Rubber is classified by many physical properties but generally falls under two primary classifications: Dense and Sponge rubber.

This page outlines properties that are necessary to consider when designing a seal or gasket product.

Choosing the right sponge product is important in proper seal and gasket design. Engineers must consider the following:

• Force in pounds per square inch required for proper closing
• How the seal responds to compression over time or to being compressed and released
• The elements the seal will be exposed to

The below technical information will serve as a guide to comparing materials with their physical properties. We also give a brief synopsis on how we classify flexible cellular materials based on:

• Type: Open or Closed cell
• Class: A, B, C, or D (characteristics of a material)
• Grade: 0 through 5 (compression deflection rating)
• Line call outs: (special industry specifications met)
• Suffix: A, B, C etc. (special tests required)

Classification of Flexible Cellular Materials

All of Cooper Standard ISG’s sponge products are identified by a three-character Grade Number (example: 2A2) per ASTM D-1056.

The three characters represent type, class and grade, and are defined as follows:

Type

• Type 1 = Open cell
• Type 2 = Closed cell

Suffix

Once testing is complete, a Line Call Out is assigned to the compound according to the basic and Suffix Requirements the compound met.

Suffix Letter Test Required

• A. Heat resistance
• B. Compression set
• C. Ozone or weather resistance
• D. Compression deflection resistance
• E. Fluid resistance (Fuel B)
• F. Low temperature resistance
• G. Tear resistance
• H. Abrasion resistance
• I. Adhesion resistance
• J. Water absorption
• K. Flammability resistance
• L. Impact resistance
• M. Staining resistance
• N. Resilience
• O. Density
• Z. Any special requirements

Class

• Class A = Non-oil resistant (example: EPDM)
• Class B = Oil resistant, low swell (example: Nitrile)
• Class C = Oil resistant, medium swell (example: Neoprene)
• Class D = Extreme temperature resistance (example: Silicone)

Grade

Grade ratings represent compression deflection, or the amount of force in pounds per square inch to deflect the sample 25% of its height. They are as follows:

• Grade 0 = less than 2 psi
• Grade 1 = 2-5 psi
• Grade 2 = 5-9 psi
• Grade 3 = 9-13 psi
• Grade 4 = 13-17 psi
• Grade 5 = 17-25 psi

Example Line Call Out for Sponge ASTM D-1056 2C2 A1 B2 E1 Z

(Z = material passes FMVSS 302)