Corona ageing of the epoxy nanocomposites surface exhibits a high influence on contact angle of the material. A reduction in corona inception voltage due to water droplet, upon corona ageing, is less with epoxy composites, which has Wollastonite as filler followed with nano-micro silica filler added epoxy composites. Charge accumulation studies indicate that charge retention time drastically reduces with corona aged epoxy composite specimen. Epoxy composites with Wollastonite as filler have shown higher mean charge lifetime. Adoption of laser induced breakdown spectroscopy (LIBS) technique for characterisation of samples is unique. Measure of threshold fluence and plasma temperatures through LIBS studies enables to classify the ageing condition of the composite material. Plasma temperature and threshold fluence are clear indicators to classify different materials. Plasma temperature is also an indicator of the hardness of the material. Epoxy composite with Wollastonite as filler is not affected by laser abrasion, which is in accordance with its superior performance with corona ageing, proving as discharge resistant material.

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Epoxy nanocomposites being used in the high-energy radiation zones as an insulant may undergo changes in their dielectric properties during service. In the present study, the performance of base epoxy resin (S1) is compared with epoxy resin with ion trapping particle (Sample S2) and epoxy resin with nanotitania (Sample S3) particle. The influence of gamma irradiation on nanocomposites was analysed. Corona inception voltage due to water droplet initiated discharge and contact angle reduces post-gamma-ray irradiation. Surface potential decay time constant reduced drastically for gamma-ray-irradiated specimens. Trap distribution characterisation indicated that charge mobility increases after irradiation. The surface roughness of the sample increases with the irradiation dosage. Dielectric relaxation spectroscopy shows that permittivity reduces and loss tangent increases with the gamma-irradiated specimens. Water diffusion rate increases for the gammaray-irradiated specimen. No change in elemental composition, measured using laser-induced breakdown spectroscopy, of test specimens was observed. The hardness of the material and plasma temperature formed during laser shine decreases with gamma-ray irradiation intensity for Sample S1, whereas samples S2 and S3 showed only marginal variation. The performance of Sample S2 is found to be better than Samples S1 and S3.

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The performance of low-density polyethylene (LDPE) clay nanocomposites was analysed. The inclusion of nano montmorillonite (MMT) clay in LDPE material has significantly increased the contact angle, corona ageing resistance, water droplet initiated corona inception voltage and surface discharge inception voltage of the composites. The surface charge decay rate of the samples significantly reduced on the inclusion of clay indicating modified trap distribution characteristics due to the inclusion of the filler. Dynamical mechanical analysis indicates increased storage modulus and reduced tan (δ) due to nanofillers inclusion. Laser-induced breakdown spectroscopy indicates that on inclusion of nanofillers the plasma temperature increases and crater depth decreases. In particular, increased discharge resistance, improved thermomechanical properties are observed with LDPE-MMT clay composites compared to pure LDPE.

Corona inception voltage (CIV) due to water droplet sitting over the surface of epoxy nanocomposite material depends on supply voltage frequency, the conductivity of water droplet and the contact angle of the test specimens. The contact angle of the specimen and CIV due to water droplet has a direct correlation. It is realised that the CIV is high under negative DC and the least under AC voltages. Surface charge accumulation studies indicate that the accumulated charge and its decay time constant reduces in the damage-caused zone due to corona activity. The ultra-high frequency (UHF) signal generated due to water droplet-initiated corona activity has frequency content in the range of 0.8-1 GHz. The localisation of incipient discharges is demonstrated by using the non-iterative technique and the cross recurrence plot (CRP) technique is used to estimate the time difference of arrival (TDOA) of UHF signals generated due to water droplet-initiated discharge. Laser-induced breakdown spectroscopy (LIBS) depicts the elemental composition and reveals the difference in plasma temperature and threshold fluence between all the test specimens. In short, the performance of ion trapping particle filled epoxy nanocomposite performance is found to be best followed by titania filled epoxy nanocomposite and the base epoxy resin.