| The history of the development of epoxy curing agent has more than 80years.The variety,quantity of epoxy curing agent has become more and more,and it has been widely used in many fields.Among the epoxy curing agent,the amount of amine curing agent has been used most.It has high curing activity and good process performance,but it has a poor hydrophobicity,the cured brittleness and other shortcomings.With the development of dams,reservoirs and other underwater projects,amine curing agent can not meet the requirements of underwater construction,only a small part of the amine curing agent can be used in underwater construction,but it is very different from the construction and strength without water.Therefore,how we can work out a good cured epoxy curing agent breed with high adhesive strength in the water,has a very important practical significance.As Mannich modified amine curing agent has high activity and excellent underwater curing performance characteristics,in this paper,we have changed the kind and ratio of the monomer and synthesized a hydrophobic high toughness underwater epoxy curing agent by using Mannich reaction.The monomer of modified MXDA are m-xylylenediamine,nonyl phenol,formaldehyde.Among the monomer,xylylenediamine has low viscosity,high activity which can improve the characteristics of the curing agent process performance.Nonylphenol molecular structure has benzene,C9 aliphatic chains such high hydrophobic group.So the hydrophobicity of the curing agent has greatly enhanced and the impact toughness of cured resin has also increased significantly.This paper has studied the effects of different amount of monomer,curing agent,reaction time and reaction temperature on the adhesive properties of the curing agent,and discusses the effects of different monomer amount on cured mechanical,thermal,absorption/dissolution water rates.The results show that:among the monomer,nonylphenol could improve the hydrophobicity of the curing agent and the adhesive properties of the curing agent,and the toughness of cured prouducts is significantly improved.When the molar ratio of m-xylylenediamine,nonylphenol,formaldehyde is1.6:1.4:0.8,the amount of the curing agent is 60phr,the comprehensive properties of curing agent and epoxy resin cured product is best.Underwater strength of the cured adhesive agent is up to 10.2MPa,which has improved 673%comparing with the unmodified;The adhesive strength?steel/steel tensile shear strength?is 18.2MPa at room temperature,which has improved 62.5%comparing with the unmodified.Its impact strength of the cured epoxy resin is 31.1kJ/m2,which has improved 453%comparing with the unmodified.Meanwhile,this paper has proposed a new hydrophobic characterization methods of underwater epoxy curing agent.We has studied m-xylylenediamine,nonylphenol,formaldehyde content on the curing agent hydrophobicity of water absorption/water soluble.The results show that:nonylphenol and formaldehyde are conducive to reducing the absorption of the cured product absorption/solution ratio;m-xylylenediamine could enhance absorption of the cured product absorption/solvent water rates.When the molar ratio of m-xylylenediamine,nonylphenol,formaldehyde is 1.6:1.4:0.8,the synthesis of the curing agent is preferably hydrophobic,The water absorption of the cured product is 0.25%,the water soluble rate is 0.06%.In this paper,we has studied the effects of m-xylylenediamine,nonylphenol,formaldehyde on the amine value and viscosity,and the cured product has used the Fourier transform infrared spectroscopy to study the molecular structure of curing agent.The results show that:m-xylylenediamine has great effects on the viscosity and amine value of the curing agent,formaldehyde has some effects on the viscosity and amine value of the curing agent,nonylphenol has little effects on the viscosity and amine values of curing agent;In the modified MXDA infrared spectra,there is no absorption peak of carbonyl group,and in the area of the benzene characteristic peak,there are ortho-and para-substitution reaction peaks,indicating that the desired product was synthesized. |
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