Durometer is a measure of how hard a material is. Technically, it’s a measure of how hard it is to permanently indent a material. There are actually 12 different durometer scales each measured from 0 (softest) to 100 (hardest), but for the we’ll mainly be talking about Shore A since it’s the most common in fluid sealing applications.
How is Durometer Measured?
Measuring durometer is fairly simple. You put a standard metal rod at a standard pressure on to a material for 15 seconds, then you measure the depth of the indentation. For example, in Shore A durometer testing, 1.1 to 1.4 mm diameter steel rod with is applied with .822 Kg of mass (1.81 lb) on a sheet of rubber for 15 seconds.
PTFE (polytetrafluoroethylene) or Teflon® joint sealant is a fluid sealing product that offers many advantages of traditional gasketing.
How it works?
PTFE joint sealant comes on a spool. It’s known as “form-in-place” gasket, because the material is applied directly to surface that needs to be sealed, rather than cut to shape from a sheet before hand. Before it is compressed, the joint sealant is soft. This allows it to conform to and seal very rough or serrated surfaces. After compression is applied, however, it forms a thin, hard ribbon that fills in surface irregularities and creates an extremely tight seal.
What are the advantages of PTFE Joint Sealant?
Form in place: Because the joint sealant can be applied to any shape surface, this makes it an extraordinarily versatile. There’s no need to stock multiple gasket sizes, all you really need is joint sealant and knife to cut it. This also provides advantages for large and irregularly shaped gaskets, where storage, measurement, and gasket sheet sizing can all become issues.
The PTFE itself: PTFE is an offers amazing chemical resistance. W.L. Gore, manufacturer of Gore GR® joint sealant, states, “PTFE is chemically resistant to virtually all industrial chemicals.” It’s able to withstand high temperature and pressure ranges as well. Because it is fairy soft before compression, it is able to conform to a wide variety of surfaces.
Some Brands are FDA Approved: Some brands of PTFE joint sealant are FDA Approved for incdiental food contact. The PTFE is approved under 21 CFR 177.1550 and the adhesive under 21 CFR 175.105. Although most brands are nearly identical chemically, some brands (for example Gore and Produra) have chosen to forego the FDA approval process.
What are the disadvantages of PTFE Joint Sealant?
Price: PTFE Joint Sealant is not the most economical solution for many sealing solutions. For applications where standard gaskets will work or chemical resistance is not important, cheaper cut gaskets exist.