| As we all know,the pigment filler in the paint under the influence of the external environment,loses the vivid color or appears the discoloration phenomenon.The paint needs to be repaired again,virtually increasing people's burden and cost.In fact,people can protect the pigments and fillers through micro-capsule technology,which reduces the influence of the environment on the pigments.This cost-saving strategy can greatly increase the service life and use range of colored coatings.If the thermochromism material is microencapsulated to make a reversible thermochromism paint,the scope of use of the colored paint can be further expanded to enrich people's lives.In this thesis,a reversible thermochromism epoxy resin coating was successfully prepared.At first,crystal violet lactone,bisphenol A and n-decanoic acid diester were compounded in a certain proportion to prepare a reversible thermochromism capsule core material.To obtain a darker color mixture of core material,the amount of the three substances was investigated by a UV spectrophotometer.The optimum ratio of the three components is n(crystal violet lactone):n(bisphenol A):n(n-decanoic acid diester)=1:2:25.The core material is then emulsified with sodium lauryl sulfate and a styrene-maleic anhydride macromolecular emulsifier.At the same time,monomer styrene and crosslinker divinylbenzene were added.After the initiation of AIBN,the monomer was in situ polymerized on the surface of the core material to form the shell,and a reversible thermnochromism microcapsule emulsion was obtained.The microcapsule emulsion was blue at 0 ?.As temperature rises,the blue color becomes lighter,finally milky white at 70 ?.After 50-time repeated heating and cooling,the color of the emulsion changed regularly.These prove that the emulsion has good thermal reversible discoloration.In this experiment,the structure of the synthesized styrene-maleic anhydride macromolecular emulsifier was basically characterized by FT-IR(FourierTransmission Infrared Spectroscopy),and the particle size and distribution of the microcapsule emulsion were characterized using a particle size analyzer and a transflectron microscope.DSC(Differential Scanning Calorimeter)was used to test the properties of the microcapsule shell.Finally,the stability of the emulsion was systematically tested.The results indicate that the initial minimum crystallization temperature of the core material in DSC-tested was 4 ?,meaning that the shell shows the best performance,when the microcapsule emulsion reaction temperature is 80 ?,the initiator dosage is 0.7%of the monomer mass,and the mass ratio of the capsule wall to the capsule core is 2:1.The microcapsule emulsion had the smallest average particle size of 1545 nm,while the emulsifier concentration was 0.02 mol/L and the reaction speed was 1200 r/min.At the same time,the amount of macromolecular emulsifier is 4%of the core mass,and the solid content of the microcapsule emulsion is 10-30%,a good-stable emulsion can be obtained.Next,the microcapsule emulsion and the epoxy resin emulsion are mixed to obtain a reversible thermochromism epoxy resin emulsion.Followed by auxiliary agents added,a reversible thermochromism paint can be obtained.First,a PEG(polyethylene glycol)-modified epoxy resin was used to allow the modified epoxy resin(PME)to emulsify the epoxy resin and the microcapsule emulsion to obtain a stable,reversible thermochromism epoxy resin emulsion.Finally,the emulsion is added with a curing agent and other additives to prepare a reversible thermochromism epoxy resin coating.Reversible thermochromism coating In 50 cycles of repeated heating and cooling,the color of the paint film changed from blue(0 ?)to colorless(70 ?),with good reversible thermochromism.In this experiment,the structure of PME was determined by FTIR(Fourier transform infrared spectroscopy).The effects of microcapsule emulsion on the viscosity,particle size and distribution of the reversible thermochromism epoxy emulsion were characterized using a rotational viscometer and a particle size analyzer.Adhesion tester,elastic tester,mirror gloss meter,pendulum hardness tester,salt spray test box,and ultraviolet light aging tester were used to test the adhesion,elasticity,gloss,hardness,and corrosion resistance of the paint film,respectively.The results showed that the epoxy resin E44 was modified with PEG having a molecular weight of 4000,6000 and 10000,respectively.E44 can be emulsified by the modified PME44,and the amount of PME44(wt.%)needs to be above 9.7%.At the same time,the epoxy resin E20 was modified with PEG with a molecular weight of 4000 and 6000,respectively.E20 is emulsified by PME20 and the amount of PME20(wt.%)needs to be above 14.55%.The paint film's adhesion and corrosion resistance will be reduced.Because of the increase in the amount of PME will affect the performance of the reversible discoloration epoxy paint film.Therefore,the amount of PME(wt.%)is controlled to be less than 19.4%.When the particle size of the microcapsule emulsion is larger than that of the pure epoxy resin emulsion,both of them are emulsified by PME.With the increase of the amount of microcapsule emulsion,the particle size of the reversible thermochromism epoxy resin emulsion increases and the distribution increases.If the particle size of the microcapsule emulsion is smaller than the particle size of the pure epoxy resin emulsion and the amount of the microcapsule emulsion is increased,the particle size of the reversible thermochromism epoxy resin emulsion decreases and the distribution increases.When the particle sizes are close,the amount of microcapsule emulsion has little effect on the particle size and distribution of the reversible thermochromism epoxy resin emulsion.At the same time,the amount of microcapsule emulsions increased,the stability and viscosity of reversible discolored epoxy emulsions decreased,and the gloss,adhesion,elasticity,abrasion resistance,and corrosion resistance of reversible discolored epoxy resin coatings decreased..Therefore,the amount of microcapsule emulsion(wt.%)should be controlled below 15%.The three room temperature curing agents used in this experiment were tetraethylenepentamine,cyclohexyldiamine and W60.Among them,the film obtained by curing with cyclohexanediamine was the best in performance.In general,epoxy E20 coatings are superior to epoxy E44 in terms of film gloss,hardness,salt spray resistance,and aging resistance.The thermally reversible thermochromism epoxy resin coating synthesized in this experiment has the characteristics that is safe,environmentally friendly,and has a certain degree of corrosion resistance of waterborne epoxy resin coating.At the same time,it also showed changes in reversible color,broadening the scope of application of waterborne epoxy resin coatings.It is of guiding significance to study the synthesis of microcapsule emulsion and broaden the application of waterborne epoxy resin coating. |
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