UV Curable Cationic Electrodeposition Coating Of Modified Acrylic Resin

Acrylic resin containing N, N-dimethyl amino group and vinyl group applicable for UV curable cationic electrodeposition coating was synthesized via radical polymerization of acrylic monomers followed by modification with methacrylic oxyethyl isocyanate (MOI). The effect of the content of dimethylaminoethyl methacrylate (DMAEMA) on the solubility, stability, and deposited yield of the electrodeposition coating were also studied. And the influence of MOI, multifunctional monomers, and photoinitiator on the curing time and properties of the film was also discussed.Infrared spectroscopy (IR) results showed the presence of vinyl group and N, N-dimethyl amino group in the modified acrylic resin, indicating that the acrylic resin applicable for UV curing and cationic electrodeposition was gotten.It was found that the dispersibility and stability of acrylic resin in water was improved greatly after introducing DMAEMA into acrylic resin. With an increase of the DMAEMA content, the amine value of the modified acrylic resin increased linearly, the particle diameter of the electrodeposition coating decreased significantly, and the stability also improved greatly. The deposited yield, coating thickness, and the water content of the deposited film before UV curing increased with increasing the DMAEMA content. Considering properties of the electrodeposition and the film, the suitable DMAEMA content in acrylic resin was around 14.4%.With an increase of MOI content, the content of vinyl group increased, but the dispersibility and solubility of the modified acrylic resin, and the stability of the electrodeposition coating in water decreased. The UV curing time, the adherence, and the water content of the film decreased with increasing MOI content. The solvent resistance and hardness of the film improved after modification of acrylic resin by MOI. Considering the properties of the electrodeposition and the film, the suitable molar ratio of MOI to 2-hydroxy ethyl methacrylate (HEMA) in acrylic resin was 0.8.The multifunctional monomer can increase UV curing speed and some properties of the film. Higher UV curing speed, better gloss, solvent resistance, adherence, and harder film can be gotten with increasing the degree of functional group. With the increase of multifunctional monomer content, the particle size of the electrodeposition coating, the deposited yield, UV curing speed of the deposited film, gloss, solvent resistance, adherence, and hardness of the film increased, while the viscosity, and stability of the electrodeposition coating, and the water content of the deposited film decreased.The photoinitiator content has great effect on both the UV curing speed and the properties of the film. The complex photoinitiators was more efficient than the single one.During the electrodeposition, the resin content, voltage, electrodeposition time, pH, and temperature have a great effect on properties of the film, such as appearance, thickness, and deposited yield.