It is the resistance of a material to indentation. the hardness of an elastomer is more accurately thought of as two related properties Inherent hardness and Processed hardness. Due to different chemical structure, every rubber has its own inherent hardness. This inherent hardness can be modified via compounding and vulcanization. Hardness has a direct relationship with crosslink present in a rubber matrix.
We are having both Multi Unit Hardness Tester (MUHT) and Durometer to provide hardness of different type:
Shore A: ASTM D2240, ISO7619 IRHD: ASTM D1415, ISO 48
Thickness of a rubber specimen before testing should be measured carefully. It has influence on many physical properties like hardness tensile properties. Every test specimen has its own thickness specification according to standard test method.
ASTM D3767, ISO 4648
Sp. Gr. of rubber is very important in determining batch volume during mixing and compound formation of rubber. Since the volume of Mixer (Banbury/Internal Mixer) is fixed so we have to calculate batch volume keeping optimum fill factor. Volume is calculated from specific gravity and this is why it is so important.
Elasticity of a rubber is measured by Resilience, and is important for certain applications. Damping elements are generally show low resilience, while elastic materials have high resilience. This is determined by dropping a hammer on to the rubber material from a specific height and measuring how far it bounces back up to its original height. The modulus of resilience is defined as the maximum energy that can be absorbed per unit volume without creating a permanent distortion.
ASTM D7121, ISO 4662