Room Temperature Vulcanized Research Articles

Investigation on leakage current, erosion, and hydrophobic performance ofhigh-voltage insulator coatings of different thicknesses

Room-temperature vulcanizing (RTV) silicone rubber is used as a high-voltage insulator coating to enhance the pollution performance of conventional insulators, and the electrical performance of RTV coating depends on the several parameters. The present study shows the effects of the thickness on the leakage current, erosion, and hydrophobic performance of high-voltage insulator coating. Several different thicknesses of RTV silicone rubber were taken into consideration on porcelain substrates. Erosion and leakage current performances of the samples were evaluated by using inclined-plane tests (IPTs) based on the IEC 60587 standard. Eroded masses and fundamental and harmonic components of the leakage currents were investigated with respect to coating thicknesses. On the other hand, hydrophobic features of the samples were evaluated by using dynamic drop tests (DDTs) with regard to CIGRE TB442 documentation. Time to loss of hydrophobicity and the level of the leakage currents were investigated in DDTs considering the thicknesses.

Studies on composites based on HTV and RTV silicone rubber and carbon nanotubes for sensors and actuators

Nanofillers such as carbon nanotubes (CNT) are well known to significantly improve the properties of composites. In this work, CNTs were used as a reinforcing nanofiller in high-temperature vulcanized (HTV) silicone rubber, and room-temperature vulcanized (RTV) silicone rubber. At a low CNT content of 3 phr in HTV silicone rubber, the compressive and tensile moduli improved by 65% and 96%, respectively, and the resistance fell to 13 kΩ. Similarly, at 3 phr of CNT in RTV silicone rubber, the compressive and tensile moduli improved by 110% and 105%, respectively, and the resistance fell to 0.4 kΩ. The improved properties were used for applications in piezo-electric actuation and piezo-resistive strain sensors. With increase in voltage supply from 2 kV to 12 kV at 2 phr CNT, the piezoelectric actuation displacement increases to 920% (RTV silicone elastomer slab) and 1025% (HTV silicone elastomer slab). In addition, the rubber-based piezoresistive strain sensors showed a higher gauge factor with RTV silicone rubber than HTV silicone rubber. The piezoresistive strain sensors showed >100% stretchability. A series of experiments demonstrate that the use of CNTs improves the reinforcing, electrical properties, actuation, and strain sensors based on RTV and HTV silicone composites.

The dielectric and magnetic properties of RTV-silicon rubber Ni–Cr ferrite composites

In this work, polymeric composites based on room-temperature vulcanized (RTV) silicon rubber incorporated with different NiCr0.2Fe1.8O4 (NCF) content are prepared. The results indicate the well dispersion of various micron-sized particles of NCF with low agglomerations. The decrease in the density is the most advantage property that allows us to obtain the light magnetic material for industrial applications. It is shown that the rubber occupies the porous and defects between NCF particles. It is found that dielectric constant is enhanced with RTV content and decreases with increasing selected frequency for all samples. The electrical conductivity of composite is enhanced with both RTV content and the heat treatment temperature of composites. The saturation magnetization is strongly dependent on NCF content in RTV matrix.

Room-temperature vulcanized silicone rubber/barium titanate–based high-performance nanocomposite for energy harvesting

Rubber composites were prepared for elastomer slab by mixing barium titanate (BaTiO3), carbon nanotube (CNT), carbon black (CB), and room-temperature vulcanized (RTV) silicone rubber. An electrode was prepared from composite for energy harvesting with fillers such as CB and CNT, and RTV thinner was used to improve the processing of the specimen. At 50 phr of BaTiO3, there is an increase in compressive modulus by 180%. There was a correlation between prestrain and biaxial strain in enhancing the energy generation. After poling of the rubber composite containing 50 phr of BaTiO3 at 11 kV/mm, the energy harvesting was increased at all strains. In durability test at 70 phr of BaTiO3 for 60% cyclic biaxial strain, the drop in voltage from the piezoelectric energy harvesting was almost zero for 3000 cycles.

Preparation and properties of room temperature vulcanized silicone rubber using triethoxy(2-(4-methylcyclohex-3-en-1-yl)propyl)silane as a novel cross-linking agent

Limonene is an important subsidiary agricultural product obtained from orange peel that can also be prepared by microbial engineering, but its application degree of deep processing is relatively lower. By studying the application of limonene to silicone rubber, the application field of limonene has been expanded. Triethoxy (2-(4-methylcyclohex-3-en-1-yl)propyl)silane (LTES) was synthesized by a hydrosilylation reaction in the presence of Karstedt's catalyst using limonene and triethoxysilane as raw materials. FT-IR and 1H NMR were used to determine the structure of the product (LTES). Thereafter, a series of room temperature vulcanized (RTV) silicone rubbers was modified with the LTES cross-linking agent and hydroxy silicone oil under the catalytic action of dibutyltin dilaurate. The results showed that the tensile strength, elongation at break and heat resistance of the synthetic silicone rubber modified with LTES were significantly higher.

Optimization of TriboelectricNanogenerator for Small Power Electronics

TriboelectricNanogenerators (TENGs) is a new era energy source to power portable small electronic devices. This paper presents the fabrication of vertical contact separation mode TENGs. Three different TENGs device prototypes are fabricated: (1) Kapton-Aluminium; (2) Teflon-Aluminium and (3) Room Temperature Vulcanizing (RTV)-Aluminium. To optimize the performance of TENGs the effect of various parameters such as thickness of dielectric layer, contact time between two layers and contact separation movement of layers have been observed. Experimental result demonstrates that the output voltage increases initially and then decreases with the increase in thickness of dielectric layer. It is also reported that output voltage of TENGs decreases and increases with the increase in contact time and contact separation movement respectively. In this work, an output voltage obtained from TENGs is suitable to drive applications based on small power electronics.

Analysis of the Attenuation Coefficient of Composite Silicone Rubber and Gliceryn for Soft Tissue Phantom Applications

Introduction: Phantom is an object that can be used to investigate the accuracy of radiation dose delivered to patients. Phantom is usually produced from the combination of the silicone rubber as a matrix and glycerin as a filler to form a composite for the replacement of the human soft tissue. The composite is imaged using computed tomography (CT) simulator for the determination of the attenuation coefficient. Material and Methods: The Phantom in the current study has been synthesized from silicone rubber with and without the addition 10% and 20% of glycerin. The type of silicone rubber in this study was Room Temperature Vulcanized (RTV) 52 with blue catalyst by a ratio of 100:5 (wt%). Samples were scanned using CT simulator to obtain the images and then exported to the Eclipse treatment planning system for analysis. The region of interest (ROI) was at the center of an area of 50×50 pixels to determine the CT number. Results: The ROI results for the sample without and with the addition of glycerin 10% and 20% resulted in the CT values of 287.4, 280.5, and 225.2 HU, respectively, which were within the ROI range of the human soft tissue. The attenuation coefficients of the 3 samples were 0.239, 0.238±0.001, and 0.233±0.001 cm-1 for no glycerin, glycerin 10%, and glycerin 20%, respectively. The values of the half-value layer were 2.902±0.001, 2.911±0.001, and 2.980± 0.001 cm for phantom with no glycerin, glycerin 10%, and glycerin 20%, respectively. Conclusion: Phantoms in the current study were indicative of high potentials as an object of research for radiotherapy and educational purposes. Moreover, the composite with glycerin 20% could be the best surrogate of tissue in order to study human liver.

RUBBER NANOCOMPOSITES REINFORCED WITH SINGLE-WALL AND MULTIWALL CARBON NANOTUBES FOR INDUSTRIAL APPLICATIONS

ABSTRACT Nanofillers of type carbon nanotubes (CNTs) were investigated as reinforcing agents in silicone rubber matrix. Two types of CNT, namely, single-wall CNTs (SWCNTs) and multiwall CNTs (MWCNTs), were tested as reinforcing agents in rubber matrix. These CNTs were characterized with different purity, morphology, and sonication treatment (MWCNTs). Rubber nanocomposites were prepared by mixing room temperature vulcanized (RTV) silicone rubber with CNTs. At a filler loading of 3 phr, the modulus increased by 190% for specimens with MWCNTs and 150% for specimens filled with SWCNTs. Sonication was used to de-bundle the MWCNT aggregates into individual particles and to improve filler dispersion in the rubber matrix. The resistance of the MWCNTs was almost 750 times lower than that of the SWCNTs at 3 phr. The sonicated MWCNTs (2.2 kΩ) show lower electrical resistance than the pristine MWCNTs (3 kΩ) at 2 phr. These improvements could be useful for new devices such as flexible electrodes or actuators.

Influence of Weather on Hardness and Surface Roughness of Maxillofacial Elastomeric Materials

The purpose of this study was to assess the influence of hot and dry weather on the hardness and surface roughness of four different maxillofacial silicone elastomeric materials (MFSEM) including two room-temperature vulcanized (RTV) and two high-temperature vulcanized (HTV) materials. Eighty test specimens were fabricated according to the manufacturer's instructions into rectangular test specimens. The hardness and surface roughness were tested, after 6 months of exposure to natural hot and dry weather. The hardness was measured through the International Rubber Hardness Degree (IRHD) scale using an automated hardness tester. The surface roughness was measured using a novel 3D optical noncontact technique using a combination of a light sectioning microscope and a computer vision system. Statistical Package for Social Sciences software SPSS/version 24 was used for analysis and a comparison between two independent variables was done using an independent t test, while more than two variables were analyzed, F test (ANOVA) to be used followed by a post hoc test to determine the level of significance between every two groups. The hot and dry weather statistically influenced the hardness and surface roughness of MFSEM. Cosmesil M-511 showed the least hardness in test groups while A-2000 showed the hardest material (p < 0.05). A-2000 showed significant changes from rough in case of nonweathered to become smoother in weather followed by A-2186 (p < 0.05). Cosmesil M-511 showed the roughest material. Cosmesil M-511 showed the least hard MFSEM after outdoor weathering while A-2000, the highest and least material showed hardness and surface roughness, respectively. A-2000 had a high IRHD scale hardness. This makes this material more suitable for the replacement of ear and nose defects. Cosmesil M-511 is soft and easily adaptable material that makes the material more appropriate for the replacement of small facial defect with undercut area to be easily inserted and removed. Whilst A-2000 is smoother and finer in test specimens after weathering, Cosmesil M-511 became rougher after weathering.

Interfacial bonding enhancement of the RTV recoating with sandwiched contaminant by plasma jet

Room temperature vulcanised (RTV) silicone rubber is widely used in electrical power system, applied to the glass or porcelain insulator surface to enhance insulation. RTV coatings get contaminated after long-term operation and need to be recoated. Contaminants accumulate and embed into the surface of base RTV coating, forming a hard-to-remove inorganic transition layer. Such sandwiched contaminant layer destroys the adhesion between original and reapplied silicone rubber coating greatly. Authors’ study innovatively reports a method to enhance interfacial bond properties of the RTV recoating with sandwiched contaminant layer, by using an atmospheric-pulsed discharge plasma jet (APPJ) for surface treatment. Water boiling test and 180-degree peel test were conducted to evaluate interfacial bond properties macroscopically. Scanning electron microscopy (SEM) was applied to observe the cross-section of recoating interface, while Fourier-transform infrared spectroscopy (FTIR) to detect chemical changes of contaminant layer, giving out microscopic and theoretical explanation.

Highly stretchable and sensitive conductive rubber composites with tunable piezoresistivity for motion detection and flexible electrodes

Highly stretchable conductive polymer composites and highly sensitive flexible strain sensors have broad application prospects for wearable electronic devices such as human motion monitoring. In this paper, excellent stretchable and high conductive rubber composites based on room temperature vulcanized (RTV) silicone rubber with carbon fiber (CF) and carbon black (CB) are prepared through the solution method and the ultrasonic dispersion technology. The morphology results show that CF and CB in the composites formed a 3D collaborative conductive network of bridge connection. Then, both the sensitive characteristic and strain-sensing mechanism of CF/CB-RTV silicone rubber sensors have been investigated, which exhibits excellent stretchability as high as 700% and has a good linear relationship with 0–375% strain range and the maximum gauge factor of 182. Also, it has been found that the composites with 12.5 wt% CB maintained good electrical conductivity in the case of large deformation. Finally, CF/CB-RTV conductive composites have been used for human motion monitoring with high sensitivity, and as flexible electrodes in LED bulbs, which still have significant brightness under the 300% strain of the composites with 12.5 wt% CB.

Structure-property relationship in silicone rubber nanocomposites reinforced with carbon nanomaterials for sensors and actuators

A small amount of nanofillers can significantly improve the mechanical and electrical properties of nanocomposites, which have a wide range of applications such as sensing and actuation. In this work, rubber nanocomposites were prepared with 0-dimensional (0-D) carbon black (CB), 1-D carbon nanotube (CNT), 3-D graphitic nanofiller (GR), and room temperature vulcanizing (RTV) silicone rubber. The different structures of the CB, CNT, and GR nanofillers were characterized. In addition, the effects of the structures on the mechanical properties and electromechanical applications of the nanocomposites were experimentally demonstrated. At a filler loading of 6 phr, the elastic modulus was improved by 150, 350, and 130 % with the nanofillers of GR, CNT, and CB, respectively. We found that the CNT-based silicone rubber nanocomposite exhibited the highest tensile strength and the reinforcing effect compared to that of others. Based on the improved mechanical, electrical properties of RTV rubber by the nanofillers, the nanocomposites were successfully adopted for strain sensing and actuation applications. The CNT- and CB-based nanocomposites have been used as piezoresistive strain sensors with a gauge factor of 1.3 and 7.8, respectively. The stretchability of strain sensor is up to 80 and 100 % for CNT and CB nanocomposites, respectively, while both of them show high durability. In addition, the nanocomposites are used as an electrode for piezoelectric actuation, and the mechanical displacement was 2.5, 0.34 and 0.5 mm for CNT-, GR-, and CB-based nanocomposite, respectively, under identical actuation voltage of 12 kV. A series of experiments demonstrate the dependency of properties of nanocomposites on the structural characteristic of carbon nanofillers.

Thermochromic transition analysis of elastomer prepared from azo dye-siloxane blend

In the search for portable thermochromic material, this work presented a simple preparation of a thermochromic elastomer using a commercialized dye indicator. The material was prepared using polydimethylsiloxane as a polymer matrix and methyl red as a thermochromic dye via room-temperature vulcanization of spin-coated glass slides. A sample was heated at 10 °C interval and was shown to have a reversible visual thermochromic behavior (orange ↔ yellow). The presence of saturated iodine to the system improved the thermochromic behavior (gray ↔ olive green ↔ yellow) at ≈50 °C and ≈80 °C. Furthermore, this work used graphical and L*a*b* analysis in aiming to correct the imperfection of the naked eye in defining colors.

Gamma-ray shielding characteristics of flexible silicone tungsten composites

Silicone being a hybrid elastomer is well known for its excellent thermal and mechanical properties, chemical resistance, compatibility with organic and inorganic fillers, nontoxicity, and flexibility. As the reported literature on silicone tungsten composite is rare, thus, a complete possible spectrum of silicone tungsten composites series with tungsten loading of 0–88.1 %wt has been fabricated by RTV method and studied as a flexible gamma shielding material. Flexible silicone/tungsten composite formulations containing different weight percentages of tungsten powder (0, 30.1, 47.8, 59.8, 68.1, and 88.1 wt %) were developed by the room-temperature vulcanization route. Two lead collimators with diameters of 0.6 cm were used to make a narrow beam geometry for gamma rays emitted from a137Cs (gamma-ray energy of 662 keV) point source. Uncollided flux was measured with a NaI(Tl) scintillation detector enclosed in lead shielding to reduce the background radiation level. The measured mass attenuation coefficient for our composites with 88.1 wt % tungsten was 0.1035 cm2/g, which is nearly 3.5% higher than that of commercially available silicone/tungsten composites named T-Flex (nearly 0.095 cm2/g) containing the same tungsten loading. Similarly, superior half value layers (HVL) of our composites with 88.1 % wt loading of tungsten i.e 1.01 cm versus 1.27 cm for the reported T-Flex counterpart with additional advantage of insitu fabrication on complex geometries. It was also found that the effectiveness of gamma-ray shielding increases with increase in density of the composites, which is due to the increase in the weight percent of tungsten powder. Our material will have applications as shielding material for both mobile and stationary radiation sources and it can also be used as fabrication material for gloves, safety shoes, coats, etc. to protect workers in a radiation environment.

Physical Characteristics of Soft Tissue Phantom from Silicone Rubber Based Vulcanization System

Phantom from silicone rubber base material has been synthesized without glycerin and with additional glycerin of 10%, 20%, 30% and 40%. The type of Silicone rubber used is Room Temperature Vulcanized (RTV) 52 with a vulcanization system at room temperature. The concentration of catalyst is 5% from silicone rubber. Sample has characterized by using physical testing, Fourier Transform Infra Red (FTIR) and elastic modulus measurements. Physical testing result shows that phantoms have low degradation and can be applicated in a long time. FTIR data shows a phantom structure is poly (dimethylsiloxane) that has Si-CH3 bond at wavenumber 1261 cm-1 and 802 cm-1 and the Si-O-Si siloxane group at wavenumber 1024 cm-1. The elastic modulus values of phantom are 244 kPa for without glycerin, 210 kPa for 10% glycerin and 126 kPa for 20% glycerin. From the data indicated phantoms has range of the liver elastic modulus value at 0.6-4000 kPa. It means that phantom can be used as a substitute for the soft tissue of the human liver.

Fabrication and characterization of silicone rubber/multiwalled carbon nanotubes nanocomposite sensors under impact force

Fabrication of miniature and macro elastic sensors from dispersed multiwalled carbon nanotubes (MWCNTs) in room temperature vulcanization (RTV) silicone rubber (SR) is described. The nanocomposite sensor displays a very low percolation threshold of 3 wt.% (i.e. 2.16 vol%) of MWCNT in SR. The nanocomposite samples are characterized by scanning electron microscope (SEM) to show the formation of three-dimensional conductive networks of the MWCNTs within the SR matrix. Characterization and fabrication procedures of four SR/MWCNT sensors with different electrode configurations are shown. An impact-resistance model is developed to describe the SR/MWCNT sensor response subjected to impact force range (0.030 to 45 N). The analysis of the impact model shows a good agreement with the experimental data. The effect of sensor initial resistance on its sensitivity and force range is also shown.

Effects of RTV Coating on the Discharge Characteristics of A Suspension Glass Insulator

DOI : 10.26650/electrica.2019.19024 The present study shows the effects of room temperature vulcanizing (RTV) silicone rubber high voltage insulator coatings on the discharge characteristics of a cap-and-pin type suspension glass insulator. The study covers both laboratory investigations and 3D electric field analysis, considering the coated and uncoated glass insulators. An ultraviolet corona camera is used to detect the location of the discharges, and a partial discharge test system is used to obtain the discharge patterns and pulse magnitudes. The experimental work is only conducted for 50 Hz power frequency voltage. In addition to the laboratory investigations, 3D electrostatic field analysis is performed to determine how the RTV coatings on the glass insulators affect the field distributions. Cite this article as : Ilhan S. Effects of RTV Coating on the Discharge Characteristics of A Suspension Glass Insulator. Electrica, 2019; 19(2): 173-181.

Synthesis and Characterization of Room Temperature Vulcanized Silicone Rubber Using Methoxyl-Capped MQ Silicone Resin as Self-Reinforced Cross-Linker.

Methoxyl-capped MQ silicone resin (MMQ) was first synthesized by the hydrosilylation of vinyl-containing MQ silicone resin and trimethoxysilane and then used in condensed room-temperature vulcanized (RTV) silicone rubber as a self-reinforced cross-linker. Results show that modified silicone rubber exhibits good light transmission. Compared with unmodified silicone rubber, the hardness, tensile strength and elongation of MMQ at the break are increased by 26.4 A, 2.68 MPa and 65.1%, respectively. In addition, the characteristic temperature of 10% mass loss is delayed from 353.5 °C to 477.1 °C, the temperature at maximum degradation rate is also delayed from 408.9 °C to 528.4 °C and the residual mass left at 800 °C is increased from 1.2% to 27.7%. These improved properties are assigned to the synergistic effect of the rigid structure of MMQ, the formation of a dense cross-linking structure in polymers and the uniform distribution of MMQ cross-linking agent in RTV silicone rubber.

Improved adhesion, heat resistance, anticorrosion properties of epoxy resins/POSS/methyl phenyl silicone coatings

A series of coatings composed of hydroxyl-terminated methyl phenyl silicone rubber (PSi) and silanized epoxy resins (SERs) were prepared in a facile way. Four kinds of SERs with different structures and degree of functionality were synthesized successfully and used to modify the silicone coating. The obtained room temperature vulcanized (RTV) silicone coatings showed excellent adhesion, great heat resistance and anticorrosion properties. Compared with pure PSi, the coatings containing 25 wt% SERs showed better thermal properties, manifested as delayed degradation temperature and greatly increased char yield at 800℃. The adhesion of coatings all reached the highest level (degree 0) which exceeded that of pure PSi coating (degree 2). Furthermore, the anticorrosion property of the coatings in 5 wt% acid, alkaline, and saline environments was all improved. The incorporation of SERs improved the compatibility between the silicone rubber and epoxy resins, in which the epoxy group created more adhesion of cured blended coating and POSS led a significant enhancement in thermal and anticorrosive properties. Their combined effect endowed silicone coatings with more application prospects.

Preparation and Capacitance Properties of Nickel-Cobalt Sulfide/Graphene Composites

In order to explore the supercapacitor electrode material with high energy density, a composite material that nickel-cobalt sulfide loaded in graphene (NiCo2S4@rGO) with core-shell structure was successfully prepared by hydrothermal, room temperature vulcanization and annealing. The core-shell structure of the material greatly increased the contact area between the material and the electrolyte and improved the electrochemical performance. In addition, the energy density has been significantly improved. NiCo2S4@rGO was characterized by field emission scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectrometer. The electrochemical properties of the material were evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The results show that the capacitance can reach 1100 F/g at the current density of 0.5 A/g. Furthermore, the NiCo2S4@rGO as positive electrode and reduced graphene oxide (rGO) as negative electrode were assembled into an asymmetric supercapacitor (ASC). The device exhibits a high energy density of 74.78 Wh/Kg at a power density of 400 W/Kg, as well as excellent cycling stability of 88.9% after 3 000 cycles, which reflects the excellent electrochemical performance of the material.