Synergetic Effect of Complex Nucleation Agent on the Crystallization Behaviors and Mechanical Properties of Polylactic Acid

ABSTRACT Controlling the crystallization behavior of poly(lactic acid) (PLA) to optimize its mechanical properties is critical for expanding its scope of application. In this work, a complex nucleation agent system comprising octamethylenedicarboxylic dibenzoylhydrazide (TMC‐300) and D‐sorbitol (DS) was engineered and integrated into the PLA matrix through melt‐blending, with the objective of enhancing both crystallization and mechanical performance. Systematic investigations via differential scanning calorimetry (DSC), thermogravimetric analysis (TG), polarized optical microscopy (POM), and mechanical property evaluations revealed that the TMC/DS complex nucleation agent significantly accelerated PLA crystallization, leading to markedly improved mechanical properties in the resultant PLA composites. The crystallization behaviors of PLA are investigated using DSC. The addition of a complex nucleation agent could remarkably increase the crystallization temperature, onset crystallization temperature, and crystallinity under nonisothermal conditions from 97.2°C, 114.5°C, and 3.5% of neat PLA to 124.7°C, 130.3°C, and 40.8%. The overall crystallization rate is also promoted obviously according to the isothermal crystallization kinetic parameters analyzed by the Avrami equation. Meanwhile, analysis of Lauritzen‐Hoffman's theory shows that the complex nucleation agent has superior nucleation efficiency to a single agent and accelerates the crystallization of PLA with the formation of denser spherulitic crystals observed by POM. Consequently, these improvements in crystallization behaviors result in a 17%, 50% and 23% increase in tensile strength, Young's modulus, and elongation at break, respectively.