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.

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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.

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.

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.

Herein, we present a facile reinforcement method for the large-scale fabrication of highly flexible, mechanically stable, temperature-resistant ceramic lightweight membranes based on the cross-linked assembly of zirconia–silica (ZrO2–SiO2) nanofibrous and montmorillonite (MMT) nanosheets through electrospinning and a subsequent calcination process. The resulting MMT@ZrO2–SiO2 membranes exhibit high flexibility with a bending rigidity of 0.2 cN mm–1, robust mechanical performance with a tensile strength of up to 1.83 MPa, robust fire resistance, and temperature-invariant mechanical stability from −196 to 1000 °C. The thermal superinsulation with a thermal conductivity as low as 0.026 W m–1 K–1 and the improved mechanical strength can be attributed to the cross-linked interfacial interaction between the ZrO2–SiO2 nanofibers and the MMT nanosheets. Additionally, a firefighter uniform with MMT@ZrO2–SiO2 membranes inside features a superior thermal protective property up to the A2 level (combined flame and radiant exposure) and an excellent fire resistance of up to 1000 °C, which is ideal for next-generation firefighter uniform manufacturing.

Reported herein is the synthesis of biobased and sustainable chitosangraf t-castor oil (CHI-g-CO)copolymer that can be used for paper coating. CHI-g-CO was obtained via chemical grafting of castor oil-capped isocyanate (CO-capped-NCO) onto a chitosan polymer backbone. The CHI-g-CO copolymer was then employed as a waterborne coating for Kraft unbleached paper to render the coated paper both water-and oil-resistant. The formulation of the CHI-g-CO-coated paper was optimized by using the response surface methodology. The oil and water resistances of the coated paper substrates were determined via kit rating measurements and Cobb60 value tests, respectively. Water and oil contact angles were also determined for the coated paper. In addition, the water vapor permeability and mechanical properties of the coated paper were evaluated. Scanning electron microscopy (SEM) was also used to evaluate the effect of the coating on the microstructures and the porosity of the paper. Considering the biobased nature of the coating materials (e.g., chitosan and castor oil), this fabrication strategy can offer an environmental-friendly, sustainable, and economical approach toward water-and oil-resistant paper.

Biodegradable coated paper materials represent one of the most promising alternatives to petroleum-based materials, including plastics and plastic−paper composite materials. Herein, fully biodegradable and food-safe coated paper substrates are reported with excellent water-and oil-resistant properties. The fabrication approach is facile and economical and utilizes a dual-layer coating that is obtained via the application of a base layer comprising polyvinyl alcohol to offer oil repellency and the subsequent application of a zein-based coating as a hydrophobic top layer. The water and oil resistances of the obtained coated paper were evaluated based on their Cobb60 values, water vapor transmission rate, kit rating, and contact angles. The obtained coated paper shows outstanding water-and oil-resistant performance with Cobb60 values below 3.00 g/m 2 and kit ratings reaching up to 12/12. Scanning electron microscopy results validated the absence of any pores on the coated paper. Thermogravimetric analysis was performed to determine the thermal stability along with the coating content of the paper substrate. The closed-loop nature of this approach was validated via pulp recovery from coated paper with benign solvents.