Dielectric relaxation spectrum, temperature effect

The relaxation behavior of the PVC-copolymer (styrene-methyl-methacrylate-acrylonitryle) was studied by the dielectric method. The Cole-Cole parameters, characterizing the distribution of relaxation time (relaxation spectra) and its temperature dependence have been calculated (Figure 7.18). It is seen that with an increase of filler amount, the parameter of relaxation time distribution decreases, i.e., the broadening of the spectra occurs. These effects, similar to analogous effects described in Chapter 5 for filled polymers, are explained by the restriction of molecular mobility of alloy components in the surface layers and by their contribution to the total relaxation spectrum. 

Dielectric measurements have been made by Buckingham and Belling [96] on ethylene/propylene copolymers. The data show an increase in the loss in range of 10 -10 Hz due to some more polarity of PP. Unlike low dielectric losses in PE, the copolymer spectrum exhibits a a-relaxation peak at 10 Hz at room temperature. The effect of oxidation on the microwave behaviour of PE can be seen in the data of Ref. [95]. A loss peak at 10 Hz (room temperature) increased with time of oxidation. 

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