Chitosan–Graft–Poly(dimethylsiloxane)/Zein Coatings for the Fabrication of Environmentally Friendly Oil- and Water-Resistant Paper

Excessive use of synthetic nondegradable polymers has led to the proliferation of microplastics in the oceans as well as polluted landscapes. Herein, we report a new sustainable approach for the development of oil- and water-resistant paper. Chitosan–graft–poly­(dimethylsiloxane) (CHI–g–PDMS) copolymers were prepared by the reaction of poly­(dimethylsiloxane) (PDMS) with chitosan. The CHI–g–PDMS graft copolymer was characterized by ¹H nuclear magnetic resonance (NMR) analysis. Zein, a coproduct of the bioethanol industry, was blended with CHI–g–PDMS in a water/ethanol solution and subsequently applied as a coating on an unbleached Kraft paper. The coated paper substrates were evaluated for their oil resistance via kit rating and oil contact angle measurements, while the water resistance was determined via Cobb60 value and water contact angle measurements. In addition, the pulp was successfully recovered from the coated paper. Scanning electron microscopy (SEM) analysis was used to investigate the variation in the texture of the paper before and after the coating treatment. Thanks to the efficient pulp recovery and the biodegradable nature of the coating ingredients (chitosan and zein), this novel water- and oil-resistant paper will positively impact the environment by offering potential replacements for single-use plastic applications, and will thus help to minimize ocean microplastics and the burdens placed on landfills.