UV-curable Waterborne Polyurethane Acrylate Resin

With petroleum resources gradually exhausted and environment pollutionseriously caused by non-degradable synthetic polymer, the development andutilization of renewable resources and environmental friendly materials as one of thefrontiers in polymer science has attracted more and more attention.Waterborne UV-curing systems have advantages of non-contamination,nontoxicity,non-skin irritation and safety of production, and become an attractiveresearch and application areas. It has become one of the main development directionof UV-curing systems and the green environmental product for 21st century.In this article, two series of waterborne UV-curing polyurethane acrylate (PUA)resins, which include polyether PUA and polyester PUA were prepared from differentmaterials.As for polyether PUA, UV-curable waterborne polyether PUA resin wasprepared from TDI,polypropylene glycol(PPG),dimethylol propionic acid (DMPA)and HEA.As for polyester PUA, UV-curable waterbome polyester PUA resin was preparedfrom TDI,polybutylene adipate glycol(PBA),dimethylol propionic acid (DMPA)and HEA. The synthesis, hydrophilicity, the effects of hydrophilic group content andneutralization degree on emulsions were studied for above-mentioned two kinds ofPUA resins. The effects of neutralization degree,drying condition,the type andconcentration of photoinitiator,neutralization agent type and structure of prepolymerson curing rate were discussed in detail. The properties of UV-cured films were alsodetermined.The results show that with the increase of content of hydrophilic group andneutralization degree, hydrophilicity of molecular chains increases and particle sizesdecrease whereas emulsion dispersability and stability both increase. As for polyetherPUA, Darcocur 4265 is preferred and curing rate is fastest when neutralization degreeis 80%. As for polyester PUA, Irgacure 1000 is preferred and curing rate decreases with the increase of neutralization degree. Curing rate is fastest when the amount ofphotoinitiator is 3%. Drying condition has considerable impact on curing rate andcuring rate is fastest without drying. When NaOH is used as neutralization agent,curing rate is faster than that of triethylamine UV-cured films of the said two kinds ofPUA resins have good water resistance,solven resistance and acid resistance, butstrong alkaline resistance thereof is on general level.In addition, the research finds that the tensile strength and tear strength allincreased by adding nano-silica to the recipe of polyurethane-acrylate system, and theviscosity increased simultaneously. The curing speed of the adhesive became slowerbecause of the absorption of UV-light by nano-silica.The polyurethane-acrylate formed IPN structure with the added HTPB, and theadhesion properties of adhesive enhanced obviously. While with the additionalamount of HTBN increasing, the adhesion properties of adhesive raised at first andthen decreased, the most suitable amount of which was 8%. The structure of theadhesive became more regular with the addition of HTBN. The curing speed bothdecreased with the addition of liquid rubber.