Preparation And Study Of Triple Shape Memory And Light Electromagnetic Shielding Polymer Composites

With the rapid development of electromagnetic technology,electromagnetic radiation has become an increasingly important problem in various fields of society.Therefore,constructing a multifunctional composite material with simple preparation method and good electromagnetic shielding effect has become an urgent problem to be solved.On the one hand,the shape of the existing electromagnetic shielding material is fixed and cannot change with the shape of the protected device,which makes it unable to be flexibly used in the field of electromagnetic shielding.Therefore,in order to adapt to electrical equipment with different shapes and sizes,this thesis endows electromagnetic shielding materials with the characteristics of shape memory,and develops a new kind of intelligent materials to meet this application demand to a certain extent.On the other hand,in the military,there is a kind of shielding smoke screen that can be applied to different ranges of shielding scenes and interfere with infrared waves,so as to achieve the effect of stealth.But so far,the smoke screen material can not achieve broadband interference.Therefore,in order to achieve the purpose of broadband interference,this thesis designs a core-shell structure and studies prepares an electromagnetic shielding smoke screen material that can interfere with broadband interference.Firstly,a rubber based electromagnetic shielding material which can adapt to different shapes of equipment and devices through triple shape memory performance is studied and prepared.Trans polyisoprene(TPI)was physically blended with crystalline small molecule Rice bran wax(R)and conductive Carbon black(CB),and the TPI phase was chemically crosslinked.The crystalline small molecule rice bran wax was introduced into the TPI crosslinking network,and a two-component crystalline reversible triple shape memory elastomer was successfully prepared.On this basis,the inorganic filler CB was introduced.The original insulated shape memory elastomer has certain conductivity,and the triple shape memory elastomer with electromagnetic shielding is successfully prepared for the electromagnetic shielding of devices with different shapes.Then,a broadband interference smoke screen with core-shell structure is studied and prepared to be suitable for different ranges of shielding scenes.The surface of polymethylmethacrylate(PMMA)microspheres was coated with inorganic nano metal silver,and the electromagnetic shielding composite microspheres with core-shell structure were successfully prepared for electromagnetic shielding smoke screen,which is suitable for a wide range of shielding scenes.The main research is divided into the following parts:(1)Study on TPI electromagnetic shielding elastomer with triple shape memoryUsing rice bran wax as raw material,the elastomer material with triple shape memory was prepared by using TPI and R with great difference in crystallization and melting temperature.Taking the crystallization content of R as a variable,the multiple shape memory properties of the composite were explored.Through a series of tests,the properties of composites with different content of R were characterized.Among them,TPI/50 R had the best comprehensive performance.The fixation rates of the first stage and the second stage were as high as 54% and 98.9%,respectively,and the recovery rates of the first stage and the second stage were as high as 70.9%and 99.2%,respectively.On the basis,the electromagnetic shielding composites were prepared by adding inorganic conductive CB filler to improve the conductivity of the composites,and then give the electromagnetic shielding performance of the materials.By controlling the content of conductive CB,the shape memory performance and electromagnetic shielding performance were studied.Through a series of tests,the properties of composites with different CB content are characterized.Among them,15CB/TPI/50 R has the best comprehensive performance.The fixation rates of the first stage and the second stage are as high as 94.7% and 98.7%,respectively,the recovery rates of the first stage and the second stage are as high as 45.5%and 74.8%,respectively,and the electromagnetic shielding efficiency is26.8 d B.(2)Electromagnetic shielding composites based on PMMA silver coated microspheresIn the chapter 3,a kind of light microspheres with conductivity coreshell structure was prepared,which was innovatively applied to electromagnetic shielding smoke screen,and its electromagnetic shielding performance was regulated and studied by controlling the content of silver.Based on PMMA microspheres with particle size of 5 um,nano metal silver ions were coated on the surface of the microspheres by electroless silver plating.Through a series of characterization tests,the surface morphology and electromagnetic shielding performance of 54% Ag/PMMA were analyzed.The effective suspension time of 54% Ag/PMMA was 2375 s,and the highest shielding rate was 0.82.