The Shore durometer (pictured right) is a scale for measuring the hardness of a material, such as rubber, plastic, thermal plastics (TPE), and rigid plastics. The term "durometer" is often used to describe a material's rating on the scale, for example “this material has a durometer of 60.”
It's worth noting, there are a variety of durometer scales since elastomeric and plastic resins vary over a wider range than one scale can accommodate. Download our comparison chart to see how these scales overlap.
Durometer hardness is one of many physical properties considered when selecting a material for a specific application. Beware of some common misconceptions. Durometer hardness is often inaccurately confused with the properties described below.
Compression Force Deflection
Durometer is sometimes confused with or taken as the same as compression force deflection (CFD). A CFD test measures the amount of force required (in PSI) to compress a sample of a compound a prescribed distance. While the two, durometer and CFD, are related and may be relative within the same elastomer or plastic, two different elastomers can have the same durometer but have different CFD values.
Durometer is sometimes confused with or taken as the same as compression force deflection (CFD). A CFD test measures the amount of force required (in PSI) to compress a sample of a compound a prescribed distance. While the two, durometer and CFD, are related and may be relative within the same elastomer or plastic, two different elastomers can have the same durometer but have different CFD values.
Flexibility
Durometer can be used as a predictor of flexibility within the same compound. In other words, a product made of 30 durometer Neoprene will be more flexible than the same product made of 70 durometer from the same Neoprene. However, durometer alone is a poor predictor of other properties of rubber and plastics related to flexibility such as wear and abrasion resistance, tensile strength, and elongation. All of these properties will vary from one compound to the next based more on the chemistry of the compounds rather than the durometer hardness.
Durometer can be used as a predictor of flexibility within the same compound. In other words, a product made of 30 durometer Neoprene will be more flexible than the same product made of 70 durometer from the same Neoprene. However, durometer alone is a poor predictor of other properties of rubber and plastics related to flexibility such as wear and abrasion resistance, tensile strength, and elongation. All of these properties will vary from one compound to the next based more on the chemistry of the compounds rather than the durometer hardness.
Density
In sponge and foam materials, it is sometimes wrongly assumed that the lower the density of the foam the softer the foam will be (as measured on the Shore 00 Scale). This is definitely not true. There are foams with high density that are quite soft such as Rogers Corporation Poron 4701-30-25 (25 lb density and 60 durometer), and others like Armacell Ensolite IV3 (8 lb density and 65 durometer) and Sekisui-Voltek's Volara Type 2A (only 2 lb density, yet 50 durometer).
In sponge and foam materials, it is sometimes wrongly assumed that the lower the density of the foam the softer the foam will be (as measured on the Shore 00 Scale). This is definitely not true. There are foams with high density that are quite soft such as Rogers Corporation Poron 4701-30-25 (25 lb density and 60 durometer), and others like Armacell Ensolite IV3 (8 lb density and 65 durometer) and Sekisui-Voltek's Volara Type 2A (only 2 lb density, yet 50 durometer).
Remember to be aware of these three common misconceptions when selecting rubber, plastic, or foam material for an application. Click the button below to learn more about durometer and Shore hardness testing or to download the durometer scale comparison chart.
Marian converts foam and sponge materials of different density, thickness, hardness, and composition. We are proud to say our sales engineers have an average of 15 years of experience working with foam and sponge materials. This wealth of knowledge enables our team to understand the various different physical attributes of the materials, including Durometer. When in doubt, contact Marian Sales Engineers for help with material recommendations and rapid samples.
