Preparation And Electricail Conductivity Functionalization Of Polyimide Aerogel-Based Paper

With the continuous innovation of papermaking technology and the gradual increase of application fields,functional paper has received wide attention.However,the prepared functional paper is prone to decomposition at high temperature and accompanied by a decrease in mechanical strength,which is a major challenge for the current paper technology.Functional paper is also very important in the choice of materials,which relates to the special properties of paper and application areas.With the rapid progress in aerospace,microelectronics and other fields,commercial polyimide paper and aramid paper appeared in people’s view,but the temperature resistance level and mechanical properties of these two commercial papers were not satisfactory,so scientists have begun to research functional papers with both high temperature resistance and high mechanical properties.In this paper,two polyamido acid salt solutions containing straight-chain rod-like benzimidate units and highly rigid benzimidazole units containing intermolecular hydrogen bonds were prepared,and the solutions were co-blended to prepare anisotropic polyimide aerogel by unidirectional freeze-drying,and the three-dimensional structure of polyimide aerogel was converted into two-dimensional aerogel-based paper by hot extrusion strategy and thermal imidization process.The rigid polyimide backbone structure resulted in good thermal properties(T_d5%>552°C,CTE decreased from 88.99 ppm/K to 23.12 ppm/K during25～400°C)and flame retardancy（LOI:39.4%）.The microscopic morphology of the multilayer structure obtained by hot extrusion method imparted excellent mechanical properties to the material.The tensile strength of PI-1 was 3 and 5 times higher than that of commercial polyimide and aramid papers at 25°C,and PI-1 tensile strength was 3 and 24 times higher than theirs at 400°C,respectively.It also had excellent cycling stability（over 5000 cycles）.Through the design of microstructure and macrostructure,the multilayer interconnected structure of aerogel-based paper possessed better performance and outperformed commercial polyimide and aramid papers in various aspects.The MWCNT/polyimide aerogel-based paper was prepared by adding multi-walled carbon nanotubes in polyamido acid salt solution and used hot extrusion strategy.It had similar morphology of polyimide aerogel-based paper with more orderly multilayer structure,which gave it excellent thermal（good thermal stability and low CTE）and mechanical properties（tensile strength up to 117.1 MPa）.The structure of the sample changed during bending,with the layers approached each other and the interlayer gap recovered after bending,so the paper had a good response,and theΔR/R0 value of CNT-2 could reached-0.57 when tested in bending at 25°C.In addition it had a low volume resistivity（down to 0.17Ω·cm）.Both polyimide aerogel-paper and MWCNT/polyimide aerogel-based paper prepared by thermal pressurization strategy have excellent properties.They are very promising for applications such as aerospace and microelectronics.In addition,aerogel papers endowed with electrical conductivity have promising future prospects in fields such as biosensors.