| Tinplate is one of the most frequently used packing materials, and the print of tinplate is a very important process in its application in industry. As the most important process in the print of tinplate, the white undercoat is the basic material that touch with the tinplate directly. When applied in the packing industry, the white coating is required with the properties of soft molecular structure and strong physical strength. Recently, the most used way to cure the white coating from liquid to solid is the way of heat-curing which is a traditional way in this industry. Although the traditional heat-curing method could ensure that the using properties of the cured white coating is eligible, it could cause a lot of damages to the environment because of the solvent that evaporate in the process of heating, and the working condition in the related companies is also very horrible. Besides, the efficiency of the heat-curing method to cure white coating is really low. This paper used a novel way of ultraviolet(UV) curing to study the properties of white un dercoat which is used on tinplate to see how different conditions influence the curing result and physical strength of the coating. This paper aims to find a better way to get a kind of better white coating that can be used in industry.The best recipe of the white coating is find through comparing different kinds of oligomer and other assistant reagent: urethane acrylate and polyester acrylate are used as the main resin, IBOA and DPGDA are used as the reactive monomer, 819, 184 and TPO is used as the UV initiator, the rutile titanium dioxide is used as the white pigment, the silane coupling agent is used as the adhesion promoter, the Silicone Polyether is used as the substrate wetting agent, a kind of acid polymer is used as the pigment wetting agent, organic silicon is used as the flatting agent and the crylic acid is used as the defoamer.The FTIR spectrum show that some of the carbon-carbon double bond in the UV cured white coating system disappeared after exposure under UV light and some of the carbon-carbon double bond still exist. The disappeared functional groups react and formed the cross-linking structure of the coating. The SEM pictures show that the amount of titanium dioxide has very obvious influence on the surface appearance of the coating. It causes the surface to form many mini gaps and the more the titanium dioxide is in the coating system, the deeper gaps it would form. The contact angle test show that as the amount of titanium dioxide used in the white coating system grew, the surface energy of the coating rise at first time and fall later. The DSC and TG test results show that the amount of photo initiator, the energy of the UV and the after-curing temperature could influence the degree of cure. And 5% of photo initiator, 360 MJ/cm2 of UV energy, 170℃ of after-curing temperature could led to the best efficiency of curing. The result of several physical test of the white coating show that the white coating’s impact resistance, level of adhesion, boiling resistance and level of whiteness are related to each other. And 5% of photo initiator, 360 MJ/cm2 of UV energy, 170℃ of after-curing temperature, 0.6% of adhesion promoter could make the UV cured whited coating with the best physical properties. |
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