This part of ISO 6721 specifies two methods (A and B) for determining the linear dynamic mechanical properties of plastics, i.e. the storage and loss components of the torsional modulus, as a function of temperature, for small deformations within the frequency range from 0,1 Hz to 10 Hz.
The temperature dependence of these properties, measured over a sufficiently broad range of temperatures (for example from 50 °C to 150 °C for the majority of commercially available plastics), gives information on the transition regions (for example the glass transition and the melting transition) of the polymer. It also provides information concerning the onset of plastic flow. The two methods described are not applicable to non-symmetrical laminates (see ISO 6721-3, Plastics — Determination of dynamic mechanical properties — Part 3: Flexural vibration — Resonance-curve method). The methods are not suitable for testing rubbers, for which the user is referred to ISO 4664-2, Rubber, vulcanized or thermoplastic — Determination of dynamic properties — Part 2: Torsion pendulum methods at low frequencies.