What is POM-H?
POM-H (polyoxymethylene homopolymer / acetal homopolymer) – semi-crystalline engineering thermoplastic
Technical data
| Property | Value | Test method |
|---|---|---|
| General Properties | ||
| Density | 1.42 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 | 75 MPa | DIN EN ISO 527 |
| Elongation at break | 30 % | DIN EN ISO 527 |
| Tensile modulus | 3200 MPa | DIN EN ISO 527 |
| Notched impact strength | 10 kJ/m² | DIN EN ISO 179 |
| Shore hardness | 83 scale D | DIN EN ISO 868 |
| Thermal Properties | ||
| Melting temperature | 175 °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 | 100 ·10⁻⁶/K | DIN 53752 |
| Service temperature, long-term | -50 bis 90 °C | Average |
| Service temperature, short-term (max.) | 150 °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 | 10¹⁵ Ω·cm | DIN EN 62631-3-1 |
| Surface resistivity | 10¹⁵ Ω | DIN EN 62631-3-2 |
| Comparative tracking index | 600 | IEC 60112 |
| Dielectric strength | 25 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-H in detail
1What is POM-H?+
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-H has a particularly high degree of crystallinity and, as a result, the highest mechanical values among the acetals – high strength, stiffness, hardness as well as pronounced creep and fatigue strength. The best-known trade name is Delrin.
2How does Liedtke machine POM-H?+
Like POM-C, POM-H is one of the best machinable plastics – 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 thick-walled parts we check the stock for possible centreline porosity and take the comparatively high thermal expansion 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-H?+
POM-H pays off whenever high mechanical load, precision and dimensional accuracy are required – for example:
- Highly loaded gears, bearings and drive elements with tight tolerances
- Spring and snap-fit connections that need lasting restoring force
- Sliding applications with a low coefficient of friction and low wear
- Precision turned and milled parts where dimensional accuracy matters
- As a metal replacement for weight and cost reduction in dry running
4What determines the price of a POM-H part?+
POM-H 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-H not the right choice?+
Just as important are the limits of the material:
- Permanent contact with hot water, steam or alkalis – POM-C or another material is more suitable here
- Strong acids and strongly oxidising media – POM is not resistant
- Continuous use above approx. 100 °C or requirements for flame retardancy (only UL 94 HB)
- Very thick-walled round parts with a dense core – risk of centreline porosity; then choose POM-C
- Applications with UV/weathering exposure outdoors without a stabilised grade
6Advantages and disadvantages of POM-H+
Both types are very similar but differ in detail:
- POM-H (homopolymer, e.g. Delrin) – highest strength, stiffness and hardness, very good creep and fatigue strength; ideal for highly loaded functional parts
- POM-C (copolymer) – better resistance to hot water, alkalis and hydrolysis, lower tendency to voids/centreline porosity; ideal for thick-walled and precise machined parts
- With thick-walled rods of POM-H, watch out for possible centreline porosity – POM-C is often the safer choice here
Typical properties
- Low moisture absorption
- Good wear resistance
- High mechanical strength
- High stiffness
- Good toughness
- High tracking resistance
- Good machinability
- Good dimensional stability
Typical industries
- Electronics
- Conveyor technology & automation
- Mechanical and plant engineering
- Oil and gas
- Hydrogen industry
- Automotive engineering
Downloads for POM-H
Related materials
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A drawing or a sample is enough. We calculate concretely and advise openly whether POM-H is optimal for your application or an alternative makes more sense.
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