The oscillatory properties (storage and loss moduli, represented by
and
, respectively) should always be provided. For most polymer melts,
the measurement of the oscillatory properties is easy. Storage and loss moduli are
usually obtained over several decades. The most typical measurement device is the
cone-plate rheometer. Measurements can be taken at one temperature if an isothermal
model is being considered, or at various temperatures if a non-isothermal model is
being considered.
In general, measurements can be taken at various temperatures in order to obtain
master curves of and
at a suitably selected temperature. For this, the time-temperature
equivalence can be used in order to properly shift the curves. By doing so, it is
possible to expand the range of experimental data for the linear properties,
provided that the material exhibits visible temperature dependence. See Empirical Rules and Principles for details.