A new strategy to prepare bio-based polylactic acid modifier for multi-functionality: Dopamine-grafted modified lignin

Currently, to address the performance deficiencies associated with high brittleness, inadequate thermal stability, and susceptibility to hydrolysis in polylactic acid (PLA), it is common practice to incorporate multiple or high proportions of additives. However, this approach raises concerns regarding interface compatibility, energy consumption, and environmental impact. In this context, we introduce an environmentally friendly, bio-based PLA modifier that is facile to prepare and facilitates multi-functional applications at a minimal dosage. The presence of a benzene ring structure in lignin endows the material with ultraviolet (UV) resistance, thermal stability, and hydrophobic characteristics, while the exceptional adhesion properties of polydopamine (PDA) enhance interfacial compatibility. A novel biomass polylactic acid modifier, designated as OL@PDA, has been synthesized by modifying low-molecular-weight lignin (OL) with PDA. Comparative analysis of OL@PDA/PLA composite materials reveals a 14.08 % increase in tensile strength and a 42.00 % enhancement in elongation at break relative to pure PLA. The incorporation of the lignin-derived benzene ring structure effectively transforms PLA from a hydrophilic to a hydrophobic material. Furthermore, the UV transmittance at 400 nm (T400 nm%) is recorded at 65.8 % for pure PLA, which significantly decreases to below 5 % for OL@PDA/PLA composites. The integration of OL@PDA as a modifier in PLA materials yields comprehensively performance enhancements while maintaining a low additive concentration.