Role of N,N'-bis(1H-benzotriazole) adipic acid acethydrazide in crystallization nucleating effect and melting behavior of poly(L-lactic acid)

The enhancement of crystallization performance is very important in semicrystalline polymers for broadening their practical application. In this study, N,N'-bis(1H-benzotriazole) adipic acid acethydrazide (BA) was synthesized from 1H-benzotriazole and adipic acid in order to evaluate the heterogeneous nucleating performance of poly(L-lactic acid) (PLLA). Through the investigation of non-isothermal crystallization behavior of PLLA containing different BA content using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD), it was clear that BA was able to significantly promote the crystallization of PLLA compared to pristine PLLA, and the addition of BA resulted in an increase in the onset and peak crystallization temperatures and in the non-isothermal crystallization enthalpy. Furthermore, 1 wt% BA was found to be the optimal concentration, achieving the best nucleating effect for PLLA. The cooling rate was a key factor affecting the non-isothermal crystallization peak. The set final melting temperature also affected crystallization, as a result of the solubility of BA in the PLLA matrix and the thermal decomposition of PLLA at the set temperature. Comparative study of the melting behavior of PLLA and PLLA/BA further confirmed the nucleating interaction of BA with PLLA. Differences in melting behavior were largely dependent on the competition between the crystallization rate and the relevant heating or cooling rate.