RESEARCH ARTICLE Improved thermal and electrical properties of epoxy resin composites by dopamine and silane coupling agent modified hexagonal BN Yiran Zhang 1 | Rui Tuo 2 | Wei Yang 3 | Jiale Wu 1 | Jie Zhu 1 | Chong Zhang 3 | Jun Lin 1 | Xingming Bian 1 1 State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing, 102206, China 2 Secondary Maintenance Center, State Grid Hunan Electric Power Company Maintenance Company, Changsha, 410029, China 3 State Key Laboratory of Advanced Power Transmission Technology, Global Energy Interconnection Research Institute, Co., Ltd., Beijing, 102211, China Correspondence Xingming Bian, State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China. Email: bianxingming@ncepu.edu.cn Funding information National Key Research and Development Program of China, Grant/Award Number: 2017YFB0903800; State Key Laboratory of Advanced Power Transmission Technology, Grant/Award Number: GEIRI-SKL-2018-014; State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Grant/Award Number: EERIKF2019002; Fundamental Research Funds for the Central Universities, Grant/Award Number: 2019MS011 Abstract The high thermal conductivity epoxy resin composites filled with inorganic filler can improve the low thermal conductivity of epoxy resin. However, a large number of fillers with high thermal conductivity will reduce other prop- erties of the composites, which limits their use under high voltage, high tem- perature and strong mechanical force during operation. In this study, the dopamine-modified BN (DBN) and k-DBN (DBN modified by coupling agent KH-560) were prepared by employed the dopamine with catechol groups and coupling agent to modify boron nitride. The thermal conductivity, thermal sta- bility, and dielectric properties of composites with different contents of modi- fied fillers were studied. The results showed that surface modification improved the dispersibility of BN in the resin matrix and compatibility with the resin. Among BN/EP, DBN/EP, k-DBN/EP composites, k-DBN/EP com- posites had the highest thermal conductivity at the same number of additions. When the k-DBN/EP content was 30 wt%, the thermal conductivity of the composite was 0.892 W/(mK), which was an increase of 25.5% compared with the BN/EP composite. The appropriate amount of BN filling (20 wt%) can improve the breakdown strength of the composite material. KEYWORDS double surface modified, electrical properties, epoxy resin, polydopamine, thermal conductivity 1 | INTRODUCTION AS the rapid development of AC/DC power transmission and electronic technology, electrical equipment and elec- tronic equipment tend to be miniaturized, integrated, and high-powered. Working in the high-frequency and high-power environments, the equipments generate a great amount of heat and therefore the dielectric temper- ature continues to increase. At the same time, the insula- tion material in the equipments work for a long time and the insulation performance could be weakened. [1,2,3] As a result, more attention has been paid to thermal Received: 7 May 2020 Revised: 21 June 2020 Accepted: 12 July 2020 DOI: 10.1002/pc.25746 Polymer Composites. 2020;1–13. wileyonlinelibrary.com/journal/pc © 2020 Society of Plastics Engineers 1