ABSTRACT
Hardness of rubber, defined as the resistance to indentation, gives a conveniently rapid indication of its deformation behavior. The hardness test specified in the International Standard (ISO) is based on measurement of the indentation of a needle with spherical tip or a rigid ball with diameter 2.5 mm into a test piece. The standard test piece is a cylinder with smooth and parallel upper and lower surfaces, with diameters of 50 mm and thickness 10 mm. The measured indentation is converted into International Rubber Hardness Degrees (IRHD). The often used Shore A method is similar and yields almost the same numerical values of hardness as the IRHD method for rubbers in the interval 30-80 IRHD.
