What is POM-C?
POM-C (polyoxymethylene copolymer / acetal copolymer) – semi-crystalline engineering thermoplastic
Technical data
| Property | Value | Test method |
|---|---|---|
| General Properties | ||
| Density | 1.41 g/cm³ | DIN EN ISO 1183-1 |
| Moisture absorption | 0.2 % | DIN EN ISO 62 |
| Flammability (thickness 3 mm / 6 mm) | HB/HB | UL 94 |
| Mechanical Properties | ||
| Yield stress | 67 MPa | DIN EN ISO 527 |
| Elongation at break | 30 % | DIN EN ISO 527 |
| Tensile modulus | 2800 MPa | DIN EN ISO 527 |
| Notched impact strength | 6 kJ/m² | DIN EN ISO 179 |
| Shore hardness | 81 scale D | DIN EN ISO 868 |
| Thermal Properties | ||
| Melting temperature | 165 °C | ISO 11357-3 |
| Thermal conductivity | 0.31 W/(m·K) | DIN 52612-1 |
| Specific heat capacity | 1.50 kJ/(kg·K) | DIN 52612 |
| Coefficient of linear thermal expansion | 110 ·10⁻⁶/K | DIN 53752 |
| Service temperature, long-term | -50 bis 100 °C | Average |
| Service temperature, short-term (max.) | 140 °C | Average |
| Heat deflection temperature | 110 °C | DIN EN ISO 75, method A, HDT |
| Electrical Properties | ||
| Dielectric constant | 3.8 | IEC 60250 |
| Dielectric dissipation factor (50 Hz) | 0.002 | IEC 60250 |
| Volume resistivity | 10¹³ Ω·cm | DIN EN 62631-3-1 |
| Surface resistivity | 10¹³ Ω | DIN EN 62631-3-2 |
| Comparative tracking index | 600 | IEC 60112 |
| Dielectric strength | 40 kV/mm | IEC 60243 |
POM-C or POM-H in direct comparison
| Property | POM-C | POM-H |
|---|---|---|
| Density | 1.41 g/cm³ | 1.42 g/cm³ |
| Yield stress | 67 MPa | 75 MPa |
| Tensile modulus | 2800 MPa | 3200 MPa |
| Notched impact strength | 6 kJ/m² | 10 kJ/m² |
| Shore hardness | 81 scale D | 83 scale D |
| Melting temperature | 165 °C | 175 °C |
| Coefficient of linear thermal expansion | 110 ·10⁻⁶/K | 100 ·10⁻⁶/K |
| Service temperature, long-term | -50 bis 100 °C | -50 bis 90 °C |
| Service temperature, short-term (max.) | 140 °C | 150 °C |
| Volume resistivity | 10¹³ Ω·cm | 10¹⁵ Ω·cm |
| Surface resistivity | 10¹³ Ω | 10¹⁵ Ω |
| Dielectric strength | 40 kV/mm | 25 kV/mm |
| Hot water, alkalis, hydrolysis | more resistant | more sensitive |
| Centreline porosity, thick-walled | low tendency | possible tendency |
POM-C in detail
1What is POM-C?+
POM (polyoxymethylene, also polyacetal or acetal resin) is a semi-crystalline engineering thermoplastic and is offered in two variants: as a homopolymer (POM-H) and as a copolymer (POM-C). POM-C is characterised by a very uniform crystal structure, high dimensional stability and better resistance to hot water, alkalis and hydrolysis. Thanks to its low moisture absorption the material is particularly dimensionally accurate.
2How does Liedtke machine POM-C?+
POM-C is one of the best machinable plastics of all – turning, milling, drilling and sawing produce clean results with excellent surface finish and tight tolerances. The low moisture absorption ensures high dimensional accuracy even after machining. For very tight tolerances and thick-walled parts we take the comparatively high thermal expansion and possible stress relieving into account. This lets us reliably produce precision parts down to ±0.02 mm – from single parts to series production.
3When should I choose POM-C?+
POM-C pays off whenever precision, dimensional accuracy and good sliding properties at a moderate price are required – for example:
- Precision turned and milled parts with tight tolerances and good surface finish
- Thick-walled parts where a dense, low-porosity core is important
- Sliding applications (bearings, bushings, sliding strips) with a low coefficient of friction
- Gears, spring and snap-fit elements with high restoring force
- Applications in contact with hot water or in the food sector
4What determines the price of a POM-C part?+
POM-C is one of the most economical engineering plastics. As a rough guide, semi-finished stock (natural rod/plate) ranges from about 5–12 €/kg; black, food-grade or modified grades as well as small dimensions are higher. The part price is mainly determined by the stock form and dimension, material utilisation (waste), machining effort and batch size. We are happy to quote binding prices on request based on your drawing.
5When is POM-C not the right choice?+
Just as important are the limits of the material:
- Contact with strong acids or strongly oxidising media – POM is not resistant
- Continuous use above approx. 100 °C or requirements for flame retardancy (only UL 94 HB)
- When the highest mechanical load/hardness is required – POM-H is then at an advantage
- Permanent UV/weathering exposure outdoors without a stabilised grade
- When extreme temperature or chemical resistance is needed – then PVDF, PPS or PEEK
6Advantages and disadvantages of POM-C+
Both types are very similar but differ in detail:
- POM-C (copolymer) – better resistance to hot water, alkalis and hydrolysis, lower tendency to voids/centreline porosity, very good dimensional accuracy; ideal for thick-walled and precise machined parts
- POM-H (homopolymer, e.g. Delrin) – somewhat higher strength, stiffness and hardness, but more sensitive to hot water and alkalis
- For the machining of precise parts, POM-C is usually the first choice
Typical properties
- Chemically resistant
- Low moisture absorption
- High abrasion resistance
- High flexural fatigue strength
- High stiffness
- Good impact strength
- Low creep tendency
- Good machinability
- Good electrical properties
- Good dielectric properties
- Good dimensional stability
- Good sliding properties
Typical industries
- Automotive engineering
- Electronics
- Conveyor technology & automation
- Mechanical and plant engineering
- Oil and gas
Downloads for POM-C
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A drawing or a sample is enough. We calculate concretely and advise openly whether POM-C is optimal for your application or an alternative makes more sense.
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