Biodegradable Nanocomposites from Wheat Straw

We investigate the mechanical and thermal properties of cellulose nanofiber reinforced starch based thermoplastic composites. Cellulose nanofibers were isolated from wheat straw by a chemi-mechanical technique. Their morphology, physicochemical and thermal properties were investigated to examine potential applications as reinforcement fibers in biocomposites. Transmission electron microscopy results showed that almost 60% of them have a diameter within a range of 30-40 nm and lengths of several thousand nanometers. Their average aspect ratio was found to be 95. Chemical characterization of the nanofibers confirmed that an applied alkali and acid treatment resulted in increased cellulose content from 43% to 85%. FT-IR spectroscopic analysis of the fibers demonstrated that this chemical treatment also led to partial removal of hemicelluloses and lignin from the nanofibers’ structure. PXRD measurements revealed that this resulted in an improved crystallinity of the fibers. After mechanical treatments, thermal properties of the nanofibers were studied by the TGA technique and found to increase dramatically. The nanocomposites were prepared by a solution casting method. The tensile strength and modulus of the reinforced starch films were compared with those of pure starch and were found to have considerably improved, even at 5% nanofiber loading.