Acetal (POM) and nylon (PA) are two go-to engineering plastics for gears, bushings, and structural housings. They look similar as white rods or black pellets, yet their behavior in water, heat, and machining differs. This guide compares acetal and nylon in plain words so you can pick the better polymer for your next machined or molded part.
Innehållsförteckning
- Why compare acetal and nylon before design
- Basic chemistry and typical grades explained
- Mechanical strength, stiffness, impact results
- Moisture absorption and size stability
- Friction, wear, and noise performance
- Temperature and chemical resistance limits
- CNC machining differences step by step
- Injection molding guidelines for both polymers
- Cost, availability, and color options
- Quick selection guide for common parts
- Need one-stop plastic fabrication?
- Summary checklist before final part release
Why Compare Acetal And Nylon Before Design
Both resins promise low friction and good strength, yet hidden differences can cause field failures. Nylon swells in humid air; acetal may crack under chlorine. Knowing these limits early avoids test loops and tool rework later.
Basic Chemistry And Typical Grades Explained
Acetal is a polyoxymethylene chain. Nylon is a polyamide family. Commercial suppliers tune each with fillers and lubricants.
| Material family | Common ISO name | Popular grades | Key additive |
|---|---|---|---|
| Acetal homopolymer | POM-H | Delrin 150 | Ingen |
| Acetal copolymer | POM-C | Celcon M90 | Thermal stabilizer |
| Nylon 6 | PA 6 | Ultramid B3 | Heat stabilizer |
| Nylon 6/6 | PA 66 | Zytel 101 | Ingen |
| Nylon 6/6 glass 30 % | PA 66 GF30 | Zytel 70G30 | 30 % glass fiber |
Copolymer acetal resists center-line porosity better than homopolymer. Glass in nylon boosts stiffness but raises tool wear.
Mechanical Strength, Stiffness, Impact Results
The next chart shows tensile strength and modulus at room temperature.
Property | Acetal POM-C | Nylon 6 | Nylon 66 GF30 ----------------------------------------------------------- Tensile MPa | 65 | 75 | 190 Flexural modulus GPa| 2.9 | 2.5 | 7.4 Izod notched kJ/m2 | 7 | 5 | 8
Acetal beats unfilled nylon on impact and holds stiffness over time, but glass-filled nylon outruns both on load-bearing ribs.
Moisture Absorption And Size Stability
Nylon loves water; acetal sheds it. Dimensional change matters for tight gears.
| Material | Water uptake @ 50 % RH 23 °C (%) | Linear swell at saturation (%) |
|---|---|---|
| Acetal POM-C | 0.2 | 0.4 |
| Nylon 6 | 1.2 | 3.0 |
| Nylon 66 | 0.8 | 2.0 |
Use acetal in wet pump manifolds where clearance stays tight. Add shrink compensation when molding nylon ski bindings.
Friction, Wear, And Noise Performance
Both plastics self-lubricate, yet test data helps pick the quiet driver.
Coefficient of friction (dry, steel pin) Acetal ████ 0.20 Nylon 6 █████ 0.25 Nylon GF ███████ 0.35
Acetal gears run 2–3 dB quieter than nylon at 2 m/s mesh speed. Nylon gains ground when filled with PTFE, dropping μ to 0.18.
Temperature And Chemical Resistance Limits
Heat deflection and solvent resistance guide material in hot engine bays or chemical mixers.
| Polymer | HDT @ 1.8 MPa (°C) | Short-term max (°C) | Weak solvent | Strong solvent |
|---|---|---|---|---|
| Acetal | 110 | 140 | Motor oil—ok | Chlorine—attack |
| Nylon 6 | 80 | 120 | Glycol—ok | Strong acid—attack |
| Nylon 66 GF30 | 240 | 260 | Fuel—ok | Phenol—attack |
Glass makes nylon handle higher heat. Acetal resists fuels but not strong oxidizers.
CNC Machining Differences Step By Step
Acetal machines like butter; nylon strings and warps.
- Cutting speed: 400 m/min acetal, 250 m/min nylon.
- Chip load: 0.1 mm/tooth acetal, 0.06 mm/tooth nylon.
- Coolant: Air for acetal; mist helps nylon stop gumming.
- Fixturing: Freeze clamps for thin nylon plates to stop creep.
- Burrs: Acetal leaves crisp edge; nylon needs flame polish or shave tool.
Injection Molding Guidelines For Both Polymers
Set melt and mold temperatures to fill and hold without flash.
| Setting | Acetal | Nylon 66 |
|---|---|---|
| Melt °C | 210–230 | 275–290 |
| Mold °C | 80–100 | 70–90 |
| Drying °C/h | None (sealed bag) | 80 °C >4 h to <0.2 % H2O |
| Shrink % | 1.8–2.1 | 1.4–1.7 (dry) |
Acetal needs vent depth 0.015 mm; nylon 0.025 mm due to higher viscosity.
Cost, Availability, And Color Options
Price drives material in consumer goods. Use this quick bar chart (US market 2025).
Average resin cost $/kg Acetal POM-C ██████ 4.2 Nylon 6 ████ 3.1 Nylon 66 █████ 3.8 Nylon 66 GF30 ███████ 5.2
Nylon takes dye easily; acetal prefers masterbatch during compounding. Both can be bought in natural, black, or color-matched pellets.
Quick Selection Guide For Common Parts
The table below links application demands to the better polymer.
| Part | Main stress | Miljö | Pick acetal or nylon? | Why |
|---|---|---|---|---|
| Precision gear | Wear & noise | Dry indoor | Acetal | Low swell, quiet mesh |
| Fuel tank clip | Impact | Gasoline | Nylon 66 | Tough, fuel stable |
| Kitchen faucet valve | Slide seal | Hot water | Acetal | Low friction, low water gain |
| Drone propeller hub | High load | Sunlight | Nylon GF30 | High modulus, good fatigue |
| Threaded insert boss | Creep | Humid | Acetal | Less creep than nylon |
Need One-Stop Plastic Fabrication?
We machine acetal, nylon, and many filled grades, then add sheet-metal or molded sub-components in one order. Send your STEP/STL/IGS file for a quick, consolidated quote.
Summary Checklist Before Final Part Release
- If tight tolerance in humidity, choose acetal.
- If high heat or glass fill required, pick nylon.
- Dry nylon resin before molding; acetal ships dry.
- Use sharp tools and air blast for acetal; slower feed and mist for nylon.
- Note resin type and color code on drawing for traceability.
With these points in mind, you will select the right polymer, machine it smoothly, and deliver durable parts on the first try.
