Annealing memory effect

The absolute need for a distribution of relaxation times can be illustrated by a more complicated thermal history. The sample is annealed to equilibrium above the glass-transition interval and then quenched rapidly to a temperature deep within the glass-transition region. It is isothermally annealed until its volume achieves a value consistent with a glass with a fictive temperature in the middle of the glass-transition interval. The partially annealed glass is then rapidly heated to this fictive temperature, where the sample achieves a volume exactly equal to its equilibrium value. The volume then increases spontaneously to a maximum value and finally relaxes back to its equilibrium volume. This trajectory is called the "memory effect" and is shown in Figure 8.2. 

Figure 8.2 Volume as a function of time after memory effect thermal history. Curve 1 is a pure quench. Curves 2 to 4 correspond to quenches and annealing at 10, 15, and 25°C, respectively. (From Kovacs, A.J., Glass transition in amorphous polymers a phenomenological study, Adv. Polym. Sci., 3, 394,1963. With permission.)...

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