Hardness of rubber

Expressed as Vickers hardness, the hardnesses of the engineering materials cover a vast range, broader than 1 to 100. The handful of example figures in Table 1.5 does not cover the hardnesses of rubbers, alveolar polymers and flexible thermoplastics. 

Durometer - An instrument for measuring the hardness of rubber. The "A" durometer scale is used for flexible materials and the "D" for rigids. 

This test is not in common use for polymers (except for the hardness of rubbers) but we present it here since it has, as we shall show, several advantages, at least for isotropic materials. The test consists essentially of applying a force over a spherical surface - either by placing a known weight ball on the specimen, or by pushing such a ball in with a greater force and monitoring the displacement, whence G can be calculated as shown in Chap. 2. 

Test method for indentation hardness of rubbers, international hardness Test for Durometer hardness of rubbers... 

As modifier concentration increases to 6%, all parameters increase by 1.1 times. Effects of modifiers V and IX are similar. Only increase in tearing strength and hardness of rubbers are observed, with slight changes in the rest of the parameters. 

The standard test method for measuring the durometer hardness of rubbers according to ASTM D2240-05 [6] is based on the penetration of a specified indentor forced into the material under specified conditions. The indentation hardness is inversely related to the penetration and is dependent on the elastic modulus and viscoelastic behaviour of the material. This method is an empirical test intended primarily for control purposes. No simple relationship exists between indentation hardness determined by this method and any fundamental property of the material tested. 

ASTM D2240. 1975. Indentation Hardness of Rubber and Plastics by Means of a Durometer. 

It is customary to characterize the modulus, stiffness, or hardness of rubbers by measuring their elastic indentation by a rigid die of prescribed size and shape under specified loading conditions. Various nonlinear scales are employed to derive a value of hardness from such measurements (Soden, 1952). Corresponding values of shear modulus G for two common hardness scales are given in Figure 1.18. 

Hardness. Hardness is probably the least difficult and most often measured property of vulcanized elastomers. It is in almost every fist of rubber specifications. As measured, hardness is the relative resistance of the rubber surface to deformation by an indentor. The hardness of rubber is measured by using a small spring-loaded gauge known as a durome-ter (ASTM D 2240). One measures the hardness by pressing the indentor against the rub-... 

Durometer du- ra-m9-t9r also dyu [L durus hard] (ca. 1879) n. An instrument used for measuring the hardness of rubber, plastic, or protective coatings. 

Hardness - Hardness, as applied to rubber products, is the relative resistance of the surface to indentation under specified conditions. Hardness of rubber is usually measured with a small spring-loaded hardness gauge known as a durometer (ASTM D-2240). The durometer may be handheld or mounted on a stand. The measurement is made by pressing the indentor against the sample and reading the scale, which is calibrated in arbitrary units ranging from 0 (soft) to 100 (hard). A Type A durometer is used for most soft rubber products there is also a Type D durometer for hard rubber and plastic-like materials. On the A scale, a gum rubber band would measure around 40, a tire tread 60, and a shoe sole 80. 

The hardness range of this class of materials is from 60 Shore A to 60 Shore D. Hardness, modulus and tensile strength all increase as the PP content increases. (The hardness of rubber compounds is typically measured by the Shore Durometer test an indentor is pressed into the material, under a specified load, and the amount of penetration determines the hardness. A circular tip is used for the A scale and a pointed tip is used for the D scale. D means harder materids.)... 

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