Jehbco’s silicone extrusions are used in a wide range of applications, from aircraft seals to medical grade tubing.  To make sure you have the right silicone for your application, the application requirements have to be closely matched to the silicone properties.  There are many material properties that may affect our silicone’s performance in your application.  One of the most important properties is hardness or “durometer”.

The hardness of a material refers to how easily the material resists deformation under compression.  Put more simply, if something is pressed against the surface of a material, hardness tells us how easily the material is deformed or marked.   Depending on the material, there are several standard tests that can be used to determine hardness.  Metals are often tested using the Vickers or Rockwell procedures – these press a small tool into the surface of the metal under a standard load and measure the size of the resulting mark.

For elastomers such as silicone, hardness is measured using the Shore Durometer test.  This test measures the depth that a small cone can be pressed into the surface of the silicone.  The depth that the cone sinks into the silicone is converted to a value on the Shore Durometer scale.  The cone sinks deeper into soft silicones and these have a low value on the scale.  If the silicone is hard, the cone doesn’t sink very far and the value on the Shore scale is high.

Silicone hardness and the Durometer Scale with Jehbco Silicones

There are several variations of the Shore Durometer test for different types of elastomers.  The most common are Shore Durometer A for soft elastomers and Shore Durometer D for hard elastomers.  Each test gives a hardness value from 0 to 100.  The Shore A test is generally used to measure the hardness of Jehbco silicones – most of our silicones fall between 25 and 80 Duro Shore A.  Jehbco has equipment to test Shore hardness to the ASTM D2240 standard.

To get an idea of what the different hardness scales mean, 25 Duro silicone can be easily compressed with your fingers – think of the rubber that rubber bands are made of.  80 Duro silicone is much harder to compress, more like the rubber in a shoe sole.

To ensure that the silicone you choose for your application performs as required, it must have the right durometer.  For applications such as vacuum sheeting, a low durometer might be just right, while gaskets may require a medium to high durometer.  Jehbco can tailor a silicone material to the durometer required for your application.

For any further questions about how durometer will affect your application please contact our sales team.