Bottom line first: If your part runs continuously below 200°C, carries mostly static loads, needs chemical resistance and is cost-sensitive at volume, choose glass-filled PPS. If it runs continuously at 200–260°C, needs toughness and impact resistance, must survive repeated steam sterilization, or replaces metal for weight saving under severe tribological conditions, choose PEEK. The price gap is 5–8x, so material selection is really about not paying for performance you will never use.
1. Material Property Comparison Table
Values below are taken from published datasheets of mainstream grades (PPS: Ryton R-4, Fortron 1140L4; PEEK: Victrex 450G / 450GL30). Test standards are noted; always confirm against your supplier’s TDS.
| Property |
PPS (unfilled / 40% GF) |
PEEK (unfilled / 30% GF) |
Test standard |
| Density (g/cm³) |
1.35 / 1.65 |
1.30 / 1.51 |
ISO 1183 |
| Glass transition Tg (°C) |
85–90 |
143 |
DSC |
| Melting point Tm (°C) |
280–285 |
343 |
DSC |
| HDT @1.8 MPa (°C) |
110 / ≥260 |
152 / 315 |
ISO 75-2 |
| Continuous service temp. (°C) |
200–220 |
250 (300 short term) |
UL RTI |
| Tensile strength (MPa) |
75–85 / 175–190 |
95–100 / 155–170 |
ISO 527 |
| Tensile modulus (GPa) |
3.8 / 14–16 |
3.7 / 10–11 |
ISO 527 |
| Elongation at break (%) |
2–3 / 1.3 |
40–45 / 2.2 |
ISO 527 |
| Notched impact strength (kJ/m²) |
2–3 / 9–11 |
6–8 / 9–10 |
ISO 179-1eA |
| CLTE (×10⁻⁶/K) |
50 / 20–25 |
45–55 / 22 |
ISO 11359 |
| Water absorption, 24 h (%) |
0.02–0.05 |
0.10–0.15 |
ISO 62 |
| Dielectric constant @1 MHz |
3.1 / 3.9 |
3.2 / 3.7 |
IEC 62631 |
| Flammability / LOI |
V-0 @0.4 mm / 44–53% |
V-0 @1.45 mm / 35% |
UL94 / ISO 4589 |
| Melt temp. / mould temp. (°C) |
300–330 / 130–150 |
360–400 / 170–200 |
— |
| 2026 China market reference price (USD/kg) |
6–13 (GF compounds 5.5–10) |
45–72 (imported grades 76–108) |
Market quotation range |
2. Four Differences That Actually Decide the Outcome
1) Tg is the hidden threshold. PPS has a Tg of only ~88°C. Above it, unfilled PPS loses stiffness sharply and must rely on 40% glass fibre to hold rigidity. PEEK’s Tg is 143°C and it barely softens up to 140°C. For parts under sustained load at 90–140°C — bolt preload, snap fits, gasket compression — PPS will creep and stress-relax noticeably more than PEEK.
2) The toughness gap is an order of magnitude. Unfilled PPS elongates only 2–3% before fracture; it is intrinsically brittle and poorly suited to snap fits, thin-wall drop resistance or repeated assembly. Unfilled PEEK reaches 40%+ elongation and tolerates interference fits and impact. This is the most common root cause of “cheap material” field failures.
3) Chemical resistance points in different directions. Below 200°C, PPS has no known solvent and performs excellently against acids and automotive fluids (coolant, engine oil, refrigerants), but is weaker against strong alkalis, oxidising acids and hot chlorinated solvents. PEEK resists nearly everything except concentrated sulphuric acid, nitric acid and halogenated sulphonic acids, and withstands 3,000+ steam sterilisation cycles at 134°C plus gamma radiation — which is why medical and semiconductor wet-process applications default to PEEK.
4) Processing is a full step harder. PPS crystallises fast, flows well, fills 0.3 mm thin walls and cycles quickly on standard injection machines. PEEK needs a 400°C barrel and an oil mould temperature controller above 180°C, raising tooling and equipment investment. At low volumes, conversion cost further amplifies PEEK’s total cost disadvantage.
3. Application Analysis
| Typical application |
Recommended |
Rationale |
| Automotive water pump impellers, thermostat housings, EGR valves, fuel systems |
PPS-GF40 |
≤180°C service, coolant/oil resistance, dimensional stability, cost sensitive |
| Motor insulation bobbins, EV controller covers, connectors (260°C reflow) |
PPS-GF |
Inherent V-0, very low moisture uptake, survives reflow peak |
| Semiconductor wafer carriers, CMP retaining rings, vacuum chamber parts |
PEEK (unfilled/CF) |
Low ionic extractables, plasma and wet-chemistry resistance, wear resistance |
| Surgical instruments, re-sterilisable components, implants |
Medical-grade PEEK |
134°C autoclave cycling, biocompatibility, ISO 10993 documentation |
| Oil & gas ESP components, HPHT seals, rapid gas decompression parts |
PEEK |
250°C continuous plus toughness; PPS would crack |
| High-speed bearing cages, piston rings, self-lubricating sliders |
PEEK-CF/PTFE modified |
High PV limit, low friction, creep resistance |
| Corrosion-resistant pump/valve liners, insulating washers, appliance heat parts |
Either |
PPS if ≤180°C and static; PEEK if impact or thermal cycling is present |
4. Cost-Benefit Assessment
Never compare price per kilogram alone — compare material cost per part. Example: a 20 cm³ structural component.
| Option |
Density |
Part weight |
Reference price |
Material cost/part |
| PPS-GF40 |
1.65 g/cm³ |
33 g |
USD 8.3/kg |
≈ USD 0.27 |
| PEEK-GF30 |
1.51 g/cm³ |
30 g |
USD 66/kg |
≈ USD 2.00 |
Roughly a 7x delta. The PEEK premium is justified when: failure cost is high (line downtime, recall, personal safety); service life at least doubles; it replaces stainless steel or aluminium with 50–70% weight saving; repeated sterilisation or cleanroom qualification is required. PPS remains the better buy when: continuous temperature ≤180°C, loads are mainly static, annual volume is in the tens of thousands, and there is no impact or repeated disassembly.
If neither extreme fits, walk the intermediate ladder: PPA/PA10T (150–170°C, USD 9–16/kg) → PEI/Ultem (170°C, transparent, USD 26–37/kg) → PPSU (180°C, steam resistant, USD 29–43/kg) → PEEK (250°C). Many projects that “over-specified PEEK” would be fully served by PPA or PEI.
5. Selection Guidance: Five Questions
- What is the maximum continuous service temperature? ≤180°C → PPS; 180–250°C → PEEK; >260°C → consider PEKK/PI or metal.
- Will the part see impact, drop or repeated assembly? Yes → PEEK; PPS brittleness is a real risk.
- Any strong alkali, steam cycling or sterilisation? Yes → PEEK.
- What are annual volume and failure cost? High volume + low failure cost → PPS. Low volume + high failure cost → the PEEK premium gets diluted.
- Can you verify it? Always request DSC (melting point confirms identity), TGA/ash content (verifies glass loading) and a measured HDT @1.8 MPa report.
Recommended procurement actions: lock the material class with the five questions above, then request specific grade TDS and lot COA from 2–3 suppliers. For PPS, audit ash content and melt flow rate consistency between lots; for PEEK, audit grade provenance (virgin resin versus regrind-modified compound) and crystallinity control. Before design freeze, run 1,000-hour thermal ageing plus immersion testing in your target media on production-intent samples.