UV Cureable Waterborne Polyurethane-Acrylate Dispersions

The UV curable waterborne coatings has both the advantages of UV curable coatings and waterborne coatings, such as environmental friendly, fast curable speed, energy saving, excellent performance of film,etc. It has been an important direction of coatings. The polyurethane-acrylate dispersions(PUAD) coatings has been researched and applied more than others for its best performance.In this paper, two series of PUAD were prepared by different synthesize mthods. PUAD-1 was prepared by toluene diisocyanate(TDI), poly(propylene glycol)(PPG), 2-hydroxyethyl acrylate and a compound dimethylol propionic acid (DMPA). PUAD-2 was synthesized through the reaction of Epoxy acrylic(EA), PPG and DMPA. Both the optimum conditions of the synthetic reactions and the effects such as resin framework and cosolvent content were studied. The effects of the type and concentration of photoinitiator on curing rate were discussed in detail. The properties of UV-cured films of PUAD were also determined.The results suggested that with the adding of cosolvent acetone, the time of the Phase transition point was shorted and the dispersion of prepolymer was better. However, excessive acetone content fallen down the reaction temperature and reaction rate was declined. With the increasing of content of hydrophilic groups, hydrophilicity and dispersability of emulsion improved whereas the viscosity increased. Glycol was uesd to improve the ratio of hard-segment/soft-segment, so increased the glass transition temperature(Tg) and the films can tack free when the water was removed that can be touched or stacked. During the synthesing of EA, reaction rate was accelerated with the increase of temperature, however,the double bond may polymerize if the temperature was too high caused by the too fast reaction rate. Reaction rate was accelerated remarkably with the increased of catalyzer. In regard the properties of UV-cured films, the films curing rate increased with increasing of the content of photoinitiator, and the Double bond conversion rate was increased as well. The Hardness was improved Significantly after UV-cured.Both kinds of PUAD had good properties but PUAD-2 has better water resistance and solvent resistance than PUAD-1.