Alumina Trihydrate Filler Research Articles

Effect of Combining Nano- and Microfillers for the Assessment of Thermal Class of Glass Fiber-Reinforced Epoxy Composites for Outdoor Insulation

The present work was taken up with the objective to develop a compact and reliable hybrid composite insulation, investigate the thermal properties of the developed composites and correlate the experimental data with results of mathematical modelling. A composite material made of unidirectional glass fibers reinforced with epoxy resin, and containing silica, alumina, and aluminatrihydrate fillers, was fabricated using the pultrusion technique. Thermogravimetric analysis, thermal conductivity, and coefficient of thermal expansion were conducted on the developed composites. The energy of activation was estimated from the thermograms using mathematical models to assess the thermal class of the composites. Though G-E composite is typically classified under class F insulation, the study has established that due to the unique filler combination, has a higher temperature index ranging between 156 °C - 166 °C. The improvement in thermal performance was observed when each filler is present in a weight percentage of 10%. The hybrid composites have excellent thermal conductivity (0.43 W/mK), a low coefficient of thermal expansion (22.1 μm/m°C), and hence useful for high-temperature insulation applications like circuit breakers, vacuum interrupters, transformers, switching gear etc.

The Viability of the Filler Barrier Effect During the DC Dry-Band Arcing on Silicone Rubber

This article investigates the filler barrier effect on suppressing the erosion of silicone rubber composites during the dc dry-band arcing, by supplementing main microfillers in silicon rubber, i.e., ground silica and micro-sized alumina trihydrate, with fumed silica and nano-sized alumina trihydrate fillers. A study framework employing simultaneous thermogravimetric-differential thermal analyses (TGA-DTAs), the inclined plane tracking and erosion test, and the dry-arc test is employed. Fumed silica in silicone rubber increases the amount of the crosslinked residue and suppresses silicone rubber depolymerization, whereas nano-sized alumina trihydrate releasing water of hydration may adversely impact the residue coherence and promote combustion. The viability of the filler barrier effect is synergistically achieved by adding fumed silica to the main ground silica filler, thereby maintaining the residue integrity. The inclined plane-tracking erosion test confirms the importance of the filler barrier effect of fumed silica in supplementing the volume effect of ground silica in the suppression of the dc dry-band arcing. These filler effects appear to mainly govern the erosion resistance, with insignificant effect shown for thermal conductivity under dc. The dry-arc resistance test is shown as a useful method to simulate a stable dry-band arcing and obtain reproducible surface erosion patterns that correlate with the outcomes of the dc inclined plane tracking and erosion test.

Depth profiling of surface degradation of silicone rubber composite insulators by remote laser-induced breakdown spectroscopy

High-voltage silicone rubber composite insulators are widely used for outdoor insulation in power transmission lines. Silicone rubber, which is used as a housing material, gradually degrades with long-term use in the field. Therefore, to accurately determine the lifetime of composite insulators, it is essential to evaluate this degradation. This paper describes the results of depth profiling, which shows the change in the chemical composition caused by degradation, using laser-induced breakdown spectroscopy (LIBS). A remote LIBS system was constructed for application in in-situ degradation diagnostics. Field-aged insulators were irradiated with second harmonic Nd:YAG laser pulses at a distance of 10. The emission from the plasma was received by a telescope, and a spectroscopic analysis was performed. Energy dispersive X-ray spectroscopy (EDX) was performed for a comparative study. The emission intensity ratio of silicone to aluminum, which forms an alumina trihydrate filler, decreased by approximately 30% at the degraded surface compared to the undegraded bulk. A reduction in silicones at the degraded surface up to a depth of 300 was confirmed by LIBS and EDX measurements. These results show that remote LIBS using the ratio of silicone to aluminum as an index is a promising method for the in-situ diagnostics of composite insulators.

Comparative Properties of HTV Silicone Rubber for Composite Insulators—ATH and Silica Fillers

This paper presents a comparative evaluation of high temperature vulcanizing (HTV) silicone rubber consisting of ATH and silica fillers for use as the housing of outdoor composite insulators. Various volume filler fractions (vol%) of alumina trihydrate (ATH) and silica (SiO2) and several median particle sizes are incorporated into HTV silicone rubber and evaluated for erosion and tracking resistances using the inclined-plane tracking and erosion tests (IPT), in accordance with IEC 60587 at several AC test voltages. Test durations, eroded masses, erosion depths, and leakage currents are reported. The dry-band arcing temperatures of the various samples are recorded during the tests. The results show that at 30 vol% filler fractions, ATH filled samples show lower erosion than the corresponding silica filled samples; however, at 15 vol% fraction, the silica filled samples show lower erosion. For most tested conditions, the maximum dry-band temperatures of the silica filled samples are lower than the corresponding ATH filled samples.

Investigation Break Down Voltages for High Density Polyethylene Cables Using Multiple Regression

This paper illustrated the electrical characteristic of High Density Polyethylene (HDPE) by adding an alumina trihydrate (ATH)filler At concentrations vary from 0% to 40%.
 Multiple Regression Analysis (MRA) was used to find the best suitable curve between the percentages of ATH filler and the Break down Voltages (kV/mm).

Alumina Trihydrate Effect on Flashover Voltage of Polyester Insulators by Whale Optimization Algorithm Technique

Ceramic materials are commonly used as outdoor insulators for high-voltage power transmission lines. Presently, these ceramic insulators are replaced by composite polymeric insulators with polyester, especially in rainy areas. Unlike ceramic materials, polymer materials have a shorter life, so fillers are used to improve their physical and chemical properties. This paper aims to improve the flashover voltage performance of polyester loaded with Alumina Trihydrate filler in wet weather condition. Due to the high cost of raw materials (polyester and Alumina Trihydrate filler), the Whale Optimization Algorithm model was used to predict the best concentration of Alumina Trihydrate filler to give the best value of flashover voltage. The model is based on experimental data of flashover voltage measurements. A positive correlation of the calculations from the Whale Optimization Algorithm model with experimental data has been demonstrated. The results showed that the flashover voltage performance of polyester is increased with the increase of Alumina Trihydrate filler concentration. Also, the optimum concentration of Alumina Trihydrate filler and flashover values predicted by the MATLAB Whale Optimization Algorithm are very accurate.

Correlation of free space length and surface energy of epoxy nanocomposites to surface tracking

Glass-fiber reinforced epoxy nanocomposites are widely used in high voltage outdoor applications. One of the serious problems of outdoor insulation is the surface tracking and erosion that leads to premature failure of insulation. In this paper free-space length, surface energy and surface tracking of epoxy composites with nano alumina, silica and micro alumina trihydrate fillers and unidirectional glass fiber reinforcement are discussed. Quantitative interfacial analysis has been used by determining the freespace length of the composites. The results of tracking are explained on the basis of contact angle measurements and the concept of surface energy is used to substantiate the results. The time-to-track and surface erosion of dry and water treated nanocomposites are determined by the inclined plane tracking and erosion method. The experimental results have revealed that the hydrophobic nature of glass epoxy composites improves with addition of fillers. The surface energy, wettability and interaction parameters show reduction with the addition of fillers. It is observed that the Glass Epoxy composite with combination of nano alumina, silica and micro ATH fillers exhibits good thermal, electrical and mechanical properties with improved tracking and erosion resistance.

Effects of liquids immersion and drying on the surface properties of HTV silicone rubber: Part I-contact angle and surface chemical properties

The effects of liquids immersion and subsequent drying on the surface properties of filled high temperature vulcanized (HTV) silicone rubber have been reported in this series of paper. In this first paper, the surface hydrophobicity characterized by static contact angle and surface chemical properties characterized by a comprehensive analysis of Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD) and thermal desorption gas chromatography mass spectrometry (TD-GC/MS) have been studied. The liquids employed in this study were deionized water, NaCl solution and nitric acid solution, which represented the actual liquids that composite insulators could encounter in practice use. As for the NaCl solution, the lower the concentration, the greater its impact on the hydrophobicity of the silicone rubber (the deionized water can be considered as the NaCl solution of concentration of 0 mol/L). As for the nitric acid solution, the higher the concentration, the greater its impact on the hydrophobicity of silicone rubber. During the permeation process of deionized water and NaCl solution into HTV silicone rubber, some Alumina Tri-hydrate (ATH) filler and low molecular weight (LMW) could be dissolved into the liquids. Nitric acid solution not only dissolved the ATH filler, but also interacted with the ATH filler and degraded the polymer matrix.

Effect of alumina tri-hydrate surface modification on liquid permeation and electrical performance of silicone rubber

This paper investigates the liquid permeation performance of silicone rubber containing alumina tri-hydrate (ATH) that has been modified with N-[3-(trimethoxysilyl) propyl] aniline (Y-9669). From the change in weight during immersion in water, saline solution or nitric acid, and during subsequent drying in air as well as a second immersion test, it is revealed that the majority of the absorbed liquid exists in filler and interface for silicone rubber with original ATH. Surface modification of ATH filler can protect silicone rubber from liquid permeation. It is easier for liquid to permeate into silicone rubber than to escape from it due to the hydrophobicity of the silicone rubber matrix. A cycle of immersion and drying is found to have little impact on subsequent immersion in the case of water and saline solutions; however, damage inflicted on the matrix and filler by nitric acid means that the rate of permeation increases during subsequent immersion. The volume resistivity and surface resistivity of samples with unmodified ATH also decrease more appreciably than those with modified ATH after a cycle of immersion and air drying due to the amount of the residual absorbed liquid.

Dielectric response of filled high temperature vulcanized silicone rubber

The dielectric response of three kinds of filled high temperature vulcanized (HTV) silicone rubber - SiO 2 based nanocomposite with different alumina tri-hydrate (ATH) micro-filler contents are investigated over a wide range of frequency and temperature. The results are analyzed in terms of the many-body Dissado-Hill dielectric response theory. In all three kinds of silicone rubber, a quasi-DC (QDC) process, a Dissado-Hill loss peak process and a diffusion process are observed. Specifically, the ATH filler contributes a QDC electrical transport/hopping process, which at higher temperatures causes the formation of a diffusion layer at the electrodes. The nano-SiO 2 particles combined with rubber matrix give a Dissado-Hill loss peak dielectric relaxation. These two dispersion processes are shown to be associated with the interior interfaces of filled HTV silicone rubber. The effects of ATH filler content and temperature on the dielectric response are also analyzed in depth.

Analysis of service-aged 200 kV and 400 kV silicone rubber insulation in the Gulf region

This paper analyzes silicone rubber housing materials that have been aged in service in 200 kV and 400 kV transmission line systems in the Gulf region. Non-uniform discoloration with traces of white residue are more evident across the upper and lower sides of the 400 kV as compared to the 200 kV sheds located near both the energized and the ground ends of the insulators. Scanning electron microscopy (SEM) showed an increase in the roughness for all the surfaces of the materials analyzed as compared to the bulk. Surface oxidation was indicated by the increase in the Oxygen/Carbon (O/C) ratio determined using energy dispersive X-ray (EDX) and the existence of the silanol groups (Si-OH) as detected in the Raman spectroscopy. The effect of electric field causing surface discharges oxidizing the surface was more evident on the 400 kV as compared to the 200 kV materials, particularly on the lower side of the sheds located near the energized end of the insulators. The effect of photo-oxidation due to ultra violet radiation appears to be increasing as compared to the electric field enhancement on the upper side of the sheds, particularly for those located near the ground end of the insulators. Thermogravimetry analysis is found useful in indicating the relative amount of alumina tri-hydrate filler and the polymer in the silicone rubber housing composition. Both O/C ratio determined using EDX and the silanol groups detected using Raman spectroscopy are proposed as reliable aging indicators to assess the condition of the silicone rubber surfaces that have been aged in service under relatively light polluted conditions. Raman spectrometry has the additional advantage as portable Raman spectrometers can be used to conduct field measurements on site.

Electrical Characteristics of Silicone Rubber as Insulation Materials

This paper presents the results of a study carried out to examine electrical characteristics of high voltage Silicone Rubber (SIR) insulators under weather pollution conditions. The specimens of SIR with and without Alumina tri-hydrate (ATH) filler have been chemically prepared. The AC (50 Hz) surface aging of SIR specimens have been evaluated under salt fog chamber. Furthermore, the relationship between the leakage current and time to failure for SIR specimens with various concentrations of ATH filler under different weather pollution conditions has been measured in this work.

Influence of micro and nanofillers on mechanical properties of pultruded unidirectional glass fiber reinforced epoxy composite systems

This paper reports, fabrication and characterization of unidirectional glass fiber reinforced epoxy composite filled with nano-size alumina, silica and micron-size alumina trihydrate fillers using pultrusion technique. Tensile, flexural and impact strengths were determined to evaluate the effectiveness of fillers on the mechanical properties. Results show that the micro and nanofillers act as secondary reinforcement. The tensile, flexural and impact strengths of 10 wt% (combined alumina, silica and alumina trihydrate)-filled glass fiber reinforced epoxy composite improved by 9, 20 and 28%, respectively, as compared to the unfilled and alumina/silica-filled glass fiber reinforced epoxy composites. The enhanced performance of micro and nanofillers-filled glass fiber reinforced epoxy composites is due to better adhesion and good dispersion of particulates in the epoxy matrix providing increased surface area for strong interfacial interaction and better load transfer. The improved mechanical properties indicate that the unidirectional glass fiber reinforced epoxy with combined micro- and nanofillers-filled composite is a good candidate for structural application.

Mechanical properties of silicone rubber under high loadings of alumina trihydrate filler

It is known that Young’s modulus of elastomers increase strongly due to high filler loadings, which is critical for practical applications and processing. An experimental study was performed in order to investigate the mechanical properties of silicone rubber, which was highly filled with alumina trihydrate (ATH) under uniaxial tensile tests. Different sizes of ATH particles having different surface conditions were used. The composites were prepared in a Z-blade mixer, and the particles were partly in situ modified. In preliminary investigations, the correct amount of silane for the in situ modification was determined and the effect of the mixing time on the mechanical properties of the cured rubber was studied. Long mixing times show generally a decrease in the modulus. This is explained by the increasing formation of bound rubber. A substantial dependence of the particle size and particle surface modification on the Young’s modulus was found. This effect can be simulated using a model based on a stiff particle surrounded by a soft shell, which has a higher modulus than the polymer. Smaller particles show a stronger increase of the modulus than larger ones, which is due to (1) higher volume of interphase area and (2) shorter distance between the particles increasing the modulus of the interphase.

Mechanical properties of fire-retardant glass fiber-reinforced polymer materials with alumina tri-hydrate filler

Alumina tri-hydrate (ATH) can be effectively used to increase fire resistance of Fiber-Reinforced Polymer (FRP) materials. This paper studies the effect of ATH filler on mechanical properties of Glass FRP (GFRP) material, based on compression, tension, shear and flexural test results from three types of GFRP materials with the amount of 0% (control), 25%, and 50% ATH filler by weight of the resin. It was found that the control was the strongest for all tests except for flexure, which is 3% lower than the flexural strength of 25% ATH sample. The compressive strength dropped 19% and 25% for 25% and 50% ATH loadings, respectively, compared to the control. For shear and tensile strengths, the 25% ATH sample acted similarly to the control, but the 50% ATH sample had a significantly lower strength. For stiffness, changing the additive amount from 0% to 50% had only small changes for compression, tension, and flexure. It can be concluded that adding ATH generally decreases the strength and makes FRP more brittle. The performance of a 25% ATH loading is comparable to the control except compression, while a 50% ATH loading has a more significant effect on the mechanical properties of the GFRP. The data presented in this paper can be used to develop fire-resistant FRP systems.

Electrical and flammability properties of alumina trihydrate filled polypropylene/ethylene propylene diene monomer composites as insulators in cable applications

Polymeric insulators role in power systems and insulation is one of the most important subjects in high voltage applications. This study investigates the effect of alumina trihydrate (ATH) loading on electrical and flammability properties of polypropylene (PP)/ethylene propylene diene monomer (EPDM) blend. ATH fillers were incorporated into the matrix to improve the tracking and flammability resistance of the composites. PP/EPDM (60:40) was used as matrix and compounding of ATH filled PP/EPDM composites was done using a twin-screw extruder. Electrical and flammability tests of composites were performed. The results show that flammability decreased with increasing ATH loading in PP/EPDM composites. The effects of electrical stresses are investigated by measuring the carbon tracking (CT) and leakage current (LC) on the surface of composites. The CT and LC of PP/EPDM/ATH composites were found to decrease with increasing ATH content; however calculating the normalized degradation index (NDI) illustrated that all the sample were in accepted range. Field emission scanning electron microscope was used to relate the electrical properties with the morphological analysis, which showed that addition of ATH prevents the degradation of the matrix. POLYM. ENG. SCI., 54:493–498, 2014. © 2013 Society of Plastics Engineers

Suppression effect of ATH filler on the erosion of filled silicone rubber exposed to dry band arc discharge

This paper describes the results of experiments made to examine the suppression effect of alumina trihydrate (ATH) filler on the erosion of filled silicone rubber(SR) exposed to dry band arc discharge. In this study, one simulated electrolyte electrode system was used to generate the dry band arc discharge and the eroded mass of SR filled with 0–50 wt% ATH was measured. Thermogravimetric differential thermal analysis (TG-DTA) was applied to study the thermal characteristics of filled SR and clarify the suppression mechanism of ATH on the heat erosion. In addition, physicochemical analyses on the degraded specimens were carried out by using the techniques of Fourier transformed infra-red (FT-IR) spectroscopy and scanning electron microscopy (SEM) after the heat treatment caused by arc discharge. It is demonstrated that the erosion of filled SR due to dry band arc discharge can be well suppressed through the dehydration of ATH filler and the depression effect of ATH filler on erosion can be improved with increase of filler content.

Studies on Polymeric Composites Containing Alumina Trihydrate and Aswan Clay Fillers

Polymeric composites prepared from unsaturated polyester resin based on poly(1,2 propylene-maleate-o-carboxy phthalanilate) were used with styrene monomer (40% by weight) as a binder and alumina trihydrate (ATH) (Al2O3 · 3H2O) or clay as fillers. The effects of the type and concentration of the two fillers on the physical, chemical, mechanical, thermal, and electrical properties of the formed composites were studied. The fire retardant efficiency of the prepared composites was also investigated. The results indicated that the use of ATH filler reduces both the flammability and smoke density whereas Aswan clay increases the thermal stability. Both fillers enhance electrical characteristics of the formed composites as insulators when compared to the styrenated polyester resin used alone. The obtained polymeric composites would be excellent candidates for potential applications.

The role of inorganic fillers in silicone rubber for outdoor insulation alumina tri-hydrate or silica

A systematic study to understand how alumina tri-hydrate (ATH) and silica fillers improve the erosion resistance of silicone rubber during dry band arcing showed that the thermal conductivity of the resulting composite material is the main criterion governing material erosion. The thermal conductivity of the composite material is dependent on the thermal conductivity, concentration, particle size, and bonding of the filler particles to the silicone matrix. In this context, either filler can be shown to perform better than the other, depending on the formulation, in the ASTM inclined plane tracking and erosion test. Therefore, the industry perception that ATH filler imports better erosion resistance than silica in silicone rubber can be misleading. The release of water of hydration from ATH appears to have a secondary effect that may be more relevant in silicone compositions having a low concentration of a filler.

Tracking and erosion resistance stability of highly filled silicone and alloy materials against electrical and environmental stresses

Tracking and erosion resistances of highly filled silicone rubbers (SIRs) and of polymer alloys made from SIR and ethylene vinyl acetate copolymer (EVA) were evaluated after being aged by the stress of acid rain, UV, corona or water absorption. It was demonstrated whether or not high-level fillers could sufficiently protect tracking and erosion resistances against ageing. Acid rain dissolved alumina trihydrate filler at the surface layers of various polymers tested, thereby reducing the tracking and erosion resistances of those polymers. UV and corona stresses affected the basic polymers rather than the fillers, decreasing the polymers' resistances to tracking and erosion, while highly filled SIR and alloys maintained their tracking and erosion resistances after absorbing large amounts of water.