Design,Preparation,and Mechanism Of Polyurethane-based Repeatable Self-healing Antifouling And Anti-corrosion Bionic Coating

With the rapid development of our maritime economy,shipping freighters are advancing into deep and distant oceans,meaning that large freighters need to operate for long periods of time in marine environments with high humidity,high salt,and even high temperatures.The harsh working environment of the ocean poses severe challenges to the key components of cargo ships,such as marine corrosion and biofouling.Due to the lack of a comprehensive three-dimensional anti-fouling and anti-corrosion technology system,the damage caused by marine biofouling and various forms of corrosion on key components of marine cargo ships is increasingly prominent.Therefore,it has become a hot issue in this field to improve the antifouling and anticorrosion performance of key components of ocean freighters.In nature,the fat layer in the skin of dolphins relies on its elasticity and toughness to resist the impact of water current when swimming rapidly.Inspired by this,a highly elastic and tough polyurethane-based antifouling and anticorrosion bionic coating was designed.On this basis,drawing inspiration from the self-healing mechanism of animal epidermal tissues and the super-strong mechanical properties of cartilage tissues,dynamic bonding and hydrogen-bonded graphene are introduced into the bionic coatings to ensure that the mechanical properties are based on the self-healing properties.Thereafter,the coating is modified with epoxy to improve its adhesion,to fulfill industrial application needs.This study has conducted a detailed exploration of the anti-fouling,anti-electrochemical corrosion,anti-cavitation,and self-healing properties and mechanisms of the bionic coating,with the main research contents and conclusions as follows:（1）A series of polyurethane coatings（Si PU-X,where X denotes the mass percentage of OH-PDMS in polybutylene glycol）modified with OH-PDMS were prepared utilizing toluene diisocyanate,1,4-butylene glycol,and mocarbon as the hard segments,and polybutylene glycol and end-hydroxypolydimethylsiloxane（OH-PDMS）as the soft segments.Mechanical property tests demonstrated that the mechanical properties of Si PU-15,which contains 15 wt%OH-PDMS,were optimal,showing a32%increase in tensile stress compared to Si PU-0.Cavitation erosion test and electrochemical impedance spectroscopy test（EIS）revealed that Si PU-15 exhibited superior resistance to cavitation,and the mass loss rate is reduced by approximately 30%after continuous cavitation for 60 h.And its antielectrochemical corrosion performance is improved compared with Si PU-0,and|Z|_0.01Hz can still maintain 3.33×10⁷Ω·cm²after immersing in 3.5 wt%Na Cl for 10 d.In addition,the antifouling performance test was carried out on Si PU-X,and the results show that Si PU-15 has the best antifouling performance,and its antimicrobial rate（Paracoccidioides panniculatus）reaches 67.4%.（2）Inspired by the regeneration principle of animal epidermal damage and the super strong mechanical properties of cartilage tissue,disulfide bonds are introduced into the polyurethane-based antifouling and anticorrosion bionic coatings to render them self-healing,and the fiber mesh structure in cartilage is simulated by utilizing functionalized reduced graphene oxide（Fr GO）,which is introduced into the polyurethane-based antifouling and anticorrosion bionic coatings with self-healing function,to synthesize antifouling and anticorrosion bionic coatings（MPU-Fr GO）with self-healing function.The effect of different Fr GO contents on the antifouling and anticorrosion properties of MPU-Fr GO was investigated.It was found that the introduction of 1 wt%Fr GO（MPU-Fr GO3）into MPU-Fr GO significantly improved its mechanical properties.The stress was increased by 40.7%compared to the polyurethane without added Fr GO.EIS indicated that the impedance value of MPU-Fr GO3 at low frequency was increased by 3 orders of magnitude compared with that of polyurethane without added Fr GO,exhibiting excellent electrochemical corrosion resistance.In order to improve the static antifouling ability of the bionic coating,an isothiazolinone antifouling agent was introduced into MPU-Fr GO3,leading to an increase in its antimicrobial rate to 99.5%.In addition,MPU-Fr GO3 has a favorable photothermal self-healing property,with a healing efficiency of up to 91%.Finally,the cavitation test of MPU-Fr GO3 was carried out for up to 60 h.The results demonstrated that the cavitation resistance of MPU-Fr GO3 was weak.（3）In order to improve the cavitation resistance of MPU-Fr GO3,DA bonds with higher bonding energy were introduced into the bionic coating instead of disulfide bonds.On this basis,the polyurethane was modified with epoxy resin to improve the adhesion and mechanical properties of the coating.It was found that the coating（EPU2）had the best mechanical properties when the epoxy resin was added at 5%,with an increase in stress of 4.7 MPa compared to EPU1（epoxy resin addition of 0 wt%）.Based on this,isothiazolinone antifouling agent and hydrogen-bonded graphene were introduced into EPU2 to prepare bionic coating（FD-EPU）.The excellent mechanical properties also contribute to the favorable cavitation resistance of FD-EPU,which is40.5%lower than that of EPU1.EIS indicated that FD-EPU has good electrochemical corrosion resistance.After 15 days of continuous soaking in 3.5 wt%Na Cl solution,the|Z|_0.01Hz value of FD-EPU is still an order of magnitude higher than EPU1.Additionally,the antifouling test showed that FD-EPU has excellent antifouling ability,with antimicrobial rate and anti-algae rate reaching 97.5%and 96.2%,respectively.However,the self-healing ability of the coating was poor.After irradiation with near-infrared light at 0.5 W/cm² for 30 s,the self-healing efficiency of the coating is only 61%.（4）In order to further improve the self-healing performance of FD-EPU,amino chain extender is adopted instead of hydroxyl chain extender to increase the dynamic bond density of the coating,which enables the coating to activate the hydrogen bond to assist the DA bond to realize high-efficiency self-healing in the self-healing process.It was found that when the molecular weight of the soft segment and its content were1000 g/mol and 41 wt%,respectively,the coating（PUE3）exhibited the best tensile stress,reaching 48.1 MPa.On this basis,isothiazolinone antifouling agents and hydrogen-bonded graphene were introduced into PUE3 to prepare a bionic coating（PUE-FD）.The excellent mechanical properties enable FD-EPU to possess outstanding resistance to cavitation erosion;after continuous cavitation for 60 hours,the mass loss was only 2.8 mg.Moreover,EIS showed that PUE-FD has good electrochemical corrosion prevention performance.After being continuously immersed in 3.5 wt%Na Cl solution for 15 days,the|Z|_0.01Hz value of PUE-FD was still one order of magnitude higher than that of PUE3.The antifouling performance of PUE-FD is also more prominent,with the antimicrobial rate and anti-algae rate reaching 99.4%and close to100%,respectively.In addition,PUE-FD also demonstrated excellent self-healing ability;under near-infrared irradiation of 0.5 W/cm²,a self-healing efficiency of 80.6%was achieved in just 60 s.