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Investigation on Mechanism of Electrical Breakdown Property and Morphology of PE/MMT Nanocomposites

Author: GaoJunGuo
Tutor: ZhangXiaoHong
School: Harbin University of Science and Technology
Course: High Voltage and Insulation Technology
Keywords: polyethylene/montmorillonite nanocomposites breakdown partial discharge space charge
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 233
Quote: 3
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Abstract


For the excellent properties performed in material mechanics, electrical insulating and diversiform workability, Polyethylene (PE) is a kind of plastic which is used widely in electrical insulation field. Though PE has been used in a wide variety of engineering applications, the innately disadvantages of PE restrict a further application occurred in high level. The rapid increment of engineering applications developed with technologies call much more rigid claims to the PE manufactures. Temporarily, revolutionary nanocomposites present a new approach to the research on modify by nanotechnology. It has been proved by researches that compounding PE with nano-inorganic particals into nanocomposites can increase the comprehensive properties saliently.PE/O-MMT nanocomposites with different compatibilizers and contents of inorganic particles were prepared by low density polyethylene, with surface modified montmorillonite as modifying agent through melting intercalation processes, respectively. Maleic anhydride grafted polyethylene (PEMA) and ethylene?vinyl acetate copolymer (EVA) will play a compatibilizer role in this system.The inter-phase morphological character of the surface on specimen of PE/O-MMT composites was characterized by scanning electric microscopy (SEM) and atomic force microscope (AFM). Microstructure of PE/O-MMT composites is characterized. Dielectric strength were measured to investigate the effect of the compatilizers, process conditions, test temperature, electrical aging and different contents of MMT on breakdown strength of composites, also the toughening mechanism was discussed. The temperature dependence of composites insulation resistance was verified by using a high resistance meter. The influence of nanoparticles to dielectric properties of the composites was investigated. Pulsed electro-acoustic method (PEA) is used to test partial discharge of composites. Space charge distribution and trap characteristic are analyzed primarily.Some conclusions were drawn by analyzing the results received from all of the tests. Since PEMA was applicated as a compatibilizer, exfoliated LDPE/O-MMT composites could be prepared via a melt intercalation process. Intercalation reaction is implemented easily at 150℃. The results of breakdown test show that electrical aging resistance of LDPE/O-MMT is obviously higher. Electrical breakdown strength of LDPE/O-MMT is obviously higher than that of LDPE, up to 1.35~1.70 times at the test temperature of 60~90℃. The electrical breakdown strength of composites was not monotone raise up with the increased concentration of MMT. It performed a complicated tendency. The PEA spectrums indicate that the involvement of nano-MMT can decrease the amount of space charge in dielectric.

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