Gaskets come in an incredible variety of materials. One thing about gaskets is it can always get softer. When compression is not an asset, usually the answer is to go even softer. For that reason, I thought I would write a blog about what options are out there when it comes to soft gaskets. However, first an education on how softness is measured on gaskets:
Education on Softness of Gasketing Materials:
There are a few levels of softness one should be aware of when it comes to gasketing materials.
The first is durometer. Durometer is usually reserved for the more stiff versions of gasketing material. This version durometer is called Shore A. However, other durometer versions are sometimes used for foam, sponge, or thermal interface materials. These include Shore 00, or Shore 000. Typically foam and sponge materials are measured with Shore 00. Many of the Shore measurements overlap. Soft thermal interface pad materials are typically measured with Shore 00 or Shore 000.
Compression/Deflection Values CFD
The second thing to look for is compression force deflection values. Typically this is measured against 25% compression. Usually foam/sponge materials are measured using this technique. Basically, the question is, how much pressure was required to compress the material 25%. Naturally, the lower the number, the better. ASTM D1056 does a good job of categorizing the different materials that are available.
There are other ways to measure the softness of gasketing materials, however these are the two main ways they are masured.
Solid Rubber for Soft Gaskets
Shore A 30 and below
I consider anything under 30 Shore A durometer a soft gasketing material. Many silicone rubbers easily can meet these specifications. Silicone rubber comes in 10A, 20A, 30A durometer. However, there are other polymers that can meet these hardness values such as urethane, however silicone is the most used. A rubber band or eraser would measure around 20A-30A durometer.
Foam/Sponge for Soft Gaskets(according to Cellular Elastomer Specification ASTM D1056)
Firm Sponge/Foam (17-25psi+ @ 25% compression) Grade 5
Medium Sponge/Foam(13-17psi @ 25% compression) Grade 4
Soft-Medium Sponge/Foam(9-13psi @ 25% compression) Grade 3
Soft Sponge/Foam(5-9psi @ 25% compression) Grade 2
Very-Soft Sponge/Foam(2-5 psi @ 25% compression) Grade 1
Super-Soft Sponge/Foam(0-2 psi @ 25% compression) Grade 0
For more information on soft gasketing materials or you believe you have an application that could utilize them, please contact firstname.lastname@example.org