Investigation of Hydrothermally Stressed Silicone Rubber/Silica Micro and Nanocomposite for the Coating High Voltage Insulation Applications
TL;DR: In comparison to neat silicone rubber, the stability of the structure and hydrophobic behavior was better for micro-silica, which was further enhanced in the case of nanocomposites, which showed the best resistance against the applied stresses.
Abstract: Silicone rubber is a promising insulating material that has been performing well for different insulating and dielectric applications. However, in outdoor applications, environmental stresses cause structural and surface degradations that diminish its insulating properties. This effect of degradation can be reduced with the addition of a suitable filler to the polymer chains. For the investigation of structural changes and hydrophobicity four different systems were fabricated, including neat silicone rubber, a micro composite (with 15% micro-silica filler), and nanocomposites (with 2.5% and 5% nanosilica filler) by subjecting them to various hydrothermal conditions. In general, remarkable results were obtained by the addition of fillers. However, nanocomposites showed the best resistance against the applied stresses. In comparison to neat silicone rubber, the stability of the structure and hydrophobic behavior was better for micro-silica, which was further enhanced in the case of nanocomposites. The inclusion of 5% nanosilica showed the best results before and after applying aging conditions.
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TL;DR: In this paper , the effect of fillers against stresses is quantified through characterization results comparison of filled composites with unfilled RTV-SiR samples, and the polarity effect on degradation is evaluated through the relative performance of each composite under the positive and negative polarity of the voltage.
9 citations
TL;DR: In this paper, the effects of high temperature and humidity on room temperature vulcanized (RTV) silicone rubber (SiR) and its composites were analyzed. And the ATH-based microcomposite was recommended over silica due to its superior thermal retardation properties of ATH.
Abstract: Degradation of silicon rubber due to heat and humidity affect its performance in outdoor applications. To analyze the effects of high temperature and humidity on room temperature vulcanized (RTV) silicone rubber (SiR) and its composites, this study was performed. Five different sample compositions including neat silicone rubber (nSiR), microcomposites (15 wt% silica(SMC 15% SiO2) and 15 wt% ATH(SMC 15% ATH), nanocomposite (2.5 wt% silica(SNC 2.5% SiO2) and hybrid composite (10 wt% micro alumina trihydrate with 2 wt% nano silica(SMNC 10% ATH 2% SiO2) were prepared and subjected to 70 ˚C temperature and 80% relative humidity in an environmental chamber for 120 h. Contact angle, optical microscopy and Fourier transform infrared (FTIR) spectroscopy were employed to analyze the recovery properties before and after applying stresses. Different trends of degradation and recovery were observed for different concentrations of composites. Addition of fillers improved the overall performance of composites and SMC 15% ATH composite performed better than other composites. For high temperature and humidity, the ATH-based microcomposite was recommended over silica due to its superior thermal retardation properties of ATH. It has been proved that ATH filler is able to withstand high temperature and humidity.
4 citations
TL;DR: In this paper , the effect of side groups on the movement of the molecular chain is analyzed by calculating the free volume, the mean square displacement (MSD), and the end distances.
Abstract: Influence mechanism of side group types on the macroscopic electrical properties of silicone rubber (SiR) are analyzed based on the experimental comparison and the molecular simulation. The insulation properties of SiR with different side group types (vinyl, phenyl, and trifluoropropyl), as well as binary compound SiR (vinyl/phenyl and vinyl/trifluoropropyl) are compared and studied experimentally. Further, the effect of side groups on the movement of the molecular chain is analyzed by calculating the free volume, the mean square displacement (MSD), and the end distances. Then the mechanism of its influence on the macroscopic properties of SiR was studied. The experimental results indicated that the resistance and breakdown performance of the phenyl SiR surpasses both vinyl SiR and fluorosilicone rubber owing to the conjugated structure of benzene ring, which has a high electron affinity and reduces free charges and carrier migration rate. Besides, when 10wt% phenyl SiR was mixed into vinyl SiR, the resistivity increased by one order of magnitude, and the breakdown field strength increased by about 8%. In the aspect of dielectric properties, the fluorosilicone rubber is more qualified than the vinyl SiR and the phenyl SiR due to the addition of trifluoropropyl as a polar group to the non-polar dielectric SiR to boost its dielectric constant and dielectric loss. The molecular simulation results indicated that the SiR containing phenyl has a tiny free volume and weak molecular chain movement, the fluorosilicone rubber has the strongest molecular chain movement. The work has important guiding significance for improving and modifying SiR in power equipment.
3 citations
01 Jan 2022
TL;DR: In this article , a review of the evolution of silicone rubber composites and the synthesis routes, reaction mechanism, and degradation mechanism are introduced and analyzed; fillers, various types of CSR based composites as well as the flame retardancy and mechanical properties are reviewed.
Abstract: Abstract Ceramifiable silicone rubber composites (CSR) are one of the most important industrially produced elastic technical materials. At present, there is a strong demand for CSR in the high-tech fields of high-speed rail, nuclear power, rocket and aerospace, which are still to be met. Many scholars have committed to the research work of improving the thermal stability, flame retardant, mechanical properties by changing the silicone rubber (SR) matrixes and filler, tremendous advances in CSR have been made for over the last decades where CSR intended for the high technology fields has evolved through different generations. In summary, the first-generation research is based on matrix reaction, the second-generation research is on reaction products, and the third-generation research is on fillers effects. In this review, the evolution of CSR and the synthesis routes, reaction mechanism, and degradation mechanism are introduced and analyzed; fillers, various types of CSR based composites as well as the flame retardancy and mechanical properties are reviewed. Finally, the problems of developing high-performance CSRs are proposed and discussed. This review provides a theoretical basis and supporting data for the application of high-performance CSR, as well as provides details on the fire prevention mechanism of CSR.
3 citations
TL;DR: In this article , the Swedish Transmission Research Institute (STRI) classification and contact angle measurement techniques were used for hydrophobicity analysis of long-term and short-term aged samples, respectively.
Abstract: Epoxy resins have demonstrated remarkable properties with potential for usage as high voltage insulators. However, a loss of these properties has been observed in high temperature and humid environments. In order to enhance the hydrothermal stability of epoxy resins, micro (15% SiO2) and nano (5% SiO2) silica-based composites of epoxy were fabricated and subjected to standard long term and short term accelerated hydrothermal conditions. To analyze the effect of these stresses, the samples were analyzed periodically through Fourier transform infrared spectroscopy (FTIR) for structure analysis; scanning electron microscopy (SEM) for surface analysis of long-term aged samples; and optical microscopy for the surface topography of short-term aged samples. The Swedish Transmission Research Institute (STRI) classification and contact angle measurement techniques were used for hydrophobicity analysis of long-term and short-term aged samples, respectively. After aging in both conditions, the nanocomposite showed better results as compared to the other samples. After 1000 h of aging, it showed HC-5 class of hydrophobicity, whereas EMC and NE degraded to the HC-6. In case of short-term aging, the contact angle decreased to the 64.15° and 75.05° from 104.15° and 114.9° for ENC and EMC, respectively. Also, in terms of structural degradation, ENC showed the highest structural stability after 1000 h of aging with the highest stable peak of aromatic ether at 1300–1500 cm−1. Microscopic observation through scanning electron and optical techniques also revealed superior performance of the nanocomposites.
3 citations
References
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TL;DR: In this article, a review article intended to present information about diverse classes of natural fibers, nanofiller, cellulosic fiber based composite, nanocomposite, and natural fiber/nanofiller-based hybrid composite with specific concern to their applications.
Abstract: The increasing demand for greener and biodegradable materials leading to the satisfaction of society requires a compelling towards the advancement of nano-materials science. The polymeric matrix materials with suitable and proper filler, better filler/matrix interaction together with advanced and new methods or approaches are able to develop polymeric composites which shows great prospective applications in constructions and buildings, automotive, aerospace and packaging industries. The biodegradability of the natural fibers is considered as the most important and interesting aspects of their utilization in polymeric materials. Nanocomposite shows considerable applications in different fields because of larger surface area, and greater aspect ratio, with fascinating properties. Being environmentally friendly, applications of nanocomposites offer new technology and business opportunities for several sectors, such as aerospace, automotive, electronics, and biotechnology industries. Hybrid bio-based composites that exploit the synergy between natural fibers in a nano-reinforced bio-based polymer can lead to improved properties along with maintaining environmental appeal. This review article intended to present information about diverse classes of natural fibers, nanofiller, cellulosic fiber based composite, nanocomposite, and natural fiber/nanofiller-based hybrid composite with specific concern to their applications. It will also provide summary of the emerging new aspects of nanotechnology for development of hybrid composites for the sustainable and greener environment.
520 citations
TL;DR: In this article, a critical review of the latest hot debated themes in the field of physical aging in polymers and polymer nanocomposites is provided, highlighting its relationship with the polymer segmental mobility.
Abstract: Physical aging is a ubiquitous phenomenon in glassy materials and originates from the fact that they are generally out-of-equilibrium. Due to the technological and fundamental implications, this phenomenon has been deeply investigated in the last decades especially in glassy polymers. Here we provide a critical review of the latest hot debated themes in the field of physical aging in polymers and polymer nanocomposites. We first summarize the fundamental aspects of physical aging, highlighting its relationship with the polymer segmental mobility. A review of the methods employed to monitor physical aging is also provided, in particular those probing the time dependent evolution of thermodynamic variables (or related to) and those probing the (quasi)instantaneous polymer segmental mobility. We subsequently focus our attention on the two following debated topics in the field of physical aging of polymers: (i) the fate of the dynamics and thermodynamics of glassy polymers below the glass transition temperature (Tg), i.e. the temperature below which physical aging occurs; (ii) the modification of physical aging induced by the presence of inorganic nanofillers in polymer nanocomposites. With respect to the former point particular attention is devoted to recent findings concerning possible deviations from the behavior normally observed above Tg of both dynamics and thermodynamics deep in the glassy state. Regarding the effect of the presence of nanofillers on the rate of physical aging, the role of the modification of the polymer segmental mobility and that of purely geometric factors are discussed with particular emphasis on the most recent advances in the topic. The modification of the rate of physical aging in other nanostructured systems, such as polymer thin films, is discussed with particular emphasis on the analogy in terms of a large amount of interface with polymer nanocomposites.
204 citations
01 Jan 2011
TL;DR: In this paper, the authors present the state of the art on the most common micro/nanofillers for dielectric applications and special attention is put on the property modification of silicone rubber brought about by filler incorporation for outdoor insulation applications.
Abstract: Among the new insulating materials widely used in high-voltage outdoor insulation, silicone rubber has received the most attention. Indeed, silicone rubbers are gaining in popular- ity as an effective counter-measure to insulator contamination problems. However, pure silicone rubber shows little tracking and erosion resistance. So, some properties of silicone rubber need to be improved to extend service life. The fillers are added to the polymer to promote specific properties and also to reduce costs. To improve the surface hydrophobicity, electrical conductivity, relative permittivity and thermal conductivity of polymeric materials, micro/nanofillers are added. In this review, we present the state of the art on the most common micro/nanofillers for dielectric applications. Special attention is put on the property modification of silicone rubber brought about by filler incorporation for outdoor insulation applications. A need for comprehensive and exhaustive review of micro/nanofiller used in the area of outdoor insulator is being felt. This paper is intended to fulfil it. Literature surveys showed some filler as potential candidate for outdoor insulator application. However, much work is still needed to fully characterise and to optimise their property to establish for commercial application.
129 citations
TL;DR: In this article, the authors discuss the mechanisms by which inorganic fillers in silicone rubber dielectrics enhance the properties of thermal conductivity, relative permittivity, and electrical conductivity making them useful in outdoor high voltage insulation applications.
Abstract: The paper discusses the mechanisms by which inorganic fillers in silicone rubber dielectrics enhance the properties of thermal conductivity, relative permittivity, and electrical conductivity making them useful in outdoor high voltage insulation applications. The addition of alumina trihydrate or silica fillers to silicone elastomers, forming binary composites with enhanced thermal conductivity, is discussed in relation to filler type, particle size, shape, and concentration, and its use as a housing material for non-ceramic insulators to minimize material erosion at dry band arcing sites by lowering hot spot temperature. Also discussed is the enhanced relative permittivity of silicone dielectrics that is obtained through the addition of barium titanate powder which can be further increased with the addition of aluminium powder forming a tertiary composite, resulting in a significant grading of the surface electric field when applied as a housing material to high voltage bushings. Controlled electrical conductivity of silicone dielectrics is discussed through the use of antimony-doped tin oxide filler binary composites and when applied as a housing material to outdoor bushings, the pollution performance is greatly enhanced.
124 citations
"Investigation of Hydrothermally Str..." refers background in this paper
...Polymeric composites replace polymeric insulators because they offer substantial enhancement in electrical, mechanical and thermal properties [16,17]....
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TL;DR: The strength of composites prepared from one of the monomer systems and quartz silanation with methacryloxypropyltrimethoxysilane was higher than those silanated with acryl oxygenpropyl Trimethoxy compounds, which supports the use of the wet and flow point values as screening tests for estimating the dispersability of fillers.
Abstract: The effect of silanation on the dispersion of quartz and zirconia-silica fillers by monomers used to formulate composites was studied. Sixteen silane coupling agents and three methods were used, and the amounts of the monomers needed to reach wet and flow point values were determined. The silanes were selected to have a variety of organofunctional and hydrolysable groups. Silanation was done from an ethanol-water solution of the silanes and by adding the silanes directly to the filler at room temperature (24 degrees C) and at the boiling temperature of the silanes. The amount of silane used was either that required to produce minimum uniform coverage on the fillers or three times the minimum coverage. All silanes and all methods of treatment decreased the flow values for both fillers compared to the unsilanated controls. Generalizations were that the effectiveness of silanation on the dispersion of the filler particles was greater (i) when silanation from ethanol solution was used compared to direct addition; (ii) when three times the minimum uniform coverage was used; (iii) when the silane contained methoxy rather than ethoxy groups; (iv) when the silanes were trialkoxy rather than dialkoxy compounds; (v) when the length and bulkiness of the organic functional group was smaller; and (vi) when the organic functional group was methacrylate rather than acrylic. The strength of composites prepared from one of the monomer systems and quartz silanated with methacryloxypropyltrimethoxysilane was higher than those silanated with acryloxypropyltrimethoxysilane, which supports the use of the wet and flow point values as screening tests for estimating the dispersability of fillers.
113 citations
"Investigation of Hydrothermally Str..." refers methods in this paper
...Fumed silica filler was treated with ethanol to increase its dispersion in the polymer matrix [30]....
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