No abstract

The current open-loop practices employed to render paper substrates water- and oil-repellent for packaging and non-packaging applications have generated ocean pollution and have placed daunting burdens on landfills.

Water-and oil-resistant materials are useful for many applications, but turning polar and porous cellulosic substrates such as paper, corrugated board, cardboard, and fabrics into a water-and oil-resistant materials is very challenging. Herein, we report an innovative method for fluorine-free water-and grease-resistant surface fabricated from a fully porous cellulosic substrate. A chitosan coating was applied to fill the pores of the paper, followed by a polydimethylsiloxane (PDMS) coating to render paper water and oil resistant. A response surface methodology (RSM) was applied to optimize the concentrations of chitosan and PDMS to obtain the desired water-and oil/grease-resistant properties. Paper coated with a load of 8.6 wt % chitosan and 2.2% PDMS showed an excellent grease/oil kit rating value of 12/12 (maximum fat resistance) as well as excellent water resistance (water contact angles of 95.2°). The coating is robust, as confirmed by solvent extraction tests of the coated paper. This coating approach was also successfully demonstrated for paperboard. Because of the simplicity of the coating application method and fluorine-free coating ingredients, these coatings will find many applications in the real world related to paper, corrugated board, cardboard, and fabrics.

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.

Paper-based materials are highly desirable as packaging materials due to their numerous advantages that include low cost, renewability, and biodegradability. However, their hydrophilicity has limited their range of applications. Reported herein is a facile and economical approach for the preparation of biodegradable water-resistant paper for food-contact applications. Commercial printing paper and cup papers are coated with melamine, which is FDA approved for food-contact applications. Subsequently, a water-repellent outer layer is applied using poly(dimethylsiloxane) (PDMS)–isocyanate. A relationship between the PDMS concentration and water contact angles (WCAs) of the obtained coating was studied. Typically, the coated cup paper and printing paper had coating loadings of 1.61 ± 1.10 and 0.93 ± 0.74 wt %, respectively. After the coatings had been applied, the WCAs were very high (>125°), and water absorption had decreased by 70% for printing paper and by 35% for cup paper. Considering the facile fabrication method and the low-cost food-safe raw materials, herein, this approach will have great potential for the large-scale production of materials for use in food- and nonfood contact applications.