POM

POM (Polyoxymethylene), widely known by the DuPont brand name Delrin® and generically as Acetal, is a highly crystalline engineering thermoplastic celebrated for its exceptional dimensional stability, high stiffness, and excellent fatigue resistance. POM's near-zero moisture absorption (less than 0.25%) means that mechanical properties and dimensions remain virtually unchanged across varying humidity conditions — a critical advantage over nylon in precision mechanical applications. Its natural lubricity, high strength-to-weight ratio, and ability to be machined to very tight tolerances have made it the material of choice for precision gears, cams, and fasteners in industries ranging from automotive to medical devices.

Mechanical Properties

• Density: 1.42 g/cm³
• Tensile Strength: 70 MPa
• Yield Strength: 65 MPa
• Elongation at Break: 30–75%
• Flexural Modulus: 2,900 MPa
• Hardness (Rockwell): R 80 (M scale: M90)
• Heat Deflection Temperature: 110°C @ 1.8 MPa; 170°C @ 0.45 MPa
• Melting Point: 175°C
• Thermal Conductivity: 0.31 W/m·K
• Coefficient of Thermal Expansion: 10 × 10⁻⁵ /°C
• Water Absorption: 0.22%
• Flammability Rating: HB (UL94); flame-retardant grades available in V-0

Advantages

🟢  Near-zero moisture absorption (<0.25%) — dimensions and mechanical properties remain stable regardless of environmental humidity

🟢  Excellent dimensional stability and tight machining tolerances; achievable to ±0.02 mm in precision CNC operations

🟢  Outstanding fatigue resistance — retains mechanical properties through millions of flex cycles; ideal for living hinges and snap-fits

🟢  Natural self-lubricating surface with low friction coefficient (COF ~0.2); excellent for sliding and bearing applications without external lubrication

🟢  High stiffness and strength-to-weight ratio; POM is significantly stiffer than most engineering plastics

🟢  Excellent electrical insulating properties; suitable for electrical enclosures and connector applications

Machining & Manufacturing

Common Applications