The study reports the effects of cellulose nanofibers (CNF) and an ultrasound-assisted method dispersed cellulose nanocrystals (CNC) on the mechanical and water resistance properties of starch-polyvinyl alcohol (PVA) films. Starch-PVA (SP) based films are prepared by casting method, compared with the original SP films, the ultrasound-assisted and CNF are beneficial to the dispersion of CNC in nanocomposites, and the tensile strength (TS) of the ultrasound treatment starch/PVA/CNC/CNF (USPCF) film is increased to 10.63 MPa, an increase by 60%. The cross-section morphology of the USPCF film is smoother and more homogeneous, indicating the particle size of CNC is small. The structure of blend films is homogeneous and compact due to the CNC full playing to the nano-effect, which is the main reason for the improvement of SP-based films in mechanical properties. Fourier Transform Infrared spectroscopy shows the hydrogen bonding is formed between SP and the fillers, while X-ray diffraction shows that the crystallinity of nanocomposite films is decreased with ultrasonication. From the results, it can be concluded that CNF and ultrasound-assisted dispersed nanoparticles could reinforce the SP-based films efficiently to prepare green nanocomposite films.

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