| Energy-saving environmental protection coating is the world’s research hotspot.Epoxy resin coating with high bonding strength,mechanical properties and dimensional stability,good corrosion resistance,etc.,has important applications in the anti-corrosion field.However,epoxy resin coating is brittle,low elongation at break,poor flexibility and other issues,and commercially available epoxy resin coatings are mostly volatile organic solvents as a dispersion medium,which is bad for the human health and will cause pollution to the environment if exhausted into the atmosphere.Epoxy emulsion with water as a dispersion medium,safe and pollution-free,accord with environmental requirements.In this paper,the epoxy resin was modified by toughening,and the nonionic epoxy emulsion was synthesized.Then,an end-amino nonionic waterborne epoxy curing agent(ATNCA)was prepared.The properties of the emulsion and coating were investigated.And the curing process of epoxy emulsion was studied.In this paper,chemical modification method is adopted,using polyethylene glycol monomethyl ether(MPEG),isophorone diisocyanate(IPDI)and bisphenol A epoxy resin E44 as raw materials,frist to obtain a semi-blocked prepolymer by the chemical reaction between isophorone diisocyanate and polyethylene glycol monomethyl ether,and then with bisphenol A type epoxy resin side of the hydroxyl group grafting reaction,the hydrophilic segment into the epoxy resin molecular chain,The synthesis of a solvent-free,low-cost non-ionic epoxy resin,and finally emulsified in water to get epoxy emulsion.The structure of the nonionic epoxy resin was characterized by Fourier transform infrared spectroscopy(FTIR),and the graft reaction was confirmed.The reversal emulsification of epoxy resin was analyzed by the change of conductivity in the emulsification process.The effects of different emulsifying conditions on the emulsion properties were studied emphatically,and the optimum emulsification process was found.The effects of MPEG molecular weight,amount of epoxy resin and reaction conditions on the particle size and stability of the emulsion were investigated.The results show that a stable epoxy emulsion can be prepared by introducing a nonionic hydrophilic segment into the molecular structure of epoxy resin.With the increase of the molecular weight of the MPEG,the particle size of the emulsion becomes smaller and the particle size distribution becomes narrower.When the MPEG molecular weight is 500 can be a stable waterborne epoxy resin emulsion,the room temperature storage stability of up to six months or more.With the increase of the amount of epoxy resin,the particle size of the emulsion becomes larger,the particle size distribution does not change obviously,and the stability of the emulsion decreases.Using isophorone diisocyanate,polyethylene glycol monomethyl ether and polyamine as raw materials,the chemical modification method is adopted to synthesize the end-amino nonionic waterborne epoxy curing agent(ATNCA).The structure of ATNCA was confirmed by FTIR and gel permeation chromatography(GPC).The effects of the molecular weight of MPEG and the properties of different polyamines on the properties of ATNCA were studied.The waterborne epoxy curing agent was dispersed evenly in the epoxy emulsion.In this paper,D230-E44 and ATNCA-E44 coatings were obtained by mixing polyether amine D230 and ATNCA as water-based epoxy curing agent and epoxy emulsion.The curing process of ATNCA-epoxy emulsion system was studied experimentally,and the curing kinetics was analyzed by differential scanning calorimetry(DSC).The effects of MPEG molecular weight on the properties of D230-E44 coatings and the effects of different amounts of polyamines and curing agents on the properties of ATNCA-E44 coatings were investigated.The results show that with the increase of curing temperature,the mechanical properties of the coating are enhanced,and the time required for curing can be shortened.In addition,the toughness of the nonionic epoxy resin film prepared by the chemical modification method is remarkably improved.With the increase of MPEG molecular weight,D230-E44 coating hardness,tensile strength and thermal stability decreased,elongation at break and water absorption increased.The tensile strength and tensile strength of the ATNCA-E44 coating were increased and the tensile strength and elongation of the ATNCA-E44 coating were increased with the increase of the number of polyamine nitrogen atoms.Water absorption decreased.Experiments show that the use of ATNCA as a water-based epoxy curing agent can get better performance of the coating. |
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