Soft Gaskets, Soft Gasket Material
Stockwell Elastomerics manufactures custom soft gaskets from various soft gasket materials to customer specification. "Soft gasket" is a relative term; for heavy industrial applications a 40 durometer rubber may be considered a soft gasket material, but in an electronics application, a 40 durometer rubber would be considered hard.
Typical solid rubber gaskets range from 10 - 70 durometer on the Shore A scale. In order to make even softer materials, common polymers are expanded into open and closed cell rubber materials. Neoprene, silicone, EPDM, fluorosilicone and other rubber compounds can be chemically expanded to introduce air pockets. This is analogous to adding yeast to dough to make it rise. These air pockets make sheet materials even softer.
Expanded rubber materials are available in a variety of densities and firmness. The hardness or firmness is commonly measured by Compression Force Deflection (CFD) as opposed to durometer. CFD is a measurement of pressure at 25% deflection per ASTM D 1056.
Compression Force Deflection
Stockwell Elastomerics has applied the ASTM D1056 CFD test to a range of soft gasket materials to give a relative sense of hardness.
|Material||Description||CFD @ 25% (psi)|
|BF-2000||Ultra Soft Open Cell Silicone Foam||1.6|
|BF-1000||Extra Soft Open Cell Silicone Foam||2.5|
|PORON, 4790-92||Extra Soft Open Cell PORON (urethane)||2.6|
|PORON, 4701-30||Very Soft Open Cell PORON (urethane)||3.2|
|R10480S||Soft Closed Cell Silicone Sponge||6|
|R10470M||Medium Closed Cell Silicone Sponge||10|
|R10490M||Fluorosilicone Closed Cell Sponge||13.3|
|SE2010||10 Durometer Liquid Silicone Rubber (LSR)||25.2|
|SE2020||20 Durometer Liquid Silicone Rubber (LSR)||48.2|
More detailed information about soft gasket materials, including compression curves, cycle testing and short term stress relaxation, is available upon request for most materials offered by Stockwell Elastomerics.
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