Preparation And Performance Of Waterborne Epoxy Anticorrosion Coatings Based On Nonionic Emulsifier And Curing Agent

Epoxy resin coatings have become one of the key organic protective coatings that people have focused on at present due to their excellent chemical resistance,brilliant adhesion,and significant corrosion resistance.Among them,compared with solvent-based epoxy coatings,water-based epoxy anti-corrosion coatings have attracted much attention because of their green and environmentally friendly properties.However,they still have problems such as long drying time,poor water resistance and so on,all of which can affect the final performance of the coating film.In this paper,waterborne epoxy emulsifiers and waterborne epoxy curing agents with excellent performance are designed and synthesized as film-forming base materials,and waterborne epoxy coating products with good corrosion resistance are developed in order to improve the shortcomings of the current waterborne epoxy coatings and provide strong support for long-term protection of metal materials.A special emulsifier PNWEP with similar structure to epoxy resin was synthesized by epoxy resin E-44,polyethylene glycol diglycidyl ether(PEGDGE),and diglycolamine(DGA)with molar ratio n(E-44/PEGDGE/DGA)of 1/2/0.75,reaction time of 4 hours and reaction temperature of 80℃.By using the phase inversion technology,a stable and uniform waterborne epoxy emulsion WEP with an average particle size of 9.445 nm was developed under the optimal conditions of 9 wt.%PNWEP emulsifier concentration,60 mL distilled water,60℃emulsification temperature,600 rpm dispersion speed and 30 min emulsification time.Compared with similar products in the domestic market with a particle size of 8.038 nm,the performance is relatively close.Through triethylenetetramine(TETA),ethylene glycol glycidyl ether(EGDE),and y-glycidyl ether oxypropyl trimethoxysilane(KH-560),the addition product TETA-EGDE was prepared with the molar ratio n(TETA/EGDE)of 2.3:1,n(TETA/PM)of 1.75:1,reaction time of 4 hours,and reaction temperature of 70℃.The nonionic waterborne epoxy curing agent SNWECA was prepared with n(epoxy/amino)of 1:1,reaction time of 4 hours,and reaction temperature of 75℃.The properties of waterborne epoxy varnish coating(EP)and waterborne epoxy paint coating(EP/ZP)was studied by using self-made WEP and SNWECA as film forming substrates,using zinc phosphate(ZP)as active antirust pigments.In electrochemical testing,the EP coating without ZP,the low-frequency impedance modulus |Z|0.01 Hz of the coating can reach up to 5.87× 109 Ω·cm2,and the minimum Icorr can reach 4.705 × 10-9 A cm-2.When 35 wt.%ZP is added,the low-frequency impedance modulus |Z|0.01 Hz of the coating can reach up to 1.16×1011 Ω·cm2,and the minimum Icorr can reach 4.690×10-12 A cm-2.And both of them can achieve surface drying after 0.5 hours and solid drying within 6 hours at room temperature.Compared with the industry standard of anticorrosion coatings(4 hours of surface drying and 24 hours of solid drying),the coating drying time is significantly shortened.At the same time,the EP coating can withstand water for 336 hours,and the EP/ZP coating can withstand water for 504 hours.The water resistance performance of the coating is significantly improved compared to similar research with a water resistance of 168 hours,indicating that the coating developed in this paper has the advantages of short drying time and good water resistance.Its basic performance meets the industry standard of anticorrosion coatings.