Surface Micro-treatment And Antibacterial Functionalization Of Aluminum Alloy

Aluminum alloy has a wide range of applications for its excellent performance.Alumina film on the surface can effectively protect the aluminum alloy from further oxidization and corrosion,but can not help resist the adhesion and reproduction of bacteria.The adhesion of bacteria on the aluminum alloy will pollute the material,impair the properties,and hinder its application.Therefore,the antibacterial functionalization of aluminum alloy is of great significance.Common methods include preparation of antibacterial alloy and antibacterial surface modification.While the former is a complex technique that changes the composition of the material system,it is desirable to consider the more environmental-friendly surface funcationalization way.And the most commonly used means is to apply antibacterial coating on the surface.Nonetheless,the coating‘s tendency to fall off over time is the problem to be solved.Thus it is of great importance to improve the bonding strength between the antibacterial coating and the aluminum alloy substrate,or to achieve the antibacterial function in a simple way without doing harm to the environment or affecting the mechanical strength of aluminum alloy.Taking the above background into consideration,we have choosen the 5A06aluminum alloy as investigation object and projected to realize the antibacterial modification on the aluminum alloy surface by means of microprocessing,coating with epoxy resin,grafting antibacterial quaternary ammonium salt and development of special nano-arrays on the surface.1.The aluminum alloy was treated with H₂O₂ to develop three-dimensional nano interconnects on the surface.The nanostructure was observed in SEM images.Then the epoxy resin doped with 75 g/L concentration of[3-（trimethoxysilyl）propyl]ammonium chloride（DC5700）was injected into the nanostructure on the surface using a molding machine.Subsequent adhesion test showed the bonding strength between the coating and substrate and tensile test showed the mechanical property of the modified alloy.The results demonstrated the interconnected network structure greatly enhanced adhesion force between the alloy and the epoxy resin.With a thickness thin as 20-50μm,the transparent epoxy layer barely made any difference to the appearance of the aluminum alloy,nor did it affect the mechanical property of the aluminum alloy too much.The coated sample exhibited excellent antibacterial activity against gram negative bacteria and gram positive bacteria.When the mass ratio of DC5700:epoxy resin was 1:100,the antibacterial rate on Escherichia coli（E.coli）and Staphylococcus aureus（S.aureus）was over 99%.2.5A06 aluminum alloy was first treated with hot water.The surface activation degree was characterized by infrared spectrum analysis and surface wettability.Then the hydrolysed DC5700 was grafted onto the surface of aluminum alloy through a coupling reaction under certain temparature,and the surface antibacterial func-tionalized aluminum alloy was obtained.Infrared spectroscopic analysis and XPS analysis proved the suscessful grafting of DC5700 and efficient activation of hot water treated aluminum alloy.Mechanical strengh of the treated alloy did not fall but increased for a bit.In this way,the7.5 g/L DC5700 grafted aluminum alloy,when treated with 40℃water,exhibited antibacterial rate against S.aureus of over 99%,and when treated with 80℃water,the antibacterial rate against E.coli was over 99%.3.Interesting nano-phosphorus structures were observed on the surface of aluminum alloy after subjecting to a boiling water and DMF solution two-step processing method.By carefully adjusting the processing temperature and period,we tried to regulate the morphology of the nanostructure in the hope that this nano-structure possessed physical antibacterial property.However,the results showed the antibacterial property of the aluminum alloy with such special surface against S.aureus and E.coli were not much prominent due to the instability of the tip phosphorus structure size.