UV-thermal Dual-cure Epoxy Acrylate Flexible Varnishes

Ultraviolet (UV) light used for coatings began in the1960s. UV curable coatings haveseveral excellent characteristics, such as fast curing speed, low energy consumption, low-volatile solvent. With gradually strengthened consciousness of environmental protection, theapplication of UV curing coating is more and more widely in recent years. However, the UVcurable coatings also have some shortcomings, such as the acquired flat and regular shapes ofthe curing objects, the limited curing depth, difficult application in colorful paints etc.Therefore, in order to make the UV technology more widely used, the dual curing technologyof the UV technology is invented at this required times. The dual curing technology not onlyretains the advantages of UV-curing, but also overcomes some disadvantages.Epoxy acrylate (EA) has been widely applied because of the advantages of excellent fastUV curing speed, resistance against the chemical corrosion, high hardness, good adhesion, etc.At the same time, it also has some disadvantages, such as the high viscosity, heavy brittleness,as well as inflexibility. In this thesis, the polyethylene glycol and the trimethylolpropanediallyl ether were used to modify the epoxy acrylate, which had successfully prepared theUV-thermal dual curing epoxy acrylate (EA) that had a low viscosity and good flexibility.This thesis firstly used polyethylene glycol and trimethylolpropane diallyl ether,respectively, to modify epoxy acrylate in order to obtain two kinds of modified EA. Themodified epoxy acrylate A was obtained by the physical mixture of the two kinds of modifiedepoxy acrylate I and II. With the investigation of the effects of raw materials, catalysts,polymerization inhibitors, temperatures, time and other process conditions, the optimalprocess conditions for epoxy acrylate A were ultimately determined. Firstly, the polyethyleneglycol modified epoxy acrylate Ⅰ was prepared and optimized when the molar ratio ofglycol and epoxy resin was0.25:1, the catalyst dosage was0.5%~0.8%, the polymerizationinhibitor was0.04%~0.05%, the reaction temperature was90℃~95℃, the reaction timewas3h~4h, respectively. Secondly, the trimethylolpropane diallyl ether modified epoxyacrylate Ⅱ was prepared and optimized in the first step of preparation when the molar ratioof epoxy and carboxyl was1:1.05, the catalyst dosage was0.5%~0.8%, the amount ofinhibitor was0.04%~0.05%, the optimum temperature was90℃~100℃respectively.The trimethylolpropane diallyl ether modified epoxy acrylate Ⅱ was prepared and optimizedin the second step of preparation when the later temperature was raised to110℃, thereaction temperature of TDI and TMPDE was80℃, the polymerization inhibitor was0.04% ~0.05%, the dosage of prepolymer was20%~25%.The modified resins Ⅰ and Ⅱ were mixed according to the equivalent ratio of3:2.Then, the vanished were prepared by the adding of such additives as the defoaming agent andthe flatting agent. After UV-thermal dual curing, a variety of mechanical properties of vanishfilms were tested. Their results showed that the modified epoxy acrylate A had severaladvantages as the low viscosity of4000mpa.s (25℃), the curing time of1h at50℃, theflexibility of1mm, the hardness of H, the impact resistance of50cm, and good thermalstability, etc.The aforementioned process was a little complex. An improved technology was inventedand tested. The modified epoxy acrylate B was prepared on the base of the modified epoxyacrylate A when the polyethylene glycol modified epoxy acrylate I reacted with TDIprepolymer to prepare the modified epoxy acrylate B. The effect of the TDI content on thepolymer surface drying time, the impact resistance, the storage stability, the wear resistance,the thermal stability and the other properties of the vanish films were discussed. The optimalcontent of TDI was23.08%. When the TDI prepolymer content was23.08%, the viscosity ofmodified resin was2398.8mpa.s, the surface drying time (50℃) was60min, the flexibilitywas1mm, the hardness was H, the impact resistance was50cm.