Nylon and POM are the two materials customers ask about most, because both are mechanical-grade engineering plastics, similarly priced, and interchangeable in many jobs. But the details differ in ways that decide how long the part lives. Choose correctly and service life improves dramatically.
What are Nylon and POM, and where do they differ?
Nylon (PA6, PA66, MC Nylon)
The most popular engineering plastic. Its headline traits are toughness and abrasion resistance — it absorbs impact well and runs quietly against metal. Standard for bushes, gears, rollers and wear pads. MC Nylon (Cast Nylon) is the cast version: available in very large sizes with more uniform properties.
POM (Acetal / Polyacetal)
Its strengths are stiffness, spring-back, and dimensional stability. It machines to crisp, slick surfaces and absorbs almost no moisture, so it holds size precisely. Standard for gears, precision mechanisms, and parts in constant motion.
How do Nylon and POM compare, property by property?
| Property | Nylon | POM (Acetal) |
|---|---|---|
| Toughness / impact | Better — tough, absorbs shock | Good, but more brittle |
| Abrasion resistance | Excellent — its main selling point | Good, slicker surface |
| Moisture absorption | Up to 2–3%, dimensions swell | Almost none — size stays put |
| Dimensional precision | Moderate (humidity-dependent) | Very high — precision work |
| Machined finish | Good | Crisper, cleaner |
| Continuous service temp | ~80–100°C | ~90–100°C |
| Wet / humid service | Not recommended if precision matters | Better suited |
| Price | Slightly cheaper | Slightly higher |
What are the actual numbers?
Typical values for the grades most common in Thailand — extruded PA6 and POM-C copolymer (the datasheet of your batch governs):
| Property | PA6 (Nylon) | POM-C (Acetal) |
|---|---|---|
| Tensile strength | ~70–85 MPa | ~60–70 MPa |
| Density | ~1.14 g/cm³ | ~1.41 g/cm³ |
| Moisture absorption (saturation) | Up to ~9% in water, ~2.5–3% in humid air | <0.8% |
| Continuous service temp | ~80–100°C | ~90–100°C |
| Friction coefficient vs steel | ~0.35–0.40 | ~0.30–0.35 |
| Relative price | ~10–20% lower | Slightly higher |
Read the numbers carefully: Nylon looks stronger on paper, but that value is measured dry. Once it absorbs moisture, strength drops and dimensions can swell 0.5–2% of the part size — while POM keeps its properties regardless of humidity. That is why nearly all precision gears and mechanisms choose POM despite the lower headline strength.
Which grades are available?
- PA6 (Extruded Nylon) — standard extruded grade, small-to-medium sizes, best price
- PA66 — slightly harder and more heat-resistant than PA6, better abrasion resistance
- MC Nylon (Cast Nylon) — cast into very large sizes (thick plate, large-diameter rod) with more uniform crystal structure; the go-to for large bushes and gears; available in ivory and blue (MC901)
- POM-C (Copolymer) — the standard grade in the Thai market; better hot-water/chemical resistance than homopolymer; white and black
- POM-H (Homopolymer / Delrin) — slightly stronger and harder-surfaced than POM-C, for higher loads
So which one should you use?
Choose Nylon when...
- Heavy sliding wear — shaft bushes, rollers, wear pads
- Impact exists in the system and you need toughness
- The part is large — MC Nylon casts economically at big sizes
Choose POM when...
- The part must hold precise, stable dimensions for life — gears, sliding mechanisms
- It works in humid conditions or touches water
- You want slick machined surfaces and low friction
Read next
For the full selection method see How to Choose the Right Engineering Plastic, or browse all 9 material groups. We stock both Nylon and POM as sheet and rod, cut to size, and can machine them into finished parts for you.