ZnO nanoparticles enhanced hydrophobicity for starch film and paper

The incorporation of ZnO NPs (2% wt) in the starch solution under ultrasonic and magnetic mixing enhanced the hydrophobicity of starch film significantly; and the coated papers also showed high contact angles, leading to a promising process suitable for hydrophobic modification of green-based materials. [Display omitted] •ZnO NPs were incorporated into starch solution via improved approach for mixing.•The resulting starch film and coated paper are highly hydrophobic.•Stable DCAs of were obtained for the starch film containing 2% (wt) ZnO NPs.•SEM images revealed an enhanced roughness on films and intact coated layer on papers. Since hydrophobicity can improve the usability and functionality of materials in humid condition, enhancing the hydrophobic behavior of starch films or papers is of importance. In this work, ZnO nanoparticles (NPs) were introduced into the starch solution under ultrasonic and magnetic-stirring, followed by cast filming and paper coating. The contact angles of resulting film and coated paper containing 2% (wt) NPs were increased from 85.73° to 121.45°, 64.47° to 103.94°, respectively. The results from comprehensive characterizations confirmed the hierarchical structure created by ZnO nanoparticles on the surface of starch film as well as the formation of intact layers on coated paper. The excellent miscibility between starch and ZnO NPs was also achieved. The approach developed is promising and facilitates the hydrophobic modification of green-based materials.