Progress on the polymer composite insulating materials with high thermal conductivity

The continuing miniaturization and increasing power density of electrical and electronic equipment have created higher requirements for the heat dissipation capacity of packing and insulating materials. Long-term operation of electronic devices will cause local overheating of core components, which will significantly affect the reliability and service life of the components. Heat dissipation has even become a technical bottleneck in the development of electronic devices with high integration. Therefore, developing new composite materials which offer excellent thermal conductivity has attracted significant interest worldwide in recent years. To address these issues, researchers improve the thermal conductivity of polymer materials mainly through the following two aspects. One is to modify the polymer body so that the internal molecular and chain structure of the polymer has a high degree of crystallization or orientation, thereby improving its thermal conductivity, but this method is a cumbersome preparation process and is still in the laboratory research stage. Second, inorganic fillers with high thermal conductivity can be filled in the polymer preparation process to form a thermal conductivity channel, thus improving the thermal conductivity. The latter composite material has been widely used in electronic packaging, electric machine potting and other fields because of its low cost, simple processing and convenient industrial production. This paper reviews the research status and progress of the preparation and application of composites with high thermal conductivity in recent years. Firstly, the factors that affect the thermal conductivity of materials are mainly introduced from two aspects: (1) The crystallinity of polymer matrix, the interaction between molecular chains and the micro-scale ordered structure; (2) the particle size, doping amount and geometry of thermal conductivity filler. Researchers have found that the key to obtaining composites with high thermal conductivity is to increase the ordered structure of the polymer or make the thermal conductivity packing form the maximum density thermal conductivity path consistent with the heat transfer direction in the polymer system. In view of the above key factors, we summarize five preparation methods that significantly improve the thermal conductivity of composites: Functionalized packing surface treatment, random blending, electrostatic spinning, field control and three-dimensional skeleton construction. Among them, constructing the 3D skeleton is considered as the most promising method at present. A large number of papers reported the use of casting technology, 3D printing technology and other methods to prepare three-dimensional thermal conductivity networks. In the casting technology, the 3D thermal skeleton is firstly formed by the ice template method or salt template method, and then the polymer matrix such as epoxy resin and PDMS is poured into the 3D skeleton to obtain the composite material with high thermal conductivity. This method fundamentally improves the thermal conductivity of composites. Finally, in view of the current situation of polymer insulating materials with high thermal conductivity in industry applications, we provide an outlook on the future directions for the development of composite materials. It is hoped that material properties can be optimized from the microscopic point of view in the future to obtain polymer composites with higher thermal conductivity with less filler and lower cost.