Effects of MDF surface treatments on the coating performance of UV printing

UV curing digital inkjet printing is an efficient surface decoration technology. After exposure to high energy ultraviolet light, the digital printing pattern is cured immediately and forms a thin film. This technique shows significant advantages of low energy consumption, fast and reliable room-temperature curing, etc. The UV curing inkjet printing can be used in numerous applications such as textiles, wall paper, glass, wood-based products, metal, plastic, marble, leather, etc. It is not only able to print 2D pattern, but could realize 3D decoration by stacking the polymeric ink. Especially, when being used in wood-based furniture finish, the UV curing inkjet printing is environmentally friendly and able to print customized and high-resolution digital patterns comparing with other surface decoration methods, such as coating and decorative papers. In order to achieve the best UV curing coating effects, it is of great importance to optimize the wood-based substrate pre-treatment method to improve the coating performance. In this work, MDF was selected as the substrate for the UV inkjet printing due to its wide application in the furniture industry. Firstly, the surface roughness and surface contact angle of the MDF were measured after treated by sandpaper with different meshes to recognize the effects of surface mechanical treatment. By characterizing the performance of UV curing coatings, the optimal mesh number of sandpapers for the MDF treatment was determined. Secondly, four different polyurethane (PU) or polyester (PE) primers were applied to MDF before the UV inkjet printing. The UV curing coating performance, including the glassiness, adhesion, abrasion resistance, hardness and water adsorption, were characterized to obtain the optimal pretreatment method. The results showed that, after the MDF substrate was polished with 400# sandpaper, the surface roughness was relatively low and the surface wet ability was good. The UV curing coating glossiness and adhesion were relatively high. By comparing different types of primers and the brushing times, it could be concluded that the primer had a significant influence on the properties of the coating due to the relatively low coating thickness. By pretreating the MDF substrate with white PU primer 2-3 times, the UV curing coating showed improved adhesion and contrast, as well as low water adsorption.