Modification Of Polyurethane Acrylates Coating With Cycloaliphatic Epoxy Resins

Polyurethane acrylates (PUAs) and epoxides were important members of the matrix resin of ultraviolet (UV) curable coating. However, UV curable coatings made of traditional PUAs and epoxides used to have bad etiolation resistance and weather resistance, for the aromatic structures in the molecules of them. To overcome these drawbacks, we prepared UV curable coatings based on cycloaliphatic epoxy resins (EAs) and cycloaliphatic polyurethane acrylates (CPUAs) and studied properties of them. The research work was divided into three parts: The first part:UV curable cycloaliphatic epoxy acrylate resin (CEA) was synthesized by ring opening reaction of acrylic acid (AA) and cycloaliphatic epoxy resin. The product was characterized by FTIR and NMR. The influence of reaction conditions was discussed. The results showed that when the molar ratio of acrylic acid and epoxy group was 1.03:1, the conversion rate of the reaction reached 96.58% at 120℃for about 25.8h. Prepolymers of the UV curable coatings were prepared with reactive diluents and CEA, influence of the reactive diluents on viscosity of the prepolymers was studied. UV cured films of the prepolymers was analyzed by DSC, TG and pencil hardness tester. The results showed that the glass transition temperature (Tg) of CEA cured film was 64℃and the initial decomposition temperature was 314℃. With addition of the reactive diluents, heat resistance of the cured films was enhanced. The pencil hardness of the films could reach 6H.The second part:Cycloaliphatic polyurethane acrylates (CPUAs) was synthesized with polyester diol and polyether diol, cycloaliphatic diisocyanates and 2-Hydroxyethyl methacrylate (HEMA). The products were characterized by FTIR and DSC. UV curable prepolymers were prepared with CPUAs and reactive diluents. The cured films of the prepolymers were characterized by FTIR. Thermal and mechanical analyses were executed on the cured films. The results showed that the properties of the cured films were influenced by the kind of polyols and diisocyanates.The third part:Dual photosensitive matrix resins were prepared with cycloaliphatic epoxides and CPUAs. Radical type and radical/cation type UV curable coatings were prepared with the dual photosensitive matrix resins and reactive diluents. Influence of the structures and contents of the dual photosensitive matrix resins and kind of the reactive diluents on properties of the cured films was studied. The results showed that heat resistance of the cured film made of polyester polyurethane acrylates (CSPUAs) was better than that of polyether polyurethane acrylates (CRPUA). Hardness and heat resistance of the cured film made of tri-functional reactive diluent were better than that of bis-functional reactive diluent. The temperature change resistance of all the cured films was good. Finally, the coating formulation was chosed with optimal integrated properties.