Study on discrete relaxation time spectrum for PBO/PPA liquid crystal polymer solution

Abstract

Based on KBKZ integral type rheological equation, discrete relaxation spectra were attained by use of the least square linear and non-linear regressions. The results show that the number of relaxation mode ranging from 9 to 11 for linear regression method has little effect on the non-linear regression method. Apart from that the relaxation modulus coefficient related with the different time range was gained, the relaxation time range had little effect on the time spectrum. The trend for relaxation time spectrum of PBO solution is similar to common polymer solution except that there is not a platform modulus region for high elastic state. The relaxation time spectrum at 160°C was obviously different from that at 170°C. However, the difference diminished when the temperature exceeded 170°C, and no significant distinction was found at glass transition region. While at 170°C, the influence on the movement of the chain segment was trivial as the molecular weight increases, mainly resulting in the movement restriction of polymer chains.