Preparation And Performance Study Of MMT/PPy-PCL Composite Coating On Medical Magnesium Alloy

Magnesium alloy,as a commonly used metal material in medical implant applications,possesses favorable biocompatibility,mechanical properties comparable to those of human bones,and superior degradability.However,the rapid degradation of magnesium alloy during implantation causes issues such as mechanical failure,localized p H increase,and excessive hydrogen gas production,thereby greatly impeding its clinical application.To overcome these challenges,research on magnesium alloy’s corrosion resistance is of paramount importance.Surface modification is a popular method for enhancing magnesium alloy’s corrosion resistance.By creating a protective coating on magnesium alloy’s surface,the corrosion resistance can be significantly improved.However,a single protective coating is often insufficient to meet the protective demands of magnesium alloy.Therefore,an inorganic coating that can bond well with the magnesium alloy substrate is typically used as a primer,followed by the preparation of an organic coating with excellent corrosion resistance to achieve long-term protection of the magnesium substrate.Additionally,by treating the organic coating and altering its properties,the degradation rate can be controlled,indirectly achieving controlled degradation of the magnesium alloy.This study employed a hydrothermal method to prepare a montmorillonite coating on the surface of AZ31 magnesium alloy and investigated the impact of various hydrothermal reaction process parameters(including montmorillonite concentration,reaction time,reaction temperature,and p H value)on the corrosion resistance of the coating.Furthermore,the study explored the morphology,composition,corrosion resistance,and biocompatibility of the montmorillonite coating.Subsequently,a layer of polycaprolactone coating doped with poly-pyrrole was applied to the surface of the montmorillonite coating using an immersion method.The effects of different polypyrrole doping ratios on the morphology of the composite coating,bonding strength with the primer coating,corrosion resistance,and biocompatibility were also examined.The experimental results show that the montmorillonite coating prepared by hydrothermal method using montmorillonite as raw material has the best corrosion resistance when the montmorillonite concentration is 0.9%,the reaction time is 24 hours,the reaction temperature is 150℃,and the p H value is 11,as determined by orthogonal experiments.The experimental results show that the coating of montmorillonite can effectively improve the corrosion resistance and biocompatibility of magnesium alloy.The doping of poly-pyrrole has an effect on the morphology of the composite coating,causing pores to appear on the originally dense surface of the polycaprolactone composite coating.By adjusting the doping ratio of poly-pyrrole,the frequency of pore occurrence can be controlled to some extent,and the number of pores on the surface of the composite coating increases with the increase of poly-pyrrole particle doping ratio.The doping of poly-pyrrole has a certain degree of influence on the bonding strength of the composite coating,but there is basically no effect on the bonding strength of the coating when the doping amount is small.The pores on the surface of polycaprolactone caused by the doping of poly-pyrrole will affect the corrosion resistance of the composite coating,and the corrosion resistance of the composite coating decreases as the number of pores increases.By adjusting the amount of poly-pyrrole doping,the corrosion resistance of the composite coating can be adjusted to some extent.The composite coating doped with poly-pyrrole has good biocompatibility.