KOBAYASHI Airi, a second-year pre-doctoral student in the Applied Chemistry Program at the Graduate School of Science and Technology (NAGAI Kazukiyo Lab.), won the Student Poster Award at the 34th Annual Meeting of the Society of Packaging Science & Technology, Japan held at the Etchujima Campus of the Tokyo University of Marine Science and Technology on August 28 and 29, 2025. The presentation title is “Water vapor permeability, solubility, and diffusivity of chitosan acetate films,” selected from papers submitted from both domestic and international sources.
The depletion of fossil resources, the primary raw material for plastics, is currently a major concern. Consequently, attention is turning to the use of biomass resources — non-depletable alternatives to fossil fuels — with particular focus on balancing their allocation between food and industrial feedstocks. We are focusing on chitosan, a natural polymer obtained by deacetylation of chitin, which can be harvested from inedible parts such as crab and shrimp shells.
Chitosan is insoluble in water, but when acetic acid is added, it forms a salt that readily dissolves in water. Furthermore, in general, water-soluble polymers deform when just exposed to water vapor. However, KOBAYASHI proceeded with her research unconstrained by this conventional wisdom and discovered that specific chitosan salts are water-soluble yet resistant to water vapor and possess water vapor barrier properties. She also elucidated the mechanism behind this barrier effect.
In this review, the design of packaging materials using chitosan and acidic aqueous solutions — substances safe for humans, animals, and plants that do not adversely affect the global environment — and the experimental verification of their properties were highly evaluated.
