Preparation And Properties Of Magnetic Microcapsule

With the rapid development in the fields of information and material, more and more tiny particles have been applied to the display. Due to its density, magnetic particles are easy to precipitate in organic solvent. Thus the display stability is poor using traditional magnetophoresis technology. Magnetic fluid can be encapsulated by polymer material. Microencapsulation, which defines magnetic particles in a tiny area, can reduce the interaction among the magnetic particles and extend service life. Magnetic microcapsules, that possessing magnetic orientation and biocompatibility,, are widely used in targeting drug delivery, controlled release, protein separation, magnetophoresis display and nondestructive inspection. But the display technology of magnetic microcapsule is monopolized by Japanese, and the majority of magnetophoresis display boards used in China are imported from Japan.In this paper, magnetic nano-particles (MNP) were prepared by chemical co-precipitation. The surface modification of MNP was carried out with oleic acid. Properties of MNP were characterized by XRD, TEM, FT-IR, VSM, TGA and contact angle test respectively. Magnetic microcapsules, which containing tetrachloroethylene and Fe3O4nanoparticle as core material, were prepared from gelatin and arabic gum by means of complex coacervation method. And the influence of preparation process parameters on properties of magnetic microcapsules were studied in detail, such as gelatin-Arabic gum mass ratio, reaction pH value, stirring rate, reaction time, rate of adding acid, core-wall ratio and curing reaction. Properties of magnetic microcapsules were characterized by Zeta Potential, particle size distribution analyzer, optical microscopy, SEM, VSM, TGA. Moreover, magnetic microcapsules were prepared by solvent evaporation, using undecane as dispersion medium, polymethylmethacrylate (PMMA) as wall material and magnetic fluid as core material.The main results are summarized as following:(1)The result of XRD test show MNP prepared by chemical co-precipitation are nano-Fe3O4. FT-IR analysis indicates that mechanism between oleic acid and MNP is chemisorption. The optimal ration of Fe3O4/oleic acid (w/w) is33to10. After organic modification, MNP can stably suspend in tetrachloroethylene medium. Contact angle test shows that MNP became more lipophilc from.hydrophilic feature. TEM shows that MNP exhibites stable dispersion in tetrachloroethylene without any aggregatation after organic modification. The mount of oleic acid on the surface of MNP is about23%according to the data of TG. The saturation magnetic strength of Fe3O4and modificated Fe3O4is77emu/g and67emu/g respectively.(2) The iso-electric point (IEP) of gelatin is about5.0based on the Zeta Potential. Meanwhile, gelatin shows maximal positive charge when pH is3.8. The results show that the optimal conditions are as follow:temperature is40℃, pH is3.8, time is30min, gelatin-Arabic gum’s mass ratio is1:1, stirring rate is600r/min, adding acid rate is0.088ml/min, core-wall ratio is1:1, curing agent is glutaraldehyde, and mass ratio of gelatin/glutaraldehyde (w/w) is from1/2to1/3.Magnetic microcapsules prepared under optimal coditions have regular and sphere-like shape. Surfaces of magnetic microcapsules are smooth, with hyaline wall, narrow particle size distribution, good dispersibility and thermostabilization. MNPs disperse equably in the microcapsules, which can be applied to magnetophoresis display. The saturation magnetic strength of magnetic microcapsules is22.1emu/g. Magnetic microcapsules are expected to be used in target drug delivery because of good magnetic response.(3) Tetrachloroethylene is not a good dispersion medium used in solvent evaporation method. On the contrary, undecane is a more appropriate dispersion medium. The magnetic microcapsules were prepared under conditions of PMMA/magnetic fluid mass ratio1:4, lauryl sodium sulfate (SDS) content2%, stirring rate800r/min, temperature35℃.The results show that magnetic microcapsules reveal good dispersibility with smooth surface, transparent wall, and uniform particle size distribution. Therefor, it can be applied potentially to magnetophoresis display.