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Acetal Copolymer Comparisons — POM-C vs. Delrin, Nylon & PEEK

Acetal copolymer (POM-C) is most often evaluated against three other materials: acetal homopolymer (Delrin/POM-H — the same material family but different polymer structure), nylon 66 (the other dominant precision engineering plastic), and PEEK (the premium option for high-temperature or chemically demanding applications). This page summarizes the key comparison dimensions and links to the dedicated versus pages.

At a glance:

  • POM-C vs. POM-H (Delrin): better hot-water resistance and no centerline porosity; marginally lower fatigue
  • Acetal vs. nylon: acetal wins on dimensional stability in humidity; nylon wins on higher-temperature service
  • Acetal vs. PEEK: PEEK is dramatically higher performance and higher cost; acetal for budget-sensitive applications below 185°F
  • Acetal vs. UHMW: UHMW is softer but more abrasion-resistant; acetal is stiffer and more dimensionally precise

Acetal Copolymer vs. Acetal Homopolymer (Delrin)

The most critical comparison for anyone working in the acetal family. These are closely related but not equivalent materials.

Choose acetal copolymer when:

  • Hot water, steam, or sustained moisture above 60°C
  • Large rod diameters (>3") where centerline porosity is a concern
  • General-purpose machined parts where the fatigue advantage of POM-H is not required
  • Alkaline chemical environments (better alkali resistance)

Choose Delrin (POM-H) when:

  • High-cycle fatigue is the governing constraint (gears, snap-fits)
  • Maximum stiffness and heat deflection temperature within the acetal family
  • Print or specification explicitly calls out Delrin or POM-H

For the complete side-by-side analysis, see Delrin vs. acetal copolymer.

Acetal Copolymer vs. Nylon 66 (PA66)

Choose acetal copolymer when:

  • Dimensional stability over humidity and temperature cycling is critical
  • Wet-condition properties must remain predictable
  • Low moisture absorption is required in the finished part
  • Consistent dry-running friction is needed

Choose nylon 66 when:

  • Higher continuous use temperature (up to 250°F) is needed
  • Shock absorption is more important than stiffness
  • Lubricated service (nylon absorbs and retains oil, improving lubricated wear performance)
  • The application can tolerate dimensional variation with moisture change

Acetal Copolymer vs. PEEK

Choose acetal copolymer when:

  • Application temperature is below 185°F continuous
  • Cost is a significant constraint (acetal is ~10–15× less expensive than PEEK per pound)
  • Chemical environment is compatible with POM (no strong acids, limited hot-water above 82°C)

Choose PEEK when:

  • Temperature exceeds 200°F in service
  • Chemical exposure includes strong solvents, acids, or steam sterilization
  • V-0 flame rating is required
  • USP Class VI or higher regulatory compliance is needed

For the full analysis, see PEEK vs. Delrin (acetal).

Acetal Copolymer vs. UHMW Polyethylene

Choose acetal copolymer when: precision machined parts are needed; compressive strength matters; high-accuracy bores and features required.

Choose UHMW when: maximum abrasion resistance is the primary design driver; chemical inertness to strong acids or oxidizers is required; noise damping or soft contact with food product is needed.

Summary: Acetal Copolymer Position in the Plastic Hierarchy

Acetal copolymer (POM-C) occupies a specific niche in the engineering plastics hierarchy:

  • Better than UHMW-PE: in tensile strength, compressive strength, and dimensional precision
  • Comparable to POM-H (Delrin): with distinct advantages in hot-water resistance and large-section uniformity
  • Better than nylon 66: in dimensional stability under humidity variation
  • Below nylon 66: in continuous service temperature
  • Far below PEEK: in temperature and chemical performance — but at a fraction of the cost

For engineers selecting between materials in this space, the decision is usually POM-C vs. POM-H (for general-purpose machined parts) or POM-C vs. nylon (for humid environments). PEEK is typically only specified when the application specifically pushes past POM-C's capability.

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More related guides

Versus pages

Material hubs

Frequently asked questions — Acetal Copolymer FAQ