Production and evaluation of the properties of wood and bacterial cellulose layered nanocomposite containing epoxy resin

Background and objectives: In the last two decades, sustainable biological nanomaterials such as nanocellulose (bacterial nanofibers cellulose and wood cellulose nanofiber) have received much attention from researchers to produce products in various fields. Biocompatibility, biodegradability, renewability, cheap and plentiful raw material availability, appropriate mechanical properties, and safety are among the most important properties of biological nanomaterials. Based on these properties, many applications have been created for it. One of these products is nanofilm, which is formed by creating hydrogen bonds between cellulose nanofibers, and no additives or adhesives are used in its production. When bacterial cellulose nanofibrils (BCNF) and wood cellulose nanofibers (WCNF) are used as a film as reinforcement in the construction of layered nanocomposites, due to the presence of cellulose network structure show excellent reinforcement ability. In recent years, the focus on nanocomposite production, optimizing its properties, and using high-tech products is increasing. Considering the technical and practical importance of nanofibrocellulose, cellulose nanofilm (layer), and nanocomposite prepared them, as well as the need for investigation and evaluation of these products as much as possible for future applied research, this study, is intended to determine the physical and mechanical properties of cellulose layered wood nanocomposite and bacteria be examined and compared.
Materials and methods: wood cellulose nanofiber gel and bacterial cellulose nanofiber film were used for this study. Tomake wood cellulose nanofiber layered nanocomposites, first, wood cellulose nanolayer was made using wood cellulose nanofiber and vacuum-filtration method .In the next step, the solvent displacement of nanolayers was done with ethanol and acetone several times. Then, epoxy resin, hardener, and acetone were mixed with a ratio of 20:10:70 and placed on a magnetic stirrer to remove bubbles. In the next step, the cellulose nanolayer was coated with epoxy resin, and 4 layers were placed on top of each other, and then layered nanocomposite with a heat press machine. They were dried for 3 hours at 60°C. The manufacturing steps of bacterial cellulose layered nanocomposite are similar to wood cellulose layered nanocomposites, with the difference that to prepare bacterial cellulose nanolayer, the bacterial cellulose nanofiber film was dried in a hot press at 70°C for 3 hours, and in the next step, the related layered nanocomposite was made. To investigate the properties of the resulting nanocomposites, various tests such as scanning electron microscopy (FESEM), X-ray diffraction (XRD), infrared spectroscopy (ATR-FTIR), static tension and water absorption were used.
Results: The results showed that the average diameter of bacterial nanocellulose and wood nanocellulose was 45±15 and 38±16 nm, respectively. The water absorption of layered nanocomposite was lower than the nanolayer prepared both nanostructures. The XRD peaks of bacterial nanocellulose and wood nanocellulose are different , and their crystallinity was calculated as 87% and 69%, respectively. Elastic strength, Young's modulus, and strain of the layered nanocomposite prepared of bacterial nanocellulose were higher than the related values of the layered nanocomposite prepared of wood nanocellulose.
Conclusion: layered nanocomposites prepared of cellulose nanofibers have shown suitable physical and mechanical properties such as low water absorption and high resistance. Therefore, based on these properties and the growing trend of related research, it is expected that shortly find wider applications in the fields of aerospace, automobile, medicine, medical engineering, food industry, filmmaking, electronics and magnetism, etc.
Keywords: epoxy, bacterial cellulose nanofiber, wood cellulose nanofiber, nanofilm, layered nanocomposite.