POM‑C: What Is Polyoxymethylene Copolymer and Why Choose It?

POM‑C, also known as polyoxymethylene copolymer or acetal resin, is a high‑performance engineering plastic material. Used in mechanical, fluid‑handling and electromechanical applications, the POM‑C material offers an ideal balance of stiffness, smooth sliding (low friction), dimensional stability and excellent machinability.

In this guide updated to 2025, you will learn what POM‑C plastic is, its technical properties, key applications, advantages versus other engineering polymers, and how to process it via CNC machining, injection moulding and additive manufacturing.

What Does POM-C Mean?

POM (polyoxymethylene) is a semi‑crystalline thermoplastic belonging to the acetal resin family. There are two main variants:

• POM‑H (homopolymer) — higher stiffness and tensile strength.

• POM‑C (copolymer) — better thermal stability and hydrolysis resistance.

POM‑C material is the preferred choice in humid or chemically aggressive environments thanks to its durability, wear resistance and fatigue performance.

Technical Properties of POM-C

• Density: ~1.39-1.42 g/cm³
• Elastic modulus: high→rigidity and precision
• Tensile strength: ~60-70 MPa
• Friction: low→ excellent creep
• Hygroscopicity: low→ dimensional stability
• Temperature use: ~100-110 °C
• Chemical resistance: excellent, except for strong acids
• Electrical properties: good→ useful for gears
• Tribological: low wear, low noise

Comparison: POM-C vs Other Engineering Polymers

• POM-C vs Nylon (PA): lower water absorption and better dimensional stability.
• POM-C vs PET/PBT:easier to machine with lower friction.
• POM-C vs PTFE: a balanced compromise between low friction and stiffness.

Mechanical and Thermoplastic Processing

CNC machining:

• Easy turning and milling

• Tight tolerances achievable

• Excellent surface finish

Injection Molding:

• Fast cycle times

• Predictable shrinkage

• Care required with venting and mould humidity

Additive Manufacturing:

• Not ideal for FDM
• Better to use CNC or moulding for functional parts

Chemical and Environmental Resistance

POM‑C plastic withstands oils, greases, fuels, solvents and industrial cleaners, but is sensitive to UV radiation and strong oxidising acids. For outdoor use, consider stabilisers or appropriate surface treatments.

Design with POM-C

• Tight and stable tolerances over time
• Excellent creep behaviour
• Preferred mechanical joints (clips, inserts, screws)
• Difficult bonding → prefer welding or mechanical fasteners

Advantages of POM-C

• Superior dimensional stability
• Excellent wear and friction resistance
• Excellent CNC machinability
• Good chemical resistance
• Electrical properties for electromechanical applications

Limits

• Limited continuous operating temperature (~110 °C)
• Poor UV resistance without protection
• Limited surface adhesion

When to Choose POM-C

Use POM‑C material when you need:

• Stable dimensional precision
• Low friction without lubrication
• Components for humid or chemically aggressive environments
• Good finish and CNC machinability

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