emN, N’/em-sebacic bis(hydrocinnamic acid) dihydrazide: A crystallization accelerator for poly(L-lactic acid)

摘要

Developing more organic nucleating agent with different molecular structure is very instructive to improve the crystallization of poly(L-lactic acid) (PLLA) and explore the crystallization mechanism. In this study, N, N’-sebacic bis(hydrocinnamic acid) dihydrazide (HAD) was synthesized to serve as a nucleating agent for PLLA. The effects of HAD on the non-isothermal crystallization, melting behavior, thermal stability and optical performance of PLLA were investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and light transmittance meter. The melt crystallization behavior showed that HAD was able to promote the crystallization of PLLA via heterogenous nucleation in cooling, and it was found that, upon the cooling of 1°C/min, the incorporation of 1 wt% HAD made the crystallization temperature and non-isothermal crystallization enthalpy increase from 94.5°C and 0.1 J/g to 131.6°C and 48.5 J/g comparing with the pure PLLA. Additionally, the melt crystallization significantly depended on the cooling rate and the final melting temperature. For the cold crystallization, when the nucleation density from HAD and PLLA itself was saturated, the influence of the HAD concentration on the cold crystallization process of the PLLA/HAD samples is negligible. The melting behavior after isothermal or non-isothermal crystallization further confirmed the crystallization accelerating effect of HAD for PLLA, and the appearance of the double melting peaks was attributed to the melting-recrystallization. Unfortunately, the addition of HAD decreased the thermal stability and light transmittance of PLLA.