高导热聚合物复合绝缘材料研究进展

Progress on the polymer composite insulating materials with high thermal conductivity

近年来,电气电子设备不断向高功率密度化、小型轻量化和高度集成化的方向发展,设备单位体积发热量和温升急剧增加,热量积聚会加速绝缘老化并严重影响设备运行的可靠性和寿命.提高绝缘材料导热能力是提升电气电子设备散热能力的关键.本文综述了近年来国内外高导热复合绝缘材料的研究现状与进展,重点讨论了聚合物基体的结晶度、分子链间相互作用、微尺度有序结构和导热填料的粒径、掺杂量及几何形状等因素对绝缘材料导热系数的影响.通过静电纺丝、外场调控及构建三维骨架等方式增加聚合物的有序结构和使导热填料在聚合物基体中沿热传导方向取向,是大幅度提升绝缘材料导热系数的有效途径.

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.