoldFlow analysis and DFM review before launching tooling.

Resin Comparison (Temp Ratings & Notes)

Resin	Max Use Temp (°F / °C)	Processing Temp (°F / °C)	Mold Temp (°F / °C)	Notes
PEEK (Polyether ether ketone)	~480°F / 250°C	680–750°F / 360–400°C	350–400°F / 175–205°C	Excellent strength, chemical and creep resistance. Expensive and demanding to mold.
Torlon (PAI – Polyamide-imide)	~500°F / 260°C	650–700°F / 343–371°C	350–400°F / 175–205°C	Superior strength and dimensional stability. Hygroscopic; needs thorough drying.
Polyamide (Nylon 6/6)	~300°F / 150°C	500–550°F / 260–290°C	150–200°F / 65–93°C	Easy to process; absorbs moisture and may warp. Not ideal for ultra-high-temp applications.
Polyphenylene sulfide (PPS)	~425°F / 220°C	600–650°F / 315–343°C	275–325°F / 135–160°C	Great chemical resistance and dimensional stability. Flows well; good for thin walls.
Polyetherimide (Ultem)	~340°F / 170°C	650–750°F / 343–400°C	275–350°F / 135–175°C	Transparent amber, high heat and flame resistance. Can be brittle if not processed properly.

 

Additional Considerations

1. Material Handling

• • All these resins are hygroscopic—must be dried before molding (some require 4–16 hours at 250–300°F / 120–150°C).
  • Clean purging procedures are critical to prevent degradation or contamination.

2. Machine Capabilities

• • High-temp barrel heaters and specialized screws required.
  • Need machines rated for injection temps up to 800°F (430°C) for PEEK or Torlon.

3. Wear and Tear

• • These materials are abrasive and can erode tooling/screws.
  • Use nitrided or coated screws and barrels.

Would you like a downloadable comparison chart or need help selecting the best resin for a specific application (e.g., aerospace, automotive, medical)? Contact us at info@vitalplastics.com or call us at 715-688-4820.

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