Synthesis And Properties Of Waterborne Polyurethane Varnish Modified By Epoxy Resin

Compared with solvent-based polyurethane coatings, waterborne polyurethane (WPU) coatings have high performance of the former, while also have no solvent smell, no pollution, etc. With the environmental problem increasingly more serious, the research of WPU has become the focus of society recently. Properties of waterborne polyurethane was declined with flame retardant components introduced into chain segments in order to synthesize intrinsic flame retardant WPU. So it’s necessary to modify the WPU and to obtain a kind of WPU coatings both flame retardant and having high temperature resistance and high mechanical properties.In this paper, using graft copolymerization method, E-51and ED synthesized by epichlorohydrin and4-(4-hydroxyphenyl)-1-phth-alazinone were introduced into chains of WPU as hydroxyl components, and synthesized a series of stable WPU emulsion. FT-IR and1H-NMR confirmed the structure of ED and films of modified waterborne polyurethane (EDWPU). Using thermo-gravimetric (TG), tensile and dynamic contact Angle tests, the paper mainly discussed the effects of modification on structures and properties of paint films.Experimental results showed that the best E-51content was7%, the film with excellent performance was obtained:its hardness was up to5H, the maximum tensile stress was27MPa, and the elongation at break was180%, the elastic modulus was476.7MPa,10%thermo-gravimetric was up to290℃. The film has excellent flame retardant abilities and its oxygen index was28.ED content in polyurethane chain segment was best controled in7%～10%, and emulsions had good stability were achieved. Paint films also possessed excellent performances:its hardness reached4H, and its acid and alkali resistance, impact strength, flexibility, and mechanical properties were significantly improved,10%thermo-gravimetric increased from230℃to263℃, the oxygen indexwas still up to29, the tensile strength was10.2MPa and the elastic modulus was162MPa.The modified films’ performance was far better than the unmodified and it can be widely used in coatings and adhesives.