Modified cellulose nanofibrils as enhancers for thin UV-curable matte coatings on digital printing decorative panels

Abstract

To enhance the surface properties of a thin ultraviolet (UV)-curable matte coating film (less than 20 µm) for the digital printing decorative panels, the aldehyde-containing cellulose nanofibril (CNF) coupled with hyperbranched poly (amido amine) grafting was selected as a reinforcing agent. The viscoelastic properties of the coating and physical and mechanical characteristics of the corresponding decorative panels were evaluated. The results revealed that the incorporation of the modified CNF increased the viscosity of nanocomposite coatings at low shear rates, while at shear velocities exceeding 10 1/s, the viscosity approached that of the pure coating. The modified CNFs dispersed well in coatings and the nanocomposite coating showed excellent stability. Moreover, the incorporation of CNF clearly enhanced the tensile strength of the coating film. Additionally, the modified CNF physically and chemically bonded to the polymer chains within the UV-curable coating. Furthermore, the modified CNF facilitated the optimal distribution of silica in the acrylic polymer when added at 5 wt%. The panels with the modified matte coating exhibited marginally improved clarity compared to that of the original boards. Moreover, the inclusion of the modified CNF resulted in reduced gloss, enhanced hardness, and improved yellowing resistance compared to the original panels, thereby enhancing the quality of the new product.