Acetal Copolymer Specifications — ASTM D6100, Sizes & Tolerances
Acetal copolymer (POM-C) stock shapes — rod, sheet, and tube — are governed by ASTM D6100, the same standard that covers acetal homopolymer (POM-H / Delrin). This page covers the applicable standards, dimensional tolerances, standard stocked sizes, and procurement specification language for acetal copolymer, with notes on where POM-C specifications differ from POM-H.
At a glance:
- Primary standard: ASTM D6100 — Polyacetal (POM) rod, sheet, and tube
- Material classification: Type I for unfilled, Type II for filled grades
- Rod tolerances: ±0.010–0.030" depending on diameter (same as POM-H per ASTM)
- Sheet tolerance: ±10% of nominal thickness (ASTM default)
- Key POM-C advantage in specifications: no centerline porosity caveat for large-diameter rod
- ISO standard: ISO 9988 (POM moulding and extrusion materials); ISO 11470 (rod tolerances)
- FDA compliance: many natural-color grades meet 21 CFR 177.2480 — verify with lot documentation
Governing Standards
ASTM D6100
ASTM D6100 covers both acetal homopolymer and acetal copolymer stock shapes. For procurement and engineering drawing call-outs:
- Type I: Unfilled acetal (both POM-H and POM-C); Type I sub-classification may distinguish grades
- Type II: Filled acetal (glass fiber, PTFE-filled, etc.)
When specifying acetal copolymer on a drawing, include the polymer type explicitly: "Acetal copolymer (POM-C), ASTM D6100, Type I, natural color" — this prevents inadvertent substitution of POM-H, which is a different material.
ASTM Property Test Methods
| Property | Test Method |
|---|---|
| Tensile strength, modulus, elongation | ASTM D638 |
| Flexural strength and modulus | ASTM D790 |
| Izod impact (notched) | ASTM D256 |
| Heat deflection temperature | ASTM D648 |
| Compressive strength | ASTM D695 |
| Water absorption | ASTM D570 |
| Hardness (Rockwell) | ASTM D785 |
ISO Standards
- ISO 9988: Classification of POM molding and extrusion materials
- ISO 11470: Specification for extruded POM rod tolerances (European procurement)
- EN ISO 9988: European adoption of the ISO POM material standard
Dimensional Tolerances
Rod Tolerances (ASTM D6100)
| Diameter Range | Standard Tolerance | Precision (Special Order) |
|---|---|---|
| Up to 0.500" | ±0.010" | ±0.005" |
| 0.501" – 1.000" | ±0.010" | ±0.007" |
| 1.001" – 2.000" | ±0.015" | ±0.010" |
| 2.001" – 4.000" | ±0.020" | ±0.015" |
| 4.001" – 6.000" | ±0.030" | ±0.020" |
| 6.001" – 8.000" | ±0.040" | ±0.025" |
| Over 8.000" | ±1% of diameter | To quote |
POM-C advantage in large-diameter rod: Acetal copolymer rod in diameters above 3 inches does not develop the centerline porosity characteristic of POM-H (Delrin). ASTM D6100 acknowledges centerline porosity in POM-H as an acceptable characteristic; this exception does not apply to POM-C rod. If a print specifies "acetal copolymer" for large-diameter parts, the cross-section should be uniform throughout.
If your application requires gas-tight or structurally uniform material through the full cross-section of rod above 3 inches in diameter, specify acetal copolymer (POM-C) explicitly. Do not use Delrin (POM-H) unless the application engineer has evaluated and accepted centerline porosity.
Sheet Tolerances (ASTM D6100)
| Thickness Range | Standard Tolerance | Precision |
|---|---|---|
| 0.062" – 0.500" | ±10% of nominal | ±5% |
| 0.501" – 1.000" | ±10% of nominal | ±7% |
| Over 1.000" | ±10% of nominal | ±7% |
Sheet flatness: standard 0.025"/ft over sheet length. Ground/sanded sheet to ±0.005" total thickness variation available on request.
Tube Tolerances
| OD Range | OD Tolerance | Wall Tolerance |
|---|---|---|
| Up to 2.000" | ±0.015" | ±10% of wall |
| 2.001" – 4.000" | ±0.020" | ±10% of wall |
| Over 4.000" | ±0.030" | ±12% of wall |
Standard Stocked Sizes — Acetal Copolymer Rod
| Diameter | Standard Length | Grade/Color |
|---|---|---|
| 0.125" | 4 ft | Natural / black |
| 0.250" | 4 ft | Natural / black |
| 0.375" | 4 ft | Natural / black |
| 0.500" | 4 ft | Natural / black |
| 0.625" | 4 ft | Natural / black |
| 0.750" | 4 ft | Natural / black |
| 1.000" | 4 ft | Natural / black |
| 1.250" | 4 ft | Natural |
| 1.500" | 4 ft | Natural / black |
| 2.000" | 4 ft | Natural / black |
| 2.500" | 4 ft | Natural |
| 3.000" | 4 ft | Natural |
| 4.000" | 4 ft | Natural |
| 5.000" | 4 ft | Natural |
| 6.000" | 4 ft | Natural |
| 8.000" | 4 ft | Natural |
Standard Stocked Sizes — Acetal Copolymer Sheet
| Thickness | Sheet Size | Grade/Color |
|---|---|---|
| 0.062" (1/16") | 24"×48", 48"×96" | Natural / black |
| 0.093" (3/32") | 24"×48", 48"×96" | Natural / black |
| 0.125" (1/8") | 24"×48", 48"×96" | Natural / black |
| 0.250" (1/4") | 24"×48", 48"×96" | Natural / black |
| 0.375" (3/8") | 24"×48", 48"×96" | Natural / black |
| 0.500" (1/2") | 24"×48", 48"×96" | Natural / black |
| 0.750" (3/4") | 24"×48", 48"×96" | Natural / black |
| 1.000" (1") | 24"×48", 48"×96" | Natural / black |
| 1.500" | 24"×48" | Natural |
| 2.000" | 24"×48" | Natural |
| 3.000" | 24"×48" | Natural |
| 4.000" | 24"×48" | Natural |
Writing an Acetal Copolymer Specification for Engineering Drawings
Recommended call-out language for procurement:
Material: Acetal Copolymer (POM-C), ASTM D6100, Type I. Natural (white) color. Grade: Celcon M90 / Hostaform C 9021 or approved equivalent POM-C meeting ASTM D6100 Type I property requirements. Certificate of conformance required with each shipment.
For applications requiring FDA compliance, add: "FDA 21 CFR 177.2480 compliance letter required."
What NOT to write:
- "Acetal or Delrin" — this allows substitution of either POM-C or POM-H; if both are acceptable, say so explicitly; if only one is acceptable, name it
- "Acetal per ASTM D6100" without specifying POM-C — ASTM D6100 covers both POM-H and POM-C; if POM-C specifically is required (e.g., for hot-water service or large-diameter uniformity), the polymer type must be stated
Regulatory Compliance Summary
| Standard | Status for Acetal Copolymer |
|---|---|
| ASTM D6100 | Primary specification standard |
| FDA 21 CFR 177.2480 | Natural-color grades generally compliant; verify lot |
| NSF/ANSI 51 (Food Equipment) | Available — verify specific grade and lot |
| NSF/ANSI 61 (Drinking Water) | Available — verify specific grade and lot |
| RoHS 2011/65/EU | Compliant |
| REACH SVHC | Not listed |
| EU Regulation 10/2011 (Food Contact) | Declaration of Compliance available from European supply chain |
| ISO 9988 | POM-C classification standard |
Get acetal copolymer to ASTM D6100 — rod, sheet, tube with cert
Request a Quote →More related guides
Compare to other materials
Forms
Frequently asked questions — Acetal Copolymer FAQ