Water resistance of paperboard packaging was improved by developing a hierarchical surface roughness structure through double-layer coating. Combination coating methods for the first layer were performed by rod coating containing kaolin or calcium carbonate (CaCO₃) particle mixture in native starch solution as a coating formulation. The second layer coating was conducted by polylactic acid (PLA) electrospraying. Kaolin or CaCO₃ average particle sizes of 0.5, 1.0 and 10 μm were prepared at 5%(w/v) and mixed into a 1.0% native starch solution for the first layer coating, while PLA electrospraying was set at 1%, 0.25% and 0.125% (w/v). Coating weight significantly increased after first layer coating and after PLA electrospraying, proportional to increase of particle size and PLA concentration. Surface roughness significantly decreased after first layer coating and further decreased after second layer electrospraying due to deposition of PLA particles in the valley areas of the pre-coated layer. PLA electrospraying at all concentrations significantly promoted increase of water contact angle regardless of pre-coating formulations. Water contact angle reached superhydrophobic level at 151.29 degrees for 0.05 μm of CaCO₃ pre-coating with additional 0.125% (w/v) PLA electrospraying. The PLA nanoparticles (Ra = 0.036 μm) reduced the contact area of water molecules, enhancing water repellency. For water vapor transmission rate (WVTR), 0.05 μm kaolin pre-coating with 0.125% (w/v) PLA showed optimal improvement as a plate-like shape obstructed the water vapor. Double-layer coating improved mechanical properties when small particles and lower PLA concentrations were applied.

通过双层涂层开发出分层的表面粗糙度结构，提高了纸板包装的耐水性。通过在天然淀粉溶液中包含高岭土或碳酸钙（CaCO ₃）颗粒混合物的棒涂作为涂层制剂，进行第一层的组合涂层方法。第二层涂覆通过聚乳酸（PLA）电喷涂进行。高岭土或碳酸钙₃分别以5％（w / v）制备0.5、1.0和10μm的平均粒径，并混合到1.0％的原生淀粉溶液中进行第一层涂层，而PLA电喷涂设置为1％，0.25％和0.125％（ w / v）。在第一层涂层后和PLA电喷涂后，涂层重量显着增加，与粒径和PLA浓度的增加成比例。由于PLA颗粒沉积在预涂层的凹谷区域，第一层涂层后表面粗糙度显着降低，第二层电喷涂后表面粗糙度进一步降低。不论预涂配方如何，在所有浓度下进行的PLA电喷涂都可显着促进水接触角的增加。0.05μm的CaCO _3的水接触角达到151.29度的超疏水水平额外进行0.125％（w / v）PLA电喷涂的预涂层。PLA纳米粒子（Ra = 0.036μm）减少了水分子的接触面积，增强了拒水性。对于水蒸气透过率（WVTR），采用0.125％（w / v）PLA的0.05μm高岭土预涂层显示出最佳的改善，因为板状形状阻碍了水蒸气。当使用小颗粒和较低的PLA浓度时，双层涂层改善了机械性能。