scholarly journals Investigation of Hydrothermally Stressed Silicone Rubber/Silica Micro and Nanocomposite for the Coating High Voltage Insulation Applications

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3567
Author(s):  
Faiza Faiza ◽  
Abraiz Khattak ◽  
Safi Ullah Butt ◽  
Kashif Imran ◽  
Abasin Ulasyar ◽  
...  
Keyword(s):  
Silicone Rubber ◽  
Structural Changes ◽  
Polymer Chains ◽  
Hydrothermal Conditions ◽  
Silica Filler ◽  
Before And After ◽  
Aging Conditions ◽  
The Stability ◽  
Micro Silica ◽  
Applied Stresses

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.

The Improvement of Modified Filler on the Anti-Aging Properties of Conductive Silicone Rubber

2014 ◽  
Vol 488-489 ◽  
pp. 178-184 ◽  
Author(s):  
Bin Li ◽  
Xue Yong Zhang ◽  
Zhao Yang Fu ◽  
Peng Yu Wang ◽  
Wang Xian Quan
Keyword(s):  
Mechanical Properties ◽  
Silicone Rubber ◽  
Aging Treatment ◽  
Test Method ◽  
Mechanical And Electrical Properties ◽  
Aging Test ◽  
Aging Properties ◽  
Before And After ◽  
The Stability ◽  
Conductive Silicone Rubber

As we know that ceria (CeO2), alumina (Al2O3), aluminum (Al) and iron oxide (Fe2O3) can improve the anti-aging properties of the rubber, mixed these materials with carbon black and filling conductive silicone rubber, some samples have been prepared. Have described the anti-aging method of the silicone rubber and discussed the test method of the changes in properties after aging. Have tested the changes of mechanical properties and electrical conductivity before and after the air aging test of the conductive silicone rubber which with or without addition of modified material. Have discussed the reasons why modified materials can improve the anti-aging performance of the conductive silicon rubber. The results show that with the addition of these types of nanomaterials the stability of mechanical and electrical properties of the conductive silicone rubber can be improved before or after aging treatment.

Electrically Induced Structural Changes in Quaternized Methyl Methacrylate-N-[2-methyl-5-(dimethylamino)phenyl]maleimide Copolymer Membranes

1995 ◽  
Vol 60 (10) ◽  
pp. 1728-1732
Author(s):  
Vlastimil Kůdela ◽  
Jan Lokaj
Keyword(s):  
Methyl Methacrylate ◽  
Electric Current ◽  
Methyl Iodide ◽  
Direct Current ◽  
Structural Changes ◽  
Membrane Resistance ◽  
Internal Symmetry ◽  
Polymer Chains ◽  
Electric Force ◽  
Before And After

Homogeneous membranes were prepared by casting chloroform solutions of methyl methacrylate-N-[2-methyl-5-(dimethylamino)phenyl]maleimide copolymers containing 2.3-8.7 mole % of the imide. After quaternization with methyl iodide, diffusive permeabilities and electric resistances (both with alternating and direct current) of the membranes were determined. During the passage of electric current a substantial decrease (2-10 fold) in the membrane resistance was observed; the lower the imide content was, the greater was the effect. The decrease suggests structural changes in the membranes due to electrohydrodynamic convection of unstable polymer chains caused by electric force. Significant correlations between the imide content and the resistance, both before and after the treatment with electric current, were found. According to oriented concentration potentials, the internal symmetry of the membranes was also affected by electric current.

scholarly journals Multi-Stressed Nano and Micro-Silica/Silicone Rubber Composites with Improved Dielectric and High-Voltage Insulation Properties

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1400
Author(s):  
Faiza Faiza ◽  
Abraiz Khattak ◽  
Aqeel Ur Rehman ◽  
Asghar Ali ◽  
Azhar Mahmood ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
High Voltage ◽  
Silicone Rubber ◽  
Nano Silica ◽  
Before And After ◽  
Good Potential ◽  
High Voltage Insulation ◽  
Micro Silica ◽  
Rubber Product ◽  
Salt Fog

The scope of silicone rubber (SiR) is confined due to the deprivation of its dielectric propertiesupon exposure to various ambient stresses. The aim of this research is to develop silicone rubber-based composites by employing inorganic oxide fillers for improved dielectric and high voltage insulation properties for widening its scope in the field of electrical appliances. This study reports the preparation of different composites of silicone rubber with varying concentrations of micro and nano-silica fillers. The dielectric propertytrends of these as-prepared neat and impregnated samples were examined via an indigenously developed weathering chamber capable of applying multiple stresses of acid rain, heat, humidity, UVA radiation, and salt fog. Dielectric constant values were measured before and after applying stresses. Upon applying stresses, a periodic decline in dielectric constant was observed. Improved dielectric properties were obtained by adding micro and nano-silica as fillers. A nano silica-incorporated silicone rubber product exhibited good potential for dual applications as dielectric and high voltage insulation.

scholarly journals Structural Changes of Sodium Warfarin in Tablets Affecting the Dissolution Profiles and Potential Safety of Generic Substitution

Pharmaceutics ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1364
Author(s):  
Jan Muselík ◽  
Martina Urbanova ◽  
Eva Bartoníčková ◽  
Jakub Palovčík ◽  
David Vetchý ◽  
...  
Keyword(s):  
Structural Changes ◽  
Generic Substitution ◽  
Solid Phase ◽  
Stability Study ◽  
Particle Sizes ◽  
Warfarin Sodium ◽  
Accelerated Stability ◽  
Potential Safety ◽  
Before And After ◽  
The Stability

At present, the risk of generic substitutions in warfarin tablets is still being discussed. The aim of this study was to assess whether API interactions with commonly used excipients may affect the safety of generic replacement of warfarin sodium tablets. These interactions were observed during an accelerated stability study, and the effect of the warfarin solid phase (crystalline/amorphous form) as well as the API particle size distribution was studied. Commercial tablets and prepared tablets containing crystalline warfarin or amorphous warfarin were used. In addition, binary mixtures of warfarin with various excipients were prepared. The structural changes before and after the stability study were monitored by dissolution test in different media, solid-state NMR spectroscopy and Raman microscopy. During the stability study, the conversion of the sodium in warfarin to its acid form was demonstrated by some excipients (e.g., calcium phosphate). This change in the solid phase of warfarin leads to significant changes in dissolution, especially with the different particle sizes of the APIs in the tablet. Thus, the choice of suitable excipients and particle sizes are critical factors influencing the safety of generic warfarin sodium tablets.

scholarly journals Investigation of 9000 hours multi-stress aging effects on High-Temperature Vulcanized Silicone Rubber with silica (nano/micro) filler hybrid composite insulator

PLoS ONE ◽  
2021 ◽  
Vol 16 (7) ◽  
pp. e0253372
Author(s):  
Arooj Rashid ◽  
Jawad Saleem ◽  
Muhammad Amin ◽  
Sahibzada Muhammad Ali ◽  
Aftab Ahmad Khan ◽  
...  
Keyword(s):  
High Temperature ◽  
Silicone Rubber ◽  
Breakdown Strength ◽  
Accelerated Aging ◽  
Environmental Stresses ◽  
Aging Effects ◽  
Nano Silica ◽  
Aging Conditions ◽  
Micro Silica

Degradation in the polymeric insulators is caused due to the environmental stresses. The main aim of this paper is to explore the improved aging characteristics of hybrid samples by adding nano/micro silica in High Temperature Vulcanized Silicone Rubber (HTV-SiR) under long term accelerated aging conditions for 9000 hours. As HTV-SiR is unable to sustain environmental stresses for a long time, thus a long term accelerated aging behavior is an important phenomenon to be considered for field application. The aging characteristics of nano/micro filled HTV-SiR are analyzed by using techniques such as Scanning Electron Microscopy (SEM), Leakage Current (LC), Fourier Transform Infrared Microscopy (FTIR), Hydrophobicity Classification (HC), and breakdown strength for the aging time of 9000 hours. FTIR and leakage currents are measured after every cycle. All the co-filled samples revealed escalated aging characteristics as compared to the neat sample except the SN8 sample (8% nano-silica+20% micro-silica) after 9000 hours of aging. The highest loading of 6% and 8% nano-silica with 20% micro-silica do not contribute to the improved performance when compared with the neat and hybrid samples. However, from the critical experimental analysis, it is deduced that SN2 sample (2% nano-silica+20% micro-silica) is highly resistant to the long term accelerated aging conditions. SN2 has no cracks, lower loss percentages in the important FTIR absorption peaks, higher breakdown strength and superior HC after aging as compared to the unfilled and hybrid samples.

The stability of dislocation networks under various oxygen-doping conditions in superconducting Bi2Sr2CaCu2Oy single crystals and their influence on the flux pinning properties

1994 ◽  
Vol 52 ◽  
pp. 802-803
Author(s):  
Y. Feng ◽  
X. Y. Cai ◽  
R. J. Kelley ◽  
D. C. Larbalestier
Keyword(s):  
Single Crystals ◽  
Oxygen Content ◽  
Basal Plane ◽  
Flux Pinning ◽  
Pinning Centers ◽  
Before And After ◽  
Anomalous Peak ◽  
Basal Plane Dislocation ◽  
The Stability ◽  
Further Development

The issue of strong flux pinning is crucial to the further development of high critical current density Bi-Sr-Ca-Cu-O (BSCCO) superconductors in conductor-like applications, yet the pinning mechanisms are still much debated. Anomalous peaks in the M-H (magnetization vs. magnetic field) loops are commonly observed in Bi2Sr2CaCu2Oy (Bi-2212) single crystals. Oxygen vacancies may be effective flux pinning centers in BSCCO, as has been found in YBCO. However, it has also been proposed that basal-plane dislocation networks also act as effective pinning centers. Yang et al. proposed that the characteristic scale of the basal-plane dislocation networksmay strongly depend on oxygen content and the anomalous peak in the M-H loop at ˜20-30K may be due tothe flux pinning of decoupled two-dimensional pancake vortices by the dislocation networks. In light of this, we have performed an insitu observation on the dislocation networks precisely at the same region before and after annealing in air, vacuumand oxygen, in order to verify whether the dislocation networks change with varying oxygen content Inall cases, we have not found any noticeable changes in dislocation structure, regardless of the drastic changes in Tc and the anomalous magnetization. Therefore, it does not appear that the anomalous peak in the M-H loops is controlled by the basal-plane dislocation networks.

Sorbitol enhances the physicochemical stability of B12 vitamers

2020 ◽  
Vol 90 (5-6) ◽  
pp. 439-447 ◽  
Author(s):  
Andrew Hadinata Lie ◽  
Maria V Chandra-Hioe ◽  
Jayashree Arcot
Keyword(s):  
Ascorbic Acid ◽  
Uv Light ◽  
Heat Exposure ◽  
Water Soluble ◽  
Uv Exposure ◽  
Physicochemical Stability ◽  
Before And After ◽  
The Stability

Abstract. The stability of B12 vitamers is affected by interaction with other water-soluble vitamins, UV light, heat, and pH. This study compared the degradation losses in cyanocobalamin, hydroxocobalamin and methylcobalamin due to the physicochemical exposure before and after the addition of sorbitol. The degradation losses of cyanocobalamin in the presence of increasing concentrations of thiamin and niacin ranged between 6%-13% and added sorbitol significantly prevented the loss of cyanocobalamin (p<0.05). Hydroxocobalamin and methylcobalamin exhibited degradation losses ranging from 24%–26% and 48%–76%, respectively; added sorbitol significantly minimised the loss to 10% and 20%, respectively (p < 0.05). Methylcobalamin was the most susceptible to degradation when co-existing with ascorbic acid, followed by hydroxocobalamin and cyanocobalamin. The presence of ascorbic acid caused the greatest degradation loss in methylcobalamin (70%-76%), which was minimised to 16% with added sorbitol (p < 0.05). Heat exposure (100 °C, 60 minutes) caused a greater loss of cyanocobalamin (38%) than UV exposure (4%). However, degradation losses in hydroxocobalamin and methylcobalamin due to UV and heat exposures were comparable (>30%). At pH 3, methylcobalamin was the most unstable showing 79% degradation loss, which was down to 12% after sorbitol was added (p < 0.05). The losses of cyanocobalamin at pH 3 and pH 9 (~15%) were prevented by adding sorbitol. Addition of sorbitol to hydroxocobalamin at pH 3 and pH 9 reduced the loss by only 6%. The results showed that cyanocobalamin was the most stable, followed by hydroxocobalamin and methylcobalamin. Added sorbitol was sufficient to significantly enhance the stability of cobalamins against degradative agents and conditions.

scholarly journals Redox Mechanism of Azathioprine and Its Interaction with DNA

2021 ◽  
Vol 22 (13) ◽  
pp. 6805
Author(s):  
Mihaela-Cristina Bunea ◽  
Victor-Constantin Diculescu ◽  
Monica Enculescu ◽  
Horia Iovu ◽  
Teodor Adrian Enache
Keyword(s):  
Electron Microscopy ◽  
Mass Spectrometry ◽  
Scanning Electron Microscopy ◽  
Structural Changes ◽  
Differential Pulse ◽  
Immunosuppressive Drug ◽  
Redox Mechanism ◽  
Before And After ◽  
Dna Film ◽  
Scanning Electron

The electrochemical behavior and the interaction of the immunosuppressive drug azathioprine (AZA) with deoxyribonucleic acid (DNA) were investigated using voltammetric techniques, mass spectrometry (MS), and scanning electron microscopy (SEM). The redox mechanism of AZA on glassy carbon (GC) was investigated using cyclic and differential pulse (DP) voltammetry. It was proven that the electroactive center of AZA is the nitro group and its reduction mechanism is a diffusion-controlled process, which occurs in consecutive steps with formation of electroactive products and involves the transfer of electrons and protons. A redox mechanism was proposed and the interaction of AZA with DNA was also investigated. Morphological characterization of the DNA film on the electrode surface before and after interaction with AZA was performed using scanning electron microscopy. An electrochemical DNA biosensor was employed to study the interactions between AZA and DNA with different concentrations, incubation times, and applied potential values. It was shown that the reduction of AZA molecules bound to the DNA layer induces structural changes of the DNA double strands and oxidative damage, which were recognized through the occurrence of the 8-oxo-deoxyguanosine oxidation peak. Mass spectrometry investigation of the DNA film before and after interaction with AZA also demonstrated the formation of AZA adducts with purine bases.

scholarly journals A Vibration-Based Structural Health Monitoring System for Transmission Line Towers

Electronics ◽  
2019 ◽  
Vol 8 (5) ◽  
pp. 515 ◽  
Author(s):  
Long Zhao ◽  
Xinbo Huang ◽  
Ye Zhang ◽  
Yi Tian ◽  
Yu Zhao
Keyword(s):  
Structural Health Monitoring ◽  
Transmission Line ◽  
Natural Frequency ◽  
Health Monitoring ◽  
Structural Changes ◽  
Natural Frequencies ◽  
Transmission Tower ◽  
Health Monitoring System ◽  
Wind Speeds ◽  
Before And After

In this paper, we present a vibration-based transmission tower structural health monitoring system consisting of two parts that identifies structural changes in towers. An accelerometer group realizes vibration response acquisition at different positions and reduces the risk of data loss by data compression technology. A solar cell provides the power supply. An analyser receives the data from the acceleration sensor group and calculates the transmission tower natural frequencies, and the change in the structure is determined based on natural frequencies. Then, the data are sent to the monitoring center. Furthermore, analysis of the vibration signal and the calculation method of natural frequencies are proposed. The response and natural frequencies of vibration at different wind speeds are analysed by time-domain signal, power spectral density (PSD), root mean square (RMS) and short-time Fouier transform (STFT). The natural frequency identification of the overall structure by the stochastic subspace identification (SSI) method reveals that the number of natural frequencies that can be calculated at different wind speeds is different, but the 2nd, 3rd and 4th natural frequencies can be excited. Finally, the system was tested on a 110 kV experimental transmission line. After 18 h of experimentation, the natural frequency of the overall structure of the transmission tower was determined before and after the tower leg was lifted. The results show that before and after the tower leg is lifted, the natural frequencies of each order exhibit obvious changes, and the differences in the average values can be used as the basis for judging the structural changes of the tower.

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