Synergistic enhancement of high-barrier polylactic acid packaging materials by various morphological carbonized cellulose nanocrystals

The environmental challenges linked to petroleum-based polymers have accelerated the search for alternative materials like polylactic acid (PLA). Diverse nanofillers, ranging from inorganic to organic and hybrid inorganic/ organic varieties, are employed to bolster PLA performance. Yet, non-synergistic nanofillers often underperform due to inadequate dispersion and singular functionality within the PLA matrix. This work introduces carbonized cellulose nanocrystals (GCNC) with rod-like (R-GCNC) and spherical structures (S-GCNC), as synergistic reinforcements for PLA matrix. Unlike traditional nanofillers, the highly graphitized carbon layer on GCNC effectively mitigates CNC agglomeration while preserving cellulose morphology, fostering improved interfacial interactions and hydrogen bonding within PLA matrix. Moreover, GCNC acts as a nucleating agent, boosting the crystallization rate of PLA and enhancing its mechanical properties. Remarkable synergistic reinforcing effects of GCNC on PLA performances were observed. Particularly, the tensile strength of R-GCNC 5 % and S-GCNC 5 % composites surged by 93 % and 76 %, elongation at break increased by 29.4 % and 33.3 %, Young's modulus rose by 37 % and 18 %, and cold crystallization temperature decreased by 11.5 degrees C and 12.9 degrees C. Additionally, the GCNC/PLA composites exhibited exceptional thermal stability, UV resistance, and water vapor permeability reduced by 46 % for R-GCNC, and 35 % for S-GCNC, making them promising for industrial and sustainable packaging.