All-cellulose Materials Adhered with Cellulose Nanofibrils

Abstract

All-cellulosic materials called vulcanized fibers, in which cellulose fibers are gelatinized and adhered to each other by zinc chloride, have been known for more than 150 years. However, the swelling and adhesion mechanisms have not yet been clarified. In this study, X-ray diffraction, scanning electron microscopy (SEM) ，and specific surface area(SSA)analyses of cellulose sheets treated with different concentrations of aqueous zinc chloride solutions were performed to elucidate the behavior and mechanism of cellulose fibers adhering to one another during ZnCl 2 treatment. The X-ray diffraction analysis revealed that the ZnCl 2 treatment caused swelling of intercrystalline regions but did not significantly change the original crystal structure of cellulose I. The SEM observation of the freeze-dried sheets revealed less aggregated structures of the fine fibers and the existence of three-dimensionally entangled cellulose nanofibrils(CNFs)between the cellulose microfibers. The increased SSA values of the freeze-dried sheets supported the formation of CNFs during the ZnCl 2 treatment. These results indicate that in these all-cellulosic materials, CNFs are entangled and form dense networks that are not completely detached in water. In addition, the presence of moisture leads to more viscoelastic behavior as a result of slip between the CNFs during tensile testing.

All-Cellulose Material Prepared by Zinc Chloride Treatment

“…Using this method, the microstructure of cellulose before and after zinc chloride treatment and washing was observed (Nemoto et al 2018). Fig.…”

“…After zinc chloride treatment, the nanofiber network region can be seen between the cellulose microfibers. As the zinc chloride concentration increases, the micro-sized cellulose fiber region decreases and the nanofiber network region increases (Nemoto et al 2018).…”

“…Since the cellulose fibers adhered to cellulose in the vulcanized fiber, it can be regarded as a composite material made of the same component. Today, the material is called an all-cellulose material, in contrast to materials containing petrochemical-derived components (Nemoto et al 2018).…”

“…Advances in cellulose nanofiber (CNF) technologies have widened the knowledge about cellulose, which prompted us to reevaluate the matured vulcanized fibers. With improved basics of CNF and analytical techniques, the classical zinc chloride treatment of cellulose has been reviewed from a new perspective (Nemoto et al 2018;Burger et al 2020). In this report, we briefly describe the history, production process, and structural characteristics of vulcanized fibers and discuss the role of zinc chloride during the production process.…”

Development of Composites Using Cellulose Nanofiber and Functional Materials

“…CNF are a highly anticipated material for the next generation. Tapping into their advantages, CNF are used for the development of film and other packaging materials, filters, rubber, and reinforced resins using CNF-resin composites [3][4][5][6][7] .…”