PEEK vs. PPS: Selecting the Optimal Chemical-Resistant Polymer for Demanding Environments
PEEK vs. PPS: Two Chemical-Resistant Heavyweights
Polyetheretherketone (PEEK) and Polyphenylene Sulfide (PPS) are both semi-crystalline thermoplastics prized for exceptional chemical resistance and thermal stability. However, their performance envelopes and price points differ dramatically — PEEK costs 5-8x more than PPS — making the selection decision critical for cost-optimized engineering.
This comparison references ASTM International testing standards and manufacturer technical data from Victrex (PEEK) and Solvay/Toray (PPS).
Chemical Resistance Comparison
Both PEEK and PPS resist a broad range of chemicals, but PPS holds a slight advantage in acidic and oxidative environments. PPS is virtually inert to most solvents, acids, and bases below 200°C. PEEK shares this broad resistance but can be attacked by concentrated sulfuric acid and halogens at elevated temperatures.
- Hydrocarbons & oils: Both excellent — no measurable degradation
- Steam & hot water: PEEK superior (to 260°C+); PPS limited to ~200°C continuous
- Strong acids: PPS slightly better in concentrated sulfuric; PEEK better in hydrofluoric
- Bases: Both excellent; PEEK slightly better in concentrated NaOH at elevated temperatures
Thermal Performance
PEEK's Tg (143°C) and Tm (343°C) significantly exceed PPS's Tg (90°C) and Tm (285°C). PEEK's continuous use temperature (260°C) vs PPS (200-240°C) makes PEEK the choice for sustained high-temperature exposure. PPS crystallizes rapidly, giving excellent dimensional stability above its Tg — a key advantage in precision-molded components.
Mechanical Properties
| Property | PEEK (unfilled) | PPS (unfilled) | PEEK (30% GF) | PPS (40% GF) |
|---|---|---|---|---|
| Tensile Strength (MPa) | 100 | 80 | 160 | 140 |
| Flexural Modulus (GPa) | 3.6 | 3.8 | 10 | 14 |
| Notched Izod (J/m) | 80 | 25 | 100 | 75 |
PPS with 40% glass fiber has a higher flexural modulus than PEEK GF30 — important for stiff structural components. However, PEEK's impact toughness is 3-4x better than PPS across all formulations.
Recommendations
- Oil & gas downhole (200°C+): PEEK — superior thermal and mechanical performance justifies cost
- Automotive under-hood connectors: PPS (40% GF) — excellent chemical resistance, adequate thermal, 5-8x cheaper
- Semiconductor wet process components: PPS — broad chemical resistance at lower cost
- Medical sterilization trays: PEEK — steam resistance and biocompatibility certification
- Pump impellers (chemical processing): PPS (40% GF) — chemical resistance + stiffness at lower cost
References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- ISO. ISO 1043 — Plastics — Symbols and Abbreviated Terms. iso.org
- National Institute of Standards and Technology (NIST). Polymer Properties Database. nist.gov
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb — Material Property Data. matweb.com