冷却方式对MMT/LDPE介电性能的影响

doi:10.15541/jim20150206

摘要/Abstract

摘要：

采用熔融插层法制备了蒙脱土/低密度聚乙烯(MMT/LDPE)纳米复合材料, 探讨空气自然冷却、空气快速冷却、水冷却和油冷却四种制备工艺对复合材料介电性能的影响。利用XRD、FTIR、AFM、PLM、DSC和TSC等分别对复合材料和纳米MMT粒子的微观形态、复合材料的电导、击穿、介电频谱和空间电荷特性进行表征。结果表明, 经表面修饰的纳米MMT粒子在基体聚合物中已经剥离并均匀分散; 不同冷却方式对复合材料的结晶度有一定的影响, 其中油冷却试样结晶速率最高, 结晶尺寸最小; 纳米MMT的加入使复合材料内部陷阱密度和深度均有所增加, 且试样的介电性能有不同程度的改善。油冷却试样抑制空间电荷的作用比较明显, 在20和40 kV/mm的场强下, 试样中正电荷的峰值与空气自然冷却试样相比分别下降了63.57%和51.39%; 且油冷却试样的电导率最小, 击穿场强值最大; 在1~10⁵Hz的测试频率范围内, 与空气自然冷却试样相比, 其他三种试样的介电常数和介质损耗角正切值都有不同程度的降低。

关键词: 低密度聚乙烯, 纳米MMT, 冷却方式, 介电性能

Abstract:

The melting intercalation method was used to prepare montmorillonite/low density polyethylene (MMT/LDPE) nano-composites. Through natural air cooling, rapid air cooling, water cooling, and oil cooling methods, the effects of different preparation processes on the dielectric properties of the composites were studied. The MMT/LDPE composite materials were characterized by XRD, FTIR, AFM, PLM, DSC, and TSC test. All experimental results show that the surface modified nano-MMT particles have been exfoliated and uniformly disperse in polyethylene. Different cooling processes have influence on the crystallinity of the composites. The oil cooling sample has higher crystallization rate and smaller crystal size. The density and depth of trap in the composites with nano-MMT are increased, which effectively improves dielectric properties of the polymer. Space charge in the composites by oil cooling process is evidently inhibited under 20 kV/mm and 40 kV/mm field strength. The peak value of positive charge is decreased by 63.57% and 51.39% as compared with that of natural air cooling. The oil cooling sample shows the smallest conductivity, and the largest breakdown strength. In the frequency range of 1-10⁵ Hz, the dielectric constant and dielectric loss angle tangent of other threetypes of rapid air cooling, water cooling and oil cooling samples decrease at different degrees in contrast to natural air cooling sample.

Key words: low-density polyethylene, nano-MMT, cooling methods, dielectric propeties

中图分类号:

TB332
TM215

程羽佳, 张晓虹, 周雪冬, 郭宁, 成如如, 张天旭. 冷却方式对MMT/LDPE介电性能的影响[J]. 无机材料学报, 2015, 30(12): 1295-1302.

CHENG Yu-Jia, ZHANG Xiao-Hong, ZHOU Xue-Dong, GUO Ning, CHENG Ru-Ru, ZHANG Tian-Xu. Effects of Cooling Methods on Dielectric Properties of MMT/LDPE[J]. Journal of Inorganic Materials, 2015, 30(12): 1295-1302.

图/表 13

图1 MMT和MMT/LDPE试样XRD图谱

Fig. 1 XRD patterns of MMT and MMT/LDPE specimens

图2 MMT和MMT/LDPE试样的红外光谱图

Fig. 2 FTIR patterns of MMT and MMT/LDPE specimens

图3 MMT/LDPE的AFM照片

Fig. 3 AFM images of MMT/LDPE. (a) Height map; (b) Phase diagram

图4 MMT/LDPE的偏光显微镜照片

Fig. 4 PLM images of MMT/LDPE. (a) Natural air cooling; (b) Rapid air cooling; (c) Water cooling; (d) Oil cooling

图5 MMT/LDPE纳米复合材料升温及降温过程的DSC曲线

Fig. 5 DSC curves of LDPE and MMT/LDPE samples during heating and cooling

图6 试样的TSC图谱

Fig. 6 TSC spectra of samples

图7 四种试样电导率与电场强度的关系

Fig. 7 Relationship between conductivity and field strength for four types of samples

图8 四种试样的Weibull分布

Fig. 8 Weibull distribution parameters of four types of samples

图9 不同试样介电性能随频率的变化

Fig. 9 Frequency dependences of dielectric properties of various samples

图10 不同试样加压时MMT/LDPE空间电荷的分布

Fig. 10 Space charge distribution in MMT/LDPE samples under various electrical field. (a) Natural air cooling; (b) Rapid air cooling; (c) Water cooling; (d) Oil cooling

图11 不同试样中空间电荷分布随短路时间的变化

Fig. 11 Changes of space charge distribution in various samples with short-circuited time. (a) Natural air cooling; (b) Rapid air cooling; (c) Water cooling; (d) Oil cooling

表1 MMT/LDPE试样加压平均电荷密度

Table 1 Average charge density of MMT/LDPE samples under different electric field

Electrical field	10 kV/mm	20 kV/mm	40 kV/mm
Natural air cooling	0.58522	1.74640	2.03929
Rapid air cooling	0.59581	1.79236	2.08940
Water cooling	0.50265	1.74408	1.67510
Oil cooling	0.34720	1.19120	1.57720

表2 MMT/LDPE体系短路时平均电荷密度分布

Table 2 Charge density distribution of MMT/LDPE system with short-circuit time/ (C•m-3)

Short circuit time	60 s	900 s	1800 s
Natural air cooling	1.95505	1.16921	1.01754
Rapid air cooling	1.99370	1.16921	1.01754
Water cooling	1.60711	0.95444	0.75726
Oil cooling	1.04666	0.65901	0.59119

参考文献 28

[1]	杨挺, 程丽鸿, 钱丹. 我国聚乙烯发展现状及市场分析. 绝缘材料, 2013, 46(3): 33-36.
[2]	ALAPATI S, THOMAS M J.Electrical treeing and the associated PD characteristics in LDPE nanocomposites.IEEE Transactions on Dielectrics and Electrical Insulation, 2012, 19(2): 697-704.
[3]	张金梅. PE/MMT纳米复合材料结晶形态与树枝放电特性研究. 哈尔滨: 哈尔滨理工大学硕士学位论文, 2009.
[4]	迟晓红, 高俊国, 郑杰, 等. 聚丙烯中电树枝生长机理研究. 物理学报, 2014, 63(17): 177701.
[5]	TOSHIKATSU TANAKA, MASAHIRO KOZAKO, NORIKAZU FUSE, et al.Proposal of a multi-core model for polymer nanocomposite dielectrics.IEEE Transactions on Dielectrics and Electrical Insulation, 2005, 12(4): 669-681.
[6]	周远翔, 孙清华, 王宁花, 等. 空间电荷对低密度聚乙烯电气击穿特性的影响. 高电压技术, 2008, 34(3): 447-450.
[7]	高俊国. PE/MMT纳米复合材料结构形态与电击穿性能机理研究. 哈尔滨: 哈尔滨理工大学硕士学位论文, 2009.
[8]	张晓虹, 高俊国, 郭宁, 等. 纳米蒙脱土对聚乙烯击穿和电导特性的影响. 高电压技术, 2009, 35(1): 129-134.
[9]	CECILIEN THOMAS, GILBERT TEYSSEDRE, CHRISTIAN LAURENT.A new method for space charge measurements under periodic stress of arbitrary waveform by the pulsed electro- acoustic method.IEEE Trans. DEI, 2008, 15(2): 554-559.
[10]	TTANAKA Y, CHEN G, ZHAO Y, et al.Effect of additives on morphology and space charge accumulation in low density polyethylene.IEEE Transactions on Dielectrics and Electrical Insulation, 2003, 10(1): 148-154.
[11]	王霞, 吴超一, 何华琴, 等. 茂金属聚乙烯改性低密度聚乙烯中空间电荷机理的研究. 中国电机工程学报, 2006, 26(7): 158-162.
[12]	ZHANG XIAO-HONG, ZHANG MING-YAN, GAO JUN-GUO, et al.Investigation on Microstructure and Dielectric Properties of Polyethylene/Montmorillonite Nano-composites//2005 International Symposium on Electrical Insulating Materials (ISEIM` 2005) :Vol 1. Kitakyus hu, Japan: IEEE Press, 2005: 235-238.
[13]	莫志深, 张宏放, 张吉东. 晶态聚合物结构和X射线衍射. 北京: 科学出版社, 2010: 207-263.
[14]	CHOO W, CHEN G, SWINGLER S G.Temperature Gradient Effcet on the Conductivity of an XLPE Insulated Polymeric power cable. Solid Dielectries(ICSD), 2010 10th IEEE International Conference on, 2010.
[15]	朱诚身. 聚合物结构分析. 北京: 科学出版社, 2010: 22-45.
[16]	TIAN FU-QIANG, LEI QING-QUAN, WANG XUAN, et al.Effect of deep trapping states on space charge suppression in polyethylene/ZnO nanocomposite.Applied Physics Letters, 2011, 99(14): 142903.
[17]	张晓虹, 高俊国, 张金梅, 等. PE/MMT纳米复合材料的电击穿与耐局放性能. 高电压技术, 2008, 34(10): 2124-2128.
[18]	TAKEDA T, SUZUKI H, OKAMOTO T.Correlation between Space Charge Distribution under DC Voltage and Dielectric Breakdown Properties in XLPE under Impulse Voltage Superposed onto DC Voltage//Proceedings of 2001 International Symposium on Electrical Insulating Materials.Himeji, Japan: IEEE, 2001: 493-496.
[19]	王金锋, 郑晓泉, 柳立为, 等. LDPE结晶形态对水树枝老化特性的影响. 高电压技术, 2010, 3: 678-684.
[20]	LEI Q, WANG X, FAN Y.A new method of auto-separating thermally stimulated current.Journal of Applied Physics, 1992, 72(9): 4254-4257.
[21]	QING QUAN L, FU QIANG T, CHUN Y, et al.Modified isothermal discharge current theory and its application in the determination of trap level distribution in polyimide films.Journal of Electrostatics, 2010, 68(3): 243-248.
[22]	MA D I, HUGENER T A, SIEGEL R W, et al.Influence of nanoparticle surface modification on the electrical behaviour of polyethylene nanocomposites. Nanotechnology, 2005, 16(6): 724-731.
[23]	田付强. 聚乙烯基无机纳米复合电介质的陷阱特性与电性能研究. 北京: 北京交通大学博士学位论文, 2012.
[24]	CHEN G, TANAKA Y, TTAKADA T, et al.Effect of polyethylene interface on space charge formation.IEEE Transactions on Dielectrics and Electrical Insulation, 2004, 11(1): 113-121.
[25]	GREEN C D, VAUGHAN A S.Morphology and Crystallisation Kinetics of Polyethylene/Montmorillonite Nanocomposites. IEEE International Conference on Solid Dielectrics, 2007: 368-371.
[26]	TATSUO TAKADA, YUJI HAYASE, YASUHIRO TANAKA.Space charge trapping in electrical potential well caused by permanent and induced dipoles for LDPE/MgO nanocomposite.IEEE Transactions on Dielectrics and Electrical Insulation, 2008, 15(1): 152-160.
[27]	莫志深, 张宏放, 张吉东. 晶态聚合物结构和X射线衍射. 北京: 科学出版社, 2010: 207-263.
[28]	TIAN FU-QIANG, LEI QING-QUAN, WANG XUAN, et al.Effect of deep trapping states on space charge suppression in polyethylene/ZnO nanocomposite.Applied Physics Letters, 2011, 99(14): 142-144.