This guide gives you the JSLT EngPlastics decision tree for picking PA6, POM, or PEEK bushings — with PV limits, temperature ranges, chemical resistance, and 2026 FOB China pricing. Real engineering, no sales fluff.
1. The 30-second decision tree
If you only read one section, read this:
- POM (Acetal/Delrin) — General-purpose first choice. Dry running, low cost, dimensionally stable. Use if PV ≤ 0.18 MPa·m/s and temperature ≤ 90 °C.
- PA6 / PA66 (Nylon) — Higher load capacity than POM, especially with oil-filling. Best if you have intermittent grease lubrication and don't mind 2-3% moisture absorption. Use if PV ≤ 0.4 MPa·m/s and temperature ≤ 100 °C.
- PEEK — Premium choice for high temperature (up to 250 °C continuous), aggressive chemicals, or critical aerospace/medical applications. 15-25× the cost of POM. Use only when other options fail.
2. Side-by-side property comparison
| Property | PA6 (Nylon) | POM (Delrin) | PEEK | Winner |
|---|---|---|---|---|
| Continuous service temp | 100 °C | 90 °C | 250 °C | PEEK |
| Tensile strength (MPa) | 70 - 85 | 65 - 78 | 90 - 110 | PEEK |
| PV limit (MPa·m/s, dry) | 0.10 | 0.18 | 0.50 | PEEK |
| PV limit (MPa·m/s, oil) | 0.40 | 0.30 | 1.20 | PEEK |
| Moisture absorption (24 h) | 1.5 - 2.5% | 0.2% | 0.15% | POM/PEEK |
| Coefficient of friction (vs steel) | 0.20 - 0.30 | 0.15 - 0.20 | 0.20 - 0.30 | POM |
| Chemical resistance (acid) | Poor | Good | Excellent | PEEK |
| Chemical resistance (alkali) | Good | Excellent | Excellent | POM/PEEK |
| Machinability | Good | Excellent | Difficult | POM |
| Price (USD/kg, FOB Qingdao) | $3.50 - 5.00 | $4.50 - 6.50 | $95 - 140 | PA6 |
3. Understanding the PV limit
The most important number in plastic bushing design is the PV limit:
PV = Pressure (MPa) × Sliding velocity (m/s)
Pressure is the load on the bushing divided by projected bearing area (shaft Ø × bushing length). Velocity is the shaft surface speed (π × D × RPM / 60).
If PV exceeds the polymer's limit, frictional heat generation outpaces dissipation — bushing softens, melts, or seizes. Industry rule of thumb: design for PV at 50% of the catalog limit for continuous duty, 80% for intermittent.
Example: a 30 mm shaft at 200 RPM (V = 0.314 m/s) with 5 kN radial load on a 30 mm long bushing → P = 5,000 / (30 × 30) = 5.5 MPa → PV = 1.7 MPa·m/s. POM and PA6 both fail; only PEEK survives.
4. When to oil-fill or graphite-fill the polymer
Three modified grades dominate JSLT engineering plastic sales in 2026:
- PA6-MoS₂ (oil-filled nylon) — 5-10% molybdenum disulfide pre-mixed in polymer. Friction drops 30%, PV doubles. Color is dark grey. Used for cranes, agricultural machinery, conveyor rollers.
- POM-PTFE (filled acetal) — 15-20% PTFE filler. Friction at half of standard POM, ideal for high-cycle automation bushings. Slightly weaker mechanically but acceptable for low-load, high-speed.
- PEEK-30CF (carbon-fiber-filled PEEK) — 30% carbon fiber. Mechanical strength +50%, dimensional stability +200%. The premium choice for aerospace, medical, semiconductor wafer handlers.
5. Machining tips — what your shop needs to know
Each polymer has machining quirks. Pass these to your CNC operator:
- POM: Sharpest tools (rake angle 15-20°), high spindle speed, small depth of cut. Stringy chips — use compressed air for chip clearance.
- PA6: Cools poorly, deforms under heat. Use coolant, slow feed, and let the part cool between passes. Watch for moisture absorption causing post-machining dimensional drift (allow 24 h conditioning).
- PEEK: Hard to machine; tooling life is 30-50% of POM. Use carbide or diamond-coated tools. Pre-heat the stock to 150 °C to reduce internal stresses before fine cuts.
6. Real-world selection examples
- Conveyor return idler bushing (PV = 0.05): POM solves it for $4.50/kg. Don't over-spec.
- Pump shaft sleeve in cooling water (60 °C, mild chloride): POM-PTFE handles it; PEEK is overkill.
- Sterilizable medical device joint (steam autoclave 134 °C): PEEK only. POM hydrolyzes; PA6 absorbs water.
- Agricultural disc harrow bearing (heavy load, dust, intermittent grease): PA6-MoS₂ oil-filled — best price/performance.
- Semiconductor wafer-handling pin (clean room, 200 °C IR oven): PEEK-30CF, no question.
❓ Frequently Asked Questions
❓ Can I substitute PA6 for POM if my supplier is out of stock?
Often yes for short term. PA6 has higher load capacity but absorbs moisture and may grow 1-2% in dimension over months. For high-precision applications (machine tool spindles, gear boxes), don't substitute without re-checking clearances.
❓ Why is PEEK so expensive?
PEEK resin is patent-encumbered and made by only 3 global suppliers (Victrex, Solvay, Evonik). Polymerization requires diphenyl sulfone solvent at high temperatures. The combination keeps resin price at USD 80-120/kg vs USD 1.50-2.50 for PA6 resin.
❓ Can JSLT supply pre-machined bushings or just rod stock?
Both. We supply rod stock (10-300 mm Ø) for your in-house machining, or finished CNC-machined bushings to your drawing. Finished bushing pricing typically adds USD 0.50-2.00 per piece for standard sizes.
❓ What's the lead time for custom PEEK rod stock?
PEEK natural rod 30-100 mm Ø: 14-21 days from stock; larger Ø: 35-45 days production. PEEK-30CF: 35-45 days minimum due to lower production frequency. Air freight is recommended for PEEK due to high value-to-weight ratio.
❓ Do you offer FDA-grade PA6 or POM for food machinery?
Yes. JSLT supplies FDA-compliant grades of PA6 (white, blue) and POM (natural, white). FDA letter from resin manufacturer provided with every shipment. Pricing adds 5-8% to standard grades.
❓ Can JSLT engineers help me select the right grade?
Yes — free of charge. Send us your application details (load, speed, temperature, chemical environment, lubrication, dimensions) to claire@uhwmpe-produce.com and our engineering team responds within 48 hours with a recommended grade and PV calculation.
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Email Claire for full pricing, samples, and CIF delivery to your nearest port.
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