Waterborne blocked isocyanate crosslinked cationic starch/polyvinyl alcohol coating for improving barrier and mechanical properties of paper-based materials.

Green and renewable paper-based packaging materials are gaining more and more popularity, however, issues such as poor barrier and mechanical properties need to be solved. Herein, cationic starch (CS) and polyvinyl alcohol (PVA) were used as paper coatings, with waterborne blocked isocyanate (WBI) serving as a cross-linking agent to eliminate the hydroxyl groups. CS/PVA and CS/PVA/WBI were coated on kraft paper using a bar coating machine at 8 g/m2. The composite paper exhibited excellent liquid and gas barrier properties with water and oil absorption values of 8.28 and 9.60 g/m2, which were reduced by 71.27 % and 57.29 %, respectively, compared to the control sample. The WVTR and OTR were reduced from the original 2393.38 g/(m2⸱24 h), 13,235.68 cm3/(m2⸱24 h⸱0.1 MPa) to 600.20 g/(m2⸱24 h) and 951.25 cm3/(m2⸱24 h⸱0.1 MPa), respectively. Furthermore, the composite paper showed high mechanical strength (tensile strength: 11.51 kN/m, tear strength: 634.73 mN) and retained nearly 40 % of its tensile strength after 15 min of immersion in water. In addition, the composite paper had good organic solvent barrier and recyclability. This paper presents a simple and effective method for improving the barrier and mechanical properties of paper-based materials, and makes a new attempt for the research and development of paper-based packaging materials.