Preparation And Properties Of MXene-based Polymer Electromagnetic Shielding Composites

With the rapid progress and development of communication and electronic technology,the impact of electromagnetic pollution on people’s lives is gradually increasing.Transition metal carbonitride Ti₃C₂T_xMXene has attracted great attention in the field of electromagnetic shielding materials due to its unique two-dimensional structure,high electrical conductivity,and excellent solution processing properties.At present,the requirements for the performance of electromagnetic shielding materials are getting higher and higher,so it is imperative to develop new MXene-based polymer electromagnetic shielding composite materials with multiple functions.After the traditional electromagnetic shielding composite material is damaged,its shielding and mechanical properties will be greatly reduced.By introducing a self-healing matrix for structural design,an excellent conductive network structure is obtained and the material is endowed with self-healing properties,which can restore its performance when the material is damaged.By synthesizing an excellent self-healing matrix material and exploiting the interaction between polymers and MXenes,we prepared shielding composites with healing properties.The composite material not only has efficient electromagnetic shielding performance,but also has excellent photothermal,mechanical,photothermal repair and other properties.In addition,we take advantage of the interaction between polystyrene（PS）microspheres and MXene to prepare the conductive filler MXene@PS with core-shell structure.High-performance polyolefin composites are obtained by melt-blending MXene@PS with polypropylene（PP）.The non-polar nature of PS allows the conductive filler to be uniformly dispersed in the non-polar polyolefin matrix,and then a new type of MXene-based polyolefin shielding composite is synthesized.The following are the main research contents:（1）Preparation and properties of photothermally healable MXene electromagnetic shielding composite films:It is a considerable challenge to prepare shielding composites with broadband electromagnetic shielding performance and self-healing performance.Based on this,we selected waterborne polyurethane（WPU）and natural rubber（NR）as the polymer matrix,and used electrostatic repulsive interaction to obtain a continuous honeycomb conductive network to prepare a flexible WPU/NR/MXene composite film with self-healing properties.When the MXene content is only5.48 vol%,the 339μm thick WPU/NR/MXene composite film achieves an average EMI shielding performance of more than 76.1 d B over a wide frequency range of 8.2–40.0 GHz.Compared with the matrix WPU/NR,the tensile strength and toughness of the composite film are increased by 10.3times and 8.8 times,respectively.In addition,the surface temperature of the composite film can rise to>114 ^oC within 3 minutes under 200 m W/cm²near-infrared light irradiation.The increase in temperature can activate the WPU chain segment,so that the hydrogen bond between MXene and WPU in the damaged material can be re-established,and the polymer can further melt and diffuse,thus endowing the conductive film material with excellent self-healing properties.Therefore,composite films with fast photothermal repair properties can eventually restore their excellent mechanical and shielding properties,greatly expanding their practical application fields.（2）Preparationandpropertiesoffunctionalized MXene/polypropylene composites:It is still a difficult problem to be solved to uniformly disperse polar two-dimensional nanomaterials in non-polar polyolefins to endow them with excellent electrical conductivity and mechanical properties.MXene and PS microspheres with controllable particle size were combined through electrostatic interaction,so that MXene was successfully loaded on the PS surface to form a core-shell structured MXene@PS conductive filler.The multifunctional polyolefin composite material MXene@PS/PP was prepared by melt-mixing conductive fillers with PP.The MXene in the composite material has very good dispersion performance,which greatly improves the situation that the polar conductive filler cannot be well dispersed in the non-polar polymer matrix.When the content of MXene was 13.3 wt%,the composite achieved an average EMI shielding performance of more than 21.87 d B over a wide frequency range of8.2-40.0 GHz.At the same time,the mechanics of the composites were further enhanced after the introduction of MXene.When the MXene content is only0.19 wt%,the mechanical properties of the MXene@PS/PP composite reached28.7 MPa.The introduction of MXene endows the composite with excellent photothermal performance.When the MXene content is 0.38 wt%,the composite can be heated up to 103 ^oC under 240 m W cm^-2near-infrared light irradiation.The composite material has multiple excellent properties,which provides a solution for the high-performance development of polyolefin composite materials.