Durometer

Durometer is one way to measure the hardness of a material. It is frequently used to determine the resistance of the material to indentation. There are many ways to test durometer, one of the most frequently used tests is ASTM D2240. This test method utilizes the Shore Hardness scale. The Shore hardness system was created in the 1920’s by a gentlemen by the name of Albert Ferdinand Shore. There are many scales for the durometer lied out in ASTM D2240. The types are A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R. The ones most typically used in the rubber and plastic industries are A, OO, and D. A is generally reserved for rubber products and soft plastics, generally ranging from 10 Shore A to 95 Shore A. D is normally reserved for hard plastics. OO is reserved for extremely soft elastomeric materials, such as Bergquist Gap Pads/Sil Pads and/or sponges and foams. The scales are pretty easy to read, the lower the number the softer the material, the higher the number the harder the material. It is a good idea to keep in mind that some of the scales will overlap such as high A and low D, and high OO, and low A. Luckily, in practice the Shore A scale is fairly easy to administer. The test is simply administered by a device, coincidentally known as a durometer. The specification allows for pieces to be plied to achieve the necessary thickness of .24” thick, just short of a quarter inch. The test works by measuring the amount of indentation into the material, the more indentation the lower the value, the less indentation the higher the value. The presser foot is the piece that comes before the indenter in the apparatus.

The importance of durometer can not be understated. Durometer is so important that ASTM D2000 even includes the durometer as part of the standard callout. For example, ASTM D2000 BC607 actually offers the durometer of 60, indicated by the ‘6’ along with the type and class, as well as tensile. Durometer is so important because it gives a good idea of how much the elastomer will compress in a given application. The durometer of a rubber also gives a good idea of how the compound will abrade in the application. A harder compound in general will tend to abrade less than a softer compound. A good rubber enthusiast may be able to give you a reading of the durometer with his finger tips. Obviously, this is just a guess, and not an actual value, so actual test equipment should always be utilized.

NEDC provides gaskets of all durometers including Shore A, OO, and D. NEDC can test durometer with its in-house durometer. NEDC has an in-house durometer to test for Shore A. NEDC can die cut, and waterjet cut gaskets in a variety of durometers. For more information on different durometer material, please contact sales@nedc.com.

Type Materials normally utilizing type
Shore A Typically used on elastomeric materials, such as solid rubber and/or soft plastics.
Shore D Typically used on hard plastics.
Shore OO Typically used on sponges and foams.
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