PLLA-grafted cellulose nanocrystals: Role of the CNC content and grafting on the PLA bionanocomposite film properties

• Bionanocomposite films were developed by an optimized extrusion process.
• Cellulose nanocrystals (CNC) were grafted by ring opening polymerization of l-Lactide.
• Two different CNC:l-lactide ratios (20:80 and 5:95) were obtained.
• CNC grafted with the higher ratio of lactide act as a nucleating agents.
• CNC graft ratio and content influence all the final bionanocomposite properties.

Cellulose nanocrystals (CNC), extracted from microcrystalline cellulose by acid hydrolysis, were grafted by ring opening polymerization of l-Lactide initiated from the hydroxyl groups available at their surface and two different CNC:l-lactide ratios (20:80 and 5:95) were obtained. The resulting CNC-g-PLLA nanohybrids were incorporated in poly(lactic acid) (PLA) matrix by an optimized extrusion process at two different content (1 wt.% and 3 wt.%) and obtained bionanocomposite films were characterized by thermal, mechanical, optical and morphological properties. Thermal analysis showed CNC grafted with the higher ratio of lactide play a significant role as a nucleating agent. Moreover, they contribute to a significant increase in the crystallization rate of PLA, and the best efficiency was revealed with 3 wt.% of CNC-g-PLLA. This effect was confirmed by the increased in Young's modulus, suggesting the CNC graft ratio and content contribute significantly to the good dispersion in the matrix, positively affecting the final bionanocomposite properties.