UV And Low Temperature Heat Dual-curing Colorful Vanishes

UV-curable coatings has such advantages as few organic solvents, low environmentalpollution, high curing speed, excellent product performance, high labor productivity, lowcosts and fit for high speed automated coating, etc. However, theyhave shortcomings, forexample, flat shape acquirements, low curing speed in colored paints, difficult to cure in thickcoatings, shadowed area, poor adhesion, photo initiator residues,and large volume shrinkageafter curing etc. UV-heat dual curing aimed to complementation of the UV and heat curingmethods, which could probably overcome the shortcomings, and obtain thick films withbetter performance and broaden its application in colorful paints and irregular object shape.This research was done based on dual-cure coatings system using the photo-initiators andthermal-initiators to improve cure efficiency, which not only could be cured by heat at lowtemperature for a short time, but also by the UV curing. The reasons for choosing lowtemperature were because the heat-sensitive substrates were used and the energy was neededto save as much as possible.This research used modified epoxy acrylate with high hardness, high gloss as thepre-polymer. The prepared varnishes, flat lacquer, white paints and other paints with differentexcellent performance were prepared by adding10%~50%monomers,1%~6%photo initiator,1%~4%thermal initiator,0.1%~2%defoamers,0.1%~2%wetting and dispersing agent etc.Their wet films were tested by spraying, roller painting, curtaining and other processes.Finally, the films were cured by UV energy35mj/cm2~540mj/cm2, or by heat at50oC in60~120min, or both of them. As a result, the coatings films were obtained with excellentflexibility and impact resistance by adding other resins or toughener, which were based onheat curing at low temperature. The testing methods of the film appearance, viscosity, storagestability, dry time, DSC-TG, SEM, pencil hardness, impact strength, flexibility, cross-cut test,water(alcohols, acids, alkali) resisting and solids content were used to test their films.The colorful varnishes made of the commercial modified epoxy acrylate usually had abad flexibility of8~12mm. Therefore, the films with great performance, improved flexibilitywere needed to investigate. Varnishes were prepared in this thesis by adding5%~10%plasticizer or flexible resin, which were based on small changes of a short curing time or other film properties. Their SEM pictures were different even the flexibility data were similar. Thefilm of adding flexible resin looked more smoothly, which might because it had a higherdegree of polymerization.The modified colored paints had such special characters as smooth surfaces, the viscosityof100~10000Pa s, the solid content of85~95%, the glosses of higher than90, the dry-time of1.5~4h, the pencil hardness of HB~3H, the shock resistance of30~50cm, the flexibility of2~12cm, the adhesive force of level1~3and great chemical tolerance.The results of this research had the advantages of a low curing temperature, energysaving and excellent improvement after dual-cure etc. It could apply to so many differentkinds and shapes of coatings objects using several coating process, which broadened theapplications of UV coating.