Extra Firm Silicone Sponge Rubber Sheet | National Silicone

Extra Firm Silicone Sponge

Closed Cell Silicone Sponge

This extra firm silicone sponge is ideal for demanding sealing and gasket applications.

Silicone Stripping

It is produced with a fabric finish on both sides, is flexible and can handle extreme temperature environments. It also offers excellent compression set resistance and can maintain its resiliency under extended compression.

In Stock with Immediate Availability



  • Excellent for seals and gaskets
  • High compressibility
  • Low compression set
  • UV/Ozone resistant



  • ASTM D1056
  • ASTM D412
  • FAR 25.853


Available in – Continuous rolls or cut sheets
Thickness available (in) – 0.0625 to 0.500
Typical roll lengths (ft) – 25 to 100
Typical roll widths (in) – 36
Surface finishing – Fabric impression finish, both sides
Cell structure – Closed cell
Color – Red/orange, grey, black, white, *color matching available

*Subject to MOQ



-67°F to +450°F  (-55°C to 232°C)



Compression deflection (25%) psi (kPa) 18-35 (21-55) ASTM D1056
Density < 0.25” thick pcf (kg/m3) 52 (830) max. ASTM D1056
Density ≥ 0.25” thick pcf (kg/m3) 43 (692) max. ASTM D1056
Compression set (22h, 100°C) % 60 max. ASTM D1056
Tensile strength psi (kPa) 75 (517) typical ASTM D412

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More Information

ASTM D1056

  • ASTM D1056 Standard Specification for Flexible Cellular Materials—Sponge or Expanded Rubber
  • This material passes the ASTM D1056 specification for silicone materials.
  • This specification covers flexible cellular rubber products known as sponge rubber and expanded rubber, but does not apply to latex foam rubber or ebonite cellular rubber.
  • The base material for an open/closed cellular product may be made of synthetic, natural, or reclaimed rubber, or a mixture, and may contain other polymers or chemicals, or both, which may be modified by organic or inorganic additives.



  • ASTM D412 is a standard test methods for vulcanized rubber and thermoplastic elastomers—tension
  • This material passes the ASTM D412 specification for silicone materials.
  • ASTM D412 is the most common standard for determining the tensile properties of vulcanized (thermoset) rubber and thermoplastic elastomers. Compounds in this family are used to create a vast array of consumer goods such as tires, footballs, and rubber bands.


FAR 25.853

  • FAR 25.853 is a standard from the U.S. Code of Federal Regulations (CFR) used by the aerospace/aviation industry.
  • This material is compliant with the requirements of FAR 25.853.
  • The Horizontal Bunsen Burner test is used to determine the resistance of cabin and cargo compartment materials to a flame applied for 15-seconds.
  • It is most commonly used to show compliance with 14 CFR 25.853(a) or in our case 14 CFR 25.853(a) at Amdt. 25-116; Appendix F, Part I(a)(1)(iv) & (v).




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