Preparation,Structure And Properties Of Fluoroelastomer/Carbon Nanotubes/Low-Melting-Point Alloy Composites With Insulator-Conductor Transition Properties

With the development of electronic devices towards intelligence,portability,customization and lightweight,flexible conductive materials have gradually become a research hotspot and are expected to be widely used in wearable devices,electronic skin,stress sensors and other fields in the future.At present,silicone rubber is mainly used as the matrix of flexible conductive materials due to its good elasticity.However,it lacks of superior mechanical properties and medium resistance.Fluoroelastomer?FKM?is a special rubber with excellent high-temperature resistance,medium resistance,mechanical properties and insulating properties.By adding conductive fillers such as carbon nanotubes?MWCNTs?and low-melting-point alloys to the FKM,some composites with a sandwich structure are prepared by alternate stacking the carbon layer and the alloy layer together,which showing good insulator-conductor transition performance,high temperature resistance and medium resistance.The corresponding research work is listed as below.Firstly,the effect of MWCNTs and Sn₄₂Bi₅₈ content on the electrical properties of the FKM composites was investigated.The results show that MWCNTs and Sn₄₂Bi₅₈ have a synergistic conductive effect.The volume resistivity of the composites containing two conductive fillers is lower than that of the composites containing single conductive filler.The electrical properties and mechanical properties of FKM/MWCNTs/Sn₄₂Bi₅₈ composites prepared by mechanical mixing method?MM?,high-temperature-shearing and fast-evaporation-mixing method?HTS-FEM?and high-temperature-molding and solution-mixing method?HTM-SM?were investigated.The results show that when the Sn₄₂Bi₅₈ content is 2.38 vol%and the MWCNT content is 1.66 vol%,the volume resistivity of the FKM/MWCNTs/Sn₄₂Bi₅₈ composite prepared by HTM-SM is the lowest,which is 843?·cm.The morphology and distribution of Sn₄₂Bi₅₈ and MWCNTs in FKM matrix were characterized by optical microscope and scanning electron microscope,and the synergistic conduction mechanism of Sn₄₂Bi₅₈ and MWCNTs was discussed.Secondly,the FKM/MWCNTs/Sn₄₂Bi₅₈ films which can achieve pressure-induced insulator-conductor transition at high temperature were prepared,and the effects of Sn₄₂Bi₅₈content,MWCNTs content and ambient temperature on the insulator-conductor transition properties were investigated.The cyclic stability of the insulator-conductor transition of the films were tested.The structure of the FKM/MWCNTs/Sn₄₂Bi₅₈ film was characterized by scanning electron microscopy,and a conductive model was constructed to analyze the insulator-conductor transition mechanism.We also established a mathematical model to fit the insulator-conductor transition curve of the FKM/MWCNTs/Sn₄₂Bi₅₈ film.In addition,the influence of the combination of Ga In Sn and Sn₄₂Bi₅₈ on the insulator-conductor transition properties of FKM/MWCNTs/Sn₄₂Bi₅₈/Ga In Sn films at room temperature was investigated.The cyclic stability of the insulator-conductor transition at room temperature was tested and the insulator-conductor transition mechanism was interpreted.