| The waterborne epoxy curing agent is the basis for the aqueous epoxy resin to enter the substantive application stage,and is the key component determining the performance of the two-component room temperature curing waterborne epoxy resin coating.At present,the most widely used ionic waterborne epoxy curing agent in China has the disadvantages of high brittleness and poor acid resistance of cured film,which limits the application of waterborne epoxy resin coating,so the development of new nonionic waterborne epoxy curing agent has broad application prospects.Triethylenetetramine is used as base amine for modification,and the reaction is carried out with polypropylene glycol diglycidyl ether to form a "TETA-PPGDGE-TETA" sandwich type TETA-PPGDGE polyamine adduct at a molar ratio of TETA to PPGDGE is 2.2:1.Then 40% epoxy resin E20 is introduced to further extend the TETA-PPGDGE adduct to obtain TETAPPGDGE-E20 adduct.Finally,125% phenyl glycidyl ether is introduced to terminate the remaining primary amine hydrogen in TETA-PPGDGE-E20 adduct to synthesize the final product TETA-PPGDGE-E20-PGE adduct.After the reaction,water is added to adjust the solid content to 55%,which is a novel nonionic self-emulsifiable waterborne epoxy curing agent.It has an active hydrogen equivalent of 260±30 g/eq,a viscosity of 8800 cp,and a storage stability period of more than 180 days.The results of infrared spectroscopy indicate that the grafting reaction is complete.The synthesized TETA-PPGDGE-E20-PGE adduct is a multi-block compound containing hydrophobic epoxy resin segment,hydrophilic polyether segment and polyamine segment.The calculated value of HLB is 15.6.The surface tension measurement results show that it has strong surface activity that can be well dispersed in water,and the surface tension of aqueous solution can be reduced to 37.8 mN/m.At the same time,the synthesized TETA-PPGDGE-E20-PGE adduct has a strong ability to emulsify liquid epoxy resin,and the obtained emulsion has an average particle diameter of 262 nm and a dispersion index(PDI)of 0.338.The pot life of the curing agent emulsifying type waterborne epoxy resin coating system composed of the synthesized TETA-PPGDGE-E20-PGE adduct and epoxy resin E51 is 2.5 hours.Compared with the ionic waterborne epoxy curing agent currently used by Carpoly Paint,refer to the relevant test requirements of GB/T 22374-2018 "floor coating materials".The results show that the surface appearance,mechanical properties and acid resistance of the cured film obtained by the synthesized nonionic waterborne epoxy curing agent and epoxy resin E51 are relatively outstanding due to the introduction of flexible long-chain polypropylene glycol ether segments in the molecular structure.Where,pencil hardness is 2H,flexibility is 1mm,adhesion is 0 degree,impact resistance is 50 Kg·cm,and acid resistance is eligible.Scanning electron microscopy(SEM)analysis show that the cured film is more flatter and uniform.Thermogravimetric(TG)analysis indicate that the cured film has better thermal stability.DSC analysis indicate that the cured film has higher glass transition temperature. |
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