Study Of Preparation And Performances Of Thermal Conductive Aramid Paper-based Electrical Insulating Materials

Aramid nanofiber?ANF?inherits the excellent mechanical,heat-resistant,flame-retardant and electrical insulation properties of aramid fibers,which is widely used in aerospace,electrical insulation and other high-tech fields.Compared with aramid fibers,the specific surface area of ANF is larger,so more carbonyl and amino groups can be exposed on the surface.The aramid paper-based materials prepared from ANF have the advantages of high strength and good flexibility.However,ANF belongs to polymers,and there are no free electrons in the molecular chains and lattice vibration is suppressed,which leads to low thermal conductivity and difficulty to adapt to the high-end electronic and electrical fields with high integration and power.Hexagonal boron nitride?h-BN?,with excellent thermal conductivity,electrical insulation and heat resistance,is widely used in the preparation of filling type polymer-based thermal conductive and electrical insulation material.In this paper,paper-based thermal conductive and electrical insulation material was prepared by using ANF as matrix and h-BN as thermal conductive filler.The experimental results are as follows.In this paper,firstly aramid fibrid were made into ANF by chemical splitting method.Then ANF/h-BN paper-based materials were prepared by using h-BN as thermal conductive filler.The thermal stability,mechanical properties,insulation properties and thermal conductivity of the paper-based materials were characterized and analyzed.The experimental results showed that the decomposition temperature of paper-based materials was above 500?which exhibits excellent temperature resistance.The tensile strength of paper-based materials increased firstly and then decreased.Tensile strength of paper-based materials with 10 wt.%h-BN reached 92.095 MPa.The resistivity of paper-based materials was still above 1×10¹³?·m,which maintained good electrical insulation performance.The thermal conductivity of paper-based materials increased continuously with the increase of h-BN content.the thermal conductivity of paper-based materials was 0.546 W/mK and increased by 198.0%when the content of h-BN was 40 wt.%h-BN.Then,the surface of h-BN was functionalized by dopamine?DA?.ANF/h-BN@PDA paper-based materials were prepared by using h-BN@PDA as thermal conductive filler.The surface properties of h-BN before and after modification,mechanical properties,insulation properties and thermal conductivity of the paper-based materials were characterized and analyzed.The experiment proved that under weak alkaline conditions,DA was oxidized and self-polymerized to form polydopamine?PDA?,which adhered to the surface of h-BN.The surface of h-BN@PDA contains active groups such as-OH and-NH₂.When the content of thermal conductive filler was 10 wt.%,the maximum tensile strength of paper-based materials can reach 94.218 MPa.At the same time,the resistivity of paper-based materials was maintained above1×10¹³?·m,which maintained good insulation performance.The thermal conductivity of paper-based materials was significantly increased compared with that before modification.When the content of thermal conductive filler was 40 wt.%,the thermal conductivity of paper-based materials was 0.676 W/mK,which was 23.8%higher than that of ANF/h-BN paper-based materials.Silver nanoparticles?AgNPs?were synthesized on the surface of h-BN by using the synergistic effect of Ag⁺and-OH and the reduction characteristics of sodium borohydride?NaBH₄?.ANF/h-BN@AgNPs paper-based materials were prepared by using h-BN@AgNPs as thermal conductive filler.The surface topography of h-BN before and after modification,mechanical properties,insulation properties and thermal conductivity of the paper-based materials were characterized and analyzed.The experimental results showed AgNPs were successfully synthesized on the surface of h-BN.When the content of thermal conductive filler was 10 wt.%,the tensile strength of paper-based materials could reach 92.682 MPa.At the same time,when the content of thermal conductive filler was 40 wt.%,the volume resistivity of paper-based materials decreased to3.086×10¹¹?·m,which was still higher than the insulation standard.Meanwhile,the thermal conductivity of paper-based materials could reach 1.032 W/mK,which was 35.2%higher than h-BN@PDA paper-based materials.