The utilization of carbon nitride to reinforce the mechanical and thermal properties of UV-curable waterborne polyurethane acrylate coatings

The waterborne polyurethane-acrylate (WPUA and Wsi-PUA) oligomers were prepared by anionic self-emulsifying method, using isophorone diisocyanate (IPDI), polyethylene glycol (PEG), dimethylol propionic acid (DMPA), vinyl hydroxyl silicone oil (VHSO) and hydroxyethyl methyl acrylate (HEMA) as raw materials. Then, a series of UV-curable waterborne Wsi-PUA–C 3 N 4 composites containing different content of g-C 3 N 4 were obtained with oligomer and photoinitiator Darocur 1173. FTIR, XRD, TEM, SEM, and TGA were employed to investigate the structure, morphology and thermal property of the Wsi-PUA–C 3 N 4 composite films. The effect of g-C 3 N 4 content on the performance was also investigated. The mechanical performance, water resistance and gel content of UV-PUA films were measured. It was found that with g-C 3 N 4 particle was introduced into Wsi-PUA oligomer, the hardness, tensile strength, gel content, water resistance and thermal stability of composite films were significantly augmented. Moreover, when the content of g-C 3 N 4 was 1.0   wt.%, the UV-curable film had the best mechanical property. The obtained composite is promising for a number of applications, e.g., for protecting the surfaces of metal and wood.