光热响应型MXene基聚氨酯涂层的制备及其自修复防腐性能

Preparation and Self-healing Anticorrosion Properties of Photothermal Responsive MXene-based Polyurethane Coatings

涂层服役过程容易划伤产生裂纹缺陷造成被动失效,降低防护性能,研发具有自修复性能的防腐涂层对海洋工程材料的腐蚀防护具有重要意义。采用刻蚀剥离法成功合成MXene二维纳米材料,再通过一锅法合成具有丰富氢键的MXene聚氨酯本征自修复涂层。MXene优异的光热转换性促进了涂层链段的运动和氢键重组过程,进而提升了自修复性能。对MXene涂层进行5次划伤-光热自修复循环测试,低频阻抗模值均能恢复到10~8Ω·cm^(2)左右,具有优异的多循环自修复性能。通过电化学阻抗测试,MXene涂层具有较好的长效防腐性能,在浸泡的30d期内,涂层的低频阻抗模值能一直保持在10~8Ω·cm^(2)以上,一方面归因于二维材料优异的阻隔性能,另一方面涂层的自修复性不断修补微裂纹,减缓了腐蚀介质的渗入。试验结果表明,将MXene材料作为光热转换剂制备得到具有良好光热响应性和长效防腐性的聚氨酯自修复涂层。光热响应型MXene自修复涂层具备长效防护性能,能够应用于海洋工程装备提升服役寿命。

Coatings are prone to scratching and cracking defects during service,which result in passive failure and reduced protective performance.The development of self-healing anticorrosive coatings is necessary for the corrosion protection of marine engineering materials.In this study,MXene two-dimensional nanomaterials were successfully synthesized using an etching and stripping method,and MXene polyurethane self-healing coatings with rich hydrogen bonds were synthesized using a one-pot method.The microstructure of the MXene was investigated using scanning electron microscopy,energy dispersive X-ray analysis,X-ray diffraction,and X-ray photoelectron spectroscopy.The results showed that the aluminum layer of Ti3AlC2 was successfully etched by acid etching and ultrasonic stripping to obtain a two-dimensional Ti3C2 MXene material.Self-healing polyurethane coatings containing numerous hydrogen bonds were synthesized using Polytetramethylene ether glycol as the soft segment,isophorone diisocyanate and toluene diisocyanate as the hard segments,and Dimethylglyoxime as the chain extender.MXene was doped into the coating as a photothermal agent to improve the repair efficiency and protection performance.The synthesis of PU and PU/MXene was confirmed using Fourier transform infrared spectroscopy.The photothermal properties of the coatings were characterized using a near-infrared laser emitter and thermal imager.The temperature of the PU/MXene coating surface increased by more than 20℃within 1 min,reaching 43.1℃,which was significantly higher than the 29℃of the PU coatings,demonstrating that the composite coating doped with MXene exhibited a good photothermal conversion performance under near infrared light.The self-healing process of the coating was monitored using confocal laser scanning microscopy.The healing rate of the PU/MXene coating was higher than that of the PU coating.The excellent photothermal conversion of MXene facilitated the motion of the coating segments and the hydrogen bond recombination process,thereby improving the self-healing performance.The self-healing and anticorrosion properties of the coatings were investigated via electrochemical testing.The initial low-frequency(0.01 Hz)impedance mode value of the PU/MXene coating samples before scratching was close to 109Ω·cm^(2),which is significantly higher than that of the PU coating(107Ω·cm^(2)),and the corrosion resistance was better.After the first scratching,the low-frequency impedance mode value of the coated sample sharply decreased to below 105Ω·cm^(2),and the corrosion resistance decreased.After the repair,the low-frequency impedance mode value was restored to an impedance value close to the initial level.The scratch and photothermal self-healing cycle of the PU/MXene coating were tested for five times,and the low-frequency impedance modulus could be restored to approximately 108Ω·cm^(2).However,the impedance mode values of the PU-coated samples after the repair were significantly lower than those of the PU/MXene-coated samples.The MXene/PU coating exhibited excellent cycle repair performance,which significantly improved the service life.The electrochemical impedance test results show that the low-frequency impedance modulus of the coating sample can be maintained above 108Ω·cm^(2).When immersed in a 3.5 wt.%sodium chloride solution for 30 d,the low-frequency impedance mode value of the PU/MXene coating can remain above 108Ω·cm^(2),whereas the PU coating is only higher than 106Ω·cm^(2),indicating that the anticorrosion property of the PU/MXene coating can be maintained for an extended period.Two main reasons are responsible for why the PU/MXene coatings exhibit improved long-term anticorrosion performance.On the one hand,this is attributed to the excellent barrier properties of the two-dimensional materials;on the other hand,the self-repair of the coating constantly repairs microcracks and reduces the infiltration of corrosive media.The experimental results showed that a polyurethane self-healing coating with a good photothermal response and long-term anticorrosion was prepared using MXene as a photothermal conversion agent.This study provides a theoretical basis for the practical application of photothermal responsive polyurethane self-healing coatings on marine engineering equipment.