| Epoxy resin is a widely used thermoset polymer with strong adhesion,good water resistance,and other excellent performance,in coatings and adhesives and other fields,having a wide range of applications.However,because the presence of solvent,epoxy resin has environmental hazards in the use and is not easy to store and transport.In contrast,water-based epoxy resin has good performance the same as solvent-based epoxy resin,and it is in line with green requirements and excellent processing performance.However,water-resistant epoxy also has the disadvantages of insufficient heat resistance,low bonding strength and high-water absorption rate,which limit the application and development of water-based epoxy resin.In the past,the modification method was mainly to add modifiers.But most modifiers have lower solubility and the compatibility with water-based epoxy is poor after addition,resulting in less ideal modification effect.While a few soluble modifiers have low strength and heat resistance,providing unsatisfactory modification effect.Therefore,the soluble poly(amic acid)salt the pre-polymer of polyimide was used as a modified agent in the experiment.After addition of the soluble poly(amic acid)salt the pre-polymer of polyimide,the polyimide was introduced into the epoxy structure by heating the common reaction.In this paper,the bisphenol A water-based epoxy resins and A phenolic epoxy resin water-based epoxy resin were selected as modified matrix and six kinds of water-based poly(amic acid)salt the pre-polymer of polyimide were used as modified agents.The chemical structure of modified epoxy system under different curing conditions was characterized by infrared spectroscopy(FTIR)and scanning electroscope(SEM).The curing behavior was studied by differential scanning volume heat method(DSC).The thermal properties of cured resins were studied through dynamic thermodynamic analysis(DMA)and thermal weight analysis(TGA).Its bonding performance and water absorption rate were also studied.The shearing performance of bisphenol A water-based epoxy resin was tested at room temperature and high temperature and the data showed that the shear strength,bonding performance and heat resistance of the epoxy system can be improved by the addition of polyimide.It could be found that the bonding performance of bisphenol A water-based epoxy resin was good and it could be raised to a higher standard after modification,applicable to adhesives.The salt mist aging treatment of coating was carried out on the A phenolic epoxy resin water-based epoxy resin,and the adhesion test was carried out by the grid test before and after the treatment.The results showed that the bonding performance of A phenolic epoxy resin water-based epoxy resin was not outstanding,and the modification effect was limited.However,its storage modulus in high temperature was larger,the system stability was better.The adhesion of epoxy was improved by addition of polyamide as well as the salt-resistant fog properties of the material.So,it is suitable for protecting coatings. |
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