Synthesis And Investigation Of Mussel-Inspired Adhesive Polymers And Its Anticorrosion Performance And Mechanism In Waterborne Coatings

Metal materials such as iron and steel are widely used in many fields of national economy and national defense because of their excellent mechanical and processing properties.However,it corrodes easily with corrosive media in the external environment,which will not only reduce the mechanical strength and service life of steel itself,but also bring huge safety risks,even major safety accidents.So it needs corrosion protection measures to solve this problem.Coating on metal surface is one of the most economical and effective protective measures,which can effectively restrain metal corrosion and prolong its service life.The development trend of anticorrosive protective coating is long-term,environment-friendly and multi-functional.Therefore,it is of great socio-economic significance and scientific significance to develop new environmental protection coating and discuss the new anti-corrosion mechanism of coating.Mussels can almost adhere to almost all the base material by mytilus edulis foot.Studies have shown that the strong adhesive ability with various substrates in wet environment is provided by main component of MAP protein in mytilus edulis foot.In the process of adsorption,DOPA plays a major role in for this special adhesion due to its high affinity,strong coordination ability and the chemical versatility adhesion.Thus it can react with metal to generate the passivation film which has a certain anticorrosion effect and the environmental non-toxic adhesive protein.These characteristics make it have unlimited potential value in corrosion inhibitor field.At present,the preparation methods of mussel adhesive proteins mainly include two methods:extraction from mussel and genetic engineering--cloning.However,it cannot adapt to the market due to the complex preparation process,low yield and high pric.So the application and development of mussel adhesive proteins are seriously restricted.As an alternative to MAP,adhesive polymer materials containing the catechol functional group can be obtained synthetically.This synthetic process is simple with common raw starting materials,which is beneficial to industrial applications.It is the best way to the future to make better use of this kind of functional materials.The mussel adhesion protein polymer（PHEA-DOPA）was successfully synthesized by means of design and optimization.The anti-corrosion mechanism of PHEA-DOPA in coatings was discussed by EIS、surface analysis、QCM-D in waterborne epoxy coatings and GMA modified waterborne alkyd coatings,the main results were as follows:Synthesis and characterization of mussel adhesive protein polymer（PHEA-DOPA）:Here,functional group of DOPA were successfully introduced to the side chain of polyaspartamide（PSI）as non-toxic and friendly degration material based on the ammonolysis reaction between dopamine and five ring of PSI.The polymer（PHEA-DOPA）that mimic the MAP structure was got and the synthesis conditions,oxidation stability and corrosion inhibition were studied.The results showed that the synthetic process of the mussel inspried polymer would not be oxidized under the protection of nitrogen and reducing agent.It would be oxidized under the condition of air,hydrogen peroxide and other oxidants and it could be complexed with Fe³⁺,which had a certain antiseptic effect on carbon steel.Anti-corrosion mechanism of PHEA-DOPA in waterborne epoxy coatings:Protective properties and mechanism of the waterborne epoxy coating containing PHEA-DOPA were investigated by EIS,scanning electron microscope（SEM）,quartz crystalmicro balance with dissipation monitoring（QCM-D）and Raman microspectroscopy.The EIS and SEM results indicated that the addition of PHEA-DOPA could significantly improve protection properties of waterborne epoxy coatings.The evidences of QCM-D and Raman microspectroscopy demonstrated that when the DOPA group in PHEA-DOPA structure was oxidized to dopamine quinine（Dq）,it had stronger adsorptive complex effects on Fe³⁺,and could generate insoluble[Fe（Dq）₃]³⁺complexes on the surface of carbon steel and inside the coatings,which inhibited dissolution process of Fe and improved coating density.Addition of PHEA-DOPA adhesive polymer can significantly improve protective properties of waterborne coatings.PANI surface wetting modification by PHEA-DOPA and its anti-corrosion mechanism in waterborne epoxy coatings:The surface of PANI was modified by the mussel inspired polymer（PHEA-DOPA）with special adhesive ability to improve the dispersion of polyaniline（PANI）in the coating.At the same time,the protective performance of PANI and PHEA-DOPA in the coating was studied relatively and the protection mechanism was discussed.The results show that PHEA-DOPA can make good wetting modification of polyaniline surface,which improve its dispersion property in the coatings.At the coating formation stage it gradually desorbed from PANI surface and also complex with Fe³⁺,that provide excellent anti-corrosion property.These can provide provide theory support for the widely application of PANI in coating.The anti-corrosion mechanism of PHEA-DOPA in GMA modified waterborne alkyd resin coating:The alkyd resin was successful modified by introduced the glycidyl ester of acrylic（GMA）through structure design and synthesis of resin.GMA can provide some C=C double bond that was damaged in the process of waterborne alkyd resin.Thus it can provide more oxidation junction by double bonds alkyd resin to improve the performance of drying time and the crosslinking density of the resin film,which greatly improve the coating properties,such as water resistant.The protective properties and mechanism of PHEA-DOPA in alkyd system were studied by means of EIS,SEM and Raman spectroscopy.The results show that the drier such as manganese and zirconium metal elements（Mcatalyst）in alkyd system c has the strong oxidation ability and can be able to oxidize the DOPA group of PHEA-DOPA direct into dopamine quinone（Dq）.Then the Dq can quickly react with the metallic elements in the drier to form the[Dq-M_catalyst]complex,which improve the protective performance of the coating itself only,but there is no redundant PHEA-DOPA that react with Fe³⁺to improve the coating resistance.