Preparation And Microwave Repair Properties Of Polypropylene Based Magnetic Nanocomposites

Polypropylene-based nanocomposites are widely used in industrial appliances,automobiles and medical treatment due to their excellent mechanical properties,good reproducibility and convenient repair.However,in the process of forming magnetic nanopowders and PP resin matrix,because of the high viscosity and low fluidity of PP resin,magnetic nanopowders are easy to agglomerate and difficult to disperse.It is difficult to achieve uniform nano-dispersion of magnetic nanopowders in PP resin by conventional composite methods,which limits the comprehensive properties of the composites and seriously affects the development and application of magnetic resin matrix composites.FeNi_p/PP thermoplastic magnetic nanocomposites were successfully prepared by two-step blending method combining solution dispersion and melt blending.The problem that the magnetic nanopowders are easy to agglomerate in the resin matrix and difficult to achieve nano-uniform dispersion is solved.On this basis,the interface bonding,soft magnetic properties and mechanical properties of FeNi_p/PP composites were studied,and preliminary exploration was made.The microwave repairing technology of magnetic thermoplastic composites was discussed.Fe₂₀Ni₈₀ alloy nano-powders with a particle size of distribution within 100 nm and uniform particle size distribution were prepared by liquid phase reduction method.FeNi_p/PP thermoplastic magnetic nanocomposites were prepared by magnetic separation,extraction and two-step blending method.FeNi alloy nanopowders in the composites are uniformly dispersed in the matrix as single powders,and PP molecular chains enter into the surface defects of nano-FeNi powders,forming an interosmosis layer interface with thickness of 2-10 nm.When the content of FeNi powder is 2 wt%,FeNi_p/PP nanocomposites have the best mechanical properties,the tensile strength is38 MPa,which is 23%higher than that of pure PP resin.When the content of FeNi powders is 20 wt%,the value of Ms reaches 9.7 emu/g,and the shielding performance of FeNi_p/PP nanocomposites reaches 9.8 dB in the frequency range of1-100 MHz.Second,the microwave repairing technology and mechanism of FeNi_p/PP nanocomposites were preliminarily discussed.The microwave loss of FeNi_p/PP nanocomposites and the content of FeNi alloy nanopowders?0-20 wt%?have unique microwave loss percolation characteristics,and the percolation range is 0-7.5 wt%.When the composite receives the microwave signal,the resin matrix is melted while melting the matrix under high-speed vibration to repair or reduce microcracks inside the composite.The optimum time of microwave irradiation is 15 min.After microwave irradiation,the microcracks of the composites are repaired.The tensile strength of FeNi_p/PP nanocomposites can be restored to 90%of the pre-damage tensile strength.Finally,the GR and FeNi powders were prepared into a composite powders.After the GR powders were treated at 800°C,the FeNi nanopowders were uniformly attached to the GR surface.The GR has a morphology selectivity to the FeNi nanopowders attached thereto.GR powers were added when Fe₂₀Ni₈₀ nano-powders were prepared by liquid phase reduction method,and GR powers tends to promote the reaction to form columnar crystal FeNi nanopowers,and the columnar crystal FeNi nanopowers are more likely to adhere to the surface of the GR.Compared with the FeNi nanopowders,the electromagnetic loss of the GR/FeNi composite powders is mainly dielectric loss,the tan?of the GR/FeNi composite powders has reached 10.