| Epoxy resin possessed special molecular structure and excellent physical and mechanical properties,in consequence,it was used widely in coatings,adhesive and composite material field and so on,but with the increasingly stringent environmental requirements,solvent-based epoxy resin system brings a lot of volatile organic compounds that do great harm to the natural environment and human health,therefore the development of green and environmental friendly waterborne epoxy resin system has become the urgent need and research concern.Due to the hardness of epoxy resin was high,so that character of the material is brittle after being cured,this will cause the flexibility and impact resistance is inferior,the adhesion power to substrate is weak.For the preparation of waterborne epoxy resin,while giving the hydrophilic group to epoxy resin,the additional flexible chain segment is introducted into epoxy resin simultaneously,flexibility of epoxy resin is improved,adhesion power is enhanced,impact resistance strength is increased,the flexible chain segment plays an important role for improvement of performance of epoxy resin.The performance of the waterborne epoxy resin close to or even excess the one of solvent-based epoxy resin,It manifests the strong market competitiveness and powerful development momentum,was more and more gotten the favour and attention from people.In order to make further improvement on the performance of waterborne epoxy resin,to enhance its ultilization performance,through this paper research and obtained following viewpoint:First of all,this article maked use of bisphenol A type epoxy resin E-44 as graft matrix,acrylic acid,butyl acrylate,methyl methylacrylate,organosilicone with double bond as the functional monomer,propylene glycol methyl ether as reaction solvent.The epoxy resin was grafted acrylic ester with the method of solution polymerization meanwhile epoxy resin molecule chain was introduced hydrophilic group,epoxy resin was given the hydrophilic group as a result that waterborne epoxy resin emulsion was prepared.The graft product structure was characterized with infrared spectrum(FT-IR)and nuclear magnetic resonance(1H NMR)showed that the grafted polymerization product had been obtained;Grafting rate,conversion rate,epoxy value,grafted product monomer,water dispersion stability and particle size of the emulsion were characterized and analyzed detailedly,the dosage of initiator,polymerization temperature,the dosage of acrylic acid,the dosage of acrylate monomer,neutralization degree and kind and amount of organicsilicone emulsion on coating film performances were studied meanwhile the best process conditions were determined ultimately,when the mass fraction of initiator relative to epoxy resin was 3.5wt%,polymerization temperature was 110℃,dosage of acrylic acid was 16wt%,the mass ratio of acrylic ester monomer relative to epoxy resin was 8:10;neutralization degree was 90%,the monomer grafting rate was 85%,water dispersion stability was level 1,the storage stability phase was 30 days,average emulsion particle size was 185 nm,the impact resistance strength was 50 kg·cm,the flexibility was 1mm,The maximum thermal decomposition temperature was 407 ℃.By introducing organic silicon monomer into epoxy resin,the kind and amount of organic silicon were decided as the significant research for performances of modified epoxy resin emulsion and its curing coating,analysis results showed that the average particle size of emulsion,coating resistance to water,the static contact angle were influenced observably by the kind and amount of organic silicon monomer.When the dosage of organic silicon A-151 was 3wt%,the emulsion particle size was 150 nm,Transmission electron microscopy showed that its particle size was smaller,the particle size distribution was more homogeneous compared with grafted product with no organic silicon.Glass transition temperature of coating was 86.8℃,the maximum heat decomposition temperature was 409 ℃,the maximum heat decomposition rate was 0.97% /℃,which showed that its thermostability was increased to some extent.The flexibility was 0.5 mm,resistance to impact strength was 55 kg·cm,which showed the flexibility and impact resistance strength of its coating were enhanced moderately by comparison,this indicated that introduction of organic silicon can contribute to improvement of the flexibility and impact resistance strength of the coating.In the second place,epoxy resin and polyethylene glycol synthesis special epoxy resin emulsifier,noumenon epoxy resin was emulsified in order to get nonionic waterborne epoxy resin by phase reversion method.The expected emulsifier was produced by characterization analysis with 1H NMR and FT-IR.The study for emulsion viscosity and conductivity,which showed that dosage of emulsifier and emulsifying temperature had a greater influence on the emulsification process,when the dosage of emulsifier was 20wt%,emulsifying temperature was 55 ℃,the phase inversion was complete,the point of phase inversion was 20wt%,the prepared emulsion possessed optimum stability.The stability test research showed that for emulsifier,when molecular weight of PEG was selected as 6000,the mole ratio of epoxy resin and PEG was 1:1,dosage of emulsifier was 20wt%,the centrifugal stability of the emulsion was level 5,dilution stability was 0.02,freeze-thaw stability was level 5,storage stability period was 6 months.Waterborne epoxy resin emulsion and waterborne epoxy resin curing agent were mixed evenly for the preparation of coating,By analyzing for the coating corrosion resistance and mechanical properties,the results showed that enhancing the curing temperature,curing speed was accelerated obviously,the salt resistance property,the acid resisitance and the alkaline resisitance of coating was increased significantly.PEG molecular weight is 6000,dosage of emulsifier was 20wt%,the mass ratio of E-20 relative to E-44 was 5:12,curing temperature was 50 ℃,mass ratio of the emulsion relative to the curing agent was 3:1,the prepared coating had excellent mechanical properties,its hardness was 3H,flexibility is 0.5 mm,resistance to impact strength was 60 kg·cm,adhesion force was 0 level.The maximum heat decomposition temperature was 409.6 ℃,The thermogravimetic analysis of the film indicated that coating film owned admirable heat resistance.The section scanning analysis showed that the introduction of flexible emulsifier can notably improve the flexibility of epoxy resin. |
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