Preparation and properties of green UV‐curable itaconic acid cross‐linked modified waterborne polyurethane coating

Abstract Waterborne polyurethane (WPU) coating, as a kind of green product, can replace solvent polyurethane coating, but its application in the field of coating is limited since its defects such as slow curing efficiency, low strength, and water resistance. In this study, a trifunctional itaconic acid‐based crosslinking agent (IHA) was synthesized from itaconic acid and hydroxyethyl acrylate. A series of green UV‐curable WPU coatings were prepared by introducing IHA into WPU prepolymer in different proportions (2.5 ~ 10 wt.%). IHA posed as crosslinking agent in WPU, which can not only enhance strength, but also accelerate curing rate in WPU coatings. The results demonstrated that the gel content and hydrophobic angle of the modified WPU coating (WPU‐IHA) are increased by 25.6% and 34.8°, respectively, indicating a good water resistance. Most notably, due to the increase of crosslinking degree and the decrease of chain mobility, the UV‐curable WPU coating shows excellent mechanical properties with 21.9 MPa in tensile strength and a pencil hardness of 5H, which is substantially higher than that of pure WPU coatings. Therefore, the IHA shows great potential to substitute petroleum‐based crosslinking agents in the preparation of environmentally friendly UV‐curable WPU coatings with high strength and good surface scratch hardness.