Fabrication of a nonionic self-emulsifiable waterborne epoxy curing agent with high cure properties

Waterborne epoxy curing agent plays a key part in the waterborne epoxy resin coatings, directly affecting the physical and chemical properties of the coating film. Here, we present triethylene tetramine (TETA), polypropylene glycol diglycidyl ether (PPGDGE), epoxy resin E20 and phenyl glycidyl ether (PGE) as reactants to fabricate a novel nonionic self-emulsifiable waterborne epoxy curing agent for oily epoxy resin through three steps of chain extension reaction, addition reaction, and capping reaction. The curing agent achieved excellent emulsifying and curing properties under the condition that TETA reacted with PPGDGE at 65°C for 4 h with the molar ratio of 2.2:1, 40% primary amine was added with E20 at 65°C for 3 h and 125% residual primary amine was capped with PGE at 65°C for 3 h. The as-prepared waterborne epoxy curing agent was characterized by Fourier transform-infrared spectroscopy and surface tension. The cured film of emulsified oily epoxy resin (E51) prepared by the as-prepared curing agent indirectly was characterized by scanning electron microscopy, thermogravimetric analysis and differential scanning calorimetry tests. The 2K waterborne epoxy coating film prepared by the as-prepared nonionic self-emulsifiable curing agent and E51 displayed better thermal property, surface appearance, flexibility, impact resistance, adhesion, and chemical corrosion resistance.