Design And Preparation Of Multifunctional MXene/Silicone Nanocomposites For Fire Safety And Prevention Applications

MXene has excellent properties and unique structure,so it can be combined with polymer molecules to construct advanced 2D/3D MXene-based nanocomposites with excellent mechanical properties,catalytic properties,electrical properties,magnetic properties and so on,which is promising for broad application prospects in the fields of energy,environment and catalysis.Espeically,multifunctional silicone-modified MXene nanocomposite is an important development direction.However,there is an essential conflict between the hydrophilicity of MXene and the hydrophobicity of organosilicon molecules,which makes it difficult to construct the effective interaction between them.In addition,MXene sheets are prone to stack,which makes it difficult to display its unique structure and performance advantages in organosilicon materials.Therefore,how to construct novel MXene/silicone nanocomposites with multiple physical and chemical interactions is still a big challenge.In this paper,two kinds of MXene/silicone functional nanocomposites were fabricated by tuning reaction between oxygen-containing groups on the surface of MXene and the functional groups of the MXene,and their flame retardant and fire alarm response as well as the related mechanisms were explored and disclosed.The main contents are as follows:1.Flame-retardant,super-hydrophobic and electrically conductive silicone foam composites based on the interconnected MXene/cellulose nanofiber network:The accordion-like multilayered Ti₃C₂T_x MXene and exfoliated Ti₃C₂T_x MXene nanosheets with rich hydroxyl groups were prepared by efficient stripping with HCl⁺Li F.Then,combining the cellulose nanofiber/MXene hybrid fillers with the perfluorosyl silane treatment prepared the super hydrophobic,conductive and green flame retardant silicone rubber foam nanocomposites.FTIR,XRD,SEM,XPS and other structure characterizations and analysis confirmed that residual Si-H bonds on the surface of room temperature foaming silicone rubber reacted with the hydroxyl groups on the surface of MXene to form a strong interfacial interaction between coating/silicone foam.Therefore,the nanocomposites have excellent properties of acid and alkali resistance,high temperature resistance（-20-200^oC）and cyclic compression.Further,the structure feature and evolution of the composites during the combustion process were observed and analyzed,and the synergistic flame retardant mechanisms between the silicone molecules and nanofillers were proposed and discussed,which provides a new strategy for design and development of advanced multi-functional silicone composite materials.2.Novel fire cyclic warning sensor based on water-soluble polymer decorated MXene network:Based on the above research,two-dimensional MXene papers with nacre-like aligned structure were prepared by a green low-temperature induced self-assembly method;and multiple physical and chemical interactions（hydrogen bonds,covalent bonds,etc.）between the hydroxyl groups on the surface of MXene and water-soluble PEG or PVP molecules were obtained to construct a new type of fire cycle alarm sensor.It is found that this kind of sensor not only has fast flame detection response time（<2 s）and sensitive resistance change（>4 orders of magnitude）,but also shows unexpected cyclic alarm response.XRD,SEM,TEM and other microscopic characterization and analysis revealed that water-soluble PEG or PVP molecules effectively promoted the oxidation of MXene in the process of flame attack,forming a stable and dense inorganic C/N doped titanium dioxide network,which can resist the continuous attack of flame.Meanwhile,this unique structure can induce the electronic transition of titanium dioxide at high temperature,which can stimulate the cyclic transition of resistance between conduction and insulation,thus obtaining reliable cyclic fire detection response signal.Based on the above results,a green and multifunctional MXene based coating was prepared by introducing perfluorochloro silane.Such coating not only realized the flame retardancy（UL-94 V0）and surface hydrophobicity（water contact angle of>150^o）of combustible substrate materials,but also produced a stable and reliable fire cycle alarm even under complex environment.Clearly,the green MXene-based newwork developed in this work provides a novel route and strategy for monitoring fire safety and prevention of flammable materials.