Correlation between morphology and electrical breakdown strength of the polypropylene/maleic anhydride grafted polypropylene/nano-ZrO2 ternary system

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. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46842.