Construction And Gas Sensitive Properties Of Fluorosilicone Rubber-based Conductive Composite Materials

Gas-sensitive sensing materials can detect toxic and harmful volatile organic compounds,so they play a vital role in monitoring environmental pollution,air quality,and ensuring the safety of production.Conductive composite material(CPC)based resistive sensors have received extensive attentions due to the advantages of simple preparation,low cost,and strong plasticity.The development of highly selective,highly sensitive,and excellent environmentally resistant gas-sensitive composite materials is currently a hot research topic and an urgent need.In this paper,based on fluorosilicone rubber having the characteristics of both silicone rubber and fluorine rubber,combined with the external-field stimuli response behavior of conductive fillers’network,a series of organic fluorosilicone-based gas-sensitive materials were developed.The influence of matrix chain structure,conductive particle content,particles compounding,pore structure on the structure,performance and function of composite materials was carefully investigated.The details are listed as follows:(1)Firstly,trifluoropropyl group is introduced into polydimethylsiloxane to synthesize fluorosilicone oil with different fluorine content,0%,50%,and 100%,respectively.Then fluorosilicone oil and VGCF are mechanically mixed to prepare conductive polymer composite materials.The chain structure of fluorosilicone oil was characterized by Fourier Transform Infrared(FTIR)spectrophotometry and Nuclear Magnetic Resonance(NMR).The key influencing factors to electrical conductivity,gas sensitivity and mechanical properties of composites were studied.The results showed that conductive polymer composites with different fluorine content had different responses to different organic solvents(VOCs).The VGCF/0%FSi RF based composite presented the most sensitivity to cyclohexane vapor,and the VGCF/50%FSi RF and VGCF/100%FSi RF based composites were most sensitive to ethyl acetate vapor.The film-shaped composites can detect flowing organic gas as low as 2%concentration.The sensitivity of composites to organic vapors with different polarity changed regularly with the increase of fluorine content of fluorosilicone rubber matrix,due to the addition of fluoropropyl groups changed the solubility parameters of fluorosilicone rubber.(2)The conductive MXene/carbon black(CB)fluorosilicone rubber foam gas sensitive materials were prepared by in-situ reactive foaming technology using MXene/water suspension as foaming agent and CB as filling filler.The effects of CB content,MXene concentration of MXene/water suspension and foaming agent amount on the porosity and conductivity of foam were studied.The results show that adding CB with high content increases the viscosity of the silicone oil and decreases the foam porosity.However,adding MXene,the foam with little CB content have excellent electrical conductivity and remain high porosity.The resistivity of the foam reaches～10~3Ω·cm,when adding 1wt%CB and 2.5wt%MXene aqueous solution with a concentration of 500mg/g.The optimized conductive foam has good structural stability,resilience and high selectivity to ethyl acetate.