Vespel (Polyimide) — Rod & Bearing Material Guide

Vespel is DuPont's trade name for a family of direct-formed and isostatically pressed polyimide (PI) parts and stock shapes rated for continuous use at 550°F (288°C) — the highest continuous-use temperature of any unfilled engineering plastic available in rod or tube form. It does not melt; it sublimes near 500°C (930°F) without entering a liquid phase, which eliminates creep-to-failure at extreme temperatures that disqualifies every melt-processable alternative. If your application runs hot, loads a bearing beyond PEEK's range, or requires dimensional stability inside a vacuum chamber, Vespel is the material engineers reach for when nothing else works.

At a Glance

• Continuous-use temperature: 550°F (288°C); short-term excursions to 900°F (482°C)
• No melt point — sublimes near 500°C; zero risk of thermal runaway softening
• Three primary grades: SP-1 (unfilled), SP-21 (15% graphite, wear), SP-22 (40% graphite, high-load bearing)
• Tensile strength: 12,500 psi (SP-1); density approximately 1.43 g/cc
• Dimensionally stable across the entire operating temperature range; extremely low CTE
• Available as rod (1/4" through 6" diameter) and tube; custom shapes by order
• Premium pricing — most expensive unfilled plastic per pound in the high-performance line card
• Cross-compare: PEEK and Torlon (PAI) are the nearest alternatives

What Is Vespel?

Vespel is a polyimide — a polymer built around imide linkages in the backbone that give it exceptional thermal stability. Unlike PEEK or Nylon, Vespel cannot be injection-molded or extruded from a melt. DuPont manufactures it by two primary methods:

Direct forming: Powdered polyimide resin is sintered under heat and pressure in a mold, producing near-net-shape parts. This process locks in tight tolerances without secondary machining for many geometries.

Isostatic pressing: Resin is consolidated in a flexible mold under uniform pressure, then post-sintered. This produces larger billets and rod stock that are then machined to final dimension.

The result is an amorphous thermoset-like material with no crystalline melt transition. The thermal and mechanical properties remain virtually flat from cryogenic temperatures to operating limits — a characteristic no melt-processable plastic can match.

Vespel TP Grades

DuPont also produces Vespel TP thermoplastic polyimide grades, which are processable in standard injection molding equipment. TP grades sacrifice some peak-temperature performance in exchange for much lower material and processing costs for high-volume parts. They are not the same polymer chemistry as SP-series Vespel and are not discussed in detail here; consult DuPont / IST directly for TP-grade data.

Grade Overview

Vespel is available in three standard SP (sintered polyimide) grades that cover the vast majority of industrial and aerospace applications.

SP-1 is the baseline grade — natural amber/gold in color, highest electrical resistivity, best in vacuum (graphite outgassing concern eliminated), and FDA-compliance possible with appropriate contact validation. It machines cleanly and holds tight tolerances.

SP-21 adds 15% graphite by weight, dropping the coefficient of friction and improving wear rate dramatically under dynamic loading. It is the workhorse grade for jet engine wear pads, valve guides, and rotary seals where SP-1 would wear too quickly.

SP-22 pushes graphite content to 40%, producing a material optimized for high-pressure, high-temperature bearing faces. PV (pressure × velocity) limits for SP-22 exceed those of SP-21, and the compressive strength under contact stress is superior. This is the grade for heavily loaded thrust washers and backup rings.

For a full grade comparison including PV tables and selection criteria, see the Vespel grades guide.

Key Properties

Thermal Performance

The headline number is 550°F (288°C) continuous — roughly 70°F higher than PEEK's 480°F limit and more than 100°F above Torlon PAI. Short-term excursions to 900°F are survivable without structural collapse. The absence of a melt transition means no catastrophic softening at a specific temperature; Vespel degrades gradually above its continuous limit rather than suddenly losing load-bearing capacity.

Vespel also performs at cryogenic temperatures without embrittlement, making it one of the few materials that cover both ends of the aerospace envelope in a single part.

Dimensional Stability

The coefficient of thermal expansion (CTE) for Vespel SP-1 is approximately 28 × 10⁻⁶ in/in/°F — lower than most plastics and managed carefully in design. More importantly, the material does not creep significantly under sustained load at elevated temperature, which is the dominant failure mode for PEEK and Torlon in hot bearing applications.

Mechanical Properties

Vespel is notably harder to machine than PEEK — it is brittle and requires sharp, well-supported tooling. See the machining guide for tooling recommendations.

Electrical Properties

SP-1 Vespel is an excellent electrical insulator with volume resistivity above 10¹⁶ Ω·cm and dielectric strength around 500 V/mil. These properties hold through the full temperature range, making it the material of choice for semiconductor wafer carriers, plasma chamber components, and high-voltage spacers that must survive process temperatures no other insulator tolerates.

For full datasheet values including dielectric constant, dissipation factor, and thermal conductivity by grade, see the properties page.

Primary Applications

Vespel's cost — typically 5–20× higher per pound than PEEK — means it appears in applications where no cheaper alternative is qualified, not as a cost-reduction play. Typical environments:

Aerospace & Jet Engine

• Wear pads and bushings in jet engine hot sections: compressor vanes, turbine frame pads, fuel control bushings
• Thrust washers on rotating assemblies running at 400–500°F continuous
• Seals and backup rings on hydraulic actuators routed near engine bleed air
• Fastener bushings in titanium structures where galvanic isolation and dimensional stability at temperature are required

Semiconductor & Vacuum

• Wafer handling end-effectors and carriers in etch and CVD chambers
• Chuck insulators and probe card standoffs in test equipment
• Valve seats and seals in high-purity gas distribution systems
• Plasma-resistant components in RIE and ICP etch tools where PEEK would char or outgas

Industrial

• Reciprocating compressor valve plates running without lubrication
• High-temperature seal rings in steam or hot-gas service
• Bearing cages in kiln car wheels and furnace conveyor systems

For detailed application breakdowns with grade selection by environment, see Vespel applications.

Available Forms and Stocking

Vespel is stocked primarily as:

• Rod: 1/4" through 6" diameter in SP-1, SP-21, and SP-22
• Tube: Available in standard sizes; lead times vary by grade and wall thickness
• Custom near-net shapes: Direct-formed by DuPont/IST; minimum quantities and lead times apply

Vespel is not commonly stocked as flat sheet. Slab or plate forms exist but are special-order. If your application requires sheet, PEEK or PAI (Torlon) may be more practical starting points. For complete size ranges and tolerances, see the specifications page.

Comparing Vespel to Alternatives

The two most common substitution questions are Vespel vs. PEEK and Vespel vs. Torlon. The short answers:

• PEEK is adequate to 480°F continuous and costs 5–10× less. If your bearing or seal runs below 450°F, PEEK is almost certainly the right choice. Above that threshold, or where sustained load at temperature causes creep, Vespel takes over.
• Torlon (PAI) bridges the gap — rated to 500°F continuous, better wear than PEEK, lower cost than Vespel. Where Torlon is qualified, it is usually preferred economically. Vespel wins on absolute temperature ceiling and vacuum suitability.

For a side-by-side comparison of all three materials, see the Vespel vs. PEEK comparison and the Vespel comparisons hub.

Cost and Justification

Vespel's price premium is real: rod stock commonly runs $200–$800 per foot depending on diameter and grade. The economics make sense in three scenarios:

1. Thermal disqualification of alternatives — nothing else survives the environment.
2. Maintenance cost reduction — a Vespel wear pad that outlasts three PEEK pads changes the math.
3. Qualification rigidity — aerospace OEM specs that call out Vespel SP-21 or SP-22 by name leave no substitution path.

If none of those three apply to your application, a cost review against PEEK or Torlon is warranted before committing to Vespel.

FDA and Food-Grade Status

SP-1 Vespel can be formulated to meet FDA 21 CFR requirements for food contact under 21 CFR 177 applicable polymer regulations. In practice, the material's cost, long lead times, and lot-specific certification requirements make it an unusual choice for food processing equipment unless thermal requirements genuinely exceed what PEEK or Torlon can deliver. Most food contact inquiries at temperatures below 480°F resolve to PEEK with standard FDA certifications at a fraction of the cost. Where a continuous oven, retort, or packaging sealing jaw operates above 500°F in incidental contact with food, SP-1 is worth evaluating — but verify lot-specific compliance documentation before committing. For full compliance details, see the Vespel FDA page.

Machining Considerations

Vespel is machinable with carbide and PCD diamond tooling, but it behaves differently from PEEK or Torlon in several important ways. Its brittleness — elongation at break is 7.5% for SP-1, dropping to approximately 2.5% for SP-22 — means edge chipping occurs readily if chip load is excessive or tools are dull. HSS tooling will wear out after one or two parts on graphite-filled grades. Dry cutting is standard; no coolant is required or recommended for most operations.

Tight tolerances — ±0.001" on OD, ±0.002" on bored ID — are achievable with sharp carbide or PCD tooling and proper feeds. The material does not soften ahead of the tool the way thermoplastics do, which means cut depth and feed must be controlled to prevent microcracking rather than to manage heat buildup. For complete tooling recommendations, speed/feed tables, and workholding setup, see the Vespel machining guide.

Ready to source Vespel rod or tube? Visit the Vespel line card page to request a quote on stock sizes or discuss custom shapes and lead times with our materials team. Certifications (C of C, MTR, country of origin) are available for all stocked SP-series lots and are standard requirements on aerospace, defense, and semiconductor programs. Contact the materials team to confirm current stock and documentation availability before placing purchase orders on time-sensitive projects.

More related guides

Cross-cluster suggestions to help shoppers and engineers explore adjacent topics:

Applications

• Bushings Bearings

Industries

• Aerospace
• Defense Military

Compare to other materials

• Torlon Vs. Vespel
• Vespel Vs. Peek

Frequently asked questions — Polyimide Vespel FAQ