Zein and PVOH-Based Bilayer Approach for Plastic-Free, Repulpable and Biodegradable Oil- and Water-Resistant Paper as a Replacement for Single-Use Plastics

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/m2 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.