PEEK vs Delrin

Premium performance.
Or cost-effective precision.
15× price difference.

PEEK and Delrin are both engineering plastics for precision mechanical applications. PEEK handles 260 °C continuous service with aggressive chemicals. Delrin handles 85 °C with standard environments. PEEK costs 15× more. Specifying correctly matters.

Get a Quote DFM guide

01 · At a glance

Side-by-side summary.

Option A

PEEK

Polyetheretherketone. Premium engineering plastic. 260 °C continuous service, excellent chemical resistance, biocompatible medical grades. For demanding applications where Delrin would fail.

Option B

Delrin (POM)

Acetal homopolymer (DuPont Delrin) or copolymer (POM-C). Cost-effective precision mechanical plastic. 85 °C service, good dimensional stability, low friction. The workhorse for precision mechanical components.

02 · Detailed comparison

Feature-by-feature breakdown.

Attribute	PEEK	Delrin
Continuous service temp	260 °C	85 °C
Peak temp (short)	315 °C	120 °C
Tensile strength	96 MPa	70 MPa
Flexural modulus	4.0 GPa	2.8 GPa
Coefficient of friction	0.3 (0.15 for PEEK-bearing)	0.25 (unfilled)
Chemical resistance	Excellent (approaches PTFE)	Good (not hot alkalis)
Water absorption	0.5%	0.4%
FDA food contact	Yes	Yes
Medical implantable	Yes (PEEK-OPTIMA)	No
Cost (per kg billet)	$120–180 unfilled	$10–15
Machinability	Good	Excellent (best of any plastic)
Transparency	Opaque (crystalline)	Opaque
Flame rating	V-0 available	HB (not inherently FR)
Gamma/autoclave sterilization	Excellent	Limited (autoclave only)
Typical use	Aerospace, medical, chemical processing	Precision mechanical, gears, bushings

03 · Decision guide

When to choose each.

Choose PEEK when:

Service temperature above 85 °C (Delrin limit)
Aggressive chemical environments
Implantable medical devices
Autoclave sterilization required
Aerospace components requiring high performance
Applications where plastic must replace metal in demanding conditions

Choose Delrin (POM) when:

Service below 85 °C in normal environments
Precision gears, bushings, mechanical components
Cost-sensitive applications with standard requirements
High-volume production where material cost matters
Wear-resistant plastic for dry-running bearings
Most general-purpose precision mechanical plastic work

FAQ

Common questions.

Yes. Delrin machining-grade billet: $10–15/kg. PEEK unfilled billet: $120–180/kg. PEEK-OPTIMA medical grade: $300–400+/kg. For equivalent small precision part, PEEK version typically 8–15× cost of Delrin. This cost difference is the single biggest factor in material selection between these two plastics. Only specify PEEK when Delrin genuinely cannot meet requirements.

Technically yes — PEEK's mechanical properties exceed Delrin in every category. Practically no — the cost difference makes over-specification wasteful. Rule of thumb: if Delrin datasheet shows the application works, use Delrin. If Delrin fails (temperature too high, chemicals too aggressive, implantable medical), upgrade to PEEK.

Delrin is the easiest-machining engineering plastic — cuts cleanly at high speeds (300+ m/min), single-pass surface finish Ra 0.8 µm, minimal tool wear. PEEK machines well but 30-40% slower feeds, slightly more tool wear, Ra 1.6 µm single-pass. For equivalent part, PEEK machining time 1.3-1.5× Delrin. Combined with material cost, PEEK finished parts are typically 10-15× cost of Delrin.

Yes. Delrin against 316L or hardened steel: PV (pressure × velocity) up to 2,500. Delrin AF (PTFE-filled): PV to 5,000. PEEK unfilled: PV to 5,000 (similar to Delrin AF). PEEK-bearing grades (carbon + PTFE filled): PV to 10,000+. For moderate bearing applications, Delrin is adequate and much cheaper. For high-PV or elevated temperature bearings, PEEK wins.

PEEK sterilization: autoclave (121°C), gamma radiation, ETO. Retains full mechanical properties through 1000+ autoclave cycles. Delrin sterilization: limited autoclave compatibility (some grades deform), gamma radiation (some grades embrittle). For reusable autoclavable medical instruments, PEEK is dramatically better. For single-use or non-sterilized medical devices, Delrin may suffice.

Yes — laser, ultrasonic, and hot-plate welding all work on PEEK. Weld strengths 60-80% of parent material. Less common than bonding or mechanical assembly for PEEK parts. Delrin also welds via ultrasonic and spin welding. For PEEK assemblies, mechanical fastening with heat-set brass inserts is more common than welding.