外文文献翻译学 院 轻工学院 专 业 印刷工程 导 师 学 生 学 号 2015年3月20日UV-Radiation Curing of Waterborne Acrylate Coatings AbstractA kinetic study of the ultrafast curing of water-based acrylate resins upon UV irradiation was conducted by means of infrared spectroscopy. Under intense illumination, the crosslinking polymerization was found to occur in the driedfilm within less than one second to generate a totally insoluble polymer. The influence of a number of critical factors on the polymerization rate and cure extent has been investigated, namely the type of photoinitiator, the chemical structure of the acrylate functionalized oligomer, and the sample temperature. Coatings obtained from emulsions undergo a faster and more extensive polymerization than coatings obtained from dispersions, because of a greater molecular mobility in the soft low-modulus polymer formed. Very hard coatings were produced by the UV curing of dispersion-type acrylate resins, especially when the UV irradiation was performed at 80C on the sample emerging from the drying oven. Tg values up to 120C were reached when such resins were UV-cured at ambient temperature as 1-mm thick plates, because of the large amount of heat released during such ultrafast polymerization. UV-cured coatings made of aliphatic polyurethane-acrylates proved to be very resistant to accelerated weathering in the presence of adequate light stabilizers. Light-induced polymerization of multifunctional monomers or oligomers, also called UV-radiation curing, is one of the most efficient methods to synthetize rapidly highly cross linked polymer networks at ambient temperature. Upon intense illumination, a solvent-free acrylic resin can thus be transformed within afraction of a second into a solid polymer, totally insoluble in the organic solvents and very resistant to heat and mechanical treatments. Because of its distinct advantages, this environment-friendly technology has found a large variety of industrial applications, mainly as fast-drying protective coatings, printing inks, adhesives, and composites, as well as in photolithography to produce printing plates, microcircuits, and optical disks.UV-curable resins typically consist of a photo initiator, afunction alized oligomer, and a monomer serving as a reactive diluent to adjust the formulation viscosity. The Photo initiated cross linking-polymerization process can be represented schematically as follows: The multifunctional acrylate monomers commonly used as diluents still have a strong odor and may cause eyeand skin irritation. Moreover, they are enhancing the shrinkage process which yields internal stresses, and they may be responsible for curling and poor adhesion. Waterbased UV-curable systems appear as a promising alternative to overcome these drawbacks, water being used as the only diluent. The formulation viscosity can, thus, be reduced to the precise level required for spray or rolling application, simply by adjusting the water content. Moreover, water-based UV-cured coatings have been shown to combine the flexible properties of high molecular weight polymers with the hardness of cross linked acrylate polymers. The potential of water-based resins and their performance in UV-radiation curing has already been investigated. They proved particularly well suited to be used as screen inks and protective coatings for plastics, paper, and wood. We report here a new study on the high speed UV-curing of some commercial water-based acrylate coatings, by focusing on the influence of the photo initiator and the functionalized oligomer on the polymerization kinetics, namely cure speed and cure extent. The effect of the kind of water-based resin used (dispersion or emulsion) on the visco elastic properties of the UV-cured polymer will also be investigated, as well as the correlation existing between the degree of conversion and the polymer properties, in particular its hardness.EXPERIMENTALMaterialsThe UV-curable waterborne formulations used in this study consisted of aqueous emulsions or dispersions of acrylate functionalized oligomers containing a water soluble or water dispersible radical-type photo initiator. The compatibility of the initiator with the aqueous formulation and with the dried coating is essential to achieve its uniform distribution in the sample. Two types of photo cleavable photo initiators were used in this study:(1) Oil-soluble photoinitiators which are partly soluble in water: Darocur 1173 and Irgacure 2959 from Ciba Specialty Chemicals, and Lucirin TPO-L from BASF;（2） Oil-soluble photoinitiators which were dispersed in water: Irgacure 819 DW from Ciba Specialty Chemicals, and Esacure KIP/EM from Fratelli-LambertiThe chemical formulas of these photo initiators are given in Figure . They consist either of hydroxyl phenyl ketones or of acyl