Preparation And Properties Of Graphite/Nylon 66 Composite With High Thermal Conductivity

The progress of science and technology is accompanied by the miniaturization,high integrated and high energy of electronic devices,which poses new challenges to the traditional thermal management.The thermal conductivity polymer material with good heat dissipation is one of the hot spots in current research.Flake graphite not only has good thermal conductivity and meets the requirements of preparing thermal conductive polymer composites,but also has a wide range of sources and low price.At present,the methods of preparing Nylon 66 and flake graphite thermal conductivity composites are mostly twin-screw extrusion,and the thermal conductivity of the composites prepared is 10 W·m^-1·K^-1.Compared with the thermal conductivity of flake graphite,there is still a lot of room for improvement.Centered on the two problems of preparation technology and low thermal conductivity,two kinds of nylon 66(powder and plate)were used as the matrix,and two kinds of packing materials(blending type and directional type)were prepared by one-way hot pressing furnace sintering with flake graphite.Specific research contents are as follows:1.Firstly,PA66 powder was blended with flake graphite,and then the blended material was prepared by unidirectional hot pressing sintering,and the thermal properties and mechanical properties of the composite were systematically studied.The thermal conductivity test results show that the thermal conductivity of the composite is closely related to the content of flake graphite and increases with the increase of the content,while the mechanical bending resistance is opposite.When the filler content reaches 50%,the thermal conductivity of the composite reaches 13.68W·m^-1·K^-1,and the bending strength reaches 9.2 MPa.The composite prepared by one-way hot pressing has obvious anisotropy and the in-plane direction is obviously higher than the out-plane direction.When the temperature increases from 25?to 75?,the thermal conductivity of the composites with the filler content of 50%decreases by 20%,that of the composites with the filler content of 40%decreases by 21%,and that of the composites with the filler content of 30%decreases by 23%.The thermal conductivity of the composite material decreases with the increase of temperature and the degree of thermal diffusion coefficient is proportional to the filler content.2.The composite material with Nylon 66 matrix flake graphite was prepared,and the composite material with the same arrangement form was prepared after the graphitization of flake graphite.The thermal properties and mechanical properties of the composite material were systematically studied.The thermal conductivity of the laminated composite material in the in-plane direction is very excellent.The thermal conductivity of the composite material with the filler content of 50%reaches 66.3 W·m^-1·k^-1.However,its out-of-plane thermal conductivity is significantly reduced,showing significant anisotropy.The thermal conductivity of the graphitized flake graphite is better,and the thermal conductivity of the composite filled with graphitized flake graphite is nearly 2 times higher than that of the composite filled with the same filler ratio.With the addition of graphitization process,the thermal stability of the composites decreases,and the thermal stability is the worst when the content is 50%.3.An attempt was made to improve the wettability of nylon 66 and flake graphite by using coupling agent.Four kinds of coupling agent treated composites with filler content of 50%were prepared by surface modification of flake graphite with coupling agent,and the thermal and mechanical properties of the composites were systematically studied.The thermal conductivity of the composites treated with coupling agent KH570 reached 114 W·m^-1·k^-1,and the thermal conductivity of the composites prepared without coupling agent was improved by 4%,and the thermal stability was excellent.