Studies On Preparation And Properties Of 2D Thermal Conductive Composites Based On Structural Design

With the development of integrated circuit technology,electronic products are moving into a small and precise direction.Electronic circuits generate heat during operation,and the rapid and efficient dissipation of heat becomes the key to their ability of work properly.Polymer films have been widely used in the packaging of electronic products because of their flexibility,light weight and easy processing.However,its thermal conductivity is too low to meet the heat dissipation requirements.The thermal conductive filler such as graphene,boron nitride is compounded with a polymer to obtain a thermal conductive film having a high thermal conductivity.However,the thermal conductive film will face various environments in the process of practical application.In order to meet the application requirements of different environments,a thermal conductive film with various functions has been prepared through structural design.The following contents are:Improving the thermal conductivity of the polyamide?PA?film by filler structure design;Realizing the thermal conductive and electrical insulating of the nanofibrillated cellulose?NFC?film through the interlayer structure design;Realizing the thermal conductive and hydrophobic function of the NFC film through the surface structure design.The specific work content is as follows:1.Using polyamide?PA?as the matrix,one-dimensional?1D?silicon carbide whiskers?SiCw?and two-dimensional?2D?graphene nanosheets?GNs?as fillers,under the action of mixing and stirring in the internal mixer and hot pressing in the flat vulcanizing machine.A thermal conductive film with a high thermal conductivity in both directions is obtained.It can be seen from the thermal conductivity test,SEM test,etc.that the 1D SiCw plays a"bridge"role in polyamide/graphene,which prevents the accumulation and agglomeration of GNs,and also establishes a new heat conduction path in the through-plane direction,thereby increasing its?_z.When the composite contains 9wt%GNs and 36wt%SiCw,the thermal conductivity in both directions can reach 8.55?in-plane?and 2.31?through-plane?W·m^-1·K^-1,respectively.Compared with the pure matrix?PA?,the thermal conductivity enhancement?TCE? reached 187%and 508%,respectively.In addition,the mechanical properties of PASC composites have also been greatly improved.The high thermal conductivity and better mechanical properties of both directions ensure that the composite can be widely used in various heat-dissipating electronic components.2.Using a wide range of sources,high strength,biodegradable NFC as the matrix,thermal conductive and electrical conductive graphene nanosheets?G2s?and thermal and electrical insulating boron nitride nanosheets?BNs?as fillers,under the action of vacuum assisted self-assembly?VASA?and layer-by-layer self-assembly?LBL?,an antistatic and electrically insulating multilayer polymer thermal conductive film was obtained.Through SEM,EDS,electrical and other tests,it can be seen that NFC thermal conductive layers with different functions play different roles.The film formed by NFC has a better layered structure,and the inorganic filler is more uniformly dispersed in the direction of 1D NFC,thereby forming a thermal conductive path.The prepared BGCGB film?both thermal conductive,electrical insulating,antistatic?is a five-layer sandwich symmetrical structure.When the filler content is 8 wt%,the thermal conductivity can reach 7.04 W·m^-1·K^-1,and its TCE can reach 528%.In addition,the film also has high mechanical properties.These properties ensure that the flexible film can be used safely and environmentally in areas where there is a high demand for heat dissipation.3.A thermally conductive film is prepared under the action of VASA by using NFC as substrate,thermal conductive and electrical insulating boron nitride nanosheets?BNNs?,and hydrophobic silica?SiO₂?as inorganic fillers.When the content of BNNs is 7 wt%,the thermal conductivity of NB-7 film reaches 11.84W·m^-1·K^-1,and its TCE reaches 957.1%.And the film has electrical insulation and good mechanical strength.It can be seen from the contact angle test that the hydrophobic thermal conductive film was obtained after the surface structure design.This film can be used in the field of moisture and water to prevent the adverse effects of moisture on the thermal conduction and mechanical properties of the film.