Paper is envisioned as an alternative to plastics in certain applications to overcome the problems associated with the excessive use of plastics. Water and oil repellency is one of the key requirements for many packaging applications. However, the existing water and oil repellent paper products have poor biodegradability and are also difficult to recycle. Here we have reported an inexpensive approach for preparing recyclable water and oil repellent paper products using biobased materials such as starch and zein. The application of dual-layer coatings of starch and zein onto a Kraft paper yielded a “Cobb 60” value of 4.81 g/m2. In addition, the coated paper exhibited excellent grease resistance with a kit rating of 12/12. Scanning electron microscopy characterization confirmed that the dual-layer coating filled the pores of the paper substrate. The mechanical properties, as well as the thermal stability of the paper, were maintained after the coating treatments, and thus this coated paper has potential for widespread use in our daily lives while also minimizing the environmental footprint of packaging materials.

Coated paper substrates are used for a wide range of applications. The biggest challenge that remains unsolved with regard to coated paper is its recyclability. Herein, we report a unique approach that relies on 100% biobased and biodegradable food-safe materials for water- and oil-resistant papers. A 35-liner paper was coated with an oil-resistant chitosan solution and subsequently by a hydrophobic zein solution. The resultant chitosan–zein-coated paper showed remarkable water resistance (Cobb 60 value of 4.88 g/m2) and oil repellency (kit rating 12/12). Scanning electron microscopy (SEM) analysis was used to determine the changes in the surface texture of the paper before and after coating treatment. The excellent mechanical properties of the coated paper were retained after the coating treatment. In addition, the pulp was recycled from the chitosan–zein-coated paper to validate the recyclability of this novel approach.

As reported herein, a bilayer coating approach using poly(vinyl alcohol) (PVOH) and zein is employed to enhance the water vapor and oxygen barrier properties of paper materials. The coating was applied onto three different types of paper substrates to study the general applicability of this approach. The bilayer-coated paper samples exhibited a reduction of up to 65% in their water vapor transmission rate in comparison to the corresponding uncoated paper substrates at 23 C and 50% relative humidity. In addition, the bilayer-coated paper samples showed at least a 40-fold decrease in oxygen transmission rate from that of the uncoated paper samples. In addition, the coated paper showed excellent thermal stability and mechanical properties. Scanning electron microscopy confirmed that the obtained coated paper has a smooth texture without pores. Pulp was recovered from the coated paper by washing with water/ethanol. Thus, this work provides a unique coated paper with excellent barrier properties and therefore has the potential for real-world application as an alternative to single-use plastics.

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