ISO 6721-4:2008 describes a forced, non-resonance method for determining the components of the tensile complex modulus E* of polymers at frequencies typically in the range 0,01 Hz to 100 Hz. The method is suitable for measuring dynamic storage moduli in the range 0,01 GPa to 5 GPa. Although materials with moduli outside this range may be studied, alternative modes of deformation should yield higher accuracy [i.e. a shear mode for E' < 0,01 GPa (see ISO 6721‑6) and a flexural mode for E' > 5 GPa (see ISO 6721‑3 or ISO 6721‑5)].
This method is particularly suited to the measurement of loss factors greater than 0,1 and may therefore be conveniently used to study the variation of dynamic properties with temperature and frequency through most of the glass-rubber relaxation region. The availability of data determined over wide ranges of both frequency and temperature enables master plots to be derived, using frequency-temperature shift procedures, which display dynamic properties over an extended frequency range at different temperatures.