The short answer
General-purpose acetal copolymer injection grades sit around MFR 8–10 g/10 min at 190°C / 2.16 kg, with about 1.41 g/cm³ density, 59–66 MPa tensile yield strength and 90–110°C / 194–230°F heat deflection at 1.8 MPa. Reference grades in this window include Celcon M90, Hostaform C 9021, Kepital F20-03 and Duracon M90-44. Plan on about 2% mold shrinkage and a mold at 80–120°C for stable dimensions. Homopolymer is a separate family, not a drop-in swap.
Have a part number or drawing callout?
Paste it as written. A polymer chemist will tell you which grade it calls for, suggest equivalents and quote it by email.
This page covers medium-flow acetal copolymer injection grades. For homopolymer, filled and specialty grades, see the acetal page. Full typical values are on acetal (POM) properties, and the trade-offs are in acetal homopolymer vs. copolymer.
Typical spec window
| Property | Typical range | Test method |
|---|---|---|
| Melt flow (MFR) | About 8–10 g/10 min (MVR about 8 cm³/10 min) | ASTM D1238 or ISO 1133, 190°C / 2.16 kg |
| Density | About 1.41 g/cm³ | ASTM D792 or ISO 1183 |
| Tensile strength at yield | 59–66 MPa / 8,500–9,600 psi | ASTM D638 or ISO 527 |
| Flexural modulus | 2.35–2.7 GPa / 341,000–392,000 psi | ISO 178 or ASTM D790 |
| Charpy notched impact, 23°C | 5.5–8 kJ/m² | ISO 179/1eA |
| Heat deflection, 1.8 MPa | 90–110°C / 194–230°F | ISO 75 or ASTM D648 |
| Melting point | 165–166°C / 329–331°F | ISO 11357 or ASTM D3418 |
| Mold shrinkage | About 1.8–2.2% | ISO 294-4 or ASTM D955 |
| Flammability | HB | UL 94 |
Typical ranges from published data sheets for grades in this window. Your grade’s own data sheet and the lot COA are what count.
What it’s used for
- Gears, cams and bushings in light-duty mechanisms
- Clips, snap fits and fasteners
- Plumbing and fuel-system components (check the exact grade’s approvals)
- Conveyor parts and wear strips
- Appliance and precision mechanical parts
- Food-handling and dispensing parts, with the producer’s FDA letter
How to tell grades apart
- Melt flow. MFR 9 is the medium-flow workhorse. Low-flow grades (around MFR 2.5, such as Celcon M25) are tougher and suit thick parts and extrusion. High-flow grades in the mid-20s fill thin walls and multi-cavity tools but give up some toughness. Compare MFR only at 190°C / 2.16 kg.
- Copolymer vs. homopolymer. Copolymer has better hot-water and alkali resistance, better thermal stability and a wider process window. Homopolymer (Delrin) is stiffer and stronger at room temperature. Shrinkage differs, so a swap needs tool and part checks.
- Additive packages. Same-flow variants exist with UV stabilizer, low formaldehyde emission, or lubrication for low friction and wear. They carry different suffixes and are not interchangeable with the base grade on an approved part.
- Food and water contact. Many base grades are listed under FDA 21 CFR 177.2470, and some carry potable-water approvals. Approvals are grade- and color-specific, so get the letter for the exact grade and color.
- Regional names. Some producers sell the same base polymer under different names by region. Celanese lists Hostaform C 9021 alongside Celcon M90, for example. Confirm with the producer before treating two names as one grade.
What to put on your RFQ or PO
- Melt flow with the condition. MFR at 190°C / 374°F and 2.16 kg, nominal value and accepted range.
- Polymer type. Copolymer (POM-C) stated in writing, so a homopolymer is not substituted.
- Reference grade. The grade on the drawing, and whether equivalents need your approval first.
- Additives. UV stabilized, lubricated, low emission or none.
- Color. Natural, black or a color code, and whether you add masterbatch.
- Approvals. FDA, potable water, UL or automotive specs, with the producer’s letter for the exact grade and color.
- COA values to check. Melt flow on each lot, plus any other value your part qualification depends on.
- Packaging. Gaylords or 25 kg (55 lb) bags. Keep acetal sealed and away from PVC, since the two degrade each other in the barrel.
- Quantity and release size. Total quantity, how much per release and how often.
A polymer chemist reviews every request and checks the grade against your process before we quote. Every prime lot from our suppliers ships with a COA, and orders start at one gaylord.
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- Same-flow copolymer from another producer. Celcon M90, Hostaform C 9021, Kepital F20-03 and Duracon M90-44 sit in the same MFR window. Check shrinkage, color and part dimensions on first articles.
- Acetal homopolymer. Stiffer and stronger, with different shrinkage. Delrin 500P is a medium-viscosity homopolymer at about MFR 15. See homopolymer vs. copolymer.
- Nylon. Tougher, with good wear, but it absorbs moisture and changes size. See acetal vs. nylon.
- Gear and wear parts. Before changing material on a gear, see best plastic for gears.
Common processing problems
- Dimples or voids in thick sections: sink marks
- Parts shrink or move after molding: dimensional variation
- Warp in flat or uneven-wall parts: warped parts
- Brown streaks from overheating: burn marks
- Specks after a material change: black specks contamination
Common questions
What melt flow acetal copolymer do I need for injection molding?
Most general-purpose parts run on an MFR 9 grade measured at 190°C / 2.16 kg. Go lower (around 2.5) for thick, tough parts and higher (mid-20s) for thin walls or many cavities. Match the MFR of the grade that runs your mold now.
Can I swap acetal copolymer for Delrin homopolymer?
Not without checks. Homopolymer is stiffer and stronger but shrinks differently and has a narrower processing window. Run first articles and check dimensions, snap fits and any hot-water or chemical exposure.
Does acetal copolymer need to be dried?
Usually not, if it is stored sealed. If it has picked up moisture or you use regrind, dry it per the data sheet, for example about 3 hours at 80–100°C / 176–212°F for Celcon M90.
Why is acetal shrinkage so high?
Acetal is highly crystalline, so molding shrinkage runs about 2%, and parts keep shrinking slightly after molding. A hotter mold (80–120°C / 176–248°F) reduces later shrinkage. Once dimensions are approved, keep mold temperature and pack settings fixed.
Tell us the grade you run now
A polymer chemist reviews every request, then matches your grade or finds a qualified equivalent and prices it.
What to send for an accurate quote
- The grade name, from any supplier, or a data sheet
- Color (natural, black or a custom match)
- Fill type and percentage, if any
- Melt flow, if you know it
- Quantity for this order and what you use in a year
- Ship-to city and state or province