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ABSTRACT
With the aim of overcoming the slow crystallization rate of Poly(L-lactic acid) (PLLA), a heterogeneous nucleating agent, N, N, N, N’-salicylic tetra(1, 2, 4, 5-benzenetetracarboxylic acid) hydrazide (BAS), was synthesized to accelerate the crystallization of PLLA in this work. The effects of BAS on the non-isothermal crystallization, melting behavior, thermal stability, the fluidity and optical property of PLLA were evaluated using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), melt index instrument and light transmittance meter. DSC results from the non-isothermal crystallization behavior revealed that BAS acted as an excellent crystallization promoter for promoting the nuclear of PLLA. Upon the cooling of 1°C/min from the melt of 190°C, 3 wt% exhibited the best accelerating effect on the melt-crystallization of PLLA. Even the BAS as a high-efficient nucleating agent could significantly promote the crystallization of PLLA upon fast cooling at 20°C/min. Additionally, the final melting temperature was another important factor for the crystallization process, and the 200°C is the best melting temperature for melt-crystallization of PLLA. The studies on the cold-crystallization process and melting behavior of PLLA/BAS samples under different conditions further confirmed the heterogeneous nucleating effect of BAS. And for the melting behavior of PLLA/BAS, both the crystallization temperatures and heating rates affected the melting behavior, and the double-melting peaks were assigned to melting-recrystallization. Overall, the addition of BAS could effectively improve the thermal stability and fluidity comparing with the primary PLLA, but decrease the light transmittance of PLLA.
Graphical Abstract
Synthesis of nucleating agent N, N, N, N’-salicylic tetra(1, 2, 4, 5-benzenetetracarboxylic acid) hydrazide for promoting the crystallization of Poly(L-lactic acid)
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Notes on contributors
Li-Sha Zhao
Dr. Li-Sha Zhao has obtained Doctor in chemistry in 2012 from the JIlin University (China). Hers research focus on the modified PLLA materials.
Yan-Hua Cai
Prof. Yan-Hua Cai has obtained Doctor in materials engineering in 2011 from the Shanghai University (China). Now, he has more than 10 years of experience in the field of polymer technology in both academia and private industry, and he has published more than 40 research articles.
Hui-Li Liu
Dr. Hui-Li Liu has obtained Doctor in materials engineering in 2018 from the Sichuan University (China). Hers research focus on the crystallization of PLLA.