1. State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China; 2. School of Electrical Engineering Xinjiang University Urumqi 830047 China; 3. Global Energy Interconnection Development and Cooperation Organization Beijing 100031 China
Abstract：β-nucleating agents (NAs) are widely used to regulate the phase transition behavior of polypropylene. To study the influence of β-NA content on conduction current and space charge characteristics in isotactic polypropylene (iPP), iPP samples filled with different mass fractions of substituted aromatic heterocyclic phosphate β-NAs (TMB-5) were prepared. Experiments of conduction current, dielectric, and space charge under temperature fields were carried out. The results show that β-crystal content increases firstly and then decreases with the increase of β-NA content, while conduction current is opposite. Moreover, electric field distortion ratio of six groups of iPP samples are no larger than 6% under -100 MV/m at 25℃ for 30 min of polarization. On the other hand, positive charge accumulates near the cathode in all groups under -100 MV/m at 70℃ for 30 min of polarization, and electric field distortion ratio of pure iPP samples is the largest (36.7%), while that of iPP-β0.1% (containing 0.1% β-NAs) is only 13.9%. Combining polarized optical microscopy observations with statistics of the average size of crystallite clusters, cause for the changes of β-crystal content was analyzed from the dispersion and nucleation processes of β-NAs. Utilizing measurement results of space charge during polarization and depolarization processes, influence of β-NA content on the charge transit and distribution processes was explained based on the correlation between the microstructure and internal traps of materials.
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2019, Vol. 34 
