Effect of water on the breakdown and dielectric response of polypropylene/nano-aluminium nitride composites

Xinyu Wang,Ian Hosier,Thomas Andritsch,George Chen,Dayuan Qiang,Yanqiu Zhu

doi:10.1007/s10853-020-04635-1

Xinyu Wang, Ian Hosier + Show 4 more

Open Access

https://doi.org/10.1007/s10853-020-04635-1

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Abstract

The influence of water immersion and silane treatment on the AC breakdown and the complex dielectric response of polypropylene/nano-aluminium nitride (PP/nano-AlN) composites has been investigated. The as-received filler was examined to have a nanoscale particle distribution with a hexagonal shape and slight hydrolysation. Grafting the aluminium nitride with an octyl silane reduces the weight increase in samples filled with 10 wt% of aluminium nitride during water immersion by 3, from 0.29 to 0.09%. The results suggest that the AC breakdown strength and complex permittivity of “wet” composite samples are related to the silane treatment of the nanofiller. The AC breakdown strength of octyl silane-treated samples after 9 days of water immersion shows comparable results to the dry samples, while a reduction can be seen on non-treated samples. Although silane-treated samples still show an increased dielectric loss at low frequency after water immersion, a significant reduction in low-frequency dispersion of real and imaginary permittivity can be seen when compared to the non-treated composites. This indicates that significant gains can be obtained for PP/nano-AlN composites by suitable silane treatments.

Highlights

Polypropylene (PP) is considered a potential nextgeneration high-voltage cable insulation material by many researchers due to its potential to permit higher cable operating temperatures compared to traditional cross-linked polyethylene (XLPE) [1, 2]
The relaxation frequency is related to the thickness of the water shell and the mobility of the resulting water clusters [11,12,13]; PP/nano-aluminium nitride (AlN) composites show a low water absorption ability, e.g. N-10-W can only gain 0.29% of weight, while a 10 wt% non-treated nanosilica/PE composite shows more than 1.6% weight increase and relaxation peaks at 103–105 Hz can be observed
The hydrolytic instability of AlN and the resulting sensitivity of the particle surface chemistry, and subsequently the morphology, to humidity are discussed. This rigorous study using Scanning electron microscope (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA) of the as-received AlN verified the abovementioned sensitivity to humidity, as well as the AlN nanoscale, and the presence of the c-alumina is evident

Summary

Introduction

Polypropylene (PP) is considered a potential nextgeneration high-voltage cable insulation material by many researchers due to its potential to permit higher cable operating temperatures compared to traditional cross-linked polyethylene (XLPE) [1, 2]. When compared to PE/nano-AlN composites as reported in earlier research [11], where PE with 10 wt% of AlN only has an uptake of water less than 0.1% of the total weight after immersing in water for 14 days, the higher weight increase for the non-treated samples (0.29%, Fig. 8) in the present work is likely related to the smaller particle size and the increased surface area (Fig. 3).

Conclusions

Findings

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