The primary environment of rubber is dynamic. The ability of rubber simultaneously to support heavy loads and damp out mechanical vibrations by converting them to heat arises from its viscoelastic nature. The total modulus of a vulcanizate measured on a constant strain rate tester contains significant contributions from both an elastic and a viscous component. The quantitative separation of the two components can be accomplished by a forced vibration resonant device such as the shear vibrometer, resonant beam, Tangorra hysteresimeter, or vibrating reed. The same four-term equation of motion applies to all of these. It applies as a special case to forced vibration nonresonant devices such as the Payne, Takayanagi, servo-hydraulic, and certain electrodynamic testers and also to free vibration, such as torsion pendulum and Yerzley Oscillograph.
Dynamic properties of carbon black filled vulcanizates are strongly affected by compounding variables. Equally significant to rubber technologists is the high dependence on the factors in the environment of the rubber, such as temperature, frequency or strain rate, and especially strain itself. Thus, dynamic tests bear a significant relationship to important technological properties of vulcanizates. Dynamic tests are versatile, rapid to run, and have direct application to use conditions. For these reasons, an increased interest in the theory and practice of dynamic testing can be expected.