Comparing PEEK, PEI, PPS, high-temperature nylon, and other materials for demanding thermal environments.
Standard engineering thermoplastics — ABS, PC, standard nylon — handle most injection molding applications comfortably. But for parts operating continuously above 120°C, near engines or electronics generating sustained heat, in sterilization environments, or under aerospace temperature cycling, standard resins fail. High-temperature thermoplastics fill this gap.
This guide compares the major heat-resistant injection molding materials, what each is suited for, and the processing demands each places on tooling and equipment.
PEEK — Polyetheretherketone
PEEK is the benchmark high-performance thermoplastic. Its continuous service temperature reaches 240°C, its tensile strength exceeds most metals on a weight basis, it is inherently UL 94 V-0 rated, and it is biocompatible in implantable-grade formulations. It is also the most expensive widely available engineering thermoplastic — typically 10–20× the cost of nylon.
PEEK requires melt temperatures of 360–400°C and mold temperatures of 160–200°C — beyond the capability of many standard injection molding machines. It is used in aerospace structural components, orthopedic implants, semiconductor handling equipment, and demanding industrial applications where no alternative material qualifies.
PEI — Polyetherimide (Ultem)
PEI (Ultem) offers a glass transition temperature of 217°C — the highest Tg of any amorphous thermoplastic in common production use. It is inherently flame-retardant (UL 94 V-0 at 0.8 mm), transparent in unfilled grades, and steam-autoclavable at 134°C — making it the standard material for autoclave-compatible medical device components.
PEI processes at 340–425°C melt temperature with 140–175°C mold temperature — demanding, but more accessible than PEEK for many molding operations. It is used in surgical instruments, aerospace interior panels, electrical connectors, and medical device housings.
PPS — Polyphenylene Sulfide (Fortron, Ryton)
PPS is a semi-crystalline polymer with exceptional chemical resistance, inherent flame retardancy, and a continuous service temperature of 200–220°C. It is the first choice for under-hood automotive components exposed to fuels, oils, and coolants at elevated temperature — pump housings, valve bodies, impellers, and sensor housings.
PPS is brittle in unfilled form — typically used with glass or mineral reinforcement (40% GF PPS is common), which improves impact resistance while maintaining its chemical and thermal advantages.
High-Temperature Nylon (PPA, PA 4/6, PA 6T)
Beyond standard PA 6/6 (HDT ~65°C unfilled, ~240°C GF30), the nylon family extends into high-temperature grades:
- PA 4/6 (Stanyl): Higher crystallinity than PA 6/6, HDT of GF30 grade up to 280°C — automotive transmission components and gear systems.
- PA 6T / PA 6I blends (polyphthalamide, PPA): HDT of 290–300°C with 30% glass — small engine components, electrical connectors, under-hood automotive.
- PA 9T: Excellent moisture resistance combined with heat performance — electrical and automotive applications.
LCP — Liquid Crystal Polymer
LCP is unique in the engineering thermoplastic world — it has inherently very low melt viscosity, allowing it to fill extremely thin walls and intricate geometries that no other material can fill at production speed. Its continuous service temperature reaches 200–300°C depending on grade, and it is inherently UL 94 V-0.
LCP is the dominant material for miniaturized connectors, surface-mount device (SMD) packaging, and precision electronic components where thin walls, tight tolerances, and solder-reflow temperature resistance (260°C) are simultaneously required.
Material Selection Summary
| Material | Best For | Common Applications |
|---|---|---|
| PEEK | Extreme heat (240°C continuous), biocompatibility, and mechanical performance. | Aerospace, orthopedics, and semiconductor handling. |
| PEI (Ultem) | Highest Tg (217°C), steam autoclave compatibility, transparency, and inherent flame retardancy. | Medical instruments, aerospace interiors, and electrical applications. |
| PPS | Chemical resistance, heat resistance to 200°C, and inherent flame retardancy. | Automotive under-hood components, fluid handling, and electrical applications. |
| PPA / PA 6T | High-temperature nylon processing window and lower cost than PEEK or PEI. | Connectors, small-engine components, and automotive applications. |
| LCP | Thin walls, fast filling, and solder-reflow resistance. | Miniature connectors and SMD packages. |
| GF30 PA 6/6 | Cost-effective heat resistance with HDT up to approximately 240°C. | Structural under-hood components, industrial parts, and general engineering applications. |
Frequently Asked Questions
What plastic can withstand 200°C continuously?
Several high-performance thermoplastics handle 200°C continuous service: PPS (polyphenylene sulfide) and its glass-filled grades are the cost-effective choice for chemical and heat-resistant applications. PEEK and PEI handle 200°C and higher. Semi-crystalline grades of LCP can also operate in this range. Standard PA 6/6, ABS, and PC cannot.
Can standard injection molding equipment run PEEK?
Not always. PEEK requires melt temperatures of 360–400°C and mold temperatures of 160–200°C. Standard injection molding machines are typically rated to 350°C barrel temperature and 120°C mold temperature. PEEK processing requires upgraded barrel heaters, high-temperature mold temperature controllers, and often a specialized screw designed for abrasion resistance.
Related Guides
- What is ABS? Advantages and Usage of Acrylonitrile Butadiene Styrene in Injection Molding
- Polycarbonate Injection Molding: How to Design, Process, and Specify PC Parts
- How Plastic Manufacturing Works: Which Process is Right for Your Part?
- Types of Nylon: How to Choose the Right Grade for Your Part?
- Guide to Injection Molding Material Selection
