Preparation and Properties of Cellulose Nanocrystals Derived from Corn Cobs: Application as a Reinforcing Material for "Green Nanocomposite" Films

In this research, cellulose and its nanocrystals were extracted from corn cobs (Zea mays L.), by an alkali treatment and subsequently by sulfuric acid hydrolysis. The use of nanocrystals as a reinforcement agent in a polymer matrix based on chitosan was also investigated. Therefore, characteristics like flow birefringence, morphology, crystallinity, thermal stability, electrical resistivity, mechanical and physicochemical of corn cobs, purified cellulose, cellulose nanocrystals and nanocomposites were studied. The results of the chemical composition analysis, FT-IR and XRD, indicate that both hemicellulose and lignin have been extensively removed in the cellulose nanocrystals. The purified fibers presented a purity level of 90%. Cellulose nanocrystal suspensions showed flow birefringence, indicating the presence of individualized nanocrystals. The cellulose nanocrystals presented a high crystallinity, an length of 5 to 40 nm and a diameter of to 5 to 25 nm. Nanocomposite films made with the nanocrystals and chitosan have shown that these components exhibited good miscibility and strong interactions. Increasingly, chitosan:nanocrystals ratios from 15:1 to 7:1 improved the tensile strength and Young's modulus of the films by up to 110 and 156%, respectively. The films were able to maintain approx. 85% of their weight at the temperature of 210 degrees C. In addition, they displayed excellent water vapor permeability and water resistance with the incorporation of nanocrystals. The films were found to be good insulators with electrical resistivity values in the order of magnitude of 105 am.