| Powder coatings do not contain volatile organic solvents（VOC）,which do not pollute the environment and are a pure solid coating.Powder coatings are not only easy to store,easy to apply,but also economical and excellent in performance.In this paper,epoxy resin E-12 was used as the curing main substance,filler was added and various additives were mixed to prepare the coating,and the basic epoxy powder coating formula was obtained by orthogonal test to compare the coating properties.Based on this,the effects of the type and amount of resin as a curing agent in epoxy powder coatings,the type of filler and the amount of coating on the properties of the coating were researched.The effect of the amount of curing accelerator 2-methylimidazole on the curing properties of the powder coating and it’s effect on the coating properties were discussed by FT-IR and DSC.The amount of curing accelerator2-methylimidazole was determined by experiment,and the non-isothermal curing kinetics analysis of the best formulation of the coating was carried out.The theoretical curing temperature and other curing parameters are obtained,and the theoretical curing temperature is used to determine the actual curing temperature and curing time.Finally,A3 steel is used as the substrate,and three different pretreatment methods such as phosphating,phytate treatment and silane coupling agent treatment are adopted.A bond strength test test block was prepared,and a comparative test of bond strength performance was performed.（1）The coating formulation was selected by orthogonal experiment,and the obtained coating was analyzed for performance to obtain a basic formula of epoxy powder coating:E-12 resin 72 g,dicyandiamide 4 g,titanium dioxide 8 g,precipitated barium sulfate 13.3 g,leveling agent 0.7 g,benzoin 0.2 g,defoamer0.5 g,lightening agent 1.1 g and gas phase SiO2 0.2 g.（2）The polyester resin 3968-D was determined experimentally,the filler precipitated BaS04,and the curing accelerator 2-methylimidazole was used as the powder coating component.Formulated for optimized powder coatings:33 g E-12,33 g polyester resin,8 g titanium dioxide,23 g barium sulfate,0.7 g smoothing agent,0.2 g benzoin,0.5 g defoamer,1.1 g clarifying agent,0.2 g silicon and 0.4 g 2-methylimidazole.The formulation can effectively lower the curing temperature of the coating from 180℃to 155℃to achieve low temperature curing,and the coating has excellent appearance and impact strength.（3）When the addition of 2-methylimidazole to the powder coating was 0.4g,the curing kinetics of the coating was studied.At this time,the activation energy of the curing reaction of the polyester/epoxy powder coating was 9.325kJ/mol,and the reaction order n was 0.95.The factor A is 9.83×102,and the curing reaction kinetic equation:（4）Phosphating,phytate treatment and silane coupling agent treatment with A3 steel as substrate.The treated substrate and the coating were subjected to a comparison test of the bonding strength properties,and it was concluded that the substrate treated with the phytate had a better bonding strength with the coating. |
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