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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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A novel biodegradable protein-based material (UMSPIE) that consists of natural polymer soy protein isolate (SPI), ultrasonic-modified montmorillonite (UMMT), and ethylene glycol diglycidyl ether (EGDE) was produced by solution casting. Fourier infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TG), and scanning electron microscopy (SEM) were used to characterize the chemical structure and micro-morphologies of as-synthesized protein-based composite films. The results showed that the interlayer structure of MMT was destroyed by ultrasonic treatment, and the hydrogen bonding between SPI chains and the ultrasound-treated MMT plates was enhanced. The synergistic effect of UMMT and EGDE on SPI molecules made the network structure of the UMSPIE film denser. In addition, the mechanical and barrier properties of the as-synthesized films were explored. Compared with pure soy protein film, the tensile strength of the UMSPIE film has an increase of 266.82% (increasing from 4.4 to 16.14 MPa). From the above, the modified strategy of layered silicates filling combining crosslinking agents is considered as an effective method to improve the functional properties of bio-based polymer composites.