Study On The Structure And Properties Of Self-healing Brominated Butyl Rubber Anticorrosion Coatings

In recent years,with the improvement of the requirement of long-term protection ability,anti-corrosion coating with self-repairing performance has become one of the crucial research contents in the field of metal anti-corrosion.However,at present,some materials with self-repairing function often have some problems,such as poor mechanical properties and weak fracture resistance,which lead to the mutual limitation of self-repairing and mechanical properties of coatings,and it is difficult to exert the maximum anti-corrosion effect.Therefore,whether the anti-corrosion performance and mechanical properties of the coating can be restored or even enhanced under the premise of ensuring the complete repair of the substrate is a difficult problem for the future development of anti-corrosion coatings.In order to solve the above problems,this paper uses brominated butyl rubber（BIIR）as the matrix and introduces pyridine derivatives to prepare BIIR polymer with ionic bonds.BIIR polymer shows excellent anticorrosion performance as a metal anticorrosive coating.At the same time,dynamic reversible ionic bonds not only improve the mechanical properties of BIIR,but also endow it with self-repairing performance at room temperature.In order to improve the anti-corrosion ability of the coating,this paper will further study the relationship between graphene（GP）filler and BIIR coating’s protection ability.The results indicated that the anti-corrosion performance of TBP-BIIR/GP composite coating is greatly improved by the cation-πinteraction between GP and pyridine ions and the barrier effect of GP layer.Among them,the ionic bond in the composite system endows it with self-repairing performance,which greatly promotes the long-term protection ability of the coating.This idea in this paper can provide a new strategy for microstructure design and self-healing molecular dynamics of anticorrosive coatings.Specific research is carried out from the following three parts:1.According to the characteristics of dynamic bond ions,this paper innovatively uses pyridine derivatives to prepare self-repairing BIIR polymer based on electrostatic action.During the heating process of BIIR,its allyl bromide is easy to isomerize from the outer conformation to the inner conformation,thus producing active sites.Bromine with the inner conformation reacts with pyridine derivatives in the melt at high temperature to form ionic bonds.Using pyridine with different substituents on the 4th position as crosslinking agent,it is found that the stronger the electron donating effect of substituents on the 4th position of pyridine ring,the easier it is to form regular ionic aggregates with larger molecular volume,and this type of ionic aggregates is beneficial to improve the mechanical properties and self-healing efficiency of BIIR polymer.Among them,tert-butyl pyridine（TBP）,which has the strongest electron donating ability,has the most obvious improvement on the mechanical properties and self-repairing properties of the polymer.Therefore,TBP is selected as the crosslinking agent in this thesis,and the BIIR polymer formed by TBP is studied in depth.2.In this paper,a TBP-BIIR anticorrosive coating with self-repairing function was prepared by calculating the bromine content in BIIR and controlling the mole fraction of pyridine derivatives with different electron donating effects to brominated butyl rubber at1:1.TBP-BIIR polymer was coated on a tinplate,and the microstructure,composition and mechanical properties of the coating were analyzed by means of NMR,IR and DMA.By adjusting the thickness of the coating and soaking in different corrosion solutions,the corrosion resistance and self-repairing performance of the coating were deeply studied by means of electrochemical test,scanning electron microscope,optical microscope and metallographic microscope.It is found that TBP-BIIR coating can be used in three simulated corrosion environments（HNO₃,p H=2;Na OH,p H=12;3.5 wt%Na Cl）showed a protection efficiency of over 94%.TBP-BIIR polymer can complete self-repairing behavior at room temperature without external conditions triggering,and the repaired TBP-BIIR sample can keep its integrity under different strains.Moreover,in the strong corrosive solution,the protection efficiency of the self-repairing coating can still remain above 89%,and the highest can reach about 95%.Its self-repairing performance is due to the mobility of BIIR molecular chain and the synergistic effect of dynamic reversible ionic bonds in the cross-linking network.This shows that TBP-BIIR anticorrosive coating has excellent safety and durability,and can achieve long-term protection ability in extreme environments.3.In order to further improve the anti-corrosion performance of TBP-BIIR coating,we introduced GP into TBP-BIIR system to form TBP-BIIR/GP composite coating.We analyzed the microstructure of the coating by TEM,SEM and XRD,and found that GP was uniformly dispersed in the coating.When the addition of GP is 0.15%,the electrochemical research results show that its protection efficiency for metal matrix is as high as 99.74%.At the same time,TBP-BIIR/GP coating is exposed to severe corrosive environment（HNO₃,p H=2;Na OH,p H=12;3.5 wt%Na Cl）,and the coating shows low self-healing activation energy in three kinds of corrosive solutions,which can realize self-healing in corrosive solutions.Due to the two-dimensional lamellar structure of GP,the fracture stress of TBP-BIIR/GP composite coating also increased to 15.47±0.05 MPa.The experimental results show that TBP-BIIR/GP polymer is a promising self-repairing anticorrosive coating material.