| With the increasing attention on environmental protection and health, solvent-borne coatings will be restricted because of its emission of Volatile Organic Compound (VOC) and its pollution to environment. Waterborne coatings are becoming the development trends of coatings technology. Because of its environment-protection, excellent properties, flexible design of molecular structure and molecular weight, the self-emulsified waterborne polyurethane coatings have become one of the hot spots and key points in the present coatings industry. However, because of some shortcomings, such as the yellowing, low solid content, low hardness and bad water-resistance, the self-emulsified waterborne polyurethane coatings need to be modified effectively.A series of waterborne polyurethane (WPU) dispersions and waterborne polyurethane-acrylate (WPUA) hybrid dispersions were prepared and characterized. Their main materials were 1, 6-hexamethylene diisocyanate (HDI) trimer, toluene diisocyanate (TDI), polyether binary alcohol (N220), 1, 4-butanediol (BDO), dimethylol propionic acid (DMPA), epoxy resin (E-20), methyl methacrylate (MMA). The effect factors on dispersion properties and film properties, such as the initial and total mole rate of NCO/OH, HDI trimer/TDI mole ratio, dimethylol propionic acid (DMPA) contents, epoxy resin (E-20) contents, and methyl methacrylate (MMA)/polyurethane (PU) mass ratio, had been investigated. The optimal technological parameters of preparation of the polyurethane-acrylate (PUA) dispersion were as the following condition. The initial mole ratio of NCO/OH was 11~13.The total mole ratio of NCO/OH was 1.2~1.4.And the HDI trimer/TDI mole ratio was 10.5%. The contents of DMPA, E-20, MMA were about 6.0~7.0%, 3.0~5.0%, 30%, respectively.In addition, a series of waterborne polyurethane (WPU) dispersions with high solid content and low viscosity were prepared and characterized. Their main materials were polyester diols (PBA), polyether binary alcohol (N220), 1, 6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 1, 4-butanediol (BDO), dimethylol propionic acid (DMPA) and epoxy resin (E-20). The solid content of the dispersions were about 45%. When the molecular weight of polyester diols was 2000, the NCO/OH (total) molar ratio was 1.35 ~ 1.50, polyether/polyester mass ratio was 1:4, HDI/IPDI molar ratio was 1:3, the WPU dispersions with high solid content and low viscosity were easily prepared.The WPU and WPUA dispersions were characterized by Fourier Transform Infrared (FTIR), Malvern Laser Particle Analyser, Different Scanning Calorimeter (DSC), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and TG analyser and Minimum Filming Temperature (MFT). The TEM images show the particles of WPUA have obvious spherical core–shell structure. The TG and MFT analysis show excellent heat resistance and low temperature performance of the WPU dispersions with a high solid content. |
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