Preparation And Properties Of Polystyrene/Fe₃O₄ And Polylactic Acid/Fe₃O₄ Nanocomposites

Nano-Fe₃O₄ magnetic composites which have properties of superparamagnetism,biocompatibility,and small size effect of nanoparticles can be used as magnetic recording materials,electromagnetic wave-absorbing and electromagnetic shielding materials,and conductive materials.Besides,they also have a wide range of applications in the biomedical field.In this paper,polymer and nano-Fe3O4 magnetic particles were composited to prepare different types of magnetic nanocomposites,and their structures and properties were studied.The main research content is as follows:?1?The styrene-n-butyl acrylate?PSBA?/Fe₃O₄ nanocomposites were successfully prepared by in-situ bulk polymerization.And the structure and properties of the nanocomposites were studied by Fourier transform infrared?FTIR?spectrometer,transmission electron microscope?TEM?,integrated physical property tester,X-ray diffractometer?XRD?,and thermogravimetric analyzer?TGA?.The results showed that the PSBA/Fe3O4 nanocomposites with good superparamagnetism were successfully synthesized.The nano-Fe₃O₄ particles of about 5⁸ nm were uniformly dispersed in PSBA matrix without obvious agglomeration.The XRD characteristic peaks of nano-Fe₃O₄ increase with the increase of its content,meanwhile,the addition of nano-Fe₃O₄ enhances the thermal decomposition stability of PSBA.The above results indicate that the magnetic functionalization of a universal PS was successfully achieved in this work.?2?High magnetic content PLA/Fe₃O₄ composite microspheres were synthesized by physical methods of phacoemulsification and solvent volatilization.FTIR spectrometer,XRD,TEM,laser particle size analyzer,TGA,and comprehensive physical property tester were used to characterize the morphology,particle size,magnetic?Fe₃O₄?content and magnetic properties of the composite microspheres.Ang the effects of the total mass fraction of PLA and Fe3O4 in the oil phase,the mass ratio of Fe₃O₄ to PLA,and the phacoemulsification time on the particle size of the composite microspheres were systematic investigated.The results show that the smaller the total mass fraction of PLA and Fe3O4 in the oil phase,the smaller the particle size of composite microspheres;the larger mass ratio of Fe₃O₄ to PLA,the smaller the particle size of composite microspheres;the longer the phacoemulsification time,the smaller the particle size of composite microspheres.The highest content of Fe₃O₄ in composite microspheres can reach 48 wt%.The saturation magnetization is 0.136 A·m²/kg.Compared with the chemical polymerization method,this method is simpler in operation and the product prepared by the method has no monomer residue.?3?PLA/Fe₃O₄ nanocomposite films were prepared by solution casting method.The structure and properties of the composite film were characterized by TEM,FTIR spectrometer,XRD,polarized light microscopy?POM?and TGA.And the solution crystallization of PLA under room temperature,melting isothermal crystallization of PLA,and melting isothermal crystallization of PLA under the alternating magnetic field were studied.The results show that nano-Fe₃O₄ inhibits the formation of?crystals when PLA crystallizes at room temperature.Isothermal melting and crystallization:the spherulite size increases rapidly after cooling to 123 ^oC as the melting time extended at200 ^oC;the spherulite size increases monotonously as the crystallization temperature increases from 110 ^oC to 130 ^oC.The alternating magnetic field has no obvious effect on the isothermal melting crystallization of pure PLA;the size of the PLA spherulites in the composite decreases significantly as nano-Fe3O4 is added;the spherulite size decreases significantly as the magnetic field strength increases;with the magnetic field frequency gradual increases,the spherulite size shows a trend of decreasing first,then increasing,and finally decreasing.TGA results show that the addition of nano-Fe₃O₄particles reduces the thermal decomposition stability of PLA.