Effect of Temperature and Filler Content on Insulation Properties of Silicone Elastomer/Octavinyl Polyhedral Oligomeric Silsesquioxane Nanocomposites
Wang Qilong1,2, Chen Xiangrong1,2,3,4, Zhang Tianyin1, Wang Enzhe1, Ren Na2
1. College of Electrical Engineering Zhejiang University Hangzhou 310027 China; 2. ZJU-Hangzhou Global Scientific and Technological Innovation Center Hangzhou 311200 China; 3. Zhejiang Provincial Key Laboratory of Power Semiconductor Materials and Devices ZJU-Hangzhou Global Scientific and Technological Innovation Center Hangzhou 311200 China; 4. Advanced Electrical International Research Center International Campus Zhejiang University Haining 314400 China
Abstract：The silicon carbide-based wide bandgap (WBG) electronic power modules gradually develop towards a higher current, higher voltage, and miniaturization for realizing higher power density, leading to thermal and electric stress concentration. Therefore, the ideal encapsulation materials need lower permittivity, dielectric loss, electrical conductivity, and high-temperature resistance. The silicone elastomer (SE) is promising to be applied for high-temperature encapsulation in WBG power modules due to its excellent high-temperature resistance and low storage modulus. Polyhedral oligomeric silsesquioxane (POSS) is the known smallest nanofiller, which is widely used in various high-technology areas. Octavinyl polyhedral oligomeric silsesquioxane (OV-POSS) is selected in this paper due to its high reactivity with the SE matrix. This paper investigates the thermal and insulation properties of SE/OV-POSS nanocomposites with different filler contents under 20℃, 120℃, and 220℃. Moreover, the effect of the filler content on the crosslinking network of SE/OV-POSS nanocomposites and the mechanism of the temperature on the charge transport of the nanocomposites are analyzed. For the thermal experiments, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, thermal gravity analysis, and crosslinking degree measurements are performed to characterize the nanofiller distribution and analyze chemical groups, thermal stability, and molecular structure of the nanocomposites. For the electrical experiments, the dielectric spectroscopies, thermally stimulated depolarization current, and DC electrical conductivities at different temperatures are measured to analyze the effect of OV-POSS on the molecular chain relaxation process, trap characteristics, and insulation properties of the nanocomposites with different filler contents. Moreover, the quantum chemical calculations of the pure SE and SE/OV-POSS nanocomposite are performed at different electric fields to acquire the variation total density of states, molecular orbit energy level, dipole moment, and electrostatic potential distribution with the electric field. The results of the thermal and electrical experiments and quantum chemical calculations show that, the thermal degradation temperature T10, crosslinking degree and α relaxation temperature of the SE/OV-POSS nanocomposites firstly increase and then decrease as the filler content increases, and the T10, crosslinking degree and α relaxation temperature of the 3% mass fraction nanocomposites are the largest. The low-frequency dielectric loss of the nanocomposites is smaller than that of the pure SE at 20℃ to 160℃ but larger than that of the pure SE at 220℃ to 300℃. The DC electrical conductivities of the nanocomposites are lower than that of pure SE at 20℃ and 120℃ but higher than that of pure SE at 220℃. The DC conductivity of the 3% mass fraction nanocomposites is the lowest at 20℃ and 120℃ but highest at 220℃. The OV-POSS doping makes the shallow traps deeper in the nanocomposites, and the 3% mass fraction nanocomposite has the largest deep trap density. The band gap of the nanocomposite is significantly reduced at a high electric field, resulting in its valence band electrons being more easily excited to the conduction band at high temperature and high electric field. It can be concluded that, the appropriate amount of OV-POSS can effectively improve the insulation properties of the silicone elastomer at 20℃ and 120℃. A part of the vinyl group of OV-POSS reacts with the molecular chain of the matrix, improving the cross-linking degree and inhibiting the relaxation movement of the matrix molecular chain. The other part of the unreacted vinyl group behaves as deep electron traps, enhancing the insulation properties at 20℃ and 120℃.
王启隆, 陈向荣, 张添胤, 王恩哲, 任娜. 温度和掺杂含量对有机硅弹体/八乙烯基-笼型倍半硅氧烷纳米复合材料绝缘性能的影响[J]. 电工技术学报, 2023, 38(5): 1139-1153.
Wang Qilong, Chen Xiangrong, Zhang Tianyin, Wang Enzhe, Ren Na. Effect of Temperature and Filler Content on Insulation Properties of Silicone Elastomer/Octavinyl Polyhedral Oligomeric Silsesquioxane Nanocomposites. Transactions of China Electrotechnical Society, 2023, 38(5): 1139-1153.
[1] 钱照明, 张军明, 盛况. 电力电子器件及其应用的现状和发展[J]. 中国电机工程学报, 2014, 34(29): 5149-5161. Qian Zhaoming, Zhang Junming, Sheng Kuang.Status and development of power semiconductor devices and its applications[J]. Proceedings of the CSEE, 2014, 34(29): 5149-5161. [2] Chen Xiangrong, Wang Qilong, Ren Na, et al.Potential of epoxy nanocomposites for packaging materials of high voltage power modules: a validation using experiments and simulation[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2021, 28(6): 2161-2169. [3] Xue Yanming, Zhou Xin, Zhan Tianzhuo, et al.Densely interconnected porous BN frameworks for multifunctional and isotropically thermoconductive polymer composites[J]. Advanced Functional Materials, 2018, 28(29): 1801205. [4] Khazaka R, Mendizabal L, Henry D, et al.Survey of high-temperature reliability of power electronics packaging components[J]. IEEE Transactions on Power Electronics, 2015, 30(5): 2456-2464. [5] Yao Yiying, Chen Zheng, Lu Guoquan, et al.Charac- terization of encapsulants for high-voltage high- temperature power electronic packaging[J]. IEEE Transactions on Components Packaging and Manufacturing Technology, 2012, 2(4): 539-547. [6] Scofield J D, Merrett J N, Richmond J, et al. Electrical and thermal performance of1200 V, 100 A, 200℃ 4H-SiC MOSFET-based power switch modules[J]. Materials Science Forum, 2010, 645-648: 1119-1122. [7] Chi Qingguo, Cui Shuang, Zhang Tiandong, et al.SiC/SiO2 filler reinforced EP composite with excellent nonlinear conductivity and high breakdown strength[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2020, 27(2): 535-541. [8] Huang Xingyi, Zhi Chunyi, Jiang Pingkai, et al.Polyhedral oligosilsesquioxane-modified boron nitride nanotube based epoxy nanocomposites: an ideal dielectric material with high thermal conductivity[J]. Advanced Functional Materials, 2013, 23(14): 1824-1831. [9] 杨胜, 陈珂龙, 王智勇, 等. 笼型倍半硅氧烷(POSS)的官能化、杂化以及在改性环氧树脂中应用研究进展[J]. 航空材料学报, 2019, 39(3): 10-24. Yang Sheng, Chen Kelong, Wang Zhiyong, et al.Progress in functionalization, hybridization of polyhedral oligomeric silsesquioxanes(POSS) and its application in modified epoxy resin[J]. Journal of Aeronautical Materials, 2019, 39(3): 10-24. [10] 王峰, 彭丹, 牟秋红, 等. 笼型低聚倍半硅氧烷/硅橡胶复合材料的制备及性能进展[J]. 材料导报, 2020, 34(21): 21188-21198. Wang Feng, Peng Dan, Mu Qiuhong, et al.Progress in preparation and properties of POSS/silicone rubber composite[J]. Materials Reports, 2020, 34(21): 21188-21198. [11] Xin Yumeng, Wang Jiajia, Jin Kaikai, et al.A new four-arm organosiloxane with thermopolymerizable trifluorovinyl ether groups: synthesis and conversion to the polymer with both low dielectric constant and low water uptake[J]. Macromolecular Chemistry and Physics, 2017, 218(13): 1700010. [12] 李鹏新, 崔浩喆, 邢照亮, 等. 环氧/POSS复合电介质介电与热学性能[J]. 电工技术学报, 2022, 37(2): 291-298. Li Pengxin, Cui Haozhe, Xing Zhaoliang, et al.Dielectric and thermal properties of epoxy/POSS composites[J]. Transactions of China Electrotechnical Society, 2022, 37(2): 291-298. [13] Xu Yaoyuan, Long Jun, Zhang Runze, et al.Greatly improving thermal stability of silicone resins by modification with POSS[J]. Polymer Degradation and Stability, 2020, 174: 109082. [14] Misasi J M, Jin Qifeng, Knauer K M, et al.Hybrid POSS-Hyperbranched polymer additives for simultaneous reinforcement and toughness improvements in epoxy networks[J]. Polymer, 2017, 117: 54-63. [15] Zhang Wenchao, Camino G, Yang Rongjie.Polymer/polyhedral oligomeric silsesquioxane (POSS) nanocomposites: an overview of fire retardance[J]. Progress in Polymer Science, 2017, 67: 77-125. [16] Baumann T F, Jones T V, Wilson T, et al.Synthesis and characterization of novel PDMS nanocomposites using POSS derivatives as cross-linking filler[J]. Journal of Polymer Science Part A: Polymer Chemistry, 2009, 47(10): 2589-2596. [17] Huang Xingyi, Li Yong, Liu Fei, et al.Electrical properties of epoxy/POSS composites with homogeneous nanostructure[J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2014, 21(4): 1516-1528. [18] Min Daomin, Cui Haozhe, Hai Yali, et al.Interfacial regions and network dynamics in epoxy/POSS nanocomposites unravelling through their effects on the motion of molecular chains[J]. Composites Science and Technology, 2020, 199: 108329. [19] Liu Yufeng, Shi Yunhui, Zhang Dian, et al.Preparation and thermal degradation behavior of room temperature vulcanized silicone rubber-g-polyhedral oligomeric silsesquioxanes[J]. Polymer, 2013, 54(22): 6140-6149. [20] Chen Dongzhi, Liu Yan, Huang Chi.Synergistic effect between POSS and fumed silica on thermal stabilities and mechanical properties of room temperature vulcanized (RTV) silicone rubbers[J]. Polymer Degradation and Stability, 2012, 97(3): 308-315. [21] Ceresoli D, Tosatti E, Scandolo S, et al.Trapping of excitons at chemical defects in polyethylene[J]. The Journal of Chemical Physics, 2004, 121(13): 6478-6484. [22] 顼佳宇, 李学宝, 崔翔, 等. 高压大功率IGBT器件封装用有机硅凝胶的制备工艺及耐电性[J]. 电工技术学报, 2021, 36(2): 352-361. Xu Jiayu, Li Xuebao, Cui Xiang, et al.Preparation process and breakdown properties of silicone gel used for the encapsulation of IGBT power modules[J]. Transactions of China Electrotechnical Society, 2021, 36(2): 352-361. [23] 刘东明, 李学宝, 顼佳宇, 等. 高压SiC器件封装用有机硅弹性体高温宽频介电特性分析[J]. 电工技术学报, 2021, 36(12): 2548-2559. Liu Dongming, Li Xuebao, Xu Jiayu, et al.Analysis of high temperature wide band dielectric properties of organic silicone elastomer for high voltage SiC device packaging[J]. Transactions of China Electrotechnical Society, 2021, 36(12): 2548-2559. [24] Tian Fuqiang, Bu Wenbin, Shi Linshuang, et al.Theory of modified thermally stimulated current and direct determination of trap level distribution[J]. Journal of Electrostatics, 2011, 69(1): 7-10. [25] 李进, 赵仁勇, 杜伯学, 等. 量子化学计算在高压直流绝缘领域中的应用进展[J]. 高电压技术, 2020, 46(3): 772-781. Li Jin, Zhao Renyong, Du Boxue, et al.Application progress of quantum chemical calculation in the field of HVDC insulation[J]. High Voltage Engineering, 2020, 46(3): 772-781. [26] 李亚莎, 夏宇, 刘世冲, 等. 从聚酰亚胺单分子链电荷陷阱特性的改变探讨体材料的沿面放电现象[J]. 物理学报, 2022, 71(5): 119-128. Li Yasha, Xia Yu, Liu Shichong, et al.Surface discharge of bulk materials investigated from change of charge trap characteristics of polyimide single molecular chain[J]. Acta Physica Sinica, 2022, 71(5): 119-128. [27] Li Jin, Han Chenlei, Du Boxue, et al.Deep trap sites suppressing space charge injection in polycyclic aromatic compounds doped XLPE composite[J]. IET Nanodielectrics, 2020, 3(1): 10-13.
2023, Vol. 38 
