In Michigan, researchers from Michigan State University reported in ACS Applied Polymer Materials a synthesis of biobased and sustainable chitosan-graft-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 using the Response Surface Methodology. The oil- and water-resistance of the coated paper substrates were determined via kit rating measurements and Cobb60 value tests, respectably. 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.