| Waterborne polyurethane emulsion (WPU) of vinyl-terminated polyurethane was prepared by using toluene diisocyanante (TDI), polyether diol (N220), dimethylol propionic (DMPA), Triethylamine (TEA), hydroxyethyl methacrylate (HEMA) as monomers with self-emulsification method. The effects of the NCO/OH ratio, DMPA and HEMA content on PU latex particle size and its distribution, water-resistance and hardness of the PU film were studied.In order to improve the properties of WPU, the acetoacetylated polyacrylate (PA) emulsion was prepared by using butyl acrylate (BA), methyl methacrylate (MMA), acetoacetylate methyl methacrylate (AAEM) and other monomers. The WPU was modified by blending the prepared PU and PA emulsion.The composite PA/PU polymer can be self-crsslinked through the Michael reaction between the acetoacetoxyl groups in the PA chains and the vinyl groups in the PU chains. The effects of the HEMA content and the PA/PU ratio on the particle size and the storage stability of the composite emuldion, and the water-resistance and the hardness of the PA/PU film were investigated. TEM, mechanical test and the thermodynamic analysis were used to check the particle morphologies and the properties of films of WPU emulsion. The effect of the temperature on the film properties was also investigated and the results indicated that the higher termperature can accelerate the crosslinking and therefore improve the properties of the film.In the present work, the optimal application properties of the PA modified PU emulsion can be obtained with the conditions as: NCO/OH=1.6~2.0, HEMA/NCO=0.2~0.4 and PU/PA=1~1.5.
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