Self-healing Properties Of Magnetic Graphene/polyurethane Flexible Conductive Composites

Flexible conductive composite materials are widely used in biomedical,exploration,aerospace and other fields because of their good conductivity,flexibility and high sensitivity.They are mainly used in the development of multi-functional flexible sensors.However,due to m any factors,such as environment,human and so on,the flexible conductive material will appear cracks,scratches and other defects in the long-term use process,which affect the performance of the material.It needs to be replaced regularly,which will in crease the use cost,especially some high-precision flexible sensor materials.Therefore,it is of scientific significance to develop functional flexible conductive materials with high-efficiency self-healing performance while ensuring the electrical and t hermal properties of flexible conductive materials.In this paper,Graphene Oxide(GO)was used as raw material,and Fe₃O₄ was modified on graphen e sheet by chemical method,and the magnetic graphene was prepared.Then the magnetic graphene sheet in polyurethane was arranged regularl y under the control of external uniform magnetic field.At the same time,the graphene sheet supported by passivated carbon nanotubes.Finally,the magnetic graphene/polyurethane flexible conductive composite was prepared.Through the analysis of the micro morphology,chemical spectrum and physical properties of the composite,the self-healing performance of the composite was revealed.And the effects of the amount of magnetic graphene and high temperature heat treatment on the self-healing performance of the material were studied.In addition,the electrical,thermal and self-healing performance of the composite were strengthened by the introduction of Less layer graphene(LG).The experimental results show that:(1)Combined with SEM,Raman and FTIR analysis,the graphene sheet layer in the composite with magnetic interference are arrange regularly,and the lamellae outline is clear.There is no obvious stacking and agglomeration phenomen on.The most of the oxygen-containing functional groups are removed,which ensures that the composite can give full play to the excellent electrical an d thermal properties of graphene.And then ensure the self-healing performance of the material.(2)By comparing the thermal diffusivity and self-healing performance of magnetic graphene/polyurethane flexible composite with or without magnetic field,it can be seen that the thermal diffusivity is effectively increased by 10%?12%under the control of magnetic field.At different test temperatures,the average decrease of thermal diffusivity is about 0.003mm²/s,which can ensure the stability of thermal diffusivity of materials at high temperature th us improving the defect repair time by50%,and realizing the rapid and efficient self-healing of composite materials.By comparing the electrical and mechanical properties of defects before and after repair,it is also found that the difference of resisti vity and tensile strength without magnetic field control is 0.026?·cm and 7.7MPa,respectively,while those with magnetic field control are 0.006?·cm and 2.4 MPa.The adjustment of magnetic field not only makes the self-healing flexible composite have excellent conductivity and tensile properties,but also ensures the repairability of the electrical and mechanical properties of the composite.(3)Through the study of the influence of the amount of magnetic graphene on the self-healing performance of the composite,it is found that:Taking 4%and 6%of magnetic graphene as th e boundary points,respectively,the thermal diffusivit y increases first and then decreases,and the surface resistance decreases first and then increases.It is suggested that increasing the amount of magnetic graphene is helpful to enhance the electrical and thermal properties of the composite and improve the repair efficiency.Through the study of the effect of high temperature heat treatment on the self-healing performance of composite materials,it is found that:High temperature can effectively remove the residual oxygen-containing functional groups in the composite.Among them,the best state is 600?,which can ensure the composite has good repair efficiency and reduce the damage of high temperature t o the internal structure of the material.(4)It is found that the defects of LG are low after the introduction of LG through the Raman,FTIR,XRD and XPS analysis.LG has almost the same layer spacing and conjugated orbit as graphene,and ha s dispersion in solvent and water.After optimization,the self-healing time of the composite is shortened by about1min,and the rate of repeated repair is also better.At each test temperature,the thermal diffusivity of the optimized composite is about 0.0025 mm²/s higher than that of the original composite,and th e surface resistivity reduce by 0.013?·cm.The introduction of LG plays an important role in improving the performance of composite materials,and it is an effective means to strengthen the self-healing performance of materials.