Customized compatibilizer to improve the mechanical properties of polylactic acid/lignin composites via enhanced intermolecular interactions for 3D printing

Abstract

Polylactic Acid (PLA)/lignin composite shows great potential as a 3D printing material due to its eco-friendliness and cost-effectiveness, but the poor compatibility seriously reduces the mechanical properties, which restricts its wide applications. Herein, a new strategy for concurrently enhancing tensile strength, elongation, and toughness of PLA/Lignin (P/L) composites through intermolecular interactions enhancement with a lignin-based compatibilizer was firstly reported. In detail, the lignin-g-maleic anhydride-g-PLA (LMP) compatibilizer was tailor-made by a two-step method. Mechanical testing results indicated that the tensile strength, elongation, and toughness were increased by 22%, 68%, and 114%, respectively in P/L20 (20% lignin) after adding 5 wt% of LMP, which is superior to the addition of commercial compatibilizer, polyethylene glycol. SEM observation, rotational rheometer testing, DSC analysis, and molecular dynamics (MD) simulation remarkably verified that LMP distinctly increased the intermolecular interaction. In particular, the van der Waals energy of lignin-LMP and LMP-PLA was raised by 15.7% and 60.8% and the electrostatic potential energy was boosted by 11.0% and 60.7%, respectively, based on lignin-PLA. Additionally, P/LMP5/L20 achieved excellent antioxidant properties (91% radical scavenging activity rate), which could be a potential candidate to replace traditional materials for medical applications of 3D printing. Overall, this study proposes a novel approach to develop economical biodegradable composites with great mechanical and extraordinary antioxidant performances for 3D printing.