Preparation and environmental analysis of biodegradable polylactic acid and modified cellulose nanofiber composites.

[Display omitted] • Surface modification of CNFs was successfully performed through MDI-grafting reaction. • The mechanical properties of the PLA-mCNF composite can be optimized at a low content of toxic diisocyanate on the surface of CNFs. • The PLA-mCNF composites exhibit superior mechanical and thermal properties, as well as biodegradation ability but have a lower environmental impact when using a renewable source compared to corn gain-based PLA. Polylactic acid (PLA) and cellulose nanofibers (CNFs) show promise as bio-based alternatives to non-degradable plastics, which pose environmental challenges. Yet, CNFs' hydrophilicity hampers their dispersion in hydrophobic PLA. This study modifies CNF surfaces with diisocyanate compounds to create hydrophobic isocyanate-modified CNFs (mCNFs), enhancing their compatibility with PLA. One isocyanate of the diisocyanate compound is grafted onto the surface of CNF and the isocyanate content varied by adjusting grafting reaction time. PLA-mCNF composites are produced by a twin-screw extruder and show improved mechanical properties and biodegradability compared to pristine PLA and PLA-unmodified CNF composite. The environmental impacts of PLA-mCNF composites are evaluated using a life-cycle assessment method and compared to corn grain-based PLA. The optimized PLA-mCNF composite (6 h of grafting reaction) has lower environmental impacts than corn grain-based PLA, with global warming and fossil resource scarcity of 3.021 kg eq and 0.813 kg oil eq, respectively. This study underscores the feasibility of optimizing PLA composite properties by employing a small proportion of toxic diisocyanate on CNF surfaces. The findings highlight the potential of such modified composites to offer improved sustainability and performance characteristics, contributing to the development of eco-friendly materials. [ABSTRACT FROM AUTHOR]