Last updated: 2026-09-04 · 5 min read

High-Temp Resin Selection — When Do You Need PEEK, PPS, PEI or PPA Instead of Standard Engineering Resins, and What Are the Mold and Process Requirements?

High-temp resins (PEEK, PPS, PEI, PPA) are specified when the part must operate continuously above 150°C, resist aggressive chemicals, or meet flame-retardancy requirements at thin wall sections. These resins cost $15–120/kg (vs. $3–8/kg for PC, PA66 or PBT) and require mold temperatures of 150–220°C, melt temperatures of 320–400°C, and hardened steel molds with wear-resistant coatings.

Key Facts

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  • Four resins compared: PEEK (250°C, $80–120/kg), PPS GF40 (220°C, $15–25/kg), PEI/Ultem (170°C, $25–45/kg), PPA GF30 (190°C, $18–30/kg). Selection driven by maximum continuous use temperature.
  • Four mold modifications: heated mold with TC unit (150–220°C, adds $3K–8K), hardened steel H13/S136 with TiN/CrN coating ($500–1,500/cavity), high-temp barrel 350–400°C ($10K–25K machine upgrade), desiccant dryer at −40°C dew point.
  • Material cost per part: 3–10× higher than standard resins. Total cost per part: 5–8× (longer cycle + specialized equipment). PPS saves 60–80% vs. PEEK for applications below 220°C.

    • Cavity — The hollow space inside the mold that forms the part shape. Multi-cavity molds produce multiple parts per shot. Cavity count determines production output but also mold cost and complexity. Each cavity must be balanced for uniform fill. The related guide covers adjacent topics.

    How Do the Four Most Common High-Temp Resins Compare?

    Five grades compared on temperature, cost and process requirements:

    Resin Continuous Use Temp Price (per kg) Mold Temp Required Key Application
    PEEK (unfilled) 250°C $80–120 180–220°C Aerospace, oil & gas, medical implants
    PEEK GF30 250°C $90–130 180–220°C Structural brackets, gears, bearings
    PPS (GF40) 220°C $15–25 150–180°C Under-hood automotive, electrical connectors
    PEI (Ultem) 170°C $25–45 150–180°C Medical devices, aerospace interiors
    PPA (GF30) 190°C $18–30 150–170°C Electrical connectors, ECU housings

    The selection decision is driven by the maximum continuous use temperature: PEEK for above 220°C, PPS for 180–220°C, PEI for 150–170°C, and PPA for 150–190°C. PPS and PPA are the most cost-effective for automotive under-hood applications; PEEK is specified when the temperature exceeds 220°C or when chemical resistance to aggressive solvents is required.

    What Mold and Process Modifications Are Required for High-Temp Resins?

    1. Heated mold with temperature control unit. High-temp resins require mold temperatures of 150–220°C — far above the 60–100°C used for standard resins. The mold must use a dedicated high-temperature TC unit (oil-based or electric heating) that maintains the mold within ±2°C. Standard water-based controllers cannot these temperatures.
      The heated mold adds $3,000–8,000 to the mold cost.
    2. Hardened steel mold with wear-resistant coating. Glass-filled and carbon-filled high-temp resins (GF30, CF30) are highly abrasive — they wear standard P20 steel within 20,000–50,000 shots. The mold must use hardened steel (H13 at 48–52 HRC or S136 at 50–54 HRC) with a wear-resistant coating (TiN, CrN or DLC) on cavity surfaces.
      The coating adds $500–1,500 per cavity but extends mold life from 50,000 to 500,000+ shots.
    3. High-temperature nozzle and barrel. The machine must have a high-temperature barrel capable of reaching 350–400°C (for PEEK). Standard machines are limited to 300°C. The nozzle, check ring and screw must be bimetallic or tungsten-carbide-lined to resist abrasion from glass fibers. The machine upgrade adds $10,000–25,000.
    4. Material drying and handling. High-temp resins are hygroscopic and must be dried to below 0.02% moisture.
      PEEK: 150°C for 4 hours; PPS: 150°C for 3 hours; PEI: 150°C for 4 hours. A desiccant dryer with −40°C dew point is required. Insufficient drying causes hydrolysis — reducing mechanical properties by 30–50% and creating splay and bubbles.

    All four modifications are mandatory. Skipping any one of them results in premature mold wear, poor surface finish, or degraded mechanical properties.
    The total investment for running high-temp resins (mold modifications + machine upgrade) is $15,000–40,000 above a standard molding setup.

    Shrinkage — The dimensional reduction from mold cavity to cooled part. Amorphous resins: 0.4–0.7% (uniform). Semi-crystalline: 1.0–2.5% (directional). Mold makers apply shrinkage factor when machining cavity. Actual shrinkage varies with wall thickness, gate location and packing pressure. The related guide covers adjacent topics.

    PPS (GF40) at $15–25/kg is the cost-effective alternative to PEEK at $80–120/kg for applications below 220°C. PPS handles under-hood automotive temperatures, resists fuels and coolants, and saves 60–80% on material cost. PEEK is justified only when the temperature exceeds 220°C or when aggressive chemical resistance is required.

  • Key parameter identified — critical variable confirmed against spec.
  • Tolerance within achievable range — commercial ±0.15mm or tighter as needed.
  • Material matched to application — resin grade selected for end-use environment.
  • Process window validated at T1 — parameters locked after first trial.
  • Inspection method defined — CMM, visual, or functional test specified.

    • Frequently Asked Questions

    Can you use a standard mold for high-temp resins?

    A standard mold (P20 steel, water-based temperature control, standard nozzle) cannot be used — the mold temperature is too low, the steel wears too quickly, and the machine barrel cannot the required melt temperature. However, if the mold base is in good condition, the cavity inserts can be replaced with hardened steel (H13 or S136) inserts, and the mold can be fitted with heating elements and insulation plates.

    The conversion costs $5,000–15,000 depending on mold size — less than building a new mold from scratch ($15,000–40,000).

    What is the cost difference per part between high-temp and standard resins?

    The material cost per part is 3–10× higher: a 20 g part in PEEK costs $1.60–2.40 in material alone, compared to $0.06–0.16 for the same part in PC or PA66. The molding cost is also higher: cycle time is 20–40% longer, and the machine rate is 30–50% higher.

    The total cost per part for PEEK is typically 5–8× the cost of the same part in PC. The justification is the performance: PEEK parts operate at 250°C continuously and resist aggressive solvents that PC cannot withstand.

    Is PPS a viable lower-cost alternative to PEEK?

    Yes — PPS (GF40) costs $15–25/kg compared to PEEK at $80–120/kg, a 4–6× cost reduction. PPS handles continuous temperatures up to 220°C and has excellent chemical resistance to fuels, solvents and coolants. For automotive under-hood applications where the temperature stays below 200°C, PPS is the cost-effective choice.

    PEEK is only justified when the temperature exceeds 220°C, when tensile strength above 200 MPa is required, or when the application requires specific biocompatibility data — values are quoted from the resin supplier’s document for the grade you select.

    Key Takeaways

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  • High-temp resins (PEEK, PPS, PEI, PPA) specified for continuous use above 150°C.
  • PEEK: 250°C at $80–120/kg; PPS: 220°C at $15–25/kg; PEI: 170°C at $25–45/kg.
  • Mold modifications: heated mold, hardened steel + coating, high-temp barrel, desiccant dryer.
  • PPS saves 60–80% vs.
    PEEK for applications below 220°C.

    • If your application requires a high-temp resin, send the operating temperature, the chemical environment and the target volume for a resin comparison. The review recommends the lowest-cost resin that meets the temperature and chemical requirements, estimates the mold modification cost, and calculates the per-part cost difference.

    Sources: Solvay PEEK Design Guide · SABIC ULTEM (PEI) Processing Manual · Toray PPS Technical Data · ASTM International — High-Temp Plastic Testing Standards · Society of Plastics Engineers (SPE)

    — Arthur, Tooling Engineer at aCatMould