High-efficiency synergistic modification of polylactic acid by micrometer-sized cellulose fibers and cellulose nanocrystals.

With the advancement of eco-friendly biodegradable composites, polylactic acid (PLA) has attracted considerable attention. This study used micro-nanocellulose fibers-specifically, micrometer-sized cellulose fibers (MF) and cellulose nanocrystals (CNCs) extracted from office waste paper-to synergistically modify PLA. The findings revealed that CNCs interwove with MF, forming dense network structures in the PLA composites. This network enabled CNCs and MF to synergistically improve the reinforcement of PLA. As a result, the storage modulus, tensile strength, and elongation at break of PLA increased by approximately 64 %, 13 %, and 33 %, respectively. Furthermore, micro-nanocellulose fibers formed a multiscale structure in PLA composites, extending the diffusion path of water molecules and improving PLA's water vapor barrier property by 87 %. This micro-nanostructure also reduced hydrophilicity while changing the surface roughness and transparency of the PLA composites. Notably, all PLA composites exhibited excellent degradability. This study not only achieved the synergistic modification of PLA using micro-nanocellulose fibers but also introduced an innovative approach for recycling and repurposing office waste paper.