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This paper investigates the tracking and erosion of silicone rubber and EPDM insulation in the DC inclined plane tracking and erosion test. Silicone rubber filled with alumina tri-hydrate fails due to combustion in the gas phase or erosion paths, but with no evidence of tracking. EPDM fails due to tracking and surface capturing fire, from dry-band arcing leaving a black residue while impinging the surface. Carbonaceous residue on EPDM gives rise to leakage current magnitude, whereas fused silica-based residue on silicone rubber is shown to promote combustion. A high amount of alumina tri-hydrate replacing the polymeric fuel in the composite is shown as a primary factor preventing failure and changing the nature of the residue in the DC inclined plane tracking and erosion test. Depolymerization is the main degradation mechanism reported for silicone rubber and EPDM, with notable degrees of crosslinking reported only for silicone rubber. Crosslinking reduces the amount of silicone rubber undergoing depolymerization, thus, the amount of fuel prone to combustion is reported to promote a coherent residue shield against the eroding dry-band arcing. [ABSTRACT FROM AUTHOR]

This paper describes the suppression of dry-band arcing erosion of silicone rubber by alumina tri-hydrate and silica fillers in the DC inclined plane test, employing the wavelet based multiresolution analysis of leakage current. The third detail component of the leakage current as decomposed by the wavelet-based multiresolution analysis is shown to be an indicator of the effectiveness of the filler type in suppressing erosion by dry-band arcing. The addition of alumina tri-hydrate or silica filler to silicone rubber increases the thermal conductivity of the composites, retarding the development of the eroding temperature, and thus the evolution of the third detail. Additional effect is also obtained for the dehydration enthalpy, of alumina tri-hydrate in silicone rubber at a filler level of 30 wt%, in impeding the development of hot spots on the tested surface. A reduction in the magnitude of the third detail is evident with filler level, indicating that the increasing volume of silica or alumina tri-hydrate reduces the temperature of the dry-band arcing plasma. Comparable levels of the leakage current third detail is found between 30 wt% alumina tri-hydrate and silica filled composites which suggests the water of hydration plays a minor role in diluting the SiR but at 58 wt% an internal oxidation mechanism that produces gases diluting the arcing phase appears to suppress erosion. [ABSTRACT FROM AUTHOR]

This paper describes an investigation into the dry-band arcing mechanism leading to erosion of filled silicone rubber in the DC inclined plane test. Good correlation is obtained between the formation of surface residue, hotspots and the eroding dry-band arcing. The hotspots detected by infrared camera correlates well with the temperature of degradation determined by thermogravimetric analysis and differential scanning calorimetry. To characterize the physical mechanism of dry-band arcing, wavelet-based multiresolution analysis up to seven levels of resolution is applied to the leakage current waveforms. The analysis shows that both stable and intense discharges characterize the eroding dry-band arcing. A time-to-eroding parameter is proposed to determine the relative resistance to the formation of residue. Faster accumulation of residue is evident under -DC than +DC. Earlier inception of erosion is obtained for the silica filled- as compared to the alumina tri-hydrate filled- silicone, in which the release of the water of hydration is postulated to suppress the residue formation. [ABSTRACT FROM AUTHOR]

This paper presents the results of an examination of the erosion resistance of twopart room temperature vulcanizing (RTV) silicone rubber (SiR) nanocomposites. The SiR composites were filled with 7 nm size fumed silica and 1.5 ?m size micro-silica. Separate samples were prepared using conventional mechanical mixing and an electrospinning technique, and their erosion resistances were compared. The electrospinning technique allows for a higher volume fraction of nanofiller and micro-filler in the composites as compared to the conventional samples. The erosion resistances were tested using both an infrared-laser-based source and the ASTM D2303 standard inclined plane tracking and erosion method (IPT). The experimental results for the eroded mass, tracking voltage, and tracking time show that the erosion resistances of electrospun samples are much greater than those of conventional samples. Scanning electron microscope (SEM) images and variable tracking patterns of the conventional samples after the IPT tests suggest an improvement in the dispersion of the fillers within the electrospun samples compared to the conventional samples. Power analysis during the IPT tests also shows that more power is required to track and erode electrospun samples before sample failure occurs than is needed for conventional samples, which suggests improved bonding between the fillers and the silicone rubber matrix. These findings also are supported by the results of thermo-gravimetric analysis. [ABSTRACT FROM AUTHOR]

Presents the results of using the fundamental and the low frequency harmonic components of leakage current to study aging of silicon rubber in salt-fog. Determination of the onset of dry-band arcing on samples; Detection of erosion and tracking using low frequency components; Analysis of leakage current.

In this paper, electrospinning is shown to be an effective method for overcoming the agglomeration of nanosilica in silicone rubber nanocomposites. Silicone rubber nanocomposites with 7 nm silica were produced using conventional mixing and electrospinning processes. Scanning electron microscopy is used to demonstrate homogenous filler dispersion in electrospun samples as compared to conventional mixed samples. Thermo-gravimetric analysis and infrared-laser-based thermal tests show significant improvements in thermal stability and heat transfer in electrospun nanocomposites. However, no significant improvements in either the mechanical properties or relative permittivity between the electrospun and conventional mixed samples were found. The improved thermal properties of the electrospun silicone rubber nanocomposites are attributed to the significantly reduced nanofiller agglomeration and their uniform dispersion. [ABSTRACT FROM PUBLISHER]

The paper presents the results of inclined plane tests on ATH and silica composites of Silicone rubber (SiR) and EPDM to evaluate the effect of filler type and loading on the tracking and erosion resistance of the composites formed. The effect of test voltage on the outcome of the incline plane was also examined. A laser ablation test was also used to evaluate the various composites. A critical test voltage of 4.5 kV was shown to cause failures in samples which emphasizes the importance of testing composites at voltages above this critical level. In comparing the two test methods, both the inclined plane and laser ablation test methods showed the same order for EPDM composites of ATH and silica while the laser method showed silica SiR composites to perform somewhat better than in the inclined plane test which showed similar results. [ABSTRACT FROM PUBLISHER]