Study On Preparation And Properties Of High Strength And High Insulation Aramid Paper-based Materials

With the rapid development of high-speed trains,locomotive high-power traction transformers,motors and smart grid new power transmission and transformation equipment put forward higher requirements for aramid paper-based insulation materials.However,due to the low mechanical and insulating properties,domestic products are only suitable for the low-end and mid-range sectors.Therefore,it is of great significance to developing high-performance aramid paper-based insulation materials.Traditional methods for improving the properties of aramid paper-based materials either require complex equipment or require harsh processing conditions,cumbersome and uncontrollable chemical reactions,and most of them have some damage to the fibers.The most important thing is that the final composite's properties are not outstanding.Therefore,researchers have been exploring a simple,non-damaging fiber method that can significantly improve the mechanical and insulating properties of aramid paper-based materials.In this paper,we convert macro-aramid fibers into nano-fibers to increase the specific surface area and surface activity of the fibers,thereby improving the overall performance of paper-based materials.Firstly,macroscopic aramid fiber(AF)was treated wih DMSO/KOH system,and the chemical and physical changes of the fiber were studied.Then,the differences in material properties among macropaper(MP),nanopaper(NP),hot pressed papers also were compared.The results show that aramid nanofiber(ANF)has a diameter of about 20?30 nm,while ANF and AF have the same chemical structure,crystal structure and high temperature resistance.NP possesses a denser paper structure,and has a tensile strength and breakdown strength of 124.3 MPa and 63.6 kV/mm,which are about 557.7%and 371.1%higher than that of MP,respectively.It also exhibits excellent UV resistance.Finally,MP and NP were subjected to hot pressing treatment.Hot pressed macropaper have a tensile strength and breakdown strength of 29.1 MPa and 26.1 kV/mm,which are 54.0%and 93.3%higher than that of MP,respectively.The tensile strength and breakdown strength of hot pressed nanopaper are as high as 159.6 MPa and 92.8 kV/mm,which are increased by 28.4%and 45.9%compared to NP,respectively.Besides that,after hot pressing treatment,UV resistances of these samples have also been greatly improved.Subsequently,ANFs were introduced into the MP,and aramid paper-based composite materials with "reinforced concrete" structure were constructed.By adjusting AF and ANF contents,the structures of composite materials can be optimized.When the ANF content is 50%,the tensile strength and modulus reach the maximum values of 84.4 MPa and 2.4 GPa,respectively,which are about 346.6%and 84.6%higher than of MP.When the ANF content reaches 70%,the characteristic breakdown strength reaches a maximum value of 74.4 kV/mm,which is about 306.6%higher than MP.In addition,it also can be found that the mechanical properties of the MP loses 66.7%after 48 h of UV irradiation,while the mechanical loss of composite paper is 8.5%,indicating that the composite aramid paper has excellent UV resistance.The experiment also finds that the effect of ultraviolet light on the breakdown strength of the all samples is very little.Finally,based on montmorillonite's wide source,low price,easy peeling and good insulation,ANF/MTM nanocomposite film with nacre-like layer structure was successfully constructed by vacuum filtration of ANF and MTM.The film not only has good optical transparency and toughness,but also has excellent mechanical properties(tensile strength of 126.5 MPa)and insulation properties(breakdown strength of 77.2 kV/mm).When the inorganic content reaches 20%,the nanocomposite film still maintains high mechanical properties(101.5 MPa)and breakdown strength(67.3 kV/mm).When the MTM content is further increased(50%),the ANF/MTM nanocomposite film still has better mechanical properties(?98.4 MPa)and insulation properties(?44.0 kV/mm)than other typical composite materials.Interestingly,the tensile strength and breakdown strength of ANF/MTM nanocomposite film can be increased by 20%?30%compared with the original film by hot pressing treatment.In this paper,inspired by the the structure of natural nacre,high-strength,high-insulation aramid paper-based materials were fabricated by improving the structure of the material and interfacial effects.These materials are expected to be applied in the fields of flexible electronics and high-temperature insulation.