Preparation And Performance Study Of Flexible Electromagnetic Shielding Materials Based On Thiol-epoxy Click Chemistry

With the rapid development of science and technology,especially mobile communication technology,all kinds of electronic products are emerging,and the resulting electromagnetic radiation and electromagnetic pollution are also filled in people’s daily life,causing a series of environmental and health problems,so it is urgent to prepare high-performance electromagnetic interference（EMI）shielding protective materials.Common EMI shielding materials include aerogel,film,and foam,etc.Among them,EMI shielding fabric has attracted wide attention in recent years because of its unique comfort and wearable characteristics.Herein,a new connection technology,thiol-epoxy click chemistry,is proposed to connect high performance fabric and EMI shielding material to realize the effective unification of organic fiber and inorganic EMI shielding material.We hope to provide a new idea and method for the preparation of EMI shielding fabric.The results of this thesis are as follows.（1）Firstly,cotton/spandex blended fabric（CSF）with good tensile resilience was used as the substrate,and the carboxylated carbon nanotubes（CNTs）and the substrate were modified with thiol groups,and epoxy monomer molecules were used as linkers.The EMI shielding performance and durability were investigated.The results show that the prepared EMI shielding fabric M-CNTs₄₀/EP/CSF can achieve 27.3 d B of EMI shielding effectiveness（EMI SE）in X-band at a thickness of only 140μm,which meets the current basic requirements for daily EMI shielding.Benefiting from the stable C-S bond between CNTs and CSF,M-CNTs/EP/CSF shows excellent EMI shielding stability（conductivity retention rate above 80%）in strong acid（pH=2.0）,strong alkali（pH=12.0）,and ultrasonic environment,which indicates that the prepared EMI shielding fabric can be used normally even under extreme conditions,further the application prospect of EMI shielding fabric is extended.（2）Secondly,in order to endow the EMI shielding fabric with higher EMI shielding performance and multi-functionality,the conductive filler and structure design are further improved and enhanced by combining high conductivity two-dimensional transition metal carbon/nitride（MXene）with thiol modified one-dimensional carbon nanotubes（M-CNTs）,which are jointly used as EMI shielding materials,and the vacuum spraying method is used to build a light and complete conductive network on the fabric surface.At the same time,a unique wrinkled microstructure was formed on the fabric surface by taking advantage of the hydrogen bonding and structural differences between the two EMI shielding materials.Benefiting from the unique wrinkled microstructure,the PMCC EMI shielding composite fabric can achieve46.05 d B and 6.7×10³ d B cm²/g SSE/t for X-band EMI wave shielding with a coating thickness of only 138μm,which is the leading level in both EMI SE and thickness compared with other materials of the same type.The wrinkled microstructure ensures the integrity of the conductive network.Even after 1000 bending-releasing cycles,12 h of ultrasonic treatment at 20 KHz,1min of liquid nitrogen freezing and 50 times of dry rubbing,the EMI SE remains above 40 d B,which has high durability and EMI shielding stability.