Preparation And Application Of Coating Based On Michael Addition Reaction

With the development of economy and progress of science and technology,coatings are also making progress towards green,environmental protection and high efficiency.However,the traditional coating is limited by curing technology,high energy consumption,it is hard to be applied in the field of low temperature curing.Michael addition reaction has the potential to be used as a curing technology in the field of low temperature curing coatings due to its relatively mild reaction conditions and no small molecule release.The raw materials of Michael addition coatings were mostly liquid resins with low molecular weight,which contain many active groups and need to consume a large number of flexible receptors,resulting in low glass transition temperature（T_g）and poor thermal stability of the coatings.Therefore,in this work,Michael addition reaction between the prepared dicarbonyl terminated polyester and acrylate receptors and bismaleimide receptors was used to prepare a coating that could cure at a lower temperature and had excellent thermal stability.The main research results as follows:In this work,hydroxy-terminated polyester resin was prepared from neopentyl glycol and terephthalic acid.Diethyl malonate and tert-butyl acetoacetate were used to modify the polyester resin through transesterification reaction,and a dicarbonyl terminated polyester resin（malonate polyester and acetoacetate polyester）suitable for Michael addition reaction was prepared.The structure and properties of the products were characterized by ~1H NMR,FTIR,GPC,TGA and XRD.Neopentyl glycol diacrylate and trimethylol propane triacrylate were selected as receptors for Michael addition reaction.Michael addition coating was prepared by reaction of receptor and dicarbonyl terminated polyester resin.The structure of the films was analyzed by FTIR.The properties of the films were analyzed by gel content,THF swelling,hardness,TGA,DSC,DMA and other test methods.The results showed that the films could complete the curing reaction at 70℃,and the T_gof the films was 18.8～24.4℃.Compared with the films prepared by the same method in the literature,the T_gimproved.The films prepared by acetoacetate polyester have higher T_gand thermal stability than those prepared by malonate polyester.In terms of mechanical properties,the elongation at break was more than 120%,showing good flexibility.Michael addition coating was prepared with malonate polymer and bismaleimide The catalyst DBU/benzoic acid salt suitable for Michael addition reaction was prepared by using DBU and benzoic acid.The structure and surface morphology of the films were characterized by FTIR,SEM and high definition camera.The structure of DBU/benzoic acid salt was characterized by ~1H NMR.The properties of the films were analyzed by DSC,gel content,THF swelling,TGA,DMA and other test methods.The results showed that with the increase of the amount of BDM,the pencil hardness and T_gof the films increased gradually,and the thermal stability of the coating increased,while the gel content increased firstly and then decreased.According to the comprehensive properties of the films,the optimal molar ratio of active hydrogen in malonate resin to conjugated double bond in BDM was determined to be 1:0.8.T_gwas 77℃,and the degradation temperature of 10%weight loss was 376.4℃.Compared with the Michael addition coating prepared by the same method in the literature,its thermal properties are greatly improved.The coating has the advantages of simple preparation method and excellent thermal properties,which was suitable for Industrial production and has broad application prospect in high heat resistant coatings.