Durometer is an international standard for measuring the hardness of material and can be determined using a Shore Hardness Scale and a Durometer Hardness Test.


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he hardness of material is an important property that helps determine the suitability of a rubber product for its intended use. Additionally, a components’ application is critical to determining the necessary hardness. For instance, softer compounds that offer less resistance are fine for low-pressure seals where the material must conform to rough or uneven surfaces. Harder materials would be more appropriate for high-pressure seals.

Shore Hardness Scales measures the hardness of different materials. These scales establish a common point of reference for comparing materials, with durometer being bucketed into three Shore categories on a hardness scale from 0 to 100:

  • 00 – Measures light foams, sponge rubber and gels that are very soft
  • A – Measures soft rubber, plastics, and rubber-like elastomers
  • D – Measures hard rubber, plastics, and thermoplastics

The image below shows examples of different materials and what Shore hardness category they fall into. Note: It is possible for materials to fall into more than one category.

Shore Hardness Scale: Shore 00, Shore A, Shore D

In the case of rubber, a durometer is also defined by its relative resistance, or its ability to deflect the depth of indentation made by an indenter. The illustration below shows the difference between a Shore A material and a Shore D material.

Durometer hardness test, applied load vs durometer indenters

Now you can see why knowing the rubber product’s intended use helps to ensure the proper material compound is selected. Not sure what your application requires? Give us a call and our gasket specialists will be happy to assist.

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