Ready Plastics

Best Plastics for Bushings & Bearings

Selecting the right polymer for a plain bushing or sleeve bearing determines whether a mechanism runs quietly for years or seizes within months. The best plastic for bushings and bearings balances PV limit (load × velocity), operating temperature, lubrication access, and chemical environment. This guide covers every major candidate — from commodity acetal to aerospace-grade Vespel — with real specifications and a decision framework you can use immediately.

TL;DR

  • Delrin is the default choice: tight tolerances, low moisture absorption, PV to ~10,000 psi·ft/min, easy to machine.
  • Nylon handles shock better but absorbs moisture — size for worst-case swell, especially in wet or humid environments.
  • PEEK extends the envelope to 480°F (250°C) and PV values exceeding 30,000 in lightly lubricated conditions.
  • PTFE-filled grades of acetal or PEEK drop the dynamic CoF to 0.05–0.10, eliminating the need for external lubricant in many applications.
  • PET/Ertalyte resists creep better than nylon at moderate temperatures — the preferred option where dimensional stability under sustained load matters.
  • UHMW-PE excels in food-processing and wet environments; softer and lower in PV limit, but nearly immune to abrasion and chemical attack.
  • PAI/Torlon and Vespel are reserved for extreme conditions (continuous >400°F, or PV >50,000) where cost is secondary to performance.

Delrin — The Workhorse Bushing Material

Acetal homopolymer (DuPont Delrin) and acetal copolymer (Celanese Hostaform) dominate general-purpose bushing applications because they combine dimensional stability, low moisture absorption (0.2% at saturation), and a surface finish that accommodates close tolerances right off the lathe or mill.

Why acetal works in bearings

Dry PV limit of ~10,000 psi·ft/min is adequate for most light- to medium-duty pivots, slides, and oscillating joints. The material machines cleanly to ±0.001 in tolerances without secondary grinding. Moisture absorption is low enough that bore dimensions remain predictable in humid environments — unlike nylon, which can swell 0.5–1.0% in wet service.

PTFE-filled acetal grades

Adding 15–20% PTFE to acetal raises the PV limit to roughly 15,000 psi·ft/min and drops the coefficient of friction to 0.05–0.15 (dry, dynamic). Use PTFE-filled grades anywhere external lubrication is impractical: inside food-processing machinery, inside sealed housings, or on intermittently rotating pivots where a grease fitting is cost-prohibitive. Natural (white) PTFE-filled acetal is FDA 21 CFR compliant for incidental food contact.

Nylon — Tough, Inexpensive, Shock-Resistant

Nylon 6 and 6/6 are widely stocked as bushing blanks because they're cheap, tough under impact, and readily available in large diameters. The tradeoff is moisture: nylon absorbs 1.5–3.0% water by weight, swelling enough to close up a bore that was correctly sized in a dry shop.

Sizing nylon bushings for wet service

Size the bore for the worst-case swollen dimension. A bushing machined to a 1.000 in bore at 50% RH may close to 0.994 in after soaking in water. For press-fit ODs, allow additional clearance to prevent the housing bore from cracking as the nylon expands. Nylon MoS₂-filled grades (nylon 6/6 + 2% molybdenum disulfide) retain the toughness advantage while reducing CoF to 0.15–0.20 dry.

Best applications for nylon bushings

Nylon bushings perform best in dry or mildly lubricated conditions, pivot applications, and heavily shocked duty cycles such as agricultural equipment linkages, automotive suspension components, and cable sheave hubs. The impact strength (notched Izod 2.0 ft·lb/in) and vibration damping make nylon superior to acetal wherever shock load is the primary concern, even though acetal has better dimensional stability.

PEEK — High-Load, High-Temperature Bearings

PEEK (polyether ether ketone) is the benchmark high-performance bearing polymer. It handles continuous service at 480°F (250°C), withstands steam sterilization and aggressive chemical cleaning agents, and achieves compressive strength values up to 18,000 psi — roughly 4× that of acetal.

PEEK bearing grades and fillers

Unfilled PEEK has a dry PV limit around 30,000 psi·ft/min. PEEK + 15% PTFE + 15% graphite ("bearing grade" or "BG") drops CoF to 0.10–0.15 and further raises the PV limit, making it the standard in continuous high-speed shaft applications. Carbon-filled PEEK (30% CF) maximizes compressive strength and creep resistance at the cost of slight abrasiveness against soft counter-faces.

Where PEEK bearings are specified

Medical devices (autoclavable, USP Class VI), semiconductor wafer handling (chemical resistance, no outgassing), aerospace control linkages (extreme temperature), and offshore pump bearings (hydrogen sulfide resistance) are the primary markets. Price per pound runs 15–25× that of acetal, so qualifying PEEK for an application requires a genuine engineering justification.

PET / Ertalyte — Creep-Resistant Alternative to Nylon

PET (polyethylene terephthalate), sold under trade names such as Ertalyte (Quadrant) and Sustadur PET (Simona), occupies the space between acetal and PEEK. Continuous use temperature reaches 250°F (120°C), and the material resists creep significantly better than nylon under sustained compressive load.

PV limit and fatigue performance

PET's dry PV limit is approximately 12,000 psi·ft/min — above nylon, near or slightly above acetal. Fatigue endurance under cyclic bending loads is the standout property: Ertalyte outlasts nylon in cam follower and eccentric roller applications by a factor of two to three in published comparative wear tests. Moisture absorption is roughly 0.1%, comparable to acetal, so bore dimensions are stable across humidity swings.

When to choose PET over acetal

If your application involves continuous compressive load (a bushing under a loaded shaft that never stops rotating), choose PET over acetal. The lower creep rate prevents the bore from gradually enlarging into the shaft clearance zone. For oscillating or intermittent loads where creep is less critical, acetal is usually sufficient and less expensive.

UHMW-PE — Food-Grade and Wet Environments

Ultra-high-molecular-weight polyethylene (UHMW-PE, TIVAR) is the material of choice in food-processing lines, conveyor bushings in wash-down zones, and any application where chemical resistance and near-zero FDA concerns are paramount. Its dynamic coefficient of friction against steel is 0.10–0.20, and it is inherently self-lubricating.

UHMW bushing limitations

The mechanical softness of UHMW (Shore D ~65, tensile strength ~5,500 psi) limits its PV rating to roughly 6,000 psi·ft/min. Under heavy radial loads it will cold-flow (creep), gradually enlarging the bore and creating shaft slop. Design UHMW bushings with a wall thickness of at least 15% of the bore diameter to resist deformation. For flanged bushings, press-fit retention can be marginal — use a retaining ring or shoulder rather than relying on interference alone.

UHMW grades for bushings

Standard natural UHMW meets FDA 21 CFR 177.1520. TIVAR 1000 (antistatic) eliminates spark hazards in grain handling and mining. TIVAR CleanStat combines antistatic and FDA compliance. UHMW + oil-filled ("TIVAR H.O.T.") improves PV performance by about 30% for elevated-temperature food applications.

PAI / Torlon — Extreme Duty Bushings

Polyamide-imide (PAI), sold as Torlon (Solvay), is a thermoset-processable engineering polymer with continuous service to 500°F (260°C) and a compressive strength exceeding 30,000 psi. Dry PV limits in the 50,000–60,000 psi·ft/min range are achievable with graphite-filled grades. Torlon 4301 (15% graphite, 3% MoS₂) is the standard bearing compound.

Trade-offs with Torlon

Torlon is brittle in impact and requires controlled machining (sharp tools, climb cutting) to prevent micro-cracking at the surface. Cost runs 5–8× PEEK. Applications are genuine aerospace, defense, and industrial high-speed spindles — not general-purpose bearings. Autoclave compatibility and resistance to nearly all solvents make it a medical and chemical processing option where PEEK hits its limits.

Vespel / Polyimide — Highest Temperature Bearings

DuPont Vespel (SP-21 grade: 15% MoS₂, 10% graphite) holds the record for PV performance among unfilled or semi-filled polymers, with dry PV values reported above 100,000 psi·ft/min in published testing. Continuous use temperature is 550°F (288°C), with short-term excursions to 900°F. The material sees essentially zero creep under compressive loads in its operating range.

Why Vespel costs what it costs

Vespel is a sintered polyimide, not melt-processable, which means billets are expensive and slow to produce. Material cost is 10–20× PEEK. Specify Vespel only when no other polymer — and no metallic bearing — can satisfy the combination of temperature, PV, chemical environment, and weight constraints. Aerospace turbine blade seals, semiconductor ion-implant vacuum chambers, and cryogenic valve seats are the canonical applications.

How to Choose: Decision Matrix

Work through these questions in order:

1. What is the operating temperature?

  • Below 180°F → acetal or nylon are sufficient.
  • 180–250°F → PET, oil-filled nylon, or unfilled PEEK.
  • 250–480°F → PEEK (or PEEK bearing grade).
  • Above 480°F → Torlon or Vespel.

2. What is the PV load (psi × ft/min)?

  • Under 5,000 → nylon or UHMW will work.
  • 5,000–15,000 → acetal or PTFE-filled acetal.
  • 15,000–30,000 → PET or PEEK.
  • 30,000–60,000 → PEEK bearing grade or Torlon.
  • Above 60,000 → Vespel SP-21.

3. Is there external lubrication?

  • Yes, regular → standard grade (acetal, nylon, PEEK unfilled).
  • No (dry running or sealed) → specify PTFE-filled or graphite/MoS₂-filled grade.

4. Is the application FDA or food contact?

  • Yes → acetal (natural), nylon (natural), UHMW, PET, or PEEK. Avoid Torlon and Vespel.

5. What is the budget?

  • Cost-sensitive → nylon > acetal > UHMW.
  • Performance-limited → PET > PEEK > Torlon > Vespel.

Sizes & Forms Commonly Stocked

FormTypical Size RangeCommon Materials
Rod½ in – 12 in diameterAcetal, nylon, PEEK, UHMW, PET, Torlon
Tube½ in – 8 in OD, various IDAcetal, nylon, PEEK, UHMW
Finished bushingsCustom ID/OD/lengthAny of the above
Sheet/plateFor flanged or split bushing blanksAcetal, UHMW, PEEK

Tube stock is the most cost-effective starting point for bushing machining — only the OD and bore require turning rather than boring from solid rod. Most distributors stock tube in standard wall thicknesses; specify bore diameter and wall at time of order.

Spec Sheet & Test Data

Need bushing or bearing stock cut to length or machined to your bore dimension? FedMat stocks all eight materials in this guide in rod and tube form. Request a quote or reach out to specify your tolerance class and lead time requirements.

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