Abstract
Improving the crystallization performance of poly(L-lactide) (PLLA) is necessary to adapt for various applications. In the current work, N, N`-bis(isonicotinic acid) 1, 4-naphthalenedicarboxylic acid dihydrazide (NAIAH) was synthesized to be firstly aimed at promoting the crystallization of PLLA, and the NAIAH-nucleated PLLA materials were prepared using PLLA as a matrix material and NAIAH as a nucleating agent, and the crystalline nucleation, melting behavior, thermal decomposition and mechanical properties of PLLA/NAIAH samples were investigated by the relevant testing instruments. The results from the non-isothermal melt-crystallization from the melt of 190ºC indicated that the NAIHA could significantly accelerate PLLA’s crystallization, and played an efficient heterogeneous nucleation in PLLA’s crystallization. The effect of different final melting temperatures on PLLA’s melt-crystallization behavior showed that a relatively low final melting temperature was beneficial for the crystallization of PLLA, and the 170ºC was the optimum final melting temperature in this study. An increase of cooling rate could weaken PLLA/NAIAH’s crystallization ability, but the NAIAH was still able to promote PLLA’s crystallization upon the fast cooling at 50ºC/min, showing a powerful crystallization accelerating effect of NAIAH. PLLA/NAIAH’s melting behaviors after different crystallization conditions were affected by heating rate and crystallization temperature, and the double melting peaks appeared in melting DSC curves were assigned to melting-recrystallization. Thermal decomposition processes in air showed that the NAIAH decreased PLLA’s thermal stability, but the interaction of PLLA with NAIAH had an inhibition for a drop in onset decomposition temperature. Additionally, the introduction of NAIAH dramatically reduced PLLA’s tensile modulus and elongation at break.
Keywords: Poly(L-lactide); 1; 4-naphthalenedicarboxylic acid; crystallization; organic nucleating agent; thermal behavior