| UV-curable coating technology is becoming well accepted by a number of market segments due to their eco-friendly property. UV coating has several advantages (1) Excellent performance or efficient production, (2) Ecology friendly product, (3) Energy saving and (4) Economy. Since most of UV oligomers have high viscosities, lots of reactive monomers and organic solvents have been added into the coating system to adjust the viscosity for applications. Liquid monomers strongly irritate human skins, and do harm to human body together with bad odor.In this study, some water borne UV resins were evaluated by testing their basic properties, e.g. solid content and film forming. One group of those resins was acrylic emulsion. The other is poly urethane-modified acrylic resins. After resin evaluation, some testing was carried out regarding photoinitiator’s compatibility with resins and photoinitiator’s reactivity to resins. By means of evaluations and testing on those resins. UCECOAT 7200 and Alberdingk Lux 250 were screened out for future formulation development. And then investigations were started in respect with influential ingredients on scratch resistance. In this step, the starting formulation was prepared based on UCECOAT 7200. This work investigated the effect of various coating on the scratch resistance of UV coatings, such as tertiary amine (EP 115) and ultrafine Al2O3. Meanwhile, the best dosage of those ingredients was worked out. By using orthogonal test, effort went into finding out the blending of addtives. Like leveling, defoamer and thickening agent, two types of blending of additives settled down. With two blendings four formulations were achieved in combination with early two resins UCECOAT 7200 and Alberdink Lux 250.At last, a range of testings on above four formulations were performed according to 3C coating’s requirments. These testings included scratch resistance, reactivity, solvent\chemical resistance and weathering resistance. This paper also discussed sketch of deformation mechanism during scratching and compared of testing results for various scratch testing method. Eventually a desired coating formulation was developed, which can not only meet the general industrial requirements but also can provide excellent scratch resistance. Further more, an attempt was made to determine the minimized UV exposure in considering energy saving is always a gain for radiation curing. At the same time the correlations between UV exposures, double bond conversion and mechanic hardness was investigated.Screening results showed that UCECOAT 7200 and Alberdingk Lux 250 had the fasted reactivity and highest mechanical hardness. EP115 and ultrafine Al2O3 can contribute greatly to scratch resistance. By seen from UV exposure investigation, there is a direct relationship between radiation intensity and double bond conversion or mechanical hardness. At UV dosage of 800 mj/cm2 double bond conversion and hardness can be got rapidly.Besides some common advantages like those of conventional water borne UV coating. The new water borne UV coating had two additional benefits:(1) Easy process but with better performance.(2) Raw materials are the same achievable as normal water borne UV coating. However, the performance was improved a lot, and the cost was still in the budget.Moreover, at the end of the paper some ideas were suggested for future work on continuous improvement on scratch resistance, and some considering on storage stability were raised up as well. |
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