Two quotes land on your desk. Both describe a POM injection molding grade. One is DURACON® M90-44 at 9 g/10 min; the other is Hostaform® C27021 at 24 cm³/10 min.
Both numbers are correct, and the two pellets won’t fill the same mold.
The grade number is the first thing buyers compare and the last thing most datasheets explain. Any acetal injection molding grade carries one, and the number rarely states the test condition behind it. M90 and C27021 are both acetal copolymer, yet their flow differs by a wide margin. Because one value is a mass rate and the other a volume rate, the two numbers cannot be divided directly.
Put the wrong one in a thin-wall tool and you get short shots. Put it in a thick section and you get longer cycles, higher pressure, or centerline porosity.
If you have ever held two POM datasheets and wondered why the numbers don’t line up, you’re not missing something. The industry uses two naming systems, two flow units and at least three test conditions. This guide gives you the three axes that decide a POM injection molding grade, a cross-brand table with the test condition attached, an application matrix, and the checks that catch a wrong lot before it reaches your machine.
What a POM Injection Molding Grade Actually Is
A POM injection molding grade, also sold as an acetal injection molding grade, is a specific formulation of polyoxymethylene (POM), also called polyacetal, defined by three things: the polymer family, its melt flow rate or melt volume rate, and its additive package. The grade code on the bag refers to that combination, not to a quality ranking.
Buyers who search for a POM injection molding material usually need one grade, not a polymer name. That distinction matters because buyers often treat “POM” as one material. It isn’t. Two grades with the same family and the same filler can behave differently in the mold if their molecular weight differs.
Axis 1: acetal injection molding grade (POM-H vs POM-C)
POM homopolymer (POM-H) is built from a single formaldehyde-derived monomer. Its chain packs into dense crystals, which gives it higher tensile strength, higher modulus, higher surface hardness and better creep resistance. It also processes in a narrower window and is more prone to centerline porosity in thick sections.
POM copolymer (POM-C) adds a comonomer that interrupts the chain. The result is slightly lower stiffness, better hydrolysis resistance and a wider processing window, and usually better toughness. The standard injection molding grades from BASF, Celanese, Polyplastics, Kolon and Formosa are all copolymer.
The chemistry comparison sits behind the family choice and is a separate decision. For grade selection, the short version is this: if the part sees hot water, fuel, or a broad process window, start with copolymer. If it needs maximum stiffness in a dry, controlled environment, consider homopolymer.
Axis 2: flow class
Flow is measured as melt flow rate (MFR, g/10 min) or melt volume rate (MVR, cm³/10 min). It describes how far the melt travels under a fixed temperature and load.
Low-flow grades resist shear and hold pressure well. They suit thick walls, pressure-tight sections and parts that need toughness. High-flow grades fill thin walls and long flow paths at lower pressure, which shortens cycles and enables multi-cavity tools. The trade-off is real: higher flow usually means lower molecular weight, and lower molecular weight usually means lower notched impact and lower resistance to wear and creep.
Axis 3: additive package
The suffix does the application work: glass fibre raises stiffness and heat deflection, PTFE or MoS₂ lowers friction, impact modifiers raise elongation, and UV stabilisers extend outdoor life.
Antistatic and conductive packages serve electronics. Low-emission grades reduce formaldehyde and VOC release. Food-contact and medical grades carry the documentation for their intended use.
A grade isn’t better or worse in the abstract. It’s a match or a mismatch. A 45 g/10 min grade that wins a thin-wall trial is likely to fail a thick valve body. A 2.5 g/10 min grade that machines beautifully may short-shot a 0.8 mm connector.
If you already have the part drawing, wall thickness, flow length, operating temperature and chemical exposure, our team can shortlist grades against those inputs. Send the application details and we will reply with datasheets and a grade shortlist; the COA for the lot you order ships with the material.
Your Grade Number Is Not a Rating: Two POM Naming Systems
POM grade codes come from two different systems, and confusing them is the most common buying error in the category.
| System | What the number means | Examples | What it tells you |
|---|---|---|---|
| Flow-class naming | The number approximates the nominal melt flow | DURACON M25 / M90 / M270; Celcon M25 / M90 / M270; Hostaform C13021 / C27021 / C52021; KOCETAL K300 / K500 / K700 / K900; FORMOCON FM090 / FM130 / FM270 / FM450; KEPITAL F10 / F20 / F30 / F40 | Higher number means higher flow, thinner wall and faster fill |
| Molecular-weight naming | The number is a viscosity or molecular-weight class, not an MFI | Delrin 100 / 500 / 900 / 1700; TENAC 2010 / 3010 / 4010 / 5010 / 7010 / 9054 | Higher number means lower molecular weight, higher flow and lower toughness |
Celanese publishes a useful mnemonic for its unfilled Celcon M-series: divide the grade number by 10 to get the melt flow rate. M90 is 9.0 g/10 min, M25 is 2.5 and M450 is 45, measured by ASTM D1238 at 190 °C/2.16 kg.
It is a mnemonic, not a law. Hostaform C27021 is nominally a 27-flow grade but measures MVR 24 cm³/10 min. KEPITAL lists F40-03 as both 48 and 52 in the same document.
Amcel’s KP series doesn’t follow that rule either: KP20 measures 9.0 g/10 min. KEPITAL F25-03H is 13 while IUPITAL F25-03 is 16. The same grade number at two companies isn’t the same product.
POM 90 vs POM 100
This is the question that exposes the confusion fastest. POM 90 and POM 100 are not points on the same scale.
M90 is a flow class at roughly 9 g/10 min. Delrin 100 is a molecular-weight class at roughly 2.5 g/10 min. Delrin 100 is the highest-viscosity, highest-toughness grade in its line. Reading “100” as “more than 90” reverses the actual flow relationship.
RFQs still arrive with “POM 100” and nothing else. Two suppliers can answer the letter of it: Delrin® 100P at 2.5 g/10 min, and a high-flow compound at the top of the flow range. Neither answer addresses the application. The RFQ needed a wall thickness and a flow length, not a number.
Where the naming breaks
Three cases are worth memorising because they appear in real quotations:
- Hostaform® C27021 is not a Celcon® M90 substitute. C27021 measures MVR 24 cm³/10 min; M90 is MFR 9 g/10 min. We have found no Celanese documentation that supports treating them as the same resin with different regional documentation, and the flow values contradict that claim.
- The DURACON “-44” suffix is not publicly defined. No datasheet in our review explains it. Don’t guess a colour code or a flow class from it. Ask Polyplastics or your supplier for the grade’s own sheet.
- TENAC and KEPITAL numbers are ladders, not measurements. TENAC 2010 at 1.7 and 9054 at 70 sit at opposite ends of one homopolymer line. KEPITAL F10 at 3 and F40 at 48 to 52 do the same for copolymer. Read them as relative positions, then confirm the actual value on the datasheet.
POM Melt Flow Index: The Number That Sets the Grade
Melt flow index (MFI) is the umbrella term. The two reports underneath it are not interchangeable.
MFR is mass flow: grams per 10 minutes. MVR is volume flow: cubic centimetres per 10 minutes. The test is the same; the output is different.
You can convert one to the other only with the melt density at the test temperature. Don’t assume a 1:1 relationship.
POM’s standard condition is 190 °C/2.16 kg, under ISO 1133 or ASTM D1238. Most copolymer datasheets use it. Delrin catalogues sometimes quote MFI at 230 °C, which is a different condition. A 230 °C value and a 190 °C value cannot sit in the same column without a flag.
Even at the same condition, the two methods are not identical procedures. ASTM D1238 and ISO 1133 differ in die geometry and procedure detail, so the same lot can read a few percent apart under each. That is why two honest datasheets can disagree.
MFI bands and what they buy you
The bands below are a selection heuristic assembled from manufacturer grade ladders. They are a starting point, not a standard. Confirm the grade’s own datasheet before specifying.
| Flow band | MFR/MVR at 190 °C/2.16 kg | What it fills | What it costs | Typical part |
|---|---|---|---|---|
| Very low | 1.7 to 6 | Thick walls, long flow, pressure-tight sections | Cycle time, short-shot risk in thin walls | Valve bodies, thick bushings, extrusion stock |
| Low to medium | 6 to 12 | General purpose, medium walls | Balanced | Housings, brackets, general mechanical parts |
| Medium to high | 12 to 20 | Thinner walls, multi-cavity tools | Some impact and toughness | Connectors, gears, small precision parts |
| High | 20 to 32 | Thin walls, long flow paths, fast cycles | Notched impact, weld-line strength | Thin-wall housings, multi-cavity parts |
| Very high | 32 to 52 | Micro parts, very thin walls, difficult flow | Toughness, mold deposit sensitivity | Micro gears, fine-pitch components |
| Extreme | 52 to 70 | Specialty thin-wall and micro molding | Highest toughness penalty | Micro molded parts |
Three cautions before you use the table.
First, the boundaries are not industry standards. They are a reading of the grade ladders from DURACON, Celcon, Hostaform, KOCETAL, FORMOCON, KEPITAL and TENAC. A grade can sit on a boundary.
Second, higher flow doesn’t mean lower stiffness. Tensile strength and modulus show no consistent correlation with MFR across the datasheets we reviewed. The consistent penalty is notched impact and toughness, because toughness tracks molecular weight.
Third, MFR and MVR can’t be compared without the unit. A 9 g/10 min grade and a 9 cm³/10 min grade are not the same flow.
What MFI does not tell you
MFI predicts fill behavior. It doesn’t predict tensile strength, modulus, hardness, wear rate, heat deflection temperature or long-term creep. Two grades with the same MFI can differ in all of those because their comonomer content, crystallinity and additive package differ.
One product line shows the point. DURACON M25-44 and M90-44 are the same copolymer at 2.5 and 9 g/10 min:
| Grade | MFR (g/10 min) | Flexural modulus | Notched Charpy, 23 °C | DTUL at 1.8 MPa |
|---|---|---|---|---|
| DURACON M25-44 | 2.5 | 2,350 MPa | 8 kJ/m² | 90 °C |
| DURACON M90-44 | 9 | 2,500 MPa | 6 kJ/m² | 95 °C |
Raising the flow from 2.5 to 9 g/10 min moves flexural modulus by 6% and DTUL by 5 °C, while notched Charpy drops by a quarter. Flow costs toughness, not stiffness. The pattern runs across brands too: FORMOCON FM090 pairs 9 g/10 min with 60.8 MPa tensile strength and a 110 °C HDT, while Delrin 500P at 15 g/10 min lists 71 MPa. The flow number does not sort the property values.
Use MFI to choose the flow class. Use the datasheet’s mechanical and thermal data to confirm the grade. Use a trial part to confirm the mold.
How to read the MFI line on a COA
A useful COA line has five parts: the method (ISO 1133 or ASTM D1238), the temperature, the load, the value and the unit. “MFI 9” isn’t enough. “MFR 9.0 g/10 min, ISO 1133, 190 °C/2.16 kg” is.
If the condition is missing, ask. If the condition is 230 °C and your other quotes are 190 °C, convert or re-test before comparing. If the value is far from the datasheet, treat the lot as suspect until the supplier explains it.
POM Injection Molding Grade Chart: Brands Side by Side
The table below collects grades that are commonly quoted against each other. Every flow value carries its unit and condition, except the three KEPITAL rows. Rows run from the lowest published flow value to the highest, so MFR rows and MVR rows are each ordered within their own unit and are not directly comparable to one another.
Values come from manufacturer datasheets and Material Data Center records. KEPITAL’s own tables report MI and do not print the unit, so those three rows aren’t directly comparable with the ISO or ASTM rows. Confirm against the current TDS before you specify.
| Brand | Family | Grade | Flow value | Condition | Density (g/cm³) | Typical use |
|---|---|---|---|---|---|---|
| TENAC | POM-H | 2010 | MFR 1.7 g/10 min | ISO 1133, 190/2.16 | n/a | Highest viscosity homopolymer |
| Delrin | POM-H | 100P | MFR 2.5 g/10 min | ISO 1133, 190/2.16 | 1.42 | Maximum toughness, structural parts |
| Hostaform | POM-C | C2521 | MVR 2.5 cm³/10 min | ISO 1133, 190/2.16 | 1.41 | Thick wall, high toughness |
| DURACON | POM-C | M25-44 | MFR 2.5 g/10 min | ISO 1133, 190/2.16 | 1.41 | Thick wall, pressure-tight parts |
| Ultraform | POM-C | N2320 U03 | MVR 7.5 cm³/10 min | ISO 1133, 190/2.16 | 1.41 | General-purpose injection molding |
| Hostaform | POM-C | C9021 | MVR 8.0 cm³/10 min | ISO 1133, 190/2.16 | 1.41 | Standard molding, load-bearing parts |
| Celcon | POM-C | M90 | MFR 9 g/10 min | ASTM D1238, 190/2.16 | 1.41 | General purpose |
| DURACON | POM-C | M90-44 | MFR 9 g/10 min | ISO 1133, 190/2.16 | 1.41 | General purpose, low mold deposit |
| KOCETAL | POM-C | K300 | MFR 9.0 g/10 min | ASTM D1238, 190/2.16 | 1.41 | General purpose |
| FORMOCON | POM-C | FM090 | MFR 9.0 g/10 min | ASTM D1238, 190/2.16 | 1.41 | Volume workhorse |
| KEPITAL | POM-C | F20-03 | MI 9 (no unit printed) | Manufacturer table | 1.41 | General purpose |
| TENAC | POM-H | 4010 | MFR 10 g/10 min | ISO 1133, 190/2.16 | n/a | General-purpose homopolymer |
| Hostaform | POM-C | C13021 | MVR 12 cm³/10 min | ISO 1133, 190/2.16 | 1.41 | Medium flow |
| KEPITAL | POM-C | F25-03H | MI 13 (no unit printed) | Manufacturer table | 1.41 | Medium-high flow, high stiffness |
| KOCETAL | POM-C | K500 | MFR 14 g/10 min | ISO 1133, 190/2.16 | 1.41 | Medium viscosity |
| Delrin | POM-H | 500P | MFR 15 g/10 min | ISO 1133, 190/2.16 | 1.42 | General-purpose workhorse |
| TENAC | POM-H | 5010 | MFR 22 g/10 min | ISO 1133, 190/2.16 | n/a | High-flow homopolymer |
| Hostaform | POM-C | C27021 | MVR 24 cm³/10 min | ISO 1133, 190/2.16 | 1.41 | Thin-wall precision parts |
| Ultraform | POM-C | W2320 | MVR 25 cm³/10 min | ISO 1133, 190/2.16 | 1.40 | High flow |
| Delrin | POM-H | 900P | MFR 25 g/10 min | ISO 1133, 190/2.16 | 1.42 | Fine, thin-wall parts |
| DURACON | POM-C | M270-44 | MFR 27 g/10 min | ISO 1133, 190/2.16 | 1.41 | Thin wall, multi-cavity |
| KOCETAL | POM-C | K700 | MFR 27 g/10 min | ISO 1133, 190/2.16 | 1.41 | High flow |
| Hostaform | POM-C | C52021 | MVR 39 cm³/10 min | ISO 1133, 190/2.16 | 1.41 | Very high flow |
| KOCETAL | POM-C | K900 | MFR 42 g/10 min | ISO 1133, 190/2.16 | 1.41 | Very high flow |
| FORMOCON | POM-C | FM450 | MFR 45 g/10 min | ASTM D1238, 190/2.16 | 1.41 | Very high flow |
| KEPITAL | POM-C | F40-03 | MI 48 to 52 (no unit printed) | Manufacturer table | 1.41 | Maximum flow in the line |
| TENAC | POM-H | 9054 | MFR 70 g/10 min | ISO 1133, 190/2.16 | n/a | Maximum flow |
Sources: the values above were checked against manufacturer datasheets and Material Data Center or IDES records, including Hostaform C27021 and FORMOCON FM090. Confirm against the current TDS for the exact grade and lot.
The grades we supply day to day are on our POM material range page, including FORMOCON FM090 and DURACON M90-44.
How to read the suffixes
The letters after the grade usually describe the additive package, not the flow. Hostaform GV grades are glass-filled; M grades contain MoS₂; TF grades contain PTFE. Ultraform uses a letter before the number for flowability, from H (lowest) through N and S to W (highest). DURACON uses prefixes such as GH for glass-filled, NW for a low-friction blend and LW for low wear.
The safest habit is to read the suffix as a claim to verify, not a guarantee. “UV” on one brand may mean a hindered amine package, on another carbon black. The datasheet tells you which.
Equivalent grades are not interchangeable
Buyers ask for “the equivalent of Hostaform C9021” or “the Chinese version of Delrin 500P”. The honest answer is that equivalence is a starting point for trials, not a drop-in.
Two grades can share a family, a flow band and an additive class and still differ in catalyst, comonomer level, stabiliser package and shrinkage. Impact strength, mold deposit, colour and warpage can all move at the same nominal MFI.
The only safe substitution process is sequential. Compare datasheets at the same condition, mold a trial tool, measure shrinkage and warpage, then run the application test.
Qualify the lot before you release the substitute to production. Any supplier who offers a substitute without that sequence is asking you to absorb the risk.
If you need the grade-level datasheets for a shortlist, ask us for the datasheets and tell us the part and the process.
Best POM Grade for Injection Molding: Choose by Part
Brand is a constraint, not a selection method. Start with the part, then find the POM injection molding grade that fills it, then check which brands carry that grade.
| Application | First choice | Grades to shortlist | Why | Watch-out |
|---|---|---|---|---|
| Thin-wall housings, multi-cavity | High-flow POM-C | DURACON M270-44; Hostaform C27021; KOCETAL K700; FORMOCON FM270; KEPITAL F30-03 | Fill pressure and cycle time | Notched impact falls; mold deposit rises with melt temperature |
| General mechanical parts | Medium-flow POM-C | DURACON M90-44; Hostaform C9021; Ultraform N2320; KOCETAL K300; FORMOCON FM090 | Balanced flow and toughness | Confirm the exact grade, not just the family |
| Thick-wall, pressure-tight | Low-flow POM-C | DURACON M25-44; Celcon M25; Hostaform C2521; KOCETAL K500 | Lower void risk, better pressure tightness | Cycle time; centerline porosity still possible |
| Precision gears, dry running | POM-H or low-friction POM-C | Delrin 500P; TENAC 4010; DURACON NW-02 or LW-02 | Stiffness, fatigue, low friction | PV limit and counterface decide life |
| Bushings, wear pads | Low-friction POM | Delrin AF; DURACON LW-02; KOCETAL TF304; TECAFORM HPV13 | PTFE or silicone package | Wear rate depends on the counterface |
| Snap-fits, clips | Higher-MW or impact-modified POM | Delrin 100P; Ultraform N2640 Z2; KOCETAL UR305 | Elongation and repeated impact | Notch sensitivity; fatigue life |
| Glass-filled structural | GF25 or GF30 POM; POM-C, except Delrin 525GR which is POM-H | DURACON GH-25; Hostaform C9021 GV1/30; Delrin 525GR; KOCETAL GF702 | Stiffness and creep resistance | Abrasive to tooling; anisotropic shrinkage |
| Fuel systems | POM-C, grade-specific | Hostaform C27021 or C9021 fuel grades; DURACON M90-44 | Fuel and hydrolysis resistance | Permeation, static and OEM specification |
| Hot water and plumbing | POM-C | DURACON M90-44; Hostaform C9021 | Hydrolysis resistance | Chlorine and chloramine exposure |
| Food contact | FDA-compliant grade | Ultraform N2320 FC; Hostaform food grades; DURACON food grades | Regulatory compliance. In the US, POM food-contact use is governed by 21 CFR 177.2470 for copolymer and 177.2480 for homopolymer, applied at grade level | Compliance is grade-specific, not family-wide |
| Medical | USP Class VI or ISO 10993 grade | Ultraform N2320 PRO; Hostaform MT 8U01 | Documentation and sterilisation | Grade-specific certification |
| Low-emission interior | Low-VOC POM-C | Hostaform XAP2 or XAP3; Ultraform LEV | VDA 275/278 limits | Confirm the OEM test method |
| UV or outdoor | UV-stabilised POM | FORMOCON FM270UV or FM130UV; Delrin 527UV; Hostaform C9021 SW | Stabiliser package | Stabilisation is not a lifetime guarantee |
Three patterns sit behind the table.
Thin wall is a flow problem before it is a strength problem. If a 0.8 mm wall with a 90 mm flow path short-shots at 9 g/10 min, raising injection pressure may solve the trial and damage the part. A 24 to 27 flow grade usually solves it with less residual stress and a shorter cycle.
Thick wall is a shrinkage problem before it is a strength problem. A 12 mm section cooled from the outside leaves a molten core. Pack pressure cannot reach it once the gate freezes. A lower-flow copolymer, a larger gate and a longer hold often do more than a “stronger” grade. Our guide to POM shrinkage covers the dimensional side.
Wear is a system property. A low-friction grade helps only if the counterface, load and speed suit it. The same grade can wear quickly against a rough steel shaft and last for years against a polished one.
Some limits are family-wide, not grade-level. POM is UL94 HB only, and halogenated flame retardants are incompatible with acetal, so there are no V-0 POM grades. If the part has to pass a flame test, the material has to change. Strong acids, strong bases and hot chlorine also attack POM, and no additive package fixes that. Check chemical compatibility before you specify any POM grade for a chemically exposed part.
Modified POM and Acetal Injection Molding Grades: What the Suffix Buys
| Family | What it adds | Typical designations | What it costs |
|---|---|---|---|
| Glass-filled | Stiffness, creep resistance, HDT | DURACON GH-25; Hostaform C9021 GV1/30; Delrin 510GR or 525GR; KOCETAL GF702 | Impact, elongation, anisotropic shrinkage, tool wear |
| PTFE or AF | Lower friction and wear | Delrin AF; TECAFORM HPV13; KOCETAL TF304 | Mechanical strength, cost |
| MoS₂ | Dry sliding, lower friction | Hostaform C9021 M | Black colour, some impact |
| Impact-modified | Toughening elastomer | Ultraform N2640 Z2; KOCETAL UR305; FORMOCON FMT12M | Stiffness, creep, cost |
| UV-stabilised | Hindered amine or carbon black | FORMOCON FM270UV; Delrin 527UV; Hostaform C9021 SW | Colour, cost |
| Antistatic or conductive | Carbon black or conductive filler | TECAFORM AH SD or ELS; KOCETAL CB301 | Mechanicals, colour, cost |
| Low-emission | Reduced formaldehyde and VOC | Ultraform LEV; Hostaform XAP2 or XAP3 | Cost, VDA 275/278 verification |
| Food-contact | FDA or EU 10/2011 formulation | Ultraform N2320 FC Aqua; DURACON food grades | Cost, documentation |
| Medical | USP Class VI or ISO 10993 | Ultraform N2320 PRO; Hostaform MT 8U01 | Cost, limited colours |
Glass-filled POM injection molding grades
Glass-filled grades from GF10 to GF30 raise tensile modulus, creep resistance and heat deflection temperature. DURACON GH-25, a 25% glass copolymer, reaches 136 MPa tensile strength and a 162 °C HDT at 1.8 MPa. The cost is impact, elongation and tool wear, and the shrinkage becomes directional.
Low-friction POM grades
PTFE, MoS₂ and silicone packages lower the coefficient of friction for gears, bearings and sliding parts. Delrin AF, DURACON LW-02 and NW-02, KOCETAL TF304 and TECAFORM HPV13 are common starting points. Wear rate still depends on the counterface and the PV limit, so ask for the grade’s wear data at your operating point.
Impact-modified, UV and specialty grades
Impact-modified grades raise elongation for snap-fits and clips. UV-stabilised grades extend outdoor life. Antistatic, conductive, low-emission, food-contact and medical grades each carry a specific additive package and a specific documentation set. Verify the grade, not the family.
Processing Window and Grade-Related Defects
Manufacturer guides do not agree on one POM window, and they should not. The window depends on grade, wall thickness and machine. The table below reports each source’s own numbers rather than an average.
| Source or grade | Melt or cylinder | Mold | Drying | Shrinkage |
|---|---|---|---|---|
| Celcon (Celanese POM-044) | 182 to 199 °C; ceiling 238 °C | 82 to 121 °C in the table; 38 to 127 °C in the body text | 82 °C for 3 h | 1.2 to 2.4% lab; M90 1.8 to 5.0% |
| DURACON M90-44 | 190 to 220 °C | 80 to 120 °C | 80 to 90 °C for 2 to 4 h | 2.3% flow, 2.1% cross-flow |
| Hostaform C52021 | 190 to 210 °C | 90 to 110 °C | 100 to 120 °C | 1.9% flow, 1.8% cross-flow |
| KOCETAL K300 or K700 | 160 to 200 °C; max 220 °C | 60 to 80 °C | 80 to 90 °C for 3 to 4 h | About 2.0% |
| FORMOCON FM090 | 185 to 210 °C | 40 to 90 °C | 80 to 90 °C for 3 to 4 h | 1.8 to 2.2% |
The spread is not a contradiction. Different grades, wall sections and test methods produce different windows. What matters is that the number you use belongs to the grade in the bag.
Three process points deserve more attention than they usually get.
POM does need drying. It is not as moisture-sensitive as PA66, but surface moisture and volatiles cause splay and silver streaks. Dry according to the grade datasheet, and do not assume a hopper sitting overnight is dry. Our guide to POM material preheating temperature covers drying schedules by grade.
Residence time matters more than peak temperature. POM degrades by unzipping at the chain ends when it is overheated or held too long. A machine running at 220 °C with a short residence time can be safer than one at 200 °C with a 20-minute hold. Purge the barrel before shutdown and after a long stop.
Mold temperature changes more than surface finish. It affects crystallinity, shrinkage, warpage and cycle time. The Celanese guide’s own table and body text disagree on the range, which is a reminder to treat any single “POM mold temperature” as a starting point.
For defect troubleshooting beyond the grade, our POM processing guide covers the process side. Published POM temperature ranges vary between sources, so confirm every setting against the grade datasheet.
Defects that point back to the grade
| Defect | Likely cause | What to change |
|---|---|---|
| Centerline porosity in thick sections | Shrinkage void; low hold pressure; high melt temperature | Lower melt temperature, raise hold pressure and time, enlarge the gate, consider a lower-flow copolymer |
| Mold deposit | Formaldehyde or ammonia breakdown; long residence time; poor venting | Lower melt temperature, shorten residence time, improve venting, purge |
| Splay or silver streaks | Moisture or volatiles; contaminated regrind | Dry per datasheet, reduce regrind, check the hopper |
| Short shot | Flow too low for the wall and flow length | Move to a higher-flow grade before raising pressure |
| Weak weld line | Low mold temperature, low injection speed, poor venting | Raise mold temperature, increase injection speed, move the gate |
| Warpage | Differential shrinkage; glass orientation; uneven cooling | Balance cooling, reconsider gate location, check the grade’s anisotropy |
| Jetting | Gate design; high initial injection speed | Redesign the gate, reduce initial speed, enlarge the gate |
| Formaldehyde odour | Overheating or long residence time | Lower melt temperature, purge, check hot-runner dead spots |
| Brittle parts | Too-high flow grade; low mold temperature; regrind; moisture | Move down the flow ladder, raise mold temperature, dry, cut regrind |
A thick valve body that shows porosity after machining is the classic case. The instinct is to ask for a stronger grade. The better answer is usually a lower-flow copolymer, a higher hold pressure, a larger gate, or a low-porosity grade. Strength is usually not the problem; the section cannot be packed.
Verify a POM Injection Molding Grade Before You Run It
A datasheet describes what the manufacturer intends to make. A COA describes what was made. The gap between them is where most grade disputes start.
| Check | What it proves | Limit |
|---|---|---|
| COA | Grade, lot, MFR, tensile and density as declared | Supplier-issued; verify the lot and the test condition |
| MFR re-check | The lot matches the datasheet | Must use the same condition, 190 °C/2.16 kg or 230 °C |
| Density | 1.41 g/cm³ unfilled versus 1.59 g/cm³ for GF25 | Filled and modified grades blur the check |
| DSC melting point | About 165 to 167 °C for copolymer; about 178 °C for homopolymer | Filled grades shift the peak |
| Lot traceability | Brand and grade authenticity | Requires a supplier willing to document the chain |
| Packaging and marking | Branded prime versus rebranded regrind | Counterfeit packaging exists |
| Full TDS | The grade’s actual property set | A COA is not a TDS; ask for both |
Six questions before the second order:
- Does the COA name the brand, the grade and the lot, or only “POM”?
- Does the MFR line state the method, temperature, load and unit?
- Does the measured MFR sit inside the datasheet range, not just near it?
- Is the density consistent with the grade, filled or unfilled?
- Can the supplier trace the lot back to the manufacturer’s batch record?
- Have you received the full TDS for this grade, not only the COA?
If the answer to any of these is no, the material may still be good. You just cannot prove it, and that is a procurement risk you are carrying.
Our guide to POM resin suppliers covers the supplier qualification side in more detail. For the thermal numbers behind the DSC check, see POM melting point.
Sourcing POM Injection Molding Grades from China
Yifuhui supplies branded POM grades from BASF (Ultraform®), Celanese (Hostaform® and Amcel®), Polyplastics (DURACON®), Kolon (KOCETAL®) and Formosa (FORMOCON®). The portfolio covers standard injection molding, high-flow, wear-resistant, UV-stabilised and FDA-compliant grades.
For international buyers, four practical points matter more than the catalogue.
MOQ starts at 25 kg. That is enough for a trial molding run and a COA check before you commit to a production quantity. The same grade is available from 25 kg to full container loads; our guide to bulk POM resin covers container quantities and lead times.
Every shipment carries a COA and MSDS. Our COA traces to the manufacturer’s lot record, and we can provide that record for audit. If you need FDA, RoHS or REACH documentation for a specific POM grade, ask at quotation stage, because the answer is grade-specific.
Standard lead time is 7 to 14 days to major international ports for in-stock grades, depending on destination port and Incoterm, from our Suzhou warehouse through the Port of Shanghai. Grades that must be drawn from manufacturer stock take longer, and we confirm that at quotation.
Grade availability varies by region. Some grades are licensed or stocked for particular markets. A grade that is standard in Europe may be a special order in Asia, and the reverse is also true. Confirm availability before you write it into a drawing.
Price differences between grades follow the additive package, not just the polymer. A glass-filled or low-emission grade costs more than a standard unfilled grade from the same brand. Our POM material price guide explains the direction; for a specific grade and quantity, ask for a quote.
One supply-chain note: China’s anti-dumping duties on POM copolymer apply to imports into China, not to exports from China. If your material is landed in China before processing, the duty can affect your cost base. If you are buying for export, the duty does not follow the shipment. Confirm the current scope with your customs broker.
Frequently Asked Questions
What is the best POM grade for injection molding?
There is no universal best grade. For general parts, DURACON® M90-44, Hostaform® C9021, Ultraform® N2320, KOCETAL® K300 and FORMOCON® FM090 sit in the same flow band and are widely available. The best grade is the one that matches your wall, flow length, chemical exposure and regulatory requirement.
What MFI is best for POM injection molding?
There is no single best value. Thick walls and pressure-tight parts usually start at 2.5 to 4 g/10 min, general-purpose parts sit around 7 to 10, and thin walls and multi-cavity tools need 20 to 27. Micro parts can need 40 or more. Match the flow to the wall and flow length, then confirm the grade’s mechanical data.
What is the difference between POM 90 and POM 100?
They are from different naming systems. POM 90, as in DURACON M90 or Celcon M90, is a flow class at about 9 g/10 min. Delrin 100 is a molecular-weight class at about 2.5 g/10 min, the highest-viscosity end of its line. Comparing them as if 100 were “more” than 90 reverses the flow relationship.
Is Hostaform C27021 the same as Celcon M90?
No. C27021 measures MVR 24 cm³/10 min, while Celcon M90 measures MFR 9 g/10 min. Both are Celanese copolymers, but they sit in different flow bands and won’t fill the same tool in the same way. Treat any claim that they are interchangeable as a claim to verify with the manufacturer.
Which POM grade is best for gears?
Start with a homopolymer or a low-friction copolymer: Delrin 500P, TENAC 4010, or DURACON NW-02 and LW-02 for wear. The grade choice matters less than the PV limit, the counterface and the lubrication. A gear grade that works against a polished steel shaft can fail against a rough one.
Which POM grade is best for thin walls?
A high-flow copolymer in the 20 to 27 range, such as DURACON M270-44, Hostaform C27021, KOCETAL K700 or FORMOCON FM270. Above that, KOCETAL K900, FORMOCON FM450 and KEPITAL F40-03 cover very thin sections and micro parts. Higher flow trades away some notched impact.
Is Delrin a homopolymer or copolymer?
Delrin is POM homopolymer. It has higher tensile strength, modulus and hardness than standard copolymer, and it is more prone to centerline porosity in thick sections. For hot water, fuel or a wide process window, a copolymer is usually the better starting point.
Is POM flame retardant?
No. POM is rated UL94 HB, the lowest horizontal-burning classification, and halogenated flame retardants are incompatible with acetal, so V-0 POM grades don’t exist. If the part has to pass a flame test, the polymer has to change. POM is also attacked by strong acids and bases.
Does POM need drying before molding?
Yes. POM is less moisture-sensitive than PA66, but surface moisture and volatiles cause splay and silver streaks. Dry to the grade datasheet, typically 80 to 90 °C for 3 to 4 hours for many copolymer grades, and confirm the exact condition with the manufacturer.
What does the “-44” in DURACON M90-44 mean?
Polyplastics doesn’t define the suffix in the datasheets we reviewed. Do not read it as a flow class or a colour code. Use the grade’s own datasheet for MFR, density and properties, and ask the manufacturer if the suffix matters for your specification.
Is glass-filled POM stronger than unfilled POM?
It is stiffer and has a higher heat deflection temperature. It is not uniformly stronger. Glass raises modulus and creep resistance but lowers elongation and impact, and it shrinks differently along and across the flow. It also wears tooling faster.
Can I substitute one brand’s grade for another?
Only after a qualification sequence. Compare datasheets at the same condition, mold a trial tool, measure shrinkage and warpage, run the application test, then qualify the lot. Grades with the same nominal MFI can differ in impact, mold deposit and shrinkage because their catalyst and additive packages differ.
POM Grade Selection Guide: The Five-Step Decision
POM injection molding grade selection comes down to five questions, in this order. Good POM grade selection is a sequence, not a brand preference.
- What does the part have to survive? Temperature, chemical exposure, load, impact and regulatory requirement.
- What does the mold have to fill? Wall thickness, flow length, gate location and cavity count.
- Which family? Homopolymer for stiffness in dry conditions; copolymer for toughness, hydrolysis and a wider window.
- Which flow band? Match the MFR or MVR to the fill, then confirm the mechanical data.
- Which grade and brand? Choose a named grade, check the datasheet condition, and verify the COA on arrival.
That is POM injection molding grade selection in full: name the part, match the flow band, and verify the lot.
The grade number is a starting point, not an answer. The datasheet is the specification. The COA is the proof. The trial part is the decision.
If you send us the drawing, the wall thickness, the flow length, the operating temperature and the chemical exposure, our team will shortlist grades from the BASF, Celanese, Polyplastics, Kolon and Formosa portfolios and send the datasheets with the quote; the COA ships with each lot. Request a POM grade recommendation, or browse the POM resin grades we supply. To gain a deeper understanding of POM Homopolymer vs. Copolymer, please refer to our accompanying guide.
