Dielectric hysteresis in some polyamides

In view of the electric displacement D-the electric field E hysteresis or the polarization reversal in less crystalline polyamides derived from m-xylylenediamine we have investigated the ferroelectric nature in other types of polyamide. In this work samples employed were polyamides prepared from 1,3-bis(aminomethyl)cyclohexane (BAC) and dicarboxylic acids with the number of carbon atoms n=6,7, and 10 and from hexamethylenediamine (HMD) and isophthalic acid(I), and from HMD and 70 mol% I and 30 mol% terephthalic acid(T) which were abbreviated to nylon BAC n, nylon 6I (6, the number of carbon atoms in HMD), and nylon 6I/6T, respectively. Nylon BAC 6,7, and 10 showed the glass transition at 376, 362, and 346K, respectively, as observed by the differential thermal analysis (DTA) method. Quenched samples of nylon BAC exhibited the D-E hysteresis irrespective of the number of carbon atom, of which the remanent polarization P_I and the coercive field E_c were about 30 mC m^-2 and 80 MV m^-1, respectively. Nylon 6I and 6I/6T were amorphous, showing neither crystallization nor fusion temperature in the DTA thermogram, and exhibiting the D-E hysteresis with the same order of magnitude of P_r and E_c as those in nylon BAC n at high temperature near 370K. The remanent polarization in poled polyamides studied was depolarized near the glass transition with increasing temperature. The polarization of the amide groups in amorphous regions was considered to be responsible for the dielectric hysteresis in these polyamides