If you design surgical instrument trays, dental sterilization cassettes, or implantable-device packaging, three high-performance polymers dominate your shortlist: PEEK (polyetheretherketone), PPSU (polyphenylsulfone), and Ultem / PEI (polyetherimide). All three are proven, all three meet the major medical biocompatibility standards in their medical grades, and all three handle multiple sterilization cycles. So how do you pick?
This guide is a no-marketing comparison based on (a) polymer datasheets from the resin producers, (b) USP Class VI and ISO 10993 biocompatibility status, and (c) 1000-cycle steam-autoclave aging data published in peer-reviewed sterilization literature. We'll tell you exactly which polymer wins for each sterilization mode, and where the trade-offs lie.
JSLT supplies PEEK, PPSU and PEI in sheet, rod, tube, and CNC-machined components. MOQ from 1 piece for trial. Send your DWG/STEP to claire@jsltupe.com for a quotation in 24 h.
1. The three polymers at a glance
All three are amorphous-or-semicrystalline aromatic polymers with high glass transition temperatures, designed specifically for repeated thermal sterilization. Here's the headline comparison:
| Property | PEEK (Victrex 450G / Solvay KT820) | PPSU (Solvay R-5500) | Ultem / PEI (SABIC 1010) |
|---|---|---|---|
| Glass transition Tg | 143 °C | 220 °C | 217 °C |
| Continuous service temperature | 260 °C | 180 °C | 170 °C |
| Crystallinity | Semi-crystalline (~35%) | Amorphous | Amorphous |
| Density | 1.30 g/cm³ | 1.29 g/cm³ | 1.27 g/cm³ |
| Tensile strength @ 23 °C | 100 MPa | 70 MPa | 85 MPa |
| Notched Izod impact | 5.5 kJ/m² | 13 kJ/m² (very tough) | 5.0 kJ/m² |
| Optical clarity | Opaque tan | Translucent amber | Translucent amber |
| Cost index (PEEK = 100) | 100 | 35 | 30 |
2. Sterilization compatibility — the core decision
This table is the most important page in the guide. It summarizes how each polymer behaves under each major sterilization mode, based on published 1000-cycle aging data from the resin producers and from peer-reviewed sterilization literature.
| Sterilization mode | PEEK | PPSU | Ultem / PEI |
|---|---|---|---|
| Steam autoclave 134 °C / 18 min (gravity or pre-vac) | Excellent — >2000 cycles, no measurable property loss | Excellent — >2000 cycles, no stress cracking | Good — 500–1000 cycles, some surface hazing after 1000 |
| Steam autoclave 134 °C with detergents (alkaline) | Excellent — chemically inert | Good — slight surface dulling after 500 cycles | Marginal — alkaline chemistry attacks PEI; not recommended |
| Ethylene oxide (ETO) 55 °C | Excellent | Excellent | Excellent |
| Gamma 25–50 kGy | Excellent — minimal property loss | Excellent — color may darken slightly | Excellent |
| E-beam 25–50 kGy | Excellent | Excellent | Excellent |
| STERRAD (H₂O₂ plasma) 50 °C | Excellent — fully compatible | Excellent — fully compatible | Good — some surface oxidation after 500 cycles |
| Dry heat 180 °C / 60 min | Excellent | Marginal — at Tg, dimensional change risk | Not recommended — exceeds Tg |
3. Biocompatibility — USP Class VI and ISO 10993 status
For any device or component that contacts the body (or contacts something that contacts the body, like surgical instrument trays), the regulator will ask for biocompatibility documentation. The relevant standards are:
- USP Class VI — US Pharmacopeia plastics class for biological reactivity (in vivo).
- ISO 10993-5 — cytotoxicity (in vitro).
- ISO 10993-10 — irritation and skin sensitization.
- ISO 10993-11 — systemic toxicity.
All three polymers, in their medical grades, are documented to all four standards above. The key is to source the medical grade, not the industrial grade — the polymer chemistry is identical, but the medical grade carries the regulatory documentation, lot traceability, and resin producer's drug master file (DMF) reference.
JSLT supplies medical grades on request — when ordering for medical applications, specify medical grade in your quotation request and we'll source from Victrex, Solvay or SABIC's medical-grade product lines and pass through the producer's compliance documentation.
4. Mechanical and dimensional stability — the second-tier decision
Once you've eliminated polymers that can't handle your sterilization mode, the next decision criterion is mechanical robustness and dimensional stability. Three things matter for surgical instrument trays:
- Notched impact strength — trays get dropped. PPSU's 13 kJ/m² Izod notched impact is more than double PEEK's, which is why PPSU dominates re-usable surgical tray applications.
- Stress-cracking resistance under detergent exposure — surgical trays are washed in alkaline detergents. PEEK and PPSU are both excellent here; PEI is marginal and known to develop hairline stress cracks after 200–500 detergent cycles.
- Dimensional stability through Tg — repeated cycling through the polymer's Tg causes mild creep. PEEK's 143 °C Tg is comfortably above 134 °C autoclave temperature; PPSU and PEI sit just below their Tg during sterilization, which is why some fine features (snap-fit fingers, thin webs) can creep over many hundreds of cycles.
5. Decision tree — which polymer for your application
- Implantable component, long-term body contact? → PEEK medical grade, no question. The only polymer of the three with extensive long-term implantation history.
- Surgical instrument tray, dropped frequently, 1000+ autoclave cycles? → PPSU. Highest impact strength of the three; cheapest of the three; proven dishwasher chemistry resistance.
- Dental sterilization cassette, lower drop risk, cost-sensitive? → PEI / Ultem. Lowest cost of the three; adequate cycle life if your detergents are pH-neutral.
- Sterilization at 180 °C dry heat or higher? → PEEK only. PPSU and PEI exceed their Tg.
- Need optical transparency (visual inspection of contents)? → PPSU or PEI. Both are translucent amber; PEEK is opaque tan.
- Aerospace cabin part with FAR 25.853 fire requirements? → All three pass; choose on cost. PEI typically wins.
Send us your application brief — we'll recommend the polymer, source the medical grade, and CNC-machine to your STEP file. MOQ from 1 piece. Email Claire for a quotation in 24 h.
❓ Frequently Asked Questions
❓ Can I substitute PEEK with PPSU in an existing instrument tray design?
Often yes, with two caveats: (1) PPSU is more flexible than PEEK, so re-evaluate any snap-fit features and thin webs for stiffness. (2) Confirm your sterilization detergent chemistry is below pH 11 — PPSU is good but not as inert as PEEK to alkaline attack.
❓ Are JSLT's medical grades supplied with a Certificate of Analysis (CoA)?
Yes. When ordering medical-grade PEEK, PPSU or PEI from JSLT, the shipment includes the resin producer's lot CoA, USP Class VI / ISO 10993 statement, and our internal dimensional inspection report. Lot traceability is fully maintained from resin lot through to your part.
❓ How do you machine PEEK to tight medical tolerances?
PEEK CNC-machines beautifully with carbide tooling at moderate cutting speeds (200 m/min for PEEK 450G). Critical-dimension parts are post-anneal to relieve machining stresses (180 °C / 4 h). Tolerances down to ±0.025 mm are routine; we work with surgical implant designers regularly.
❓ What about PEEK with carbon fibre or glass fibre fillers?
PEEK CF30 (30% carbon fibre) is excellent for structural medical components — bone-screw drivers, retractor frames. Stiffness goes up 3×, strength up 50%. Biocompatibility unchanged. We stock the unfilled medical grade by default and source filled grades on request.
❓ Can JSLT supply PEEK rod, sheet, tube and machined parts from the same lot?
Yes — we order resin in lot quantities sized to your project. If you need 50 kg of PEEK across rod, sheet and finished components for a documented medical project, we'll source one resin lot and produce all forms from it. Specify in your quotation request.
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Email Claire with your DWG/DXF/PDF/STEP — full quotation, samples, and CIF delivery to your nearest port. MOQ from 1 piece.
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