Research On Preparation And Properties Of Fluororubber/MWCNTs Composites

With the development of the industry,a number of special synthetic elastomers with excellent performance have been born in order to adapt to the more demanding working environment.As a kind of high performance elastomer operating in high temperature,strong corrosive and other special environment,fluororubber meets the special needs that ordinary elastomer can not be qualified,so it has been widely used in the fields of national defense,industry,life and so on.At the same time,with the opening of the era of intelligent industry,high-precision science and technology and advanced smart materials begin to popularize the industry.However,the harsh working environment challenges the traditional polymer-based functional materials,for most of them are unable to cope with high temperature and strong corrosive environment.Therefore,it is one of the most ideal solutions to develop a batch of polymer-based functional materials that can work efficiently in special environments.In conclusion,fluororubber can be used as an ideal matrix material.However,the shielding effect of the fluorine atoms on the fluororubber molecular chain makes it difficult for fluororubber and other fillers to achieve perfect composite,which leads to more than 60%of fluororubber is only used in the preparation of various seals and insulating materials.So,solving the problem of interface compatibility between fluororubber and functional fillers will help promote the development of fluororubber in the field of functional materials.In this dissertation,the application possibilities of fluororubber/MWCNTs composites in high temperature,acid-and alkali-base corrosive environment are explored,firstly,which lays the foundation for the functional application of fluororubber in special environments.Secondly,through the modification of MWCNTs to improve the interface interaction between fluororubber and MWCNTs,and a kind of fluororubber/MWCNTs functional composite materials with excellent comprehensive performance have been prepared,revealing fluororubber's application value in the field of flexible functional materials.The specific research contents are as follows:(1)Firstly,the fluororubber/acidified MWCNTs(MWCNTs-COOH)composites were prepared by the solution blending method.The thermal decomposition kinetics analysis based on TGA and DTG tests demonstrated that the thermal decomposition mechanism of this composite was determined to be the first-order reaction,the reaction activation energy(E)was 194.67 k J/mol,the pre-exponential factor(ln A)was 29.90 and the thermal service life at 227.8?was 2 years.In the research on the acid-and alkali-corrosion resistance of fluororubber,it was found that the dielectric properties and microscopic morphology of the sample after soaked in HCl solution did not change much;While the matrix of the sample was greatly corroded after soaked in Na OH solution,the dielectric performance of the sample increased sharply,and the frequency stability decreases.It can be concluded that the fluororubber/MWCNTs-COOH composite has excellent acid resistance,so it can be used under certain acid-conditions.(2)Next,the interface compatibility between fluororubber and MWCNTs was improved by modifying the surface of MWCNTs.Based on the research that the amino-modified MWCNTs can be covalent bonded with epoxy resin,two kinds of amino-modified MWCNTs were prepared in this paper.MWCNTs-EDA was based on MWCNTs-COOH to chemically graft ethylenediamine(EDA),MWCNTs-A1120 was directly use silane coupling agent A-1120 to coated on MWCNTs.Compared with other modified MWCNTs,the interface interaction between MWCNTs-A1120 and fluororubber was the strongest,and the electrical properties of MWCNTs-A1120 was almost the same as those of original MWCNTs,thus fluororubber/MWCNTs-A1120composite had the best comprehensive performance.The comprehensive performance of fluororubber/MWCNTs-A1120 composite was further studied.At 10 k Hz,the dielectric constant of the composite with 3 wt%doping ratio increased by 92.07%compared with that of the pure fluororubber,and the composite was already conducting at 5 wt%doping.At the same time,the electrical properties of the composites were directly related to the deformation of the sample.The increase of the tensile deformation will directly lead to the decline of the electrical properties of the sample.In the case of 5 wt%doping,30%deformation can make the composite transform from conductive material to dielectric material.The results demonstrated the potential application value of the fluororubber/MWCNTs-A1120 composites in the fields of stretchable dielectric materials and flexible conductive materials.(3)Finally,in order to improve the phenomenon that the fluororubber/MWCNTs-A1120 composite reached the permeation threshold prematurely,which leads to a sudden increase of the dielectric constant and dielectric loss,Fe₃O₄@MWCNTs hybrid materials were prepared by solvent-thermal method on the basis of MWCNTs-A1120.By combining fluororubber with Fe₃O₄@MWCNTs hybrid materials and studying the electrical and magnetic properties of the composites,it was found that even at 7 wt%doping,the fillers were still uniformly dispersed in the matrix.And at 10 k Hz,the dielectric constant of the composite(7 wt%)increased by 106.8%compared with that of the pure fluororubber,while the dielectric loss remained in the low range of 0.06.At the same time,due to the introduction of the magnetic particles Fe₃O₄,with only 7 wt%Fe₃O₄@MWCNTs hybrid materials doping,the saturation magnetization of the composite increased from 0 to 2.792 emu/g.