DuPont™ Vespel® SP-21

DuPont™ Vespel® SP-21 is widely used for:

  • Thrust washers
  • Seal rings
  • Valve seats
  • Bearings
  • Seals

Performance Characteristics:

  • Low wear at high bearing PV's
  • Low coefficient of friction
  • Long-term thermal stability
  • High stiffness
  • Low elongation
  • Outstanding performance with or without lubrication
  • Good strength and impact resistance

Common Brands:

  • DuPont™ Vespel®

Authorized Distributor of DuPont™ Vespel Polyimide
Download Vespel for Valves White Paper
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DuPont™ Vespel® SP-21

Graphite-enhanced grade with low-friction properties

DuPont™ Vespel® SP-21 is graphite-enhanced with low-friction properties for use with or without lubrication in various applications. Vespel® SP-21 has maximum physical strength, elongation, and toughness. Available as custom parts or stock shapes.

DuPont™ Vespel® SP-21 is available as isostatically molded billet and unidirectionally pressed slab specified as Type II, Class 1M and Type II, Class 1P respectively per ASTM 6456-10 / MIL-R-46198. Vespel® SP-21 is specified as Class 2 per AMS 3644G.


PLAQUE Dimensions:
5 in x 5 in – 10 in x 10 in
0.062 in – 2 in
ROD Outside Diameter:
0.125 in – 6 in
COLOR Dark Brown
GRADES Graphite-Filled

Length, width, thickness, and diameter tolerances vary by size, by manufacturer, brand, and grade. Vespel® SP-21 is also available in bar.


Typical Properties OF DuPont™ Vespel® SP-21 Polyimide
Units SP-21
15% Graphite
Tensile strength
23°C (73°F)
D1708 / D638 MPa (kpsi) 65.5
Tensile strength
260°C (500°F)
D1708 / D638 MPa (kpsi) 37.9
Elongation at break
23°C (73°F)
D1708 / D638 % 4.5
Elongation at break
260°C (500°F)
D1708 / D638 % 3.0
Flexural modulus
23°C (73°F)
D790 MPa (kpsi) 3,790
Flexural modulus
260°C (500°F)
D790 MPa (kpsi) 2,550
Compressive stress at
10% strain, 23°C (73°F)
D695 MPa (kpsi) 133
Deformation under
13.8 MPa (2,000 psi) load
D621 % 0.10
Coefficient of friction at
PV = .875 MPa m/s
(25,000 psi-ft/min)*
Coefficient of friction at 
PV = 3.5 MPa m/s
(25,000 psi-ft/min)*
Static coefficient
of friction in air*
PV limit (unlubricated)**   MPa-m/s
(kpsi ft/min)
Other Properties      
Coefficient of thermal
23–300°C (73–572°F)
E831 µm/m/K
(10-6 in/in-°F)
49 (27)
Hardness D785 Rockwell E 25–45
Water absorption
24 hr at 23°C (73°F)
D570 % 0.19
*Versus carbon steel, steady state, unlubricated, in air, thrust bearing. **PV limits for any material vary with different combinations of pressure and velocity as well as other conditions.

Need more information about this material? Use our interactive plastic properties table

The information set forth herein is furnished free of charge, is based on technical data that DuPont believes to be reliable, and represents typical values that fall within the normal range of properties. This information relates only to the specific material designated and may not be valid for such material used in combination with other materials or in other processes. It is intended for use by persons having technical skill, at their own discretion and risk. This information should not be used to establish specification limits nor used alone as the basis of design. Handling precaution information is given with the understanding that those using it will satisfy themselves that their particular conditions of use present no health or safety hazards and comply with applicable law. Since conditions of product use and disposal are outside our control, we make no warranties, express or implied, and assume no liability in connection with any use of this information. As with any product, evaluation under end-use conditions prior to specification is essential. Nothing herein is to be taken as a license to operate or a recommendation to infringe on patents.

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