| Microwave curing graphene oxide/epoxy(GO/EP)composites materials are widely used in aerospace,energy,sports,and other fields because of their excellent performance advantages in thermal,electrical,and mechanical aspects.However,the current research on the curing mechanism and controllable preparation of microwave curing multifunctional epoxy resins has not been perfected.At the same time,the poor dispersibility of graphene oxide(GO)in the resin matrix and low interfacial bonding strength have affected the performance of microwave curing GO/EP composites.In this paper,the curing behavior and curing mechanism of epoxy resin under microwave irradiation were studied.At the same time,the ionic liquid-graphene oxide hybrid(IL-GO)was ultrafast synthesis by microwave method,and based on the characterization of its microstructure,the synthesis mechanism was discussed.The dispersion stability of IL-GO in epoxy diluent under microwave irradiation was systematically studied.The influence of GO and IL-GO on the curing kinetics of epoxy resin was compared and analyzed and revealed the influence of IL-GO on the thermal,dielectric,mechanical and interface properties of epoxy composites under microwave irradiation.The main work of the study is as follows:(1)Based on the comparative study of microwave curing and thermal curing trifunctional epoxy resins,the curing behavior,properties of cured products and curing mechanism were discussed.The study found that microwave curing had improved curing uniformity in both the thickness direction and the planar direction,with an average curing degree greater than or equal to 0.96.Infrared during the curing process showed that the absorption peaks of the amino groups at 3464 and 3363 cm-1 in the initial stage of microwave curing were more obvious,which proved that the trifunctional epoxy resin had less hydroxyl formation in the initial stage of microwave curing,and a large number of hydroxyl groups appeared in the later stage of the curing reaction.The isothermal curing reaction kinetics proved that the microwave curing rate was significantly increased,the activation energy of the curing reaction was reduced by?30%,and there was a non-thermal effect.The comparative study of the thermal,dielectric and mechanical properties of microwave curing and thermal curing products proved that the thermal,dielectric and mechanical properties of microwave curing products were superior to thermal curing.Microwave cured products had higher crosslink density and there was anionic polymerization during curing process.(2)Ionic liquid-graphene oxide hybrid(IL-GO)was rapidly prepared based on microwave method and its synthesis mechanism was discussed.Infrared,elemental analysis,surface structure analysis,thermal weightlessness test,scanning electron microscopy,transmission electron microscopy and atomic force microscopy showed that the IL-GO hybrid was successfully prepared,in which the grafting rate of IL was?41 wt.%.And its thickness increased from 0.69 nm of GO to 0.92 nm.Under microwave irradiation,the GO and IL were activated,the hydroxyl group on IL and the carboxyl group on GO were esterified and the anion in IL caused the epoxy group on GO to ring open.At the same time,there was a?-?/cation-? conjugate structure between IL and GO.Therefore,the synergistic effect of IL through chemical bonding and non-covalent conjugation made it easier for IL to be inserted between GO sheets to form a thinner IL-GO hybrid.(3)Based on the isothermal DSC method and the Kamal theoretical model,the curing behavior of GO/EP and IL-GO/EP under microwave curing were discussed respectively.The study found that IL-GO had better microwave absorption performance than GO,which was easier to be excited under microwave irradiation,making its non-thermal effect more obvious,and significantly reducing the curing reaction activation energy of IL-GO/EP system.The curing degree of IL-GO/EP reached 0.93 at 110?within the first 10 min,while the curing degree of GO/EP was only 0.85,the curing rate of IL-GO/EP was significantly accelerated.(4)The dispersion stability of IL-GO in epoxy diluent under microwave irradiation,the interfacial activation of IL-GO and EP,and the effect mechanism on the comprehensive properties of composites materials were systematically studied.Based on the characterization methods such as optical microscope,probability density theory of particle spacing,mechanical test,thermal test,dielectric performance test and interface performance test,it was found that IL-GO had good dispersion stability in epoxy diluent under microwave irradiation In the IL-GO/EP system before and after curing,the inter-particle dispersion coefficient of IL-GO was?1.8,which was significantly higher than that of the GO/EP system.At the same time,IL-GO and EP form a better chemically combined micro-interface,and because of the existence of the ?-?/cation-? conjugate structure between IL and GO,the microwave absorption performance of IL-GO has been enhanced,making its interface bonding stronger. |
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