Properties of thermoplastic starch films reinforced with modified cellulose nanocrystals obtained from cassava residues

Abstract

This study investigated the effectiveness of cellulose nanocrystals derived from cassava residues as a reinforcement to starch films. Thermoplastic starch films are biodegradable to a certain extent, but the scope of their applications is limited due to their strong water absorption and poor mechanical properties. Therefore, we used abandoned cassava residues to prepare cellulose nanocrystals quickly and efficiently using a mechanochemical method. Their average diameter and length were 6.281 nm and 437.232 nm, respectively, with an aspect ratio of 70; this average size is smaller than that of CNCs obtained via acid hydrolysis. Cellulose nanocrystals were ester modified using soybean oil to improve their polarity and hydrophobicity. Thermoplastic starch-based composite films were prepared using the film casting method; the mechanical and wettability properties of these films were investigated, by controlling the concentration of modified cellulose nanocrystals in the films. Scanning electron microscopy results showed that M-CNCs were evenly distributed in the composite films; thermal stability analysis showed that composite films exhibited high thermal stability; Fourier transform infrared spectroscopy results showed that the structure of cellulose nanocrystals prepared using a mechanochemical method was stable; water contact angle measurements showed promising hydrophobic effects at a contact angle of 105.7°. Moreover, mechanical tests showed that the tensile strength of the composite film increased by 73%. Therefore, soybean-oil-modified cellulose nanocrystals were excellent reinforcing agents for thermoplastic starch films, effectively improving the overall performance of the films.