Preparation Of Styrene-acrylic Emulsion And Study On Its Autophoretic Coating

Autophoresis coating is a kind of full immersion coating method which doesn't need electricity,but needs to make the paint on the surface of the steel automatically by the chemical reaction.Auto-deposition coating is acidic solution which composed of water,resin,pigment,oxidant and acid,forming micro-cell corrosion effect by steel.chemical reaction reacts in the metal surface by the demulsification of emulsion particles in the solution and form thin organic coating of high corrosion resistance,and then cured to form a film.The coating process does not require electricity and phosphating,which greatly reduces the cost compared to electrophoretic paints.In this paper,the synthesis conditions of styrene-acrylic emulsion were optimized,and the autophoretic coating was studied.In addition,the effect of the mass fraction of epoxy resin on the styrene-acrylic emulsion and the autophoretic coating was investigated.(1)The styrene-propylene emulsion was synthesized by preemulsification.The properties and structures of the emulsions were tested and characterized.The effects of polymerization temperature,stirring intensity,polymerization reaction time and emulsifier on styrene-propylene emulsion were investigated.The optical microscope,SEM,electrochemical properties and mechanical properties of coating were tested.The performance of both the emulsion and the coating determined the optimum formulation and process of the styrene-acrylic emulsion:temperature was 78?,stirring speed was 500 r/min,polymerization time was 140 min,the percentage of emulsifier was 2.5%,the ratio of anionic and nonionic emulsifier was 1/4,particle size was smaller and distribution was wide;Meanwhile,the coating was smooth,and the pencil hardness and adhesion reached the maximum value,the corrosion resistance of the coating was high.The oxidant(acetic acid,HF+Fe F₃,HF)added to the self-priming coating was changed,and the optimum oxidant under such polymerization conditions was determined by discussing the mechanical properties and corrosion resistance of the coating.At the same time,under the best performance in all aspects of the coating was determined by the discussion of the quality fraction of the activator(citric acid,acetic acid,H₂O₂):citric acid quality fraction was 0.35%,acetic acid quality fraction was 2%,and H₂O₂quality fraction was 2%.The effect of roughness on coating performance was studied in this paper.The results showed that the rougher the base surface was,the worse the coating performance was.(2)Epoxy resin is a coating resin and modifier that has excellent comprehensive properties,especially excellent adhesion,and can be used to modify coatings.The effect of epoxy resin on styrene-propylene emulsion was investigated experimentally.The modified phenylalanine emulsion was characterized by Fourier infrared spectrometer,indicating that epoxy resin was involved in the polymerization reaction.By changing the quality fraction of epoxy resin,the quality fraction of the best epoxy resin was determined to be 10%.At this time,the coatings performed best in all aspects.