Delrin vs Nylon
Stiff and stable.
Stiff and stable.
Tough and forgiving.
Two different jobs.
Delrin (POM) is stiff, dimensionally stable, doesn't absorb moisture — great for precision gears. Nylon absorbs water, softens with humidity, but has better impact resistance and wear against metal. Know when each wins.
01 · At a glance
Side-by-side summary.
Option A
Delrin / Acetal (POM)
Polyoxymethylene. Crystalline, stiff, zero moisture absorption. Excellent dimensional stability. Standard for precision gears, bushings, mechanical fittings where dimensions matter.
Option B
Nylon (PA6 / PA66)
Polyamide. Tough, impact-resistant, absorbs moisture (up to 8%). Better wear against metal but dimensions shift with humidity. Standard for bushings, gears, impact-prone parts.
02 · Detailed comparison
Feature-by-feature breakdown.
| Attribute | Delrin (POM) | Nylon (PA66) |
|---|---|---|
| Tensile strength | 70 MPa | 83 MPa |
| Flexural modulus | 2.8 GPa | 2.8 GPa |
| Impact (Izod notched) | 7-9 kJ/m² | 4-5 kJ/m² dry, 15-20 wet |
| Moisture absorption | < 0.2% | 2-3% equilibrium |
| Dimensional stability | Excellent (no moisture) | Poor (swells with humidity) |
| Wear against steel | Good | Excellent (self-lubricating) |
| Friction coefficient | 0.2 | 0.15 with PTFE additive |
| HDT (1.8 MPa) | 110°C | 70°C (dry) / 55°C (wet) |
| FDA food contact | Yes (specific grades) | Yes |
| Cost per kg | $5-9 | $4-7 |
| Machinability | Excellent | Good |
| Typical applications | Precision gears, fittings | Bushings, impact parts |
03 · Decision guide
When to choose each.
Choose Delrin / Acetal (POM) when:
- Precision mechanical parts (dimensional critical)
- Dry environment gears and bearings
- Threaded parts that must hold tolerance
- Parts requiring machining consistency
- Low-friction sliding in dry conditions
- Chemical fuel system (acetal grades)
Choose Nylon (PA6 / PA66) when:
- Bushings wearing against metal shafts
- Impact-prone parts (housings, covers)
- Outdoor parts where moisture OK
- Abrasive wear applications
- Drop-test-survival consumer products
- Cable ties, mechanical fasteners
FAQ
Common questions.
Nylon's polyamide structure contains many polar groups that attract water molecules. At 50% RH ambient, nylon 6/6 absorbs ~2.5%. At 100% RH, up to 8%. Water acts as plasticizer — softens nylon, increases flexibility, reduces tensile strength. Dimensions grow ~0.3-0.5% per 1% moisture. For precision parts, this is disqualifying. For impact parts, moisture improves toughness.
Partially. Glass-filled nylon (PA66-GF30): much better dimensional stability, still absorbs moisture but less dimensional change. Nylon 12: absorbs only 1% moisture vs 8% for PA66. Nylon 46: higher temperature grade. MDS (moisture-dimensional-stabilized) grades available. For maximum dimensional stability, specify glass-filled PA66 or Delrin.
Acetal grades suitable for food contact available. Homopolymer (Delrin 150) and copolymer (Celcon, Hostaform) variants. FDA 21 CFR compliant grades. Typical applications: conveyor wear strips, food handling equipment, beverage dispensing hardware. Good chemical resistance to cleaning solutions. Preferred over nylon for food contact requiring dimensional stability.
Delrin is DuPont brand name for polyoxymethylene (POM). Generic term is "acetal" or POM. Other brand names: Celcon (Celanese), Hostaform (Ticona), Ultraform (BASF). Minor differences between homopolymer (DuPont Delrin) and copolymer (Celcon, Hostaform): copolymer more chemically resistant to hot water and alkalis, homopolymer slightly stiffer. For most applications, interchangeable.
Delrin: machines like aluminum — clean chips, smooth finish, holds tolerance. Standard tool steel or carbide. Nylon: slightly more gummy, chips tend to drag. Sharper tools, better chip clearance. Both at moderate speeds (200-500 m/min). Cost: equivalent per machining hour. Delrin preferred for precision parts due to dimensional stability during machining and in service.
PA66-GF30 (30% glass-filled): stiffer, stronger, much better dimensional stability than unfilled. Glass abrades tools — use PCD tooling for production. Standard for structural nylon applications. Delrin-GF: less common, copolymer generally not filled (already dimensionally stable). For high-strength Delrin, use homopolymer with higher molecular weight. For stiffness, PA66-GF30 often outperforms Delrin.
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