Structural evolution and mechanism of PLA/TMC-300 films under uniaxial and biaxial stretching

Abstract

To develop high-performance polylactic acid (PLA) films, it is imperative to investigate the crystallization behaviour of the PLA/nucleating agent system under practical elongation flow field. This study utilized PLA as the matrix and decanedioic acid, 1,10-bis(2-benzoylhydrazide) (TMC-300) as the nucleating agent to explore, for the first time, the impact of mechanical stretching on the crystallization behaviour of PLA/TMC-300 films. The results revealed that TMC-300 provided nucleation sites for PLA through a self-assembly mechanism within the PLA composite system. Adjusting the final heating temperature demonstrated that fully dissolved TMC-300 formed dendritic crystalline structures, while partially dissolved TMC-300 generated microcrystals and fibrous structures. The fluctuating temperature conditions encountered during actual shear field promoted the recrystallization of TMC-300 into microcrystalline forms. During the stretching process, the contribution of TMC-300 to enhancing PLA's crystallization was overshadowed by the influence of mechanical stretching. However, TMC-300 aligned directionally, creating an ordered fibrous crystal template that facilitated the vertical crystallization of PLA, leading to a distinctive shish-kebab-like structure. As a result, the stretched PLA composite films exhibited significantly improved toughness compared to pure PLA. Additionally, hydrogen bonding interactions between PLA and TMC-300 enhanced molecular chain anchoring and crystal orientation within the PLA composite film, further contributing to its enhanced performance.