Preparation And Characterization Of Polyurethane Based Magnetic Elastomers

According to the problem of mechanical properties and magnetic properties of elastomercomposite magnetic materials can not improve at the same time which limits its application.The new preparation process which combining magnetic fluids and in situ polymerizationwere used to prevent magnetic components from aggregating. In this way, the combinationproperty including mechanical properties and magnetic properties of magnetic elastomercomposites can be optimized simultaneously.Firstly, the preparation method of Fe3O4magnetic liquids was investigated. It was provedthat the chemical co-precipitation method which used NaOH to be the precipitant was anexcellent process to synthesize Fe3O4water-based magnetic liquids with the Fe3O4particlesdirectly dispersed in water without drying process. The magnetic particles were characterized.The result showed that the magnetic particles were Fe3O4cubic spinel structure and the shapewas spherical with the the average particle size of20.2nm, and the saturation magnetizationof the magnetic particles was58.6emu/g which showed that the magnetic particles had goodsuperparamagnetic performance. The stability of the magnetic liquids was researched bychanging the magnetic field, temperature, the type of organic dispersing solvent and thesurface modification agent of magnetic particles. The result showed that magnetic fluid hadpoor stability in the gradient magnetic field and the stability was almost unchanged in thetemperature field. Ethyl alcohol and tetrahydrofuran were selected as the organic dispersingsolvents and SDBS was selected as the surfactant through the above research.Four different Fe3O4@rGO composite magnetic particles were prepared using the Fe3O4water-based magnetic liquids and graphene oxide. The synthesis and structure of Fe3O4@rGO composite magnetic particles have been proved by raman spectroscopy, fourier transforminfrared spectroscopy (FT-IR), transmission electron microscope (TEM), X-ray diffraction(XRD) and energy dispersive spectrometer (EDS).The Fe3O4/PU and Fe3O4@rGO/PU magnetic elastomer were prepared by incorporatingFe3O4magnetic liquids into polyurethane matrix using in situ polymerization method. Theperformance of the elastomer were investigated through a series of factors, including the wayof adding magnetic particles, surface modification, the species of organic dispersing solvents,the content of magnetic particles, the preparation process and molding with magnetic control.The results showed that magnetic liquids and magnetic particles without surface modificationwere used and THF was choosed as organic solvent dispersion in following studies. WhenFe3O4nanoparticles were added into the PU matrix, the mechanical properties of Fe3O4/PUmagnetic elastomer reduced. However, after the preparation process was improved, theoverall performance of Fe3O4/PU elastomers had greatly improved. At the same time, with theincrease of the Fe3O4amount in Fe3O4/PU magnetic elastomer, the thermal stability andmagnetic properties were gradually improved, and the mechanical properties were increasedand then decreased. With magnetic molding, the magnetic particles were chain-liked arrangedin the matrix. It improved the elongation at break of elastomer but had no effect for the tensilestrength.The magnetic and mechanical properties of Fe3O4@rGO/PU magnetic elastomers whichwere affected by Fe3O4@rGO composite magnetic particles were investigated in detail. Theresult showed that the saturation magnetization of magnetic elastomer reduced gradually withthe decline of the Fe3O4content in Fe3O4@rGO composite magnetic particles. Themechanical properties of the elastomers doping Fe3O4@rGO is better than the elastomersdoping pure Fe3O4. Meanwhile, the tensile strength, elongation at break, tensile modulus andloss factor of the elastomers were35.41MPa、464.30%、84.15MPa and0.41, respectively,with the incrcement of75.73%,42.53%,28.10%and57.69%with respect to the purepolyurethane.