PEEK vs PPS: Complete Engineering Comparison (2026) — Cost

Which Material Should You Choose?Choose PEEK (Polyetheretherketone) if:PEEK provides the best balance of processability, mechanical properties, and temperature capabilityChoose PPS (Polyphenylene Sulfide) if:PBI offers the highest continuous use...

When an application demands continuous operation above 200°C, the field of suitable thermoplastics narrows dramatically. Four polymers dominate the high-temperature engineering landscape: PEEK, PPS, PI (polyimide), and PBI (polybenzimidazole). Each occupies a distinct niche defined by its thermal ceiling, mechanical performance, chemical resistance, processability, and cost. Selecting the wrong material is not merely expensive — in aerospace, semiconductor, and oil & gas applications, it can mean catastrophic part failure.

Property Comparison Table

PEEK: The Balanced High-Performance Option

PEEK occupies the sweet spot between performance and processability. It is the only one of these four materials that can be injection molded while delivering a continuous use temperature of 260°C. Its semicrystalline structure provides excellent chemical resistance across a broad range of solvents, acids, and bases — only concentrated sulfuric acid, hydrofluoric acid, and a few halogenated solvents attack PEEK at elevated temperatures. PEEK's mechanical properties are strong and consistent: 100 MPa tensile strength (unfilled), excellent fatigue resistance, and a low coefficient of friction when compounded with PTFE or graphite for bearing applications.

Primary applications: Aerospace structural brackets and wire insulation, oil & gas downhole connectors and seals, medical implants (spinal cages, dental abutments), semiconductor wafer handling, automotive transmission components.

Limitation: PEEK is expensive ($80–120/lb) and requires specialized high-temperature injection molding equipment. Its Tg of 143°C means unfilled PEEK loses stiffness above this temperature — glass-fiber or carbon-fiber reinforcement is required for structural applications between 150–260°C.

PPS: The Cost-Effective Chemical Workhorse

PPS is the most chemically resistant thermoplastic in this comparison — virtually no organic solvent attacks PPS below 200°C, and it withstands most acids and bases at elevated temperatures. Its primary advantage is cost: at $8–15/lb, PPS is 5–10× less expensive than PEEK while offering continuous use temperatures of 220–240°C (depending on grade and loading). Glass-fiber-reinforced PPS (40% GF) delivers a tensile strength of 160 MPa — higher than unfilled PEEK — with excellent dimensional stability and near-zero moisture absorption.

Primary applications: Automotive underhood components (sensor housings, fuel system parts), electrical connectors and insulators, chemical pump and valve components, industrial heat-exchange components, semiconductor chemical distribution systems.

Limitation: PPS is brittle — elongation at break is only 1.5% for 40% GF grades, making it unsuitable for snap-fit designs or applications requiring impact resistance. Its Tg of 90°C is low, and while crystallinity maintains mechanical properties above Tg, PPS cannot match PEEK's load-bearing capability above 200°C. PPS also produces corrosive hydrogen sulfide gas if overheated during processing.

PI (Polyimide — Vespel): The No-Melt Thermal Champion

Polyimide (DuPont Vespel) operates continuously at 300°C in air (350°C in inert atmosphere) — 40°C higher than PEEK. It does not melt and cannot be injection molded; it is manufactured by direct forming (coining and sintering of resin powder) and then machined to final dimensions. This processing limitation means PI parts are produced as rods, tubes, plaques, or near-net shapes — never as injection-molded complex geometries. The cost reflects this: $200–400/lb for raw shapes plus significant machining costs.

Primary applications: Aerospace bushings and bearings (jet engine wear rings, compressor vanes), semiconductor waer handling at extreme temperatures, high-vacuum seals, cryogenic components (PI retains ductility to -269°C/4K), nuclear industry radiation-resistant components.

Limitation: PI is attacked by strong bases (NaOH, KOH) and concentrated acids. It absorbs more moisture than PEEK or PPS (0.24% equilibrium at 50% RH vs 0.1–0.02%), causing dimensional changes in precision assemblies. Its mechanical strength (85 MPa) is lower than PEEK, and its inability to be injection molded limits design flexibility and increases per-part cost for complex shapes.

PBI (Polybenzimidazole — Celazole): The Extreme-Temperature Frontier

PBI (PBI Performance Products Celazole) is the highest-temperature thermoplastic available — with a Tg of 425–435°C and a continuous use temperature of 310°C in air (370°C in inert atmosphere). No other thermoplastic can operate at these temperatures while maintaining structural integrity. PBI also offers exceptional mechanical properties for its temperature class: 160 MPa tensile strength and 6.9 GPa flexural modulus, comparable to glass-filled PEEK. PBI was originally developed for aerospace (space suit fibers, re-entry vehicle insulation) and remains specified where no other polymer survives.

Primary applications: Aerospace thermal protection (fire-blocking, thermal insulation seals), semiconductor high-temp process chambers, flame-resistant fiber for firefighter and military protective gear, ultra-high-vacuum components, downhole oil & gas at extreme depths.

Limitation: PBI is the most expensive engineering thermoplastic at $600–1,000/lb. Like PI, it cannot be injection molded — it is compression molded and machined. PBI absorbs significant moisture (up to 0.4% at 50% RH) and is attacked by strong acids and some polar solvents. Its market is small and lead times for raw shapes can exceed 12 weeks.

Decision Guide: Which High-Temperature Plastic?

• Below 200°C with chemical exposure: PPS — best chemical resistance at the lowest cost
• 200–260°C with mechanical loads: PEEK — best balance of temperature, strength, and moldability
• 260–300°C or cryogenic: PI (Vespel) — highest temperature among commercially available formed shapes
• Above 300°C: PBI (Celazole) — no other thermoplastic survives, but budget must accommodate extreme cost
• Complex geometry required: PEEK or PPS — only injection-moldable options in this group
• Tightest budget: PPS — 5–10× less expensive than PEEK, 20–50× less than PI or PBI

Comparison at a Glance

Equivalents & Cross-References

Related Diagnostics & Materials

References & Industry Standards

• ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
• UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
• MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
• ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org