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Extensive research has focused on enhancing the energy storage density of polypropylene (PP) to meet the demands of high-power and compact electronic devices and electrical systems. However, there is a lack of studies addressing the delicate balance between energy storage density and dielectric loss. Dielectric loss can lead to excessive heat generation, posing a threat to the operation of energy storage capacitors. In this study, PP grafted with glycidyl methacrylate (GMA) was used as a compatibilizer and incorporated into a PP/nano ZrO2 blend to form a ternary system of PP/nano ZrO2/PP grafted GMA. A comparative study was conducted to analyze the effects of GMA grafting and individual doping of nano ZrO2 on the dielectric performance of PP. The results demonstrate that the ternary system not only ensures a high breakdown voltage (382.29 MV/m) but also possesses a high dielectric constant (2.67), thereby achieving an energy storage density of 1.7275 J/cm3 while maintaining low dielectric loss. Furthermore, grafting GMA introduces a significant number of deep traps, a phenomenon substantiated by the results of thermal stimulated depolarization current tests and molecular simulation calculations. However, the ternary system partially avoids the introduction of excessive deep traps associated with GMA grafting. This ternary system exhibits excellent energy storage performance, ease of fabrication, and stability, thereby enriching the research on polymer-based high-energy density dielectric materials. [ABSTRACT FROM AUTHOR]

To improve the energy storage density while maintaining low dielectric loss is crucial for the miniaturization of capacitors. In the present study, we proposed a ternary nanocomposite system comprised of polypropylene (PP), acrylic acid grafted PP (PP-g-AA), and nano-ZrO2. The PP-g-AA was firstly prepared by a free radical grafting with the proportion fixed to 50 wt%, and the content of nano-ZrO2 ranged from 0.5 wt% to 5 wt% to tailor the ternary composite. The transmission electron microscope observation showed that PP-g-AA could significantly benefit the dispersion of nanoparticles and the differential scanning calorimetry results indicated the superior compatibility of the ternary nanocomposites. Accordingly, with the optimum nano-ZrO2 content of 0.5 wt%, the ternary nanocomposites achieved the permittivity of 2.7 and DC breakdown strength of 456.2 kV mm−1, resulting in the enhanced energy density of 2.77 J cm−3 which was 60% higher than neat PP, while the dielectric loss was kept lower than 0.003. Moreover, even at the temperature of 120 °C, the ternary nanocomposites maintained a high-performance energy storage density of 2.28 J cm−3 (with energy storage efficiency above 90%), which was 670% of the neat PP. [ABSTRACT FROM AUTHOR]

To simoutinusly achieve improved breakdown strength (BDS) and suppressed dielectric loss, a modified ternary nanocomposite composed of polypropylene (PP), maleic anhydride‐grafted PP and core‐shell structure SiO2@ZrO2 nanoparticles is proposed. By tailoring the thickness of SiO2 shell from 3 to 11 nm and the nanofillers content from 0.5 to 5 wt%, the particles disparsion is improved and meanwhile both the deep trap density and the interaction force between molecules are enhanced. In consequence, the restricted transportation of electrons along molecule chains as well as between chains together raise the DC BDS, that the BDS of optimum sample film reaches 430.8 kV/mm, 23% higher than neat PP. Besides, the ternary nanocomposites with SiO2@ZrO2 less than 3 wt% maintain the tanδ below 0.3% at a broad frequency ranging from 0.1 Hz to 100 kHz, which is an extremely low level same as neat PP. [ABSTRACT FROM AUTHOR]

A comparative study of biaxial-orientated polypropylene (BOPP) films extracted from one failed HVDC filter capacitor (serving for 10 years) and one fresh capacitor (spare capacitor from the same batch) is reported in this paper. Experimental results show that the 10-year online operation does not bring about molecular changes; however, molecule reorganization and recrystallization was detected using differential scanning calorimetry and dynamic mechanical analysis tests. Electrical measurements including dielectric spectra, DC conductivity measurement, DC breakdown strength and were also performed. The experimental results show that the aging process causes an increase in dielectric constant, dissipation factor, DC conductivity, and the DC breakdown strength. Thermal stimulated current measurements indicate that traps were introduced by aging and are responsible for such abnormal changes. The nano-cavitivies generated by molecule reorganization could possibly act as charge traps. Therefore, homo-charges can accumulate in the vicinity of the electrodes, leading to the degradation of long-term withstand strength but an enhancement of short-term breakdown strength. [ABSTRACT FROM AUTHOR]

Extensive research studies have been carried out to enhance the energy storage density of polypropylene (PP) films for power capacitor application to cater to the development of power system. However, most of the research studies failed to balance the energy storage density and dielectric loss which generates heat and threatens the operation of power capacitor. In the present study, we proposed a ternary system composited of PP, maleic anhydride‐grafted PP (PP‐g‐MAH), and nano‐ZrO2 with totally 25 compositions in an orthogonal ingredient system. Direct current (dc) breakdown test and dielectric spectra were measured and showed that the largest enhancement of 30.2% of energy storage density was achieved with both increased dielectric constant and dc breakdown strength (BDS), while the dielectric loss kept the same level of neat PP. This on the one hand was attributed to the orientation polarization, ionic polarization, and deep traps introduced by PP‐g‐MAH and nano‐ZrO2, evidenced by the thermal stimulated depolarization current test results. On the other hand, the results of dynamic mechanical analysis indicated that the compatibility of each phases was largely improved in the ternary system so that a high dc BDS was obtained due to the restricted segmental molecular motion. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48211. [ABSTRACT FROM AUTHOR]

Nano-dielectrics are sensitive to humidity and easily degraded in damp environment because of the high surface energy of nanoparticles. In order to study the effect of humidity on the dielectric properties of nano-dielectric, polypropylene (PP) was modified by polyolefin elastomer (POE) and nano-SiO2, and the samples with obvious filling concentration were pre-selected by breakdown strength for damp aging. The aging experiments were carried out in different relative humidity. The dielectric properties of new, hygroscopic saturation and samples after drying were measured and analyzed. It is found that the breakdown strength of hygroscopic saturation nano-dielectrics decreased obviously compared with new samples, and it was difficult to recover after drying. The damp degradation resulted in different changing trends of permittivity of PP and nano-dielectric, but there were relaxation loss peaks of water in both of them. The influence of damp degradation on the trap distribution was studied by thermally stimulated depolarization currents (TSDC), and it was found that the traps level introduced by water molecules was different in PP and nano-dielectrics. All experiment results showed that the performance of nano-dielectrics degraded obviously in humid environment, and it was difficult to recover even after complete drying because of the existence of bounded water molecules in nano-dielectrics. [ABSTRACT FROM AUTHOR]

A ternary system composed of isotactic polypropylene (PP), maleic anhydride grafted polypropylene (PP‐g‐MAH), and nano‐ZrO2 was designed. To investigate the influence of each composition, we systematically designed orthogonal tests with 25 samples with various PP‐g‐MAH (0–70 wt %) and nano‐ZrO2 concentrations (0–5 wt %). Microscopic observation showed that the introduction of PP‐g‐MAH could distinctively benefit the dispersion of nanoparticles. This can be understood by chemical bonds between PP‐g‐MAH and the nano‐ZrO2 surface, which was evidenced by infrared spectroscopy. Meanwhile, both the crystalline properties and aggregation structures were improved within this ternary system. Macroscopically, a great enhancement of DC breakdown strength (BDS) as high as 43.3% was achieved when the PP‐g‐MAH concentration was 50 wt % and the nano‐ZrO2 concentration was 0.5 wt %. Moreover, the effects of PP‐g‐MAH and nano‐ZrO2 were revealed respectively. The increase of nano‐ZrO2 content could cause the first increase and then decrease of BDS. The influence of PP‐g‐MAH on breakdown strength was obviously shown by the analysis of variance, and the rising PP‐g‐MAH concentration could lead to the nano‐ZrO2 content with the highest BDS shifted to higher loading, indicating that the modified dispersion of nanoparticles played the dominant role in the breakdown performance improvement. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46842. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) contains promising application prospects in thermoplastic cables for high voltage direct current (HVDC) power transmission because of its outstanding thermal and dielectric properties. However, the problem of poor toughness and space charge has restricted the application of pure PP in HVDC cables. In this paper, polyolefin elastomer (POE) and nano-silica were blended thoroughly and added into a PP mixture by a melting method. Scanning electron microscopy (SEM) was employed to observe the dispersion of POE and nanoparticles. Thermal properties were characterized by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Mechanical properties were evaluated by tensile tests. The elastomeric properties of composites were improved as the dispersed POE could transfer and homogenize external mechanical forces. DC breakdown results showed that the fail strength of composite with 10 phr POE and 1 phr nano-silica was obviously enhanced. The pulsed electro-acoustic (PEA) results showed that the injection and accumulation of space charge was increased by the introduction of POE, while it was restrained by the collective effect caused by nano-silica filling. X-ray diffraction (XRD) spectrograms showed that secondary ordered structures existed in the composites of PP, POE, and nano-silica, and that the ordered structure around the nanoparticles contributed to the enhancement of breakdown strength. The mechanical and dielectric properties were modified synergistically, which made the modified PP a propitious insulation material for HVDC cables. [ABSTRACT FROM AUTHOR]