PET (Polyester) vs POM-C (Acetal Copolymer): Both precision engineering plastics — PET wins on wear in water
PET (Polyester) vs POM-C (Acetal Copolymer)
Side-by-side chemical composition and mechanical property comparison.
Overview
PET (Polyester)
Polyethylene Terephthalate (semi-crystalline stock shape) — combines the stiffness of POM with the wear resistance of PA, without centerline porosity or moisture sensitivity. Excellent dimensional stability, low friction, very low water absorption (~0.1%). Better creep resistance than POM or PA. Widely known from bottles/packaging, but engineering PET-P is semi-crystalline and much stiffer. Trade names include Ertalyte (MCAM), Arnite (DSM), Rynite (DuPont, GF grades). Used for precision bearings in water, gears, slide elements, pump parts, and electrical insulators.
POM-C (Acetal Copolymer)
Polyoxymethylene Copolymer — the precision engineering plastic. Exceptional dimensional stability, low moisture absorption (0.2%), low friction coefficient, and excellent machinability. More hydrolysis-resistant and chemically stable than POM-H (homopolymer). No centerline porosity in stock shapes. Trade names include Hostaform (Celanese), Ertacetal C (MCAM), Duracon (Polyplastics). Used for gears, bearings, valve bodies, pump parts, electrical insulators, and food/medical contact parts.
| PET (Polyester) | POM-C (Acetal Copolymer) | |
|---|---|---|
| Material Number | — | — |
| Category | Polymers | Polymers |
| Standard | ISO 10350 | ISO 10350 |
Chemical composition (wt%) — Pro
| Element | PET (Polyester) | POM-C (Acetal Copolymer) | Overlap |
|---|---|---|---|
| Base Polymer (Polyethylene Terephthalate) | 99–99.9% | — | — |
| Polyoxymethylene (OCH2 units) | — | 95–99% | — |
| Ethylene Oxide Co-Monomer | — | 1–5% | — |
Mechanical properties — Pro
| Property | PET (Polyester) | POM-C (Acetal Copolymer) | Unit |
|---|---|---|---|
| Tensile Strength | 55–80 | 60–67 | MPa |
| Yield Strength | 50–60 | 58–62 | MPa |
| Elongation | 30–80 | 25–45 | % |
| Elastic Modulus | |||
| Density | |||
| Glass Transition Temp (Tg) | |||
| Melting Point | |||
| Water Absorption (24h) | |||
| Continuous Use Temp |
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Sign up free — 3 comparisons/day freeCompatibility Assessment
PET has no centerline porosity (unlike POM-H), better creep resistance, and excellent performance in water/steam. POM-C has lower friction, better fatigue life, and easier machinability. Choose PET for bearings running in water or wet environments; POM-C for general dry precision parts.
Frequently Asked Questions
Is PET (Polyester) the same as POM-C (Acetal Copolymer)?
PET (Polyester) and POM-C (Acetal Copolymer) have a 70% composition overlap. Both precision engineering plastics — PET wins on wear in water
Can I replace PET (Polyester) with POM-C (Acetal Copolymer)?
In many cases, yes. The compositions overlap significantly (70%). However, always verify mechanical property requirements and heat treatment compatibility for your specific application.
What is the difference between PET (Polyester) and POM-C (Acetal Copolymer)?
The main differences are in the following elements: overall alloying content. PET (Polyester) is a Polymers grade, while POM-C (Acetal Copolymer) is a Polymers grade.
Related Comparisons
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Data provided for reference only. Always verify against the applicable specification for critical applications.
All data is for reference only. Equivalents indicate similarity, not identity. Always verify against the applicable specification for safety-critical applications. materialref.com accepts no liability for decisions based on this data.