Time-temperature superposition difficulties with

One method for overcoming this difficulty is to introduce the modified (or reduced) time t which allows the use of integral relationships with different arguments. The definition of modified time is based on the principle of time-temperature superposition. This is the usual way to generalize temperature-dependent functions using the argument... 

Fig. 3.4. With a multi-frequency measurement, frequencies beyond the measurable range of the DMA can be achieved by using the superposition method. Employing the Williams-Landel-Ferry (WLF) equation, and with a treatment of the data, designated as the method of reduced variables or time-temperature superposition (TTS) it is possible to overcome the difficulty of extrapolating limited laboratory tests at shorter times to longer-term, more real world conditions. The underlying bases for TTS are that the processes involved in molecular relaxation or rearrangements in viscoelastic materials occur at accelerated rates at higher temperatures and that there is a direct equivalency between time (the frequency of the measurement) and temperature.

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