POM
ASTM D4181 · also Delrin
POM is injection-molding acetal (polyoxymethylene), a semi-crystalline engineering thermoplastic available as homopolymer (Delrin type) and copolymer and covered by ASTM D4181 and JIS K6862.
POM grades and fills
POM is supplied in 10 conditions, soft to hard.
Compare all 10 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Impact modified | Select for snap-fits, clips and cold-climate parts needing high notched impact and ductility, at the cost of stiffness and heat resistance. | 43 | 45 | 120 | 70 Shore D |
PTFE-lubricated bearing grade | Use for unlubricated bearings, slides and gears where the lowest friction and wear rate against steel is required. | 45 | 45 | 15 | 78 Shore D |
Carbon-black conductive / antistatic | Pick for fuel-system parts, conveyor and electronics-handling components that must dissipate static charge. | 47 | 48 | 6 | 82 Shore D |
internally silicone-oil lubricated | Cost-effective friction and noise reduction for gears and clips where mechanicals must stay close to unfilled acetal. | 58 | 28 | 79 Shore D | |
Molybdenum disulfide filled | Dark, wear-resistant bearing grade for moderate loads where PTFE cost or FDA compliance is not required. | 58 | 60 | 15 | 82 Shore D |
High-flow / thin-wall injection grade | Use for thin-wall, multi-cavity or long-flow-path parts; higher MFR trades some toughness for fill and cycle time. | 60 | 61 | 20 | 81 Shore D |
Acetal homopolymer | Pick when maximum stiffness, strength, creep and wear resistance are needed and hot alkali/hot water exposure is limited. | 70 | 70 | 30 | 92 HRM |
10% glass fiber reinforced | Modest stiffness and dimensional-stability boost with much lower shrinkage than unfilled, while retaining some ductility. | 85 | 7 | ||
25% glass fiber reinforced | Choose for load-bearing housings, brackets and gears needing high stiffness, low creep and tight dimensional tolerance at elevated temperature. | 130 | 3 | 90 HRM | |
30% glass fiber reinforced | Maximum-stiffness acetal for structural parts; accept brittleness, abrasive wear on tools and strong shrinkage anisotropy. | 135 | 2.5 |
Supply forms, finishes and certifications
Ways POM is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FDA | Food-contact / potable-water compliant grade | Certification |
UV | UV / weather stabilized | Grade option |
UnfilledDefault | Natural acetal copolymer injection grade | Standard supply |
What is POM?
POM is injection-molding acetal (polyoxymethylene), a semi-crystalline engineering thermoplastic available as homopolymer (Delrin type) and copolymer and covered by ASTM D4181 and JIS K6862. Engineers specify it for precision moving parts because of high stiffness, low friction, fatigue resistance and dimensional stability, with 63 MPa tensile, 30% elongation, 2.8 GPa modulus and a machinability score of 88. Glass, PTFE, silicone and MoS2 filled variants add stiffness or wear performance. Watch about 2% molding shrinkage with sink in thick sections, no solvent bonding, and formaldehyde release if the melt overheats; PA66 or PBT is the nearest alternative. POM has a density of 1.41 g/cm³ (0.0509 lb/in³), heavier than 81% of polymer grades. Its glass-transition temperature is -60°C (-76 °F). POM has a yield strength of 62 MPa (8.99 ksi) and a tensile strength of 63 MPa (9.14 ksi) — stronger than 72% of polymer grades. Elongation at break is 30% and the elastic modulus is 2.8 GPa (0.406 Msi).
What is POM used for?
- Gears
- Clips
- Fuel systems
Advantages
- Tough — resists crack growth — 4 MPa·√m (3.64 ksi·√in), better than 92% of polymer grades
- Easy to machine — 88/100, better than 92% of polymer grades
- Conducts heat well — 0.31 W/m·K (0.179 BTU/hr·ft·°F), better than 87% of polymer grades
- Polishes to a fine finish — 70/100, better than 77% of polymer grades
Limitations
- Heavy — 1.41 g/cm³ (0.0509 lb/in³), worse than 81% of polymer grades
- High mold shrinkage — 2%, worse than 81% of polymer grades
- Needs corrosion protection — 70/100, worse than 78% of polymer grades
POM properties
Typical room-temperature values in the Unfilled condition; bars are the position among polymer grades.
Physical5
POM has a density of 1.41 g/cm³ (0.0509 lb/in³), heavier than 81% of polymer grades. Its glass-transition temperature is -60°C (-76 °F).
Mechanical17
POM has a yield strength of 62 MPa (8.99 ksi) and a tensile strength of 63 MPa (9.14 ksi) — stronger than 72% of polymer grades. Elongation at break is 30% and the elastic modulus is 2.8 GPa (0.406 Msi).
Thermal11
POM is rated for continuous service to 95°C (203 °F). It conducts heat at 0.31 W/m·K (0.179 BTU/hr·ft·°F), better than 87% of polymer grades. Thermal expansion is 110 µm/m·K (61.1 µin/in·°F).
Electrical7
POM is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 78% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of POM takes about 100 MJ of energy and emits 4.5 kg of CO₂ — less than 61% of polymer grades. Typical recycled content is 0%.
Manufacturability8
POM's machinability is excellent (88/100, better than 92% of polymer grades); weldability good (55/100); formability fair (40/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. POM is highlighted; hover a dot for its name, or open the interactive family chart.
Working with POM
Is POM easy to machine?
One of the best plastics to machine: sharp positive-rake tools, high speed, light feeds, air or mist cooling; relieve molded-in stress before tight-tolerance finishing and expect springback-free chips.
Can POM be welded?
Hot-plate, ultrasonic, spin and vibration welding all work well; no solvent bonding — adhesive joints require plasma, flame or chromic-acid surface activation.
Can POM be formed, bent or molded?
Dry only if resin is wet (≤0.1%), melt 190–215 °C, mold 80–100 °C, generous gates and full packing; watch ~2% shrinkage, sink and voids in thick sections and never overheat/stagnate melt (formaldehyde release).
Manufacturability
The process limits FabDigit's quote engine applies to POM. Design inside these and the part quotes instantly; outside them it routes to an engineer.
Injection molding
| Mold shrinkage | — |
|---|---|
| Wall thickness | — – — |
| Recommended draft | — |
| Pre-drying | — |
POM chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| ethylene oxide comonomercopolymer (POM-C) only; absent in homopolymer POM-H, which is end-capped instead | 1 – 5 | 2.5 |
| heat/acid stabilizer package (antioxidanessential to prevent depolymerization | 0.2 – 1.5 | 0.6 |
| lubricant / mold release | 0 – 1 | 0.3 |
| pigment (carbon black, TiO2 etc.)carbon black also gives UV protection | 0 – 2 | 0.5 |
| oxymethylene (-CH2O-) repeat unitpolyacetal backbone from formaldehyde/trioxane | ≥ 94 (balance) |
What surface finishes work on POM?
Paints and inks need surface pretreatment or special primers; parts polish to a waxy sheen, can be laser-marked, and plating requires a dedicated acetal etch process.
Surface treatments FabDigit runs on polymer parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Injection Molding Coating
Metallization / Functional
Equivalent designations
Standards and trade names that resolve to POM in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- D4181
- Trade names
- Delrin
- Also called
- Acetal
- Similar grades
- K6862
How much does POM cost?
POM is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
POM — frequently asked
What is POM used for?
POM is typically used for gears, clips and fuel systems. In short: stiff dimensional acetal.
What is the yield strength of POM?
POM has a typical yield strength of 62 MPa (8.99 ksi) and a tensile strength of 63 MPa (9.14 ksi) — stronger than 72% of polymer grades. Strength varies by condition: see the 10 listed tempers.
Is POM easy to machine?
Yes — machinability is rated excellent (88/100, better than 92% of polymer grades). One of the best plastics to machine: sharp positive-rake tools, high speed, light feeds, air or mist cooling; relieve molded-in stress before tight-tolerance finishing and expect springback-free chips.
Can POM be welded?
Yes — weldability is rated good (55/100). Hot-plate, ultrasonic, spin and vibration welding all work well; no solvent bonding — adhesive joints require plasma, flame or chromic-acid surface activation.
What surface finishes work on POM?
Paints and inks need surface pretreatment or special primers; parts polish to a waxy sheen, can be laser-marked, and plating requires a dedicated acetal etch process.
Can POM be formed, bent or molded?
Dry only if resin is wet (≤0.1%), melt 190–215 °C, mold 80–100 °C, generous gates and full packing; watch ~2% shrinkage, sink and voids in thick sections and never overheat/stagnate melt (formaldehyde release).
What is the maximum service temperature of POM?
POM is rated for continuous use to about 95°C (203 °F), and briefly to 140°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does POM cost?
POM is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in POM?
Yes — POM is available for injection molding with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- Hostaform / Celcon POM copolymer product and processing brochures — Celanese (2023)
- Delrin acetal homopolymer design and molding guides — DuPont / Delrin USA (2022)
- CAMPUS plastics ISO datasets for POM-C and POM-H injection grades — CWFG / CAMPUS consortium (2024)
- Engineered Materials Handbook Vol. 2: Engineering Plastics — ASM International (1988)
- ISO 9988 Plastics — Polyoxymethylene (POM) moulding and extrusion materials — ISO (2020)
- ASTM D6100 Standard Classification for Polyoxymethylene (POM) Molding and Extrusion Materials — ASTM (2020)
- Ensinger TECAFORM AH / AD stock shape datasheets — Ensinger (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.