Synthesis And Application Study Of UV-curable Waterborne Polyurethane Acrylate

Polyurethane acrylate, one of the largest amount of UV-curable resin which are widely usedin coatings, adhesives, inks, and printing industry, is a very important class of UV-curableoligomers,which combines the performances of polyurethane and polyacrylate, so it can providebetter comprehensive properties such as abrasion, chemical resistance, flexibility, and pigmentcompatibility than other types of oligomers. UV-curable system has energy-saving, fast curablespeed, high production efficiency and eco-friendly advantages,which is becoming currently one ofthe key research direction.The UV-curable waterborne polyurethane acrylate remulsion is prepared using IPDI,7112T,PEG-1000, DMPA, HEMA and TEA as the main raw materials and its properties are discussed inour study. The whole content of this paper can be divided into three parts:1. Synthesis and operation parameters optimization of polyurethane acrylate2. Influence of different polyester and polyether content on PUA resin properties3. Application study of waterborne polyurethane acrylateFirst of all, the synthesis operation parameters for preparing UV-curable PUA are explored, atwhich the dibutylamine-acetone method is adopted to measure the isocyanate group content tocontrol the reaction time and temperation in prepolymerization, chain extension and end-cappingprocess. The conditions and operation parameters are shown as below: prepolymerizationtemperature75℃, time2h; chain extension temperature80℃, time4h; end-capping temperature70℃, time4h; hydrophilic group dimethylol propionic acid(DMPA) dosage6%;triethylamine(TEA) is used as the neutralizerand the neutralization degree is90%; MEHQ was chosen aspolymerization inhibitor, its dosage was0.1%of the mount of HEMA.Based on the previous study, the effects of five different ratio between7112T and PEG-1000(1:0、7:3、1:1、3:7、0:1) on properties are explored when maintaining the polyol content at constant.The result shows that with the increase of PEG content, the particle size and viscosity descendsand climbs, respectively; the water absorption improves from7.8%to53.7%, illustrating poorwater resistance; the contact angle went down to49.1℃to57.8℃. The influence of PEGconcentration on mechanical properties are also discussed, where the breaking strength reduce to6.6MPa from28.1MPa while the elongation rise from80.9%to189.9%. The film coating isimparted with excellent optical property and its light transmittance is89.7%. The thermal andre-emulsion properties decreases and increases respectively when adding the PEG concentration.When the n(7112T):n(PEG-1000)=1:1, the PUA coating has excellent anti-chemical property andthe weight loss rate at220℃is around5%, indicating the coating has relatively good thermalresistance,electronic stability, viscosity and re-emulsion properties. The application of waterborne polyurethane acrylate remulsion synthesized by the ratio1:1isdiscussed, that includes the choices of surfactants and the influence on its UV-curable rate. Thedetailed surfactant formula is as below:defoaming agent (BYK-094)0.5%,moistening agent(BYK-346)0.5%; good stability against alkaline under the environment of0.4%AMP-95whenthe neutralization degree is65~70%; nice thickening effect after adding amount of1%PUR40, thetest time improve from9s to15s. The type and quantity of initiator affect the curing rate; for solephotoinitiator, when selecting drying at30min under50℃, it has high cured rate when linervelocity at70cm/min, the efficiency of1173is better than184and Benzoin ethyl ether.Mix-photoinitiator has better cured rate than sole one, especially when the ratio betweenphotoinitiator1173and184is1:1. The neutralizer KOH is better than TEA.The more content ofdouble C=C and solid component, the higher of the UV-curable rate.