| Water-based coatings have the advantages of low pollution and easy construction,but they are limited by the anticorrosion,heat resistance and mechanical properties.The graphene is a novel carbon nanomaterial,and exhibits the merits of compact structure,stable chemical properties,and high mechanical strength.Therefore,the mechanical and anticorrosive properties of the water-based coating can be improved by adding graphene into coatings.However,the augmented performance can be restricted by the graphene agglomeration phenomenon in the polymer due to the the strong van der Waals force of the graphene sheet and high specific surface area.In this subject,graphene is effectively grafted and modified to improve its compatibility of polymers,and copolymerized with monomers during the preparation of the polymer emulsion through in-situ polymerization method to obtain stable polymers,and finally the high-performance water-based graphene polymer composite coating materials are prepared.In order to improve the compatibility of graphene oxide with acrylic monomers,vinyl tris(β-methoxyethoxy)silane coupling agent(KH-172)was selected for graft modification of graphene,and the optimal process conditions of modified graphene with coupling agent and the effect on structural properties were studied.The optimal ratio of GO to KH-172 was 1:3,the reaction temperature was 80℃ and the reaction time was 5 h.FT-IR analysis showed that KH-172 molecule was grafted on graphene oxide.XRD and SEM results showed that the degree of peeling was improved and the interlayer distance was further increased after the modification for graphene oxide.The thermal stability of modified graphene oxide and dispersibility of modified GO in organic solvents were improved from the TEM and TGA test respectively.In order to improve the stability and dispersibility of graphene in polymer emulsions,the graphene/polymer composite emulsion was prepared by in-situ polymerization,and the optimal process conditions and the synthesis mechanism of composite emulsion were discussed.The best process conditions are as follows:the ratio of soft monomer BA to hard monomer MMA is1:1.28,the amount of functional monomer MAA is 1%,the amount of emulsifier is 3%of the monomer,of which the ratio of anionic emulsifier and non-ionic emulsifier is 2:1,the amount of initiator is 0.6%,the reaction time and temperature are about 3 h and 80℃ respectively,and the optimal amount of functional graphene oxide is 0.2%.The graft copolymerization of functional graphene oxide with acrylic polymer was further confirmed by FT-IR test.The laser particle size analysis showed that the particle size distribution of the emulsion was the narrowest and average when the amount of FGO was 0.2%,the particle size is 150 nm.The synthetic mechanism of FGO composite emulsion was discussed.According to the TEM results,the composite particles showed a mosaic structure.Finally,the effects of modified graphene materials on the corrosion resistance,mechanical and thermal stability of composite coatings were studied.By studying the effect of FGO addition on the corrosion resistance of polymer composite coatings,the composite modulus of the composite coating increased by an order of magnitude,the salt spray resistance time can reach 120 h,but excessive FGO addition will decrease the anticorrosive effect of coatings;the mechanical properties of the composite coating film was studied.The results showed that the graft copolymerization of FGO and polymer was carried out by in-situ polymerization process,which forms the strong interfacial strength between two components,and the tensile strength of the composite coating film was increased by 120%.In addition,the TGA and DSC tests showed that the thermal stability of the composite coating was improved by adding FGO,and the thermal decomposition temperature increased by nearly 40℃. |
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