Influence of Gamma Irradiation and Water Aging on the Space Charge Characteristics of Epoxy Micro-Nano Composites.

Myneni Sukesh Babu,Takahiro Imai,Toshikatsu Tanaka,Ramanujam Sarathi

doi:10.3390/polym13060964

Myneni Sukesh Babu, Takahiro Imai + Show 2 more

Open Access

https://doi.org/10.3390/polym13060964

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Abstract

Epoxy micro-nano composites are well-known to exhibit enhanced electrical, mechanical as well as thermal properties compared to base epoxy resin. Yet, a clear understanding need to be achieved on the long-term aging performance of the epoxy micro-nano composites. The present review article is a comprehensive study on the impact of gamma irradiation and water aging on the space charge characteristics of epoxy micro-nano composites that are applicable as insulant in high-voltage power apparatus. Ion-trapping nanoparticles, which possess good oxidation resistance and high ion trapping ability, are being chosen as nanofillers along with silica micro fillers in epoxy micro-nano composite material for improving the reliability of electrical insulation structures. The epoxy micro-nano composite specimens were subjected to gamma irradiation (4 kGy and 8 kGy) and water aging (under room temperature and at 90 °C), to analyze the effect of aging on space charge accumulation and charge decay characteristics. The mean magnitude of accumulated space charge density of epoxy micro-nano composites tends to increase with an increase in gamma irradiation dose as well as an increment in water diffusion coefficient. The mean lifetime of the space charge decay during depoling has significantly reduced after gamma irradiation and is converse with water aged specimen. Voltage polarity reversal studies have indicated that a part of homo-charge injected from electrodes remained as hetero-charge just after polarity reversal and could result in the distortion of electric field thereby increasing the electric field enhancement factor.

Highlights

Polymeric nanocomposite insulating materials such as epoxy nanocomposites are gaining attention to be used as an insulant in power apparatus like rotating machines, cast resin dry-type transformers, and as spacers in Gas Insulating Switchgear (GIS) [1,2,3]
The epoxy micro-nano composite specimen, which consists of base epoxy resin reinforced with crystalline SiO2 micro fillers (66 wt.%) ion-trapping nano particles as nano fillers (0.7 wt.%)
The net space charge formation is dependent on processes such as charge injection/extraction and charge transportation

Summary

Introduction

Because of the high surface area of the fillers, it is possible to achieve improved properties such as higher volume resistivity, higher breakdown strength, lower space charge accumulation, and lower dielectric loss by reinforcing small quantities of micro or nano particles into the epoxy matrix [4,5,6,7]. The electrical, mechanical, and thermal properties of polymeric nanocomposites depend on the type of polymer matrix and filler, their physical properties such as size, shape, and weight percentage of the fillers [8,9,10,11,12,13]. Proper dispersion of the micro or nano particles in the polymer matrix plays a crucial role in the improvement of desired properties of the composite material [14]. It is essential to determine the optimal weight percentage of filler in a polymer matrix

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