| Since its introduction,epoxy resin has been widely used in various fields for its excellent properties.The excellent properties of epoxy resins are due to the active and non-polar groups such as epoxy groups,hydroxyl groups and ether bonds in the molecular structure.They play a vital role in the fields of coatings,adhesives,electronics and appliances,engineering plastics,composites and construction materials.Epoxy resins are usually dissolved in organic solvents to make coatings,and the volatilization of volatile organic compounds can cause damage to the environment and pose a threat to human health.At present,how to dissolve epoxy resin in water,reduce the emission of volatile organic compounds and develop new water-based epoxy coatings has become a hot research and development trend.Firstly,we used non-ionic emulsifier to prepare waterborne epoxy coatings as an exploratory study.After mixing sorbitan monooleate(SP 80),fatty alcohol polyoxyethylene ether(AEO-3)and polyethylene glycol 400 monolaurate(PEG 400ML)to emulsify E51 epoxy resin,the hydrophilic and lipophilic balance value(HLB)of the system could be regulated by changing the dosage of the three.When the dosage of Span80 and AEO-3 was 2.4 pbw(Parts by Weight),the dosage of PEG400 ML was 3.0 pbw,and the dosage of ethylene glycol mo nobutyl ether acetate was 5.0 pbw(the dosage of E51 epoxy resin was 20.0 pbw,the same below),the HLB was 7.3,and the best emulsification performance of the epoxy resin was achieved,and the particle size of the emulsion prepared by direct emulsification method was about 1.9μm,and the storage stability was about 5 days.Secondly,the alcoholysis reaction of nonylphenol ethoxylate(NP)and methyl tetrahydrophthalic anhydride(MTHPA)was used,and the intermediate products were then neutralized with Na OH to obtain sodium salt emulsifier A.The hydrophilic/oleophilic ability of the emulsifier can be adjusted by changing the number of ethoxylate of nonylphenol ethoxylate,when nonylphenol ethoxylate NP-20 and MTHPA were selected as raw materials and fed according to the molar ratio of 1:1.1.The HLB value of the emulsifier obtained was about 16.7,and the particle size of the emulsion obtained was 307.3 nm at a dosage of 4.0 pbw,emulsification speed of 10 kr/min and p H=8,and the storage stability of the emulsion reached 180 days.Once more,the aliphatic alcohol polyoxyethylene ether was replaced with nonylphenol in the ring-opening reaction with phthalic anhydride,and the sodium salt emulsifier B was obtained by neutralization with saturated sodium carbonate,also by changing the aliphatic alcohol The HLB value of the emulsifier was adjusted by changing the ethoxy content of the aliphatic alcohol polyoxyethylene ether and the type of phthalic anhydride,and it was determined that the reaction between aliphatic alcohol polyoxyethylene ether(AEO-15)and phthalic anhydride(PA)in a 1:1.1 molar ratio resulted in the best emulsification of the epoxy resin when the amount of emulsifier B was only 2.0 pbw.The particle size of the emulsion was 331.7 nm,and the storage stability was also 180 days.Finally,the homemade waterborne epoxy resin emulsion was used with diethylenetriamine,tetraethylenepentamine and polyamide 651,and the effect of curing agent was also investigated.The curing speed of diethylenetriamine was fast,and the application period of the coating was short with the addition amount of 2.4 pbw,the surface drying time was only 24 h,the film hardness was 3H,and the adhesion grade was1;the curing speed of tetraethylenepentamine and polyamide 651 was relatively slow,so the application period of the coating became longer,but the cured film was smoother,flatter and denser. |
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