Rheological Percolation of Cellulose Nanocrystals in Biodegradable Poly(butylene succinate) Nanocomposites: A Novel Approach for Tailoring the Mechanical and Hydrolytic Properties.

Although biodegradable plastics are gradually emerging as an effective solution to alleviate the burgeoning plastic pollution, their performance is currently trivial for commercialization. A proposed two-pronged strategy to overcome this limitation includes (1) preparation of the nanocomposites from biorenewable nano-fillers to preserve their biodegradability and (2) tailoring their properties to meet the diverse demands in various applications. Herein, we report the preparation of biodegradable nanocomposites composed of poly(butylene succinate) (PBS) and cellulose nanocrystals (CNCs) (loading of 0.2-3.0 wt%) and propose a rheological strategy to tailor their performances. Depending on the shear frequencies, the rheological evaluation revealed two percolation thresholds at approximately 0.8 and 1.5 wt%. At high shear frequencies, the disappearance of the first threshold (0.8 wt%) and the sole persistence of the second one (1.5 wt%) indicated the collapse of the immature network of partially interconnected CNCs. The tensile and hydrolytic properties of the nanocomposites were found to undergo drastic changes at the thresholds. The tensile strength increased by 17% (from 33.3 to 39.2 MPa) up to 0.8 wt% CNC loading. However, the reinforcing efficiency of CNC decreases sharply with further incorporation, reaching nearly zero at 1.5 wt%. On the other hand, hydrolytic degradation of the nanocomposites was rapidly accelerated above 1.5 wt% CNC loading. Therefore, a thorough understanding of the rheological properties of nanocomposites is essential for the design and development of materials with tailored properties.