The utilization of cellulose nanocrystals (CNCs) extracted from natural fibers is one way to make the most use of renewable resources. Isolation of CNCs normally requires a multi-step process that includes an alkali treatment, bleaching (using sodium chlorite) and acid hydrolysis (sulfuric or hydrochloric acid). Here, a new approach for extracting CNCs from green Luffa cylindrica biomaterial, one type of natural fiber found in tropical countries, was developed via an alkali treatment and oxidative degradation using sodium hypochlorite, without an acid hydrolysis step. The diameter and length of the obtained CNCs were about 7.5 ± 2.2 nm and 266.9 ± 25.2 nm, respectively, with a considerably higher percentage yield (40%) compared to the traditional hydrolyzed-cellulose nanocrystals (H-CNCs) (28%). The zeta potential of CNCs and H-CNCs in neutral water was −29.2 ± 0.5 mV and −13.1 ± 0.5 mV, respectively. Negative charges on CNC surfaces play an important role in the reduced aggregation of CNC suspensions. The degrees of crystallinity of CNCs (78.5%) and H-CNCs (79.2%) are comparable. Moreover, the degrees of polymerization of CNCs and H-CNCs were 297.21 and 226.64, respectively. The method developed is considered an easy operation with low pollution, low-cost chemicals and a time- and energy-saving process.
Reference: Punyarat Jantachum and Pranee Phinyocheep; Polym. Int. 2023, 72, 243-251