Preparation Of Polymer/Rust Inhibitor Microcapsules By Centrifugal-Coating Method And Characterization Of Rust Resistance

The loss of concrete durability caused by the corrosion of steel bars in concrete has become a major practical problem in concrete construction.Inorganic corrosion inhibitor has been proved to be an effective and economical way to prevent rust in many engineering practices.However,it has the disadvantages of easy loss and high toxicity,which causes the low efficiency.Microencapsulating the corrosion inhibitors is expected to solve the above problems.Centrifugation-coating method is a common kind of drug sustained release pellets processing technology.In this paper,polymer/Ca?NO₂?₂,polymer/MFP and polymer /hydroxide microcapsules were prepared by this method for the first time,and the processing technology,release characteristic,anticorrosion property of microcapsules were studied,which will provid important reference for the application of microcapsules in concrete.The process technology of microcapsules was optimized in orthogonal experiment,the rotational speed of the turntable was 500r/min,the speed of the fan was 400r/min,the speed of the peristaltic pump was 15r/min and the jet pressure was 0.10 MPa,the comprehensive property of the initial pellets was the best.The analysis on the surface morphology,thermal stability and mechanical properties of microcapsules revealed that core materials were completely capsulated by polymer wall material and the bigger the weight gain rate of the wall material can result in the thicker wall.Microcapsules have high drug loading rate and mechanical strength.The release rate of polymer/Ca?NO₂?₂ microcapsules with different wall materials and weight gain rates was measured by ion chromatography in the simulated concrete pore solution.It was found that the higher of weight gain rates,the slower of the release rate of microcapsules,the release rate was faster than the EC when microcapsules with PMMA as the wall material.PDS and EIS texts in the simulated solution showed that the microcapsules wall material was PMMA,the weight gain rates was 20wt%,the adding amount was 20g/L,the steel bars has a high corrosion potential,and the capacitive arc radius is larger,the lowest corrosion of steel bars.It was found that the mechanical properties of the concrete were improved by 0.5wt% microcapsules addition with the particle size of 60-80 mesh.Concrete RCM experiments showed that the higher amount of microcapsules,the smaller of the particle size,the chloride diffusion coefficients of concrete was smaller,and the better of the resistance to chloride ion permeability.With the increase of the microcapsules content,the corrosion potential and the capacitance arc radius of steel bars was increased,and the rust effect was better.The release rate of polymer/MFP microcapsules in the simulated solution was measured by atomic absorption spectrophotometry,and its release rate was slowed down with the increase of the weight gain rates of microcapsules wall material,and the release rate of microcapsules with EC as wall material was slower.PDS and EIS tests showed that the anticorrosion effect of microcapsules was better when PMMA as wall material with a weight gain rate of 20 wt%,for it had a higher corrosion potential and lower corrosion current density,and the larger capacitive arc radius during the whole immersion period.Increase the dosages of microcapsules can improve the corrosion potential and the capacitance arc radius of steel bars at the late stage of immersion,the steel bars corrosion harder to occur.In the concrete,PDS and EIS test showed that microcapsules can improve the corrosion potential and charge transfer resistance of steel bars,and with the extension of the experimental time,the more the amount of microcapsules added,the better rust effect.The release rate of polymer/hydroxide microcapsules with different wall materials and weight gain rates was measured by TG in the simulated solution,and the change of the p H values of the solution was measured.It was found that the hydroxide microcapsules can decrease the release rate of OH-in the simulated solution,delaying the decrease of the p H value of the solution.Electrochemical tests showed that the core material was Ba?OH?2,the wall material was PMMA,the weight gain rate was 20wt%,microcapsules had the best the anticorrosion effect,for the corrosion rate of the steel bars was kept at a low level and with a larger capacitive arc radius.Combined with the corrosion of steel bars section,found that the more the amount of microcapsules added,the lower the corrosion degree of steel bars.In concrete,microcapsules can also effectively retard the decrease of the p H values of the concrete and improve the anti-carbonization ability of the concrete.The resutlts from electrochemical tests in concrete showed that hydroxide microcapsules can improve the rust resistance of hydroxide.In the later stage of experiments,microcapsules can improve the corrosion potential,reduce the corrosion current density,and increase the charge transfer resistance of steel bars,and the more dosages of microcapsules,rust performance gradually improved.