Room Temperature Vulcanized Silicone Rubber Research Articles

Fabrication of high-durability superhydrophobic coatings based on dual-sized SiC particles

In recent years, inspired by “biomimicry”, superhydrophobic surfaces have gained significant attention. Superhydrophobic surfaces demonstrate notable advantages in addressing interfacial issues, and superhydrophobic coatings exhibit excellent waterproofness, anti-fouling, self-cleaning, anti-corrosion, and additional capabilities, making them promising next-generation waterproof materials. However, the complex preparation process, coupled with poor wear resistance and environmental durability, severely limits their practical applications. Therefore, this article started from simplifying the preparation process and improving the durability of the coatings. Epoxy resin (E51) was used as the film-forming material, and carbon nanotubes (CNTs) and dual-sized SiC particles (nano-SiC and micro-SiC) were used as the fillers. Room temperature vulcanized silicone rubber (RTV) was used as a binder interacting with epoxy resin to promote the interface interaction between the fillers and the polymers. This process resulted in the successful preparation of superhydrophobic coatings with outstanding comprehensive performance. When the ratio of μ-SiC to n-SiC was 1:1, the prepared coating exhibited the best superhydrophobic properties with a water contact angle (WCA) of 167.4° and a sliding angle (SA) of 4.6°. Even after undergoing severe mechanical tests, such as sandpaper abrasion for 1000 cycles, sand impact for 100 cycles, cross-cut test, and tape-peeling for 70 cycles, the coatings still maintained their non-wetting Cassie-Baxter state. Furthermore, even after immersion in strong acid, strong alkali and 3.5 wt% NaCl solutions for 6 days, keeping at 500 ℃ for 2 hours, and exposure to ultraviolet for 6 days, the coatings still exhibited excellent superhydrophobicity. This suggested that the prepared coating had excellent chemical stability and high-temperature resistance. In addition, the superhydrophobic coating exhibited exceptional capabilities in self-cleaning, anti-corrosion, anti-icing, and de-icing properties. Furthermore, this coating, applicable to diverse substrates including board, steel, paper, and glass, demonstrated an impressive water contact angle (WCA) and sliding angle (SA). The spraying method offers the benefits of simplicity and cost-effectiveness. This is poised to significantly broaden its practical applications in various fields, including construction, transportation, and the chemical industry.

The critical anti-icing power study of the stayed-cable cylindrical structure based on positive temperature coefficient (PTC) electrothermal film with low Curie temperature

The low temperature and high humidity regions are prone to freezing rain during winter, causing the formation of icicles on the surface of the stayed-cable cylindrical structure. When dislodged by gravity and wind, these icicles may fall and significantly impede the normal movement of vehicles, posing a danger to pedestrians. In this paper, a new organic positive temperature coefficient (PTC) electrothermal film with a Curie temperature of 1 °C is developed by mixing 107 methyl room temperature vulcanized silicone rubber, acetylene black and n-tetradecane through continuous stirring. Subsequently, a numerical simulation of the anti-icing model for the stayed-cable cylindrical structure is established based on the resistivity-temperature characteristics of the new organic PTC electrothermal film. The analysis include variations in the critical anti-icing power of the stayed-cable cylindrical structure with different diameters, horizontal angles, wind speeds and environmental temperatures are analyzed. Finally, the anti-icing experiments are conducted under natural conditions using the stayed-cable cylindrical structure covered with the PTC electrothermal film. The results of the numerical simulation are compared with the natural experimental results, showing a relative error within 3%. This indicates that the anti-icing model of the stayed-cable cylindrical structure is appropriate. The findings of this work provides a theoretical and experimental basis for the subsequent design of an anti-icing device on the basis of PTC electrothermal film.

RTV silicone rubbers cured by polyhedral oligomeric silsesquioxane and ladder-like polysilsesquioxane: Thermostability, long-term thermal properties, and pyrolysis mechanism

At present, silicone rubber has been widely used in the fields of aerospace and electronic materials, yet its long-term thermal performance still remains a challenge. In this investigation, polyhedral oligomeric silsesquioxane and ladder-like polysilsesquioxanes with multiple silicon-methoxy groups (MSPOSS, MSLPSQ) were synthesized successfully and used as cross-linkers to cure room temperature vulcanized silicone rubber (POSS-SR, LPSQ-SR). The results demonstrate that both MSPOSS and MSLPSQ can effectively improve thermostability, mechanical properties, and long-term thermal properties of RTV silicone rubber. The silicone rubber exhibits a remarkable preservation of strength and flexibility after long-time heat treatment at 400 °C. The silicone rubber demonstrates an impressive retention rate of 84.52% for tensile strength and 69.16% for elongation at break. An analysis of the pyrolysis process of the silicone rubber reveals that the 'back-biting' of polysiloxane chains were inhibited effectively by both MSPOSS and MSLPSQ. As a result of this inhibition, the silicone rubber's terminal chains are delayed from decomposing, resulting in retardation of initial thermal decomposition and significant improvement long-term thermal properties. This work may provide a new prospect for room temperature vulcanized silicone rubber for aerospace applications in extreme environments.

Robust and Durable Superhydrophobic Coatings with Antipollution Flashover Performance via Silane-Modified Polyurea.

The inadequate hydrophobicity and the degradation in usage seriously hampered the applications of the existing antipollution flashover coatings. In this paper, a superhydrophobic polyurea coating with antipollution flashover ability was fabricated through chemically grafting the silica onto the chains of polyurea by utilizing silane coupling agent and hydrophobic modification. It is demonstrated that the coating exhibits outstanding antipollution flashover performances. Noteworthy, the surface pollution flashover voltage has been increased by 33.8% compared with the room temperature vulcanizing silicone rubber (RTV silicone rubber). In addition, the volume resistivity is above 1.0 × 1012 Ω·m, and the dielectric strength achieves to 28.85 kV/mm, which represents excellent insulating property. Furthermore, the superhydrophobic polyurea coating exhibits outstanding abrasion resistance, adhesion, acid-base resistance, and durability. As a result, it holds great promise for use in preventing pollution flashover in electrical insulators.

Fabrication of superhydrophobic (CuO-SiO2) nanocomposite coating for oil/water separation

ABSTRACT The presence of oil-contaminated water due to oil spill disasters or improper industrial waste dumping is now a worldwide danger to both human health and the sustainability of the environment.The use of superhydrophobic materials has attracted considerable attention in the field of oil-water separation, owing to the increasing demand for effective and economical oil-water separation techniques.A new, easy, and inexpensive flame treatment method was used to make a nanocomposite (CuO-SiO2) in order to improve its hierarchical structure (micro-nano).The anodisation process produced copper oxide (CuO) nanostructures (NSs) on a copper mesh. Subsequently, the nanostructures were modified by dip coating with a solution of room-temperature vulcanised silicone rubber (RTV-SR).The coated mesh demonstrated remarkable characteristics of superhydrophobicity and superoleophilicity, with a water contact angle (WCA) of (160 ± 1 ° ) and an oil contact angle (OCA) of (0 ° ), as determined during the measurement of the surface’s wetability. The coated mesh surface was characterised using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy dispersive spectroscopy (EDS).The successful separation of kerosene-water and diesel oil-water mixtures is accomplished by using a coated mesh in a simple filtration procedure. Furthermore, it has the capability to separate oils with a high efficiency of (99.8%) for kerosene and (87%) for diesel oil. It also has flux values of (7352.9 L.m -2 .h -1 ) for kerosene and (6112.9 L/m 2 .h) for diesel.

Optimization of durable superhydrophobic wood with superstrong ultraviolet resistance and chemical stability

The less UV durability and weak chemical stability of superhydrophobic wood limited its wide application. Cu2(OH)3Cl nano particles, epoxy (EP), vinyltriethoxysilane (VTES), and room temperature vulcanized silicone rubber (RTV) were combined together to modify both soft and hard wood with function of superhydrophobic at once successfully. The modified wood was endowed not only superhydrophobicity as expected, such as CA more than 150°, along with anti-fouling and self-cleaning properties, but also excellent durability, including well chemical, sandpaper abrasion, water impact and tape peeling stability. Most prominently, there was almost no color changing being observed on the modified samples. Furthermore, the best UV resistance, 3168 h consistently against UV irradiation, was achieved in the field of wood superhydrophobic modification. The proposed synergistic protective mechanism by synthesizing silicon dioxide and siloxane has potential to extend the service life and improve the high value utilization of wood product.

A Simple Preparation Method to Fabricate Superhydrophobic (TiO2–SiO2) Nanocomposite for Enhancement Contact Angle

As a consequence of the regeneration of nanostructures and the development of a nanocomposite with excellent superhydrophobic properties, a simple flame treatment strategy was examined to increase surface roughness. Cotton soaked in ethanol was used as a flame source at temperatures ([Formula: see text]350[Formula: see text]C) for 30 s. The flame treatment operation takes place after the titanium dioxide (TiO[Formula: see text] nanoparticles (NPs) have been treated with room temperature vulcanized silicone rubber (RTV-SR) liquid using a dip coating approach. X-ray diffraction (XRD), contact angle (CA) measurement, field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR) and energy dispersive spectroscopy (EDS) were used to describe the superhydrophobic surface. Resulting surfaces demonstrated that the water contact angle (WCA) of the superhydrophobic surface was 168 ± 2[Formula: see text], sliding angle SA (4 ± 1[Formula: see text]).

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.

Enhanced piezoelectric energy harvesting using hybrid composites of MWCNTs and partially-reduced GO in RTV-SR for stable voltage generation

Recent studies have explored the use of flexible devices for piezoelectric energy harvesting, which can generate energy at a few volts on a laboratory scale. In this context, multiwall carbon nanotubes (MWCNTs), partially-reduced GO (p-rGO), and their hybrid composites based on room temperature vulcanized silicone rubber (RTV-SR) have emerged as innovative and novel approaches for energy production. The composites were prepared by mixing an RTV-SR solution with MWCNTs and p-rGO powder as fillers, resulting in improved mechanical properties and reinforcement of the RTV-SR matrix. The p-rGO was synthesized from graphite nanoplatelets (GNP) using the modified Hummers' method, followed by chemical and thermal reduction. The MWCNTs were used as received from the supplier. Characterization techniques such as scanning electron microscopy, x-ray diffraction, transmission electron spectroscopy, and atomic force microscopy revealed that the p-rGO consisted of less than five layers stacked in a crystalline domain. Static mechanical property analysis demonstrated that MWCNTs exhibited exceptional filler characteristics compared to other fillers studied. Piezoelectric energy harvesting measurements were performed, and the results indicated higher voltage generation for MWCNTs; however, it exhibited instability and a decline in performance after a few cycles due to electrode cracking. In contrast, the hybrid composite demonstrated stable voltage generation. Moreover, walking and running activities may generate renewable, simple, and sufficient voltage to power light-emitting diodes (LEDs).

Breakdown mechanism of RTV silicone rubber coated insulators under steep-front impulse voltage

Breakdown mechanism of RTV silicone rubber coated insulators under steep-front impulse voltage

Preparation and ablation properties study of a single component ceramifiable RTV silicone rubber

Preparation and ablation properties study of a single component ceramifiable RTV silicone rubber

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.

Characteristics stability assessment of silica/alumina trihydrate based silicone elastomer composites subjected to long-term weathering under bipolar direct current for industrial electrical insulation

Room temperature vulcanized silicone rubber (RTV-SiR) coatings co-filled with silica (SiO2) and alumina trihydrate (ATH) fillers were subjected to long-term accelerated weathering under bipolar direct current (DC). Experimentations were conducted on fabricated samples of RTV-SiR with 5% nano-silica and RTV-SiR with 20% ATH in a specially designed weathering chamber. An extended aging (10,000 h) was conducted on samples energized equally under both polarity voltages to evaluate the effect of positive and negative voltages on the performance of RTV coating under bipolar high voltage DC. The electrical stability of specimens was assessed using online leakage current measurement, hydrophobicity, volume, and surface resistivity analysis. For mechanical characteristics of test samples hardness shore-A, tensile strength, weight loss, and elongation-at-break were measured and analyzed. Variations in chemical, morphological, and thermal degradation of the samples with aging were assessed using characterization tools like Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Thermal Gravimetric Analyzer (TGA), respectively. Findings explicated that samples with nano SiO2, offer better hydrophobic recovery and hence better leakage current suppression while ATH-filled composites exhibited enhanced thermal stability and better resistance to mechanical alterations. Furthermore, the comparative analysis of voltage polarity elucidates that the impact of positive DC was more profound in aging.

Electrical Performance Study of 11kV Coated Porcelain, Coated Glass, and Polymer Outdoor High Voltage Insulators

The study in this paper investigates how contaminations and different types of pollutants affect the electrical performance of outdoor coated porcelain, coated glass, and composite insulators when subjected to an 11 kV AC voltage. The ceramic insulators (porcelain and glass) coating layer is assumed to be RTV silicon rubber material with a 0.5 mm thickness. The effect of these three pollution cases on the electrical performance were investigated using a commercial software called COMSOL Multiphysics based on the finite element method (FEM). The three pollution cases were uniform, non-uniform pollution, and water droplets. In the uniform pollution condition, the pollution layer over the surface of the insulators was assumed to be 0.5 mm; however, in non-uniform pollution condition, water patches with a thickness varying from 0.5 to 1.5 mm was used. In water droplets condition, hemispherical shapes were used to model water droplets with a diameter of 1 mm. Voltage, electrical field distributions, and dissipated power were computed along the creepage distance of the three insulators models. The simulation results indicated that for the uniform case, the lowest electrical field appeared on the silicon rubber insulator. For the non-uniform case, the electrical field distribution became more non-uniform for the three models. In the water droplets case, more fluctuations appeared in the metal end fittings where the water droplets were located. The analysis indicated that the maximum dissipated power was found to be for the coated glass. The obtained results showed that the silicon rubber insulator offered better performance compared with coated porcelain and glass. Coated porcelain offered better performance compared with the coated glass insulator.

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.

Application of Magnesium Hydroxide/Diphenoxy Phosphate in Silicone Rubber Flame Retardant Cable Material

Deketoxime–type room–temperature vulcanized silicone rubber cable materials were prepared using α, ω–dihydroxy polydimethylsiloxane, carbon black, calcium carbonate, magnesium hydroxide, piperazine bis (diphenoxy phosphate) salt (PBDP), and melamine diphenoxy phosphate (MDP). The effects of carbon black and flame retardants on the mechanical properties, flame–retardant properties, and electrical insulation properties of silicone cable coatings were investigated. The research results showed that the products obtained had good mechanical and electrical insulation properties, with tensile strength greater than 3.0 MPa, dielectric strength greater than 22 kV/mm, and volume resistivity higher than 6.5 × 1014 Ω·cm. When 30 parts of Mg(OH)2:MDP = 2:1 are added to 100 parts of resin, the flame–retardant performance of wire and cable materials can be significantly improved. Under the thermal radiation illumination of 50 kW/m2, the ignition time (TTI) of the Mg(OH)2/MDP coating increased by 16 s, and the maximum heat release rate (pkHRR) and total heat release rate (THR) decreased by 29.7% and 68.8%, respectively, compared with silicone rubber without flame retardant. The silicone rubber coatings prepared were flame retardant up to the FV–1 level.

The tough and multi‐functional stretchable device based on silicone rubber composites

AbstractRecently, the advances in stretchable electronic devices have attracted great attention around the world. New technologies are constantly updated to obtain a stretchable device with high performance and robust durability. The stretchable device‐based rubber composites were prepared with the addition of room‐temperature‐vulcanized silicone rubber (RTV‐SR) and different types of nanofillers such as graphite nanoplatelets (GNP), molybdenum disulfide (MoS2), and their hybrid. The hybrid composites contain both nanofillers in 50:50 ratios. The mechanical performance of the stretchable device was studied and presented. For example, the compressive modulus was 1.86 MPa (virgin), and at 20 per hundred parts of rubber (phr) was 3.9 MPa (GNP), 2.3 MPa (MoS2), and 2.72 MPa (Hybrid). The mechanical stretching ability of the composites was 120% (virgin), and at 20 phr was 170% (GNP), 182% (MoS2), and 171% for (Hybrid). At end of the work, a novel stretchable device based on a piezo‐electric effect is presented which provides an output voltage of ~1.2 V and high durability of >0.1 million cycles without significant degradation. This device is based on a rubber composite with the inclusion of electro‐active and dielectric materials as described in the subsequent section of the paper.

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.

Three-dimensional force detection using PVDF and room temperature-vulcanized silicone rubber layers

Three-dimensional force perception plays an extremely important role in human-computer interaction. The main objective of the present study is to propose a three-dimensional force detection sensor using room temperature-vulcanized silicone rubber, polyvinylidene fluoride (PVDF), and a silver coating layer. The sensor was designed in a cylindrical structure to detect the tangential force. The performed analyses reveal that the silver coating layer improves the surface charge output of the PVDF film. The output peak voltage of the sensing unit is 271.7% higher than that of the single PVDF film. The sensor has a response time of 40 ms. It is found that the angle detection error of the sensor along horizontal and vertical directions is less than 2.79° and 0.88°, respectively. In order to evaluate the performance of the proposed sensor, it is fixed on the mechanical hand to perform grasping and sliding tests. The tested results show that the proposed sensor can effectively identify the weight and slip of the object, and can be used in the field of manipulator clamping control.

Comparative Damages in RTV Silicone Rubber Exposed to Mineral and Natural Ester Oil

Comparative Damages in RTV Silicone Rubber Exposed to Mineral and Natural Ester Oil