Development of zinc salts of amino acids as a new class of biocompatible nucleating agents for poly(l-lactide)

• DOI: 10.1016/j.eurpolymj.2019.05.064
• Publication Date: 2019-05-31T23:54:39Z
• Authors: Zhiyong Wei; Shengnan Shao; Meili Sui; Ping Song; Maomao He; Qiang Xu; Xuefei Leng; Yanshai Wang; Yang Li
• Keywords: 01 natural sciences; 0104 chemical sciences

Abstract The slow crystallization speed of poly( l -lactide) (PLLA) during practical processing results in the low degree of crystallinity and thus poor heat resistance of the molded articles, which prevents the wider applications of PLLA. The additive of biocompatible nucleating agents is one of the most effective means to promote the crystallization of PLLA, which synchronously preserves the bio-advantages of PLLA materials for biomedical and food applications. In this work, a series of zinc salts of amino acids, including nine kinds of l -amino acids and six types of d - or dl -configuration amino acids, was prepared and evaluated as nucleating agents (NAs) for PLLA. The nucleation effect of NAs was compared in terms of the nonisothermal melt crystallization peak temperature of PLLA with 1 wt% loading of NAs under a cooling rate of 10 °C/min. It was found that the nucleation effect of the zinc salts of amino acids depends on the ligand and its configuration. The nucleation mechanism and the difference of nucleation ability were also discussed and explained. Among these tested NAs, zinc d -phenylalaninate (Zn( d -Phe)2) is the most effective one, which is comparable to the current outstanding NAs, evidenced by the crystallization peak temperature at 130 °C accompanying with the crystallization enthalpy up to 48 J/g. It is expected that Zn( d -Phe)2 is a promising nucleating agent providing high nucleation activity in injection molding and extrusion processing of PLLA articles.