Nanocellulose as a Bio-Based Reinforcement in Vitrimer Nanocomposites: Manufacturing and Mechanical Characterisation

To address issues of plastic pollution and nanoparticle toxicity, this study focuses on the synthesis and characterization of recyclable nanocomposites reinforced with nontoxic bio-based nanoparticles. Bridging the gap between thermoplastic reprocessability and thermoset durability, a novel subclass of covalent adaptable networks (CANs) with associative cross-link exchange was adopted as the matrix system, while mechanically derived cellulose nanofibrils were used as reinforcement. Four nanocomposite variants with cellulose nanofibril contents of 0.25 wt%, 0.5 wt%, 1.0 wt%, and 1.2 wt%, respectively, were prepared by ultrasonic dispersion of nanoparticles into preheated epoxy monomer and imine hardener, followed by curing. Mechanical behavior was evaluated via tensile and three-point bending tests, while the contribution of nanoparticles in failure mechanisms was confirmed in fracture surface analysis. The mechanical characterization revealed that incorporating 0.25 wt% cellulose nanoparticles increased the maximum tensile strength by 21% under both tension and flexural loading, with corresponding modulus enhancements of 4% and 22%, respectively. Experimental evaluations confirmed reshaping and shape recovery capabilities, reprocessing improved mechanical properties of unreinforced material (failure strain +38%, flexural strength +14%, modulus +12.2%), while reinforced variants underperformed their pristine counterparts due to larger particles. These findings provide valuable insight for manufacturing sustainable and reprocessable polymer nanocomposites.