The copolymer
Usually the better starting point when chemical or hydrolysis resistance is the priority. For food-contact or water projects, the named grade and current documentation still matter.
SELECTION GUIDE
POM-C vs POM-H: which should you choose?
Two closely related acetals, but not interchangeable. Start with chemical environment, mechanical load, named grade and required form.
SHORT ANSWER
The practical difference
The homopolymer
Consider it where strength, stiffness or mechanical load is the priority, after chemical and hot-water exposure have been reviewed.
Both families offer good dimensional stability, low moisture absorption and useful sliding and wear properties. The selection should not be made from one isolated datasheet value.
PUBLISHED VALUES
One POM-C grade compared with one POM-H grade
The table compares Röchling Sustarin® C and Sustarin® H. The stated method matters: it is not a universal property range for every POM grade.
| Property | POM-C Sustarin® C | POM-H Sustarin® H | Method / condition |
|---|---|---|---|
| Density | 1.41 g/cm³ | 1.42 g/cm³ | DIN EN ISO 1183-1 |
| Yield stress | 67 MPa | 75 MPa | DIN EN ISO 527 |
| Tensile modulus | 2,800 MPa | 3,200 MPa | DIN EN ISO 527 |
| Elongation at break | 30% | 30% | DIN EN ISO 527 |
| Notched impact strength | 6 kJ/m² | 10 kJ/m² | DIN EN ISO 179 |
| Shore hardness | 81 Shore D | 83 Shore D | DIN EN ISO 868 |
| Melting temperature | 165 °C | 175 °C | ISO 11357-3 |
| Long-term service temperature | -50 … 100 °C | -50 … 90 °C | Published average |
| Short-term service temperature | 140 °C | 150 °C | Published average |
| HDT/A | 110 °C | 110 °C | DIN EN ISO 75, method A |
| Water absorption | 0.2% | 0.2% | DIN EN ISO 62 |
Source for both columns: Röchling Technical Data Sheets for Sustarin® C and Sustarin® H, 18 May 2016. Actual properties may vary with grade, colour, dimensions, crystallinity and service conditions.
CHOOSE POM-C
When the copolymer is normally the better starting point
- Chemical or hydrolysis resistance matters more than a modest increase in stiffness.
- The part sees water, moisture or cleaning, and the named grade can be confirmed.
- You need a versatile acetal for wear parts, guides, machined components or fixtures.
CHOOSE POM-H
When the homopolymer deserves consideration
- Published strength, modulus, hardness or impact performance is the primary requirement.
- The part has a higher mechanical load and the chemical environment has been reviewed.
- Required form, colour, dimensions, supplier grade and commercial conditions have been confirmed.
AVOID FALSE EQUIVALENCES
What should not be generalised
Delrin® is normally associated with POM-H. It is not another name for POM-C. Röchling states that it uses Delrin® raw material for Sustarin® H.
Approvals remain tied to a named grade. FDA, EU 10/2011, drinking water, ESD, antistatic or conductive status never transfers automatically between POM-C, POM-H or their variants.
The figures are selection guidance. For a critical part, confirm the grade, source sheet, semi-finished form, dimensions and service conditions before ordering.
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We will confirm the appropriate material and grade before preparing a quotation.
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