Cassava starch biocomposites reinforced with cellulose nanocrystals from kenaf fibers

Abstract

This study highlights the potential of cellulose nanocrystals (CNCs) from kenaf fibers as reinforcing fillers in starch-based biocomposites. By hydrolyzing kenaf fibers with 65 wt.% sulfuric acid, CNCs with diameters of 12 ± 3.4 nm were obtained. Cassava starch biocomposites were prepared using a solution casting method which includes 0–10 wt.% kenaf CNCs as fillers and glycerol/sorbitol (ratio of 50:50) as plasticizer. The composites were characterized by different techniques, including tensile tests, thermal stability tests, transmission electron microscopy, field emission scanning electron microscopy (FE-SEM), water uptake tests, and observation of the physical properties of the film cast. The CNCs appeared as white, shiny dots under FE-SEM with a good dispersion of the nanofillers within the starchy matrix. The tensile strength and modulus of the biocomposite films were significantly enhanced when compared to unfilled starch films. Transparent, thin, and flexible films were obtained from both the plain matrix and 6 wt.% CNC biocomposites, confirming that CNCs may be used as fillers without affecting the composite's transparency. Furthermore, incorporation of CNCs in the plasticized matrix led to a decrease in water sensitivity.