Room Temperature Vulcanizing Silicone Research Articles

Elucidating the Changes in Molecular Structure at the Buried Interface of RTV Silicone Elastomers during Curing.

Silicone elastomers are widely used in many industrial applications, including coatings, adhesives, and sealants. Room-temperature vulcanized (RTV) silicone, a major subcategory of silicone elastomers, undergoes molecular structural transformations during condensation curing, which affect their mechanical, thermal, and chemical properties. The role of reactive hydroxyl (-OH) groups in the curing reaction of RTV silicone is crucial but not well understood, particularly when multiple sources of hydroxyl groups are present in a formulated product. This work aims to elucidate the interfacial molecular structural changes and origins of interfacial reactive hydroxyl groups in RTV silicone during curing, focusing on the methoxy groups at interfaces and their relationship to adhesion. Sum frequency generation (SFG) vibrational spectroscopy is an in situ nondestructive technique used in this study to investigate the interfacial molecular structure of select RTV formulations at the buried interface at different levels of cure. The primary sources of hydroxyl groups required for interfacial reactions in the initial curing stage are found to be those on the substrate surface rather than those from the ingress of ambient moisture. The silylation treatment of silica substrates eliminates interfacial hydroxyl groups, which greatly impact the silicone interfacial behavior and properties (e.g., adhesion). This study establishes the correlation between interfacial molecular structural changes in RTV silicones and their effect on adhesion strength. It also highlights the power of SFG spectroscopy as a unique tool for studying chemical and structural changes at RTV silicone/substrate interface in situ and in real time during curing. This work provides valuable insights into the interfacial chemistry of RTV silicone and its implications for material performance and application development, aiding in the development of improved silicone adhesives.

Chemical and structural degradation of room temperature vulcanizing (RTV) silicone at high temperatures

Room temperature vulcanizing (RTV) silicone is an insulating adhesive used on thermal protection systems of space capsules. RTV materials experience significant heating during entry into an atmosphere. To understand the response of RTV materials in entry environments, RTV 511 and RTV 560 are heated in a mass spectrometer, a thermogravimetric analyzer, and a high-temperature flow tube furnace to understand the underlying chemical and structural degradation processes occurring during the decomposition of the two RTV materials. In addition, infrared spectroscopy is used to identify the functional groups and the polymer backbone configuration. X-ray computed tomography is used to create three-dimensional volumes of the decomposed samples to examine the structure of the degraded RTV materials. The three-dimensional volumes are also used to evaluate the permeability of degraded RTV materials. It is observed that both RTV materials decompose in three stages. Analysis of the three-dimensional volumes generated through X-ray computed tomography indicates that the decomposition begins with the formation of small cavities in both RTV variants. However, as the materials are subjected to higher temperatures, RTV 511 evolves into an outer solid layer with cavities inside, while the solid material in RTV 560 is distributed more homogeneously throughout the material, resulting in a structure with better mechanical integrity. Although most regions of both RTV variants are impermeable, certain regions of RTV 511 have a permeability that is two orders of magnitude higher than the permeability of the base heat shield material. The overall analysis indicates that the response of RTV materials to heat must be considered in the design and analysis of thermal protection systems.

Thermal Aging Characteristics of Silicone Rubber Exposed to Mineral Oil

Room temperature vulcanized (RTV) silicone rubber is extensively utilized as a coating material for power transformer bushings because of its high hydrophobicity and excellent anti-pollution flashover resistance. However, the performance of silicone rubber may suffer significantly when exposed to mineral oil. Till now, literature available on understanding the degradation behavior of silicone rubber exposed to mineral oil at different temperatures is very rare. Therefore, in the present work oil immersion test is performed. RTV silicone rubber was thermally aged in mineral oil at 40°C and 80°C for 200 hours. Post ageing, to examine the changes in the surface properties of the aged specimens 3D microscopy, scanning electron microscopy (SEM) analysis, contact angle, proof tracking index (PTI), and shore hardness measurements were made. The results indicate that the degree of surface degradation was proportional to the temperature. Further, thermogravimetric analysis (TGA), differential thermal analysis (DTA), and infrared thermography were employed to evaluate the thermal properties of aged and unaged specimens. TGA-DTA and infrared thermography indicated a remarkable reduction in thermal stability and heat dissipation capability post mineral oil ageing. The effect became more adverse with increasing ageing temperature. Also, ageing resulted in a decrease in alternating current (AC) breakdown voltage and PTI. Finally, all the experimental outcomes were correlated and the degradation dynamics of mineral oil-aged silicone rubber are explained in detail through possible chemical reactions, fourier transform infrared (FTIR) spectroscopy and energy dispersive X-ray spectroscopy (EDAX) investigations.

Superhydrophobicity transfer effect in superwetting coatings for strengthening anti-pollution flashover performance

Superhydrophobic (SH) and superamphiphobic (SAP) coatings have been viewed as an alternative to conventional hydrophobic room temperature vulcanizing (RTV) silicone rubber coatings in anti-pollution flashover application. However, being one of the most important properties in RTV-based anti-flashover materials and devices, the hydrophobicity transfer property was rarely documented for SH and SAP coatings, which restricts their practical applications in environments with heavy contamination. Herein, we propose for the first time a superhydrophobicity transfer effect in superwetting (SW) coatings (e.g., SAP and SH coatings) containing low-surface-energy molecules (e.g., polydimethylsiloxane (PDMS)) as a migratory reagent. When the surface is stained by artificial simulated pollutants, PDMS molecules can migrate from the coating to the contamination layer, followed by a surface modification. Through this process, the surface wettability of the contaminant layer gradually evolves from superhydrophilicity to hydrophobicity, and finally to SH state. This evolution is investigated in relation to the amount and species of migratory reagents, migration time, pollution grade, and pollutant species. The superhydrophobicity transfer effect offers the coated glass insulators an outstanding anti-pollution flashover strength. This work can provide a novel and universal protocol to realize a superhydrophobicity transfer property in SW coatings, which may stimulate further investigation and applications in not only anti-pollution flashover but also other fields such as anti-fouling and anti-icing.

Rheological formulation of room temperature vulcanizing silicone elastomer ink for extrusion-based 3D printing at room temperature

Silicone elastomer is a versatile material that is widely used in various industries due to its exceptional properties such as resistance to extreme temperatures, thermal conductivity, and bioinert. However, conventional fabrication methods of silicone are limited by molding which has design restrictions and makes it unsuitable for highly customized applications. This study presents a novel room temperature vulcanizing (RTV) silicone formulation that enables three-dimensional printing using an extrusion-based method. The study identifies that rheological measurements such as static yield stress are critical in determining the success of 3D silicone printing. Chemical additives, including nano-silica and plasticizers, have a significant impact on the static yield stress of the silicone ink, enabling the printing of complex structures. By adding 7 wt% of nano-silica and 10 wt% of plasticizers, a static yield stress of 400 Pa was achieved, which allowed the printing of complex 3D structures, including supportless macro-porous scaffolds. The newly formulated silicone ink demonstrated printability and the ability to achieve complex structures, reducing fabrication time, improving scalability, and allowing flexibility in the scaffold's design and specifications. This novel approach opens up new possibilities for the development of highly customized and cost-effective silicone-based 3D printing ink for the fabrication of complex silicone articles and macro-porous scaffolds. The potential applications of this approach include tissue engineering and biomedical devices.

Performance Evaluation of Thermally-Aged RTV Silicone Rubber/TiO2 Nanocomposites in Mineral Oil for Transformer Bushings

The room temperature vulcanized (RTV) silicone rubber is regarded as a coating material for power transformer bushings. However, the performance of silicone rubber may get severely degraded in the event of leakage of mineral oil from the transformer. Nevertheless, little attention has been paid to exploring the viability of silicone rubber nanocomposites in retarding transformer oil-induced damages. Therefore, this article investigates the effect of mineral oil on silicone rubber material doped with Titania (TiO2) nanofillers. Silicone rubber nanocomposites with 1, 3, 5, and 7 wt.% of nano-TiO2 were synthesized and thermally aged in transformer oil at 80oC for 18 hours. Performance evaluation was done based on the experimental outcomes of 3-D microscopy, fourier transform infrared spectroscopy (FTIR), contact angle, corona inception voltage (CIV), thermogravimetric analysis (TGA), infrared thermography, surface potential, and water diffusion tests. Finally, based on the experimental investigations, 5 wt.% nanocomposite was found to be superior in performance against transformer oil-induced degradation.

Flame retardancy, combustion, and ceramization behavior of ceramifiable flame‐retardant room temperature vulcanized silicone rubber foam

AbstractTwo types of ceramifiable flame‐retardant room temperature vulcanized (RTV) silicone rubber foam containing mica power (MP) were prepared by using glass powder (GP) as fluxing agents and aluminum hydroxide (ATH) as flame‐retardant agent, respectively. The flame retardant, combustion behavior, and thermal stability of ceramifiable flame‐retardant RTV silicone rubber foams were investigated. The results show that GP is not conducive to the flame retardancy and thermal stability improvement of the foams. On the contrary, MP and ATH can significantly improve the flame retardancy and thermal stability at high temperatures of the foams. The foams with addition of MP and ATH can reach to a high limiting oxygen index value of 35.8 with V‐0 rating in the vertical combustion test, and the total heat release and total smoke production of the foams are 21.0% and 61.7% lower than of the pure RTV silicone rubber foam, respectively. Furthermore, the structural and morphological changes of the foams under different pyrolysis conditions were studied, so as to reveal its ceramifiable mechanism under different fire scenarios. The results show that GP does not promote the formation of more char residue during pyrolysis, but it can greatly lower the ceramifiable temperature, resulting in a superior ceramic phase char residue. The foams including MP and ATH have a high char residue content; nevertheless, a comparatively higher temperature is necessary to create ceramic phase char residue.

Study on NO2 Barrier Properties of RTV Silicone Rubber by Incorporation of Functional Graphene Oxide.

In this study, functional graphene oxide (f-GO) nanosheets were prepared to enhance the NO2 resistibility of room-temperature-vulcanized (RTV) silicone rubber. A nitrogen dioxide (NO2) accelerated aging experiment was designed to simulate the aging process of nitrogen oxide produced by corona discharge on a silicone rubber composite coating, and then electrochemical impedance spectroscopy (EIS) was used to test the process of conductive medium penetration into silicone rubber. After exposure to the same concentration (115 mg·L-1) of NO2 for 24 h, at an optimal filler content of 0.3 wt.%, the impedance modulus of the composite silicone rubber sample was 1.8 × 107 Ω·cm2, which is an order of magnitude higher than that of pure RTV. In addition, with an increase in filler content, the porosity of the coating decreases. When the content of the nanosheet increases to 0.3 wt.%; the porosity reaches a minimum value 0.97 × 10-4%, which is 1/4 of the porosity of the pure RTV coating, indicating that this composite silicone rubber sample has the best resistance to NO2 aging.

Investigation on comfort and water repellant properties of the Rtv-2 (Bi-component room temperature vulcanizing silicone) silicone coated woven fabric

The main goal of the study is to be obtained water repellant properties of woven fabric coated by Bi-Component Room Temperature Vulcanizing Silicone (RTV-2 silicone) and investigate the physical and thermal properties of these fabrics. In addition, the interaction between calendaring, sanforizing processes, which were known as mechanical finishing treatments, and RTV-2 coating application was investigated in terms of fabric physical performance. According to these experimental results, the possibility of the RTV-2 type silicone as alternative to C6 and C8 based fluorocarbon can be discussed. In this experiment, the woven fabric was coated by RTV-2 silicone with two different coating thickness (0.6 mm and 0.8 mm). The effect of the RTV-2 silicone onto woven fabric were examined and enlightened by physical performance and water repellence tests such as contact angle degree and spray rating tests. The results from contact angle degree and spray rating test pointed out that RTV-2 silicone coated fabric had up to 153.27° contact angle degree and ISO 3 (80) spray rating value whereas untreated fabric had 85.81° contact angle degree and 0 spray rating value. Thermal comfort test (ALAMBETA) showed that, thermal capacity value of the fabric decreased from 0.064 mm2/s to 0.040 mm2/s after RTV-2 silicone coating. On the other hand, thermal absorptivity value of the fabric increased from 117.25 to 234.95 W.%s/m2.K which leaded to increase the cold feeling of the fabric after coating RTV-2 silicone regardless of coating thickness and mechanical finishing processes. Photos from the textile surfaces were taken via Field Emission Scanning Electron Microscope (FE-SEM). It was obviously seen surface morphology after coating and mechanical finishing processes. At the end of the study, it was determined that it is possible to say that RTV-2 silicone usage can positively affect water repellant properties of the fabric while thermal comfort and tactile comfort properties is negatively affected. Fabric performance test such as pilling, abrasion resistance and color fastness to washing did not showed any change after RTV-2 silicone coating and mechanical finishing processes. As for the mechanical finishing processes interaction between RTV-2 silicone, it was seen that the RTV-2 silicone was affected by finishing processes.

Estimation Of Color Change Of Maxillofacial Silicone Elastomer After Artificial Aging

Background: Silicone elastomers are the most widely used maxillofacial materials, however, it is far away from ideal and still progresses through many improvements for replacing the facial defect, maxillofacial prostheses need renewed as early as six months and can last up to 24 months. The color change is the most essential cause for remaking new prostheses.
 Aim: The purpose of this study was to assess the color stability of maxillofacial elastomers throughout aging of about one year.
 Materials and methods: Ten specimens were prepared from Room Temperature Vulcanazation (RTV) VerSilTal (VST-06) maxillofacial silicone and pigmented using rayon the flocking, the specimens were tested using the color-ometer device before and after subjecting to 46,146, and 317h accelerated weathering. The data were collected, analyzed, and compared using SPSS (V-18) via t-test, accomplished in confidence % 95 and significant P-Value of (p ≤ 0.05).
 Results: Statistical t-test showed that the values of color changes differed among the tested groups (P≤ 0.05). The red wave value increased throughout weathering progress while the green and blue waves were decreased.
 Conclusions: This study presented that the color degradation may take place in VST-06 VerSilTal (room temperature vulcanization) silicone elastomers after it was exposed to 46h accelerated weathering and this degradation increased over time.

A Custom Silicone Foot Orthosis for Partial Calcanectomy Fabricated Using a 3D-Printed Mold

ABSTRACT Introduction Patients with partial foot amputations are prone to skin breakdown due to concentrated contact stress and shearing. A custom silicone foot orthosis (FO) can be used to redistribute the concentrated stress and reduce the shearing and discomfort of the skin of a patient with partial calcanectomy. This study presents a custom silicone FO, which is molded using a 3D-printed mold. Methods The subject's left (amputated) partial foot and right (intact) foot were scanned using a 3D scanner. A custom silicone FO was designed by modifying the models of both feet. A mold for the FO was designed using computer-aided design software and fabricated by 3D printing. Room temperature vulcanization silicone was molded to fabricate the FO. The fit of the FO was clinically evaluated by the subject walking with the FO. Results A custom silicone FO was fabricated using a 3D-printed mold. Conclusions The custom silicone FO follows the contour of the residual foot to distribute pressure away from bony prominences during standing and ambulation. 3D printing of the mold can reduce labor time and material cost while facilitating the digital record when compared with a conventional plaster casting approach. Clinical Relevance The 3D printing approach used to fabricate the custom silicone FO may be applied to develop custom silicone orthotic/prosthetic devices for other types of partial foot amputations.

Reactivity of Polysilazanes Allows Catalyst‐Free Curing of Silicones

AbstractSilicones are typically cured at room temperature by means of metal catalyst such as tin or platinum. When networks are formed, the catalyst becomes unrecoverable, which is of economic as well as environmental concern. Very few methods for producing metal catalyst‐free room‐temperature‐vulcanized (RTV) silicones exist and require conditions unavailable in industrial settings. Through the study of organic polysilazane (PSz) reactivity with simple alcohols by nuclear magnetic resonance, an unexpected fragmentation preference is discovered for breaking the SiN bond rather than the SiH; thereby, casting a new light on the fragmentation mechanism of PSzs. Utilizing the PSz fragmentation as a silyl ether coupling agent for multifunctional carbinol silicones, a method of producing catalyst‐free RTV silicone networks at ambient conditions is presented. These silicone networks are proven chemically similar to a standard condensation‐cured silicone and stoichiometric variations of PSz content demonstrate adjustable network properties.

Simple Preparation of Multifunctional Luminescent Textile for Smart Packaging.

Linen has been a significant material for textile packaging. Thus, the application of the simple spray-coating method to coat linen fibers with a flame-retardant, antimicrobial, hydrophobic, and anticounterfeiting luminescent nanocomposite is an innovative technique. In this new approach, the ecologically benign room-temperature vulcanizing (RTV) silicone rubber was employed to immobilize the environmentally friendly Exolit AP 422 (Ex) and lanthanide-doped strontium aluminum oxide (RESAO) nanoscale particles onto the linen fibrous surface. Both morphological properties and elemental compositions of RESAO and treated fabrics were examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM), wavelength-dispersive X-ray fluorescence (WD-XRF), Fourier transform infrared (FTIR) spectroscopy, and energy-dispersive X-ray spectroscopy (EDX). In the fire resistance test, the treated linen fabrics produced a char layer, giving them the property of self-extinguishing. Furthermore, the coated linen samples’ fire-retardant efficacy remained intact after 35 washing cycles. As the concentration of RESAO increased, so did the treated linen superhydrophobicity. Upon excitation at 366 nm, an emission band of 519 nm was generated from a colorless luminescent film deposited onto the linen surface. The coated linen displayed a luminescent activity by changing color from off-white beneath daylight to green beneath UV source, which was proved by CIE Lab parameters and photoluminescence spectral analysis. The photoluminescence effect was identified in the treated linen as reported by emission, excitation, and decay time spectral analysis. The comfort properties of coated linen fabrics were measured to assess their mechanical and comfort features. The treated linen exhibited excellent UV shielding and improved antimicrobial performance. The current simple strategy could be useful for large-scale production of multifunctional smart textiles such as packaging textiles.

Preparation and properties of room-temperature-vulcanized silicone rubber using modified dopamine as a crosslinking agent

This paper investigates the modification of dopamine (IDA) and uses it as a crosslinking agent to enhance the mechanical strength and hydrophobicity of room-temperature-vulcanized (RTV) silicone rubber. IDA was successfully synthesized with dopamine and 3-isocyanatopropyltriethoxysilane. The structure of IDA was verified by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. IDA was introduced into the hydroxyl-terminated polydimethylsiloxane (PDMS) system to prepare RTV silicone rubber, and dibutyltin dilaurate (DBTDL) was used as the catalyst. A combination of the scanning electron microscope, thermal gravimetric analysis, universal testing machine, and contact angle was used to analyze the morphology and properties of RTV silicone rubber. The results demonstrated that the addition of IDA significantly enhanced the thermal stability and mechanical strength of RTV silicone rubber. The mechanical strength of the novel RTV silicone rubber increased by 221%. Moreover, the IDA modified RTV silicone rubber had better hydrophobicity as compared to the PDMS polymer prepared with the traditional crosslinking agent.

Amputation to rehabilitation’ - silicone finger prosthesis: A case report

In patients where surgical reconstruction of amputated finger is not possible, a finger prosthesis provides psychological, functional and esthetic rehabilitation. The success of the prosthesis depends on the meticulous planning, precise impression procedures, designing of prosthesis and selection of appropriate materials. This clinical report presents a case of rehabilitation of a patient with three amputated fingers due to trauma by the chaff machine. The amputation was at different digit levels. The patient was successfully rehabilitated with a custom made silicone finger prosthesis fabricated from room temperature vulcanizing (RTV) silicone utilizing anatomical and mechanical modes of retention.

Comparative evaluation of tensile strength, tear strength, color stability and hardness of conventional and 1% trisnorbornenylisobutyl polyhedralsilsesquioxane modified room temperature vulcanizing maxillofacial silicone after a six month artificial aging period.

Silicone elastomers, chemically known as polydimethylsiloxane used in maxillofacial rehabilitation, over a period of time, undergo degradation and discoloration once aged, thereby reducing clinical longevity. Many previous studies reinforced the maxillofacial silicone material with stronger materials to increase its mechanical properties. However, no studies have been conducted to evaluate all the primary properties using single reinforcing agent. This study was conducted to evaluate and compare the tensile strength, tear strength, color stability, and Shore A hardness of conventional and 1% trisnorbornenylisobutyl polyhedralsilsesquioxanes (POSS) modified room temperature vulcanizing (RTV) maxillofacial silicone after a 6 - month artificial aging period. In vitro comparative study. Eighty-eight silicone samples were fabricated. Therefore for each parameter of tensile strength, tear strength, color stability and hardness, twenty two samples comprising of 11 samples of conventional RTV silicone (Group 1) and 11 for POSS modified RTV silicone (Group 2) were fabricated in stainless steel molds using ASTM D 412-06, ASTM D 624, and ASTM D 2240-15 Standards. Baseline measurements for Shore A hardness and color values were recorded. Samples were then exposed to 6 months of natural weathering process and evaluated for tensile and tear strengths, color stability (ΔE), and hardness. Paired and unpaired t-test. Intragroup and intergroup comparison was done using unpaired and paired t-test. At the end of 6-month aging period, the tensile strength and tear strength of POSS-modified RTV silicone were significantly higher than conventional RTV silicone (P < 0.0001 and P = 0.00014, respectively). Intragroup comparison of conventional group showed highly statistically notable changes in L, a, and b values (P = 0.01631, > 0.0001, and = 0.0.0067, respectively), whereas the POSS-modified RTV silicone showed statistically nonsignificant results in L, a, and b values' (P = 0.91722, 0.15174, and 0.10847, respectively) comparisons after aging. Intergroup ΔE value comparisons showed an extremely statistically difference (P < 0.0001) within the groups. Intergroup comparisons postaging hardness showed a high statistical difference between both the groups, indicating a significant increase in hardness in the conventional group (P < 0.0001). However, intragroup comparison for hardness values showed a statistically highly significant difference for Group 1 (P < 0.0001) and a nonsignificant difference (P = 0.4831) for Group 2. After the simulated 6-month aging procedure, 1% NB 1070 trisnorbornenylisobutyl POSS-incorporated RTV maxillofacial silicone showed better tensile strength, tear strength, Shore A hardness and color stability as compared to conventional RTV silicone. Hence, trisnorbornenylisobutyl POSS is a potent cross-linking agent which enhances the primary mechanical properties of RTV silicone can result in in significant increase in the mean life expectancy of RTV silicone even after 6 months of weathering.

A Hand-Held 190+190 Row–Column Addressed CMUT Probe for Volumetric Imaging

This paper presents the design, fabrication, and characterization of a 190+190 row-column addressed (RCA) capacitive micromachined ultrasonic transducer (CMUT) array integrated in a custom hand-held probe handle. The array has a designed 4.5 MHz center frequency in immersion and a pitch of 95 μm which corresponds to ≈ λ/4. The array has a 2.14 × 2.14 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> footprint including an integrated apodization scheme to reduce ghost echoes when performing ultrasound imaging. The array was fabricated using a combination of fusion and anodic bonding, and a deposit, remove, etch, multistep (DREM) etch to reduce substrate coupling and improve electrode conductivity. The transducer array was wire-bonded to a rigid-flex printed circuit board (PCB), encapsulated in room temperature vulcanizing (RTV) silicone polymer, electromagnetic interference (EMI) shielded, and mounted in a 3D-milled PPSU probe handle. The probe was characterized using the SARUS experimental scanner and 3D volumetric imaging was demonstrated on scatter and wire phantoms. The imaging depth was derived from tissue mimicking phantom measurements (0.5 dB MHz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> attenuation) by estimating the SNR at varying depths. For a synthetic aperture imaging sequence with 96+96 emissions the imaging depth was 3.6 cm. The center frequency measured from the impulse response spectra in transmit and pulse-echo was 6.0 ± 0.9 MHz and 5.3 ± 0.4 MHz, and the corresponding relative bandwidths were 62.8 ± 4.5 % and 86.2 ± 10.4 %. The fabrication process showed clear improvement in relative receive sensitivity and transmit pressure uniformity compared to earlier silicon-on-insulator (SOI) based designs. However, at the same time it presented yield problems resulting in only around 55 % elements with a good response.

Health Monitoring of RTV Silicone Rubber Coating on Insulators Based on Multimode Features of Active Infrared Thermography

Poor quality of room-temperature vulcanized silicone rubber (RTV-SIR) coating on insulators, such as damages, inclusions, debonding, uneven or substandard thickness, and so on, seriously deteriorates the external insulation performance and brings potential threats to the safety of power grids. This article proposed a convenient, quantitative, and nondestructive inspection method for room-temperature vulcanized (RTV) coating using multimode features of active infrared thermography (AIT). First, the thermal wave model of RTV coating was established to explain the theoretical basis for defect detection and thickness measurement of RTV coating based on the surface transient temperature field. Typical defects of RTV coating were detected, and the defect identification was enhanced by the statistical reconstructed thermal images. The frequency-domain features and the reciprocal square root of the minimum phase frequency (RSRMPF), which was proved to have a linear relationship with the coating thickness, were extracted from the phase spectrum of transient thermal response to quantitatively characterize the micrometer thickness of RTV coating. Particularly, the frequency aliasing phenomenon in small thickness measurement when the sampling frequency is not high enough was reported. And the genetic algorithm was adopted to implement the transient thermal response fitting to overcome the distortion of the phase spectrum induced by the frequency aliasing to obtain the accurate fitted linear calibration line. It has been demonstrated that AIT would have promising application prospects in industrial-quality inspection of RTV coating.

An Improvement on Tracking Resistance of Silicone Rubber Filled with Micro-Wollastonite/Gehlenite Synthesized by Solid-State Reaction

Enhancement of the room temperature vulcanization silicone rubber (RTV) tracking resistance with various filler loadings of synthesized wollastonite against electrical surface tracking was prepared. The X-ray diffraction (XRD), Scanning electron microscope (SEM), and X-ray fluorescent (XRF) techniques were involved in characterizing the synthesized substances. The test method IEC-60587 standard was employed to evaluate the surface tracking resistance. The results obtained from the XRF technique confirmed that the raw materials could be synthesized for wollastonite, while the XRD and SEM techniques revealed the formation of wollastonite (CaSiO3) associated with gehlenite (Ca2Al2SiO7). Moreover, it was found that the electrical surface tracking resistance of composite insulation takes a long time to track when the filler loading is increased more than 5 phr.

Flame Retardancy and Excellent Electrical Insulation Performance of RTV Silicone Rubber.

Room temperature vulcanized (RTV) silicone rubber filled with aluminum trihydrate (ATH) is substantially engaged in electrical outdoor insulation applications. The pristine silicone rubber is highly combustible. ATH filled silicone rubber offers excellent electrical insulation but lacks in providing adequate flame retardancy. This short communication reports the novel results on improved flame retardancy of pristine and ATH filled silicone rubber whilst retaining the electrical insulation properties to a great extent. Results suggest that the presence of only one percent of graphene nanoplatelets with ATH sharply reduces the heat release rate and rate of smoke release. A minor reduction in dielectric breakdown strength and volume resistivity is noticed. Furthermore, permittivity and dielectric loss at power frequency suggest that a marginal 1% concentration of nanoplatelet with ATH is an excellent approach to fabricate flame retardant silicone rubber with an acceptable electrical insulation level.