Determining the Durometer of a Gasket

Durometer is defined as one of the ways to measure the hardness of a material, specifically rubber, foam, polymers, elastomers, sponge rubber, plastic and other nonmetallic materials. The durometer of a material is determined by pressing a probe into the material, thus allowing a graduated scale to determine the measurement. The scale on which the hardness of these materials is judged was created by Albert F. Shore in the 1920s.

While there are multiple scales by which the durometer of a material can be determined, the most common are the ASTM D2240 type A and type D scales. Both scales work on the same principle: an indentation is made in the material by a specific amount of force – the depth of indentation is then measured to determine durometer.

Selecting the right durometer for a gasket is an important part of the design and engineering processes of many industrial applications. While durometer specifically refers to hardness, this measurement reflects other attributes of the material, such as elasticity, resilience, plasticity and compression resistance. These factors have to be considered when designing your part or application.

Important Questions to Ask Regarding Durometer:

• Will the application require the gasket to be exposed to heat? If so, at what temperature and for how long?
• Is it possible that abrasion, erosion or corrosion will happen around the area of the gasket?
• Will the gasket need to expand and contract? What are your requirements for elasticity?

Using the durometer scale, materials can range from incredibly hard (an example would be hardened steel, which has a durometer rating of 100) to malleable and elastic (for instance, chewing gum has a durometer rating of 20). As you can imagine, there would be a major problem if a gasket with a durometer rating of 20 were used in an industrial application where it is constantly incurring wear and tear.

For these reasons, it’s important to consider the durometer of your gasket before making a purchase. Of course, if you’re not sure exactly what your unique application requires, our experienced staff at XTO Inc. is always willing to help! Feel free to give us a call, or even ask a question by leaving a comment below!