15. Below Tg: secondary relaxations

Figure 28 shows the evolution of the dielectric loss factor ${\epsilon }^{″}\omega \left(T\right)$ of amorphous maltitol as a function of temperature, for several frequencies from 100 to 200 kHz. The temperatures cover a range on either side of T _g . For T > T _g , we note the presence of the α relaxation peak, whose temperature at the peak changes little with frequency. In other words, its characteristic frequency decreases rapidly with decreasing temperature. This leads to an effective motion freeze corresponding to T _g ...