Comparative study of mechanical and electrical relaxations in poly(etherimide). Part 2

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The curves describing the relaxation behaviour of poly(etherimide) at several frequencies shows in the dielectric loss–temperature plot γ and β relaxations centred at -95°C and 100°C, respectively, at 10Hz. The glass–rubber relaxation or α process appears at 225°C at 10Hz; at this temperature free charge conductivity and blocking electrode phenomena become dominant at frequencies below 10Hz. The same three relaxations are observed by dynamic mechanical thermal analysis (DMS). The strength of the γ and α relaxations can be estimated from the fitting of empirical relaxation functions, such as the Fuoss–Kirkwood and Havriliak–Negami equations, to the dielectric data measured in the frequency domain. An electric model was used to separate the dipolar response from conductivity contributions in the glass–rubber relaxation. Finally, the effect of water on the low-temperature relaxation has been demonstrated by dielectric and mechanical measurements. © 1998 SCI.