Water-Repelling and Reinforced Kraft Paper by Biobased Coating with Robustness, Compostability, and Mulching Potential

Growing environmental concern has led to an increase in the demand for ecofriendly coatings for paper. The use of renewable feedstock in place of synthetic raw materials is generating much interest in new scientific and technological developments. In this regard, we developed a biobased coating material using crosslinked alkyl chitosan with the objective to enhance the properties of kraft paper. Here, we used simple 1,4 conjugate addition between chitosan (Ch) and pentaerythritol triacrylate, followed by octadecyl amine (ODA), producing crosslinked ODA-grafted chitosan (Ch-ODA). The formation of Ch-ODA was confirmed by FT-IR and solid-state ¹³C NMR spectroscopic studies. The dispersion of Ch-ODA was used for the dip-coating of kraft papers, and such coated kraft papers showed significant improvement in mechanical properties (tensile index: from 17.1 to 32.8 N m/g), hydrophobicity (water contact angle (WCA): from 81.5° to 119.8°), good tolerance to sandpaper abrasion (WCA: 112–139° after 100 cycles), and adhesive tape peeling (WCA: 113°–139° after 10 cycles). The impact of the coating on the porosity of the kraft paper was analyzed by scanning electron microscopy. The coated kraft paper was found to be compostable in soil, and we explored its potential use in mulching.