Room Temperature Vulcanized Silicone Rubber Research Articles

Studies on high performance rubber composites by incorporating titanium dioxide particles with different surface area and particle size

In this work, we incorporate titanium dioxide (TiO2) particles as fillers into room temperature vulcanized silicone rubber (RTV-SR) and fabricated the RTV-SR/TiO2 composites. Herein, the effect of various surface areas of TiO2 particles on the mechanical properties of RTV-SR/TiO2 composites was investigated. The particle size of different types of TiO2 particles (147 nm, 34 nm, and 29 nm) was measured by using scanning electron microscopy (SEM), whereas the Brunauer–Emmett–Teller (BET) surface area was measured through adsorption-desorption isotherms as 3, 50, and 145 m2/g, respectively. TiO2 particles reinforced RTV-SR composites were prepared by solution mixing method. TiO2 particles with smaller particle sizes and high BET surface area exhibited higher mechanical properties. The compressive moduli were obtained as 2.2 MPa for a virgin sample and increased to 2.6 MPa, 2.8 MPa and 3.24 MPa for 3, 50, and 145 m2/g samples respectively at 6 phr filler loading. Similarly, the fracture strain of the composite was 117% for a virgin sample and changed to 94%, 130%, and 205% for 3, 50, and 145 m2/g samples, respectively, at 8 phr filler loading. The surface area and particle size of the fillers showed significant effect on mechanical properties of the composites, but no significant effect was observed on the energy harvesting values of RTV-SR/TiO2 composites.

Soft Composites Filled with Iron Oxide and Graphite Nanoplatelets under Static and Cyclic Strain for Different Industrial Applications.

Simultaneously exhibiting both a magnetic response and piezoelectric energy harvesting in magneto-rheological elastomers (MREs) is a win–win situation in a soft (hardness below 65) composite-based device. In the present work, composites based on iron oxide (Fe2O3) were prepared and exhibited a magnetic response; other composites based on the electrically conductive reinforcing nanofiller, graphite nanoplatelets (GNP), were also prepared and exhibited energy generation. A piezoelectric energy-harvesting device based on composites exhibited an impressive voltage of ~10 V and demonstrated a high durability of 0.5 million cycles. These nanofillers were added in room temperature vulcanized silicone rubber (RTV-SR) and their magnetic response and piezoelectric energy generation were studied both in single and hybrid form. The hybrid composite consisted of 10 per hundred parts of rubber (phr) of Fe2O3 and 10 phr of GNP. The experimental data show that the compressive modulus of the composites was 1.71 MPa (virgin), 2.73 (GNP), 2.65 MPa (Fe2O3), and 3.54 MPa (hybrid). Similarly, the fracture strain of the composites was 89% (virgin), 109% (GNP), 105% (Fe2O3), 133% (hybrid). Moreover, cyclic multi-hysteresis tests show that the hybrid composites exhibiting higher mechanical properties had the shortcoming of showing higher dissipation losses. In the end, this work demonstrates a rubber composite that provides an energy-harvesting device with an impressive voltage, high durability, and MREs with high magnetic sensitivity.

Stretchable piezo‐electric energy harvesting device with high durability using carbon nanomaterials with different structure and their synergism with molybdenum disulfide

AbstractRecently, polymer composite based stretchable piezo‐electric energy harvesting device have attracted a great attention in composite industry. At laboratory scale, these piezo‐electric devices have ability to generate impressive voltage (~8 V) with high durability (>0.5 million cycles) depending upon nature of the material used in electrode and substrate. In this work, composites were prepared by mixing room temperature vulcanized silicone rubber (RTV‐SR) and nanofillers such as multi‐wall carbon nanotube (MWCNT), nano‐carbon black (nano‐CB), graphite nanoplatelets (GNP), in single or hybrid with molybdenum disulfide (MoS2). These fillers differentiate on basis of their structure ranging from 0‐dimensional (0‐D) to 3‐D. The effects of these structures on mechanical properties are demonstrated. Among them, MWCNT with 1‐D, tube shape morphology, high aspect ratio of 65 shows dominating mechanical properties even at 2 per hundred parts of rubber (phr) loading followed by nano‐CB, GNP at 8 phr and MoS2 at 2 phr. A synergistic effect in mechanical properties between hybrid fillers such as tensile strength and fracture strain was demonstrated. In the end, the composites were tested for piezo‐electric energy generation and durability cycles for the best candidate such as MWCNT was tested for up to 0.5 million cycles was demonstrated.

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.

Effect of graphite nanoplatelets surface area on mechanical properties of room‐temperature vulcanized silicone rubber nanocomposites

AbstractGraphite nanoplatelet (GNP) flakes have attracted attention for the production of polymeric nanocomposites owing to their excellent mechanical, thermal, and electrical properties. In this work, the impact of three grades of GNP flakes with different surface area on the properties of room‐temperature vulcanized silicone rubber (RTV‐SR) nanocomposites was analyzed. The surface area was determined by the Brunauer–Emmett–Teller (BET) method using N2 adsorption isotherms. The BET analysis showed that the GNP grades had BET surface areas of 422, 295, and 123 m2/g. Nanocomposites based on the three grades of GNP flakes with different surface area and RTV‐SR were prepared using the solution‐casting process. Mechanical analysis of the samples showed that the compressive modulus increased from 3.8 MPa (0 phr) to 4.4, 4.34, and 5.26 MPa at the filler loading of 15 phr of GNPs with 422, 295, and 123 m2/g, respectively. In addition, the fracture strain of the nanocomposites increased from 116% (0 phr) to 228%, 198%, and 151% in the samples with 422, 295, and 123 m2/g, respectively, at the filler loading of 15 phr GNP.

Thermal stability, mechanical, and optical properties of novel RTV silicone rubbers using octa(dimethylethoxysiloxy)-POSS as a cross-linker

Abstract Octa(dimethylethoxysiloxy) POSS (ODES) was synthesized successfully and used as the novel curing agent to prepare RTV silicone rubber (SROD) with outstanding mechanical properties and thermal stability. Compared with the silicone rubber cross-linked by tetraethoxysilane (SRTE), the novel RTV silicone rubber using octa(dimethylethoxysiloxy) POSS as a cross-linker had better mechanical, thermal, and optical properties. The highest tensile strength of SROD reached 1.26 MPa, which is three times that of SRTE. Besides, the decomposition temperature of 10% weight loss reached 507.7°C, exceeding that of SRTE by nearly 150°C. In addition, it was remarkable that due to the good compatibility of ODES with the silicone rubber matrix, the series of SROD showed good transmittance, greater than 87%. The thermal decomposition process of SROD was investigated by TGA coupled with real-time FTIR, and the results revealed the rigid structure and large steric hindrance of ODES that efficiently blocked the “backbiting” of the polysiloxy chains and delayed the end-induced ring decomposition, and consequently, improved the thermal stability of SROD significantly.

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.

Performance evaluation of room temperature vulcanized silicone rubber nanocomposites aged in strong aqueous solutions

AbstractIn the present study moisture absorption behavior of titania (TiO2) and silica (SiO2) doped room temperature vulcanized (RTV) silicone rubber (SR) nanocomposites immersed in deionized water, aqueous sodium chloride (NaCl) and nitric acid (HNO3) solution was investigated. It is realized that the diffusion coefficient of the material is high with nanocomposites compared to virgin RTV SR material. To understand the surface condition of the material and characteristic variation in material properties water droplet‐initiated corona inception voltage measurements, atomic force microscopy study, surface potential variation studies, Fourier transform infrared spectroscopy and thermogravimetric analysis was carried out with the virgin and aqueous solution aged specimens. The discharge resistance of the material was analyzed using corona discharge studies. The level of hydrophobicity variations was analyzed through contact angle measurements. The experimental results confirmed that the performance of TiO2 doped RTV SR nanocomposites is superior to the SiO2 doped and virgin RTV SR material.

Enhancement of electrical, mechanical and thermal properties of silicone based coating with aluminatrihydrate/silica for ceramic insulators

The present work explores durability enhancement in various properties of room temperature vulcanized silicone rubber (RTV-SiR) coating with the incorporation of alumina trihydrate (ATH) and silica (SiO2) fillers. Test samples i.e., neat RTV-SiR, RTV-SiR +10% μSiO2, and RTV-SiR filled with micro-ATH/SiO2 (10% each) were chosen for experimentation. Long-term (10,000 h) lab aging of composite coatings is performed under bipolar direct current (DC) voltage with simulated environmental stresses in a test chamber. The effect of fillers against stresses is quantified through characterization results comparison of filled composites with unfilled RTV-SiR samples. Moreover, the polarity effect on degradation is evaluated through the relative performance of each composite under the positive and negative polarity of the voltage. Findings revealed that samples filled with a mixture of additives bring enhanced improvement into the base matrix of RTV-SiR. Amongst unfilled and micro-silica filled specimens aged under positive DC, the samples S-3 with combined silica-ATH fillers offered superior hydrophobic behavior showing hydrophobicity class HC3 and demonstrated a minimum final leakage current of 6.13 μA. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) results showed relatively lower variations in the chemical and morphological structure of cross-filed specimens (S-3). Furthermore, results of mechanical properties (tensile strength, elasticity, and weight) show a significant loss, whereas the hardness of composite increased with aging. Hybrid samples (S-3) exhibited the minimum deviation of 29.77% and 43.12% in tensile strength and elongation-at-break (EAB), respectively under positive DC voltage. Similarly, it shows enhanced resistance against weight loss and change in hardness due to aging. Moreover, thermogravimetric analysis (TGA) confirmed that filled composite gets enabled to offers the least alteration in thermal properties. In the context of the polarity, positive DC voltage incurred more devaluation of desirable properties as compared to negative polarity.

Impact of Dispersion Processes and Surfactant on Performance of Silica-Silicone Nanocomposites

In this study, various silicone nanocomposites are studied to investigate the effects of filler treatments, such as calcination, use of surfactant, and mixing methods on filler dispersion and distribution. A two-part room temperature vulcanized silicone rubber is used as a base polymer and reinforcing nanofumed silica as a filler. A fixed filler concentration of 10 wt% has been selected for the comparative studies. The electrostatic disperser (ED) that is effective in mixing nanofillers is used to prepare the composites, with or without polyalkyleneoxide modified heptamethyltrisiloxane, the surfactant. Comparisons are also made with some samples prepared using the conventional high shear (HS) mixer. Fillers were used as obtained and/or after calcination at 500 °C. The performances of prepared nanocomposites are evaluated by comparing their thermal, mechanical, morphological, and dielectric properties. The thermogravimetric analysis (TGA) and mechanical properties, tensile strength and elongation at break, show that nanocomposites prepared using ED with calcined filler in the absence of surfactant have the highest thermal stability and tensile strength. Dielectric analyses, both at room temperature and elevated temperatures of 50 °C, 75 °C, and 100 °C, further show that those composites with calcined fillers in the absence of surfactant have lower relative permittivity and loss factor than those with surfactant. The observed differences in thermal, mechanical, and dielectric properties are related to the way fillers bond with the polymer matrix and additional interfaces created by the surfactant. The morphological analysis supports the empirical correlations derived.

Efficacy of graphitic allotrope’s surface area in silicone rubber based composites for reverse piezo-electric actuation: Nano effect

Filler surface areas importantly determine the properties of rubber composites. In this study, the reverse piezo-electric actuation efficacies of three graphitic allotropes were studied in room temperature vulcanized silicone rubber (RTV-SR) based composites. The three fillers examined were graphite, nanographite, and graphene. Specific surface areas were determined using the Brunauer–Emmett–Teller (BET) method in a nitrogen atmosphere. BET testing showed graphite, nanographite, and graphene had surface areas of 30, 110, and 650 m2/g respectively. Mechanical properties showed that fillers with greater BET surface areas had higher compressive moduli, tensile strengths, fracture strains, and tensile moduli. Similarly, actuation measurements obtained at 10 kV showed that composites containing graphene produced significantly greater actuation displacements than those containing nanographite or graphite. The figure of merit showed filler BET surface areas played a key role in determining the mechanical and actuation properties of composites. For example, as the surface area increases, the properties and actuation displacement increases exponentially. To sum-up, graphene filled silicone rubber composites exhibited better mechanical properties and much better actuation displacements than graphite or nanographite filled composites.

Synthesis of a novel antiweathering nanocomposite superhydrophobic room temperature vulcanized (RTV) silicon rubber enhanced with nanosilica for coating high voltage insulators.

A new nanocomposite superhydrophobic of the RTV (room temperature vulcanized) silicon rubber reinforced with a different percentage of nanosilica was prepared by a two-stage sol-gel route to obtain a superhydrophobic surface coating on high voltage glass insulator, preventing the dust-water droplet from adhering to its surface. The cold spraying technique was utilized to build up a thin nanocomposite superhydrophobic layer on the glass insulator containing different percentages of the nanosilica particles, such as 23 wt %, 33 wt %, and 44 wt % with RTV silicon substrate. The synthesized nanocomposite was analyzed using the contact angle, roughness, adhesion, hardness, and dielectric strength tests. Moreover, the prepared RTV silicon rubber/nanosilica superhydrophobic nanocomposite layer was characterized using the field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and the particle size analysis test. Based on the results, the nanosilica particles were well-incorporated into the RTV silicon rubber, obtaining an excellent homogenous distribution thin layer on its surface, supporting its capability to be a superior superhydrophobic surface. The results reveal that the RTV silicon rubber/33wt % nanosilica was the best as a superhydrophobic behavior with a contact angle reaching higher than 158° ± 3; also, a significant change in the dielectric strength was obtained to be 25.5 kV (using a speed voltage of 5.0 kV/s). Importantly, the flashover test was also conducted, and it was found that there was a significant change in the leak current between the coated and uncoated samples. The leak current of the coated sample with a superhydrophobic nanocomposite was reduced to 2.5 mA, while the uncoated sample became 3.2 mA using a voltage load value of 60 kV. The results presented here may improve the nanocomposite material as an antiweathering superhydrophobic thin layer supported by the prepared nano-SiO2 particles against the dust-water droplets which may be adhesive to the high voltage glass insulator.

Flexible Strain Sensor Based on 3D Electrospun Carbonized Sponge

Flexible strain sensor has attracted much attention because of its potential application in human motion detection. In this work, the prepared strain sensor was obtained by encapsulating electrospun carbonized sponge (CS) with room temperature vulcanized silicone rubber (RTVS). In this paper, the formation mechanism of conductive sponge was studied. Based on the combination of carbonized sponge and RTVS, the strain sensing mechanism and piezoresistive properties are discussed. After research and testing, the CS/RTVS flexible strain sensor has excellent fast response speed and stability, and the maximum strain coefficient of the sensor is 136.27. In this study, the self-developed CS/RTVS sensor was used to monitor the movements of the wrist joint, arm elbow joint and fingers in real time. Research experiments show that CS/RTVS flexible strain sensor has good application prospects in the field of human motion monitoring.

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.

Anti-aging characteristics of RTV-SiR aided HV insulator coatings: Impact of DC polarity and fillers

Room temperature vulcanized silicone rubber (RTV-SiR) coating is applied globally on conventional ceramic insulators to combat pollution flashovers. The present research was intended to see how the polarity of direct current (DC) voltage and filler incorporation affect the aging performance of RTV-SiR based composites coating when seen in the overall context of multiple environmental stresses. Accordingly, RTV-SiR based specimens were fabricated through loading of micro, nano, and micro-cum-nano fillers in the base matrix and subjected to the multi-stress environment in a specially designed weathering cell. Keeping the rest of the parameters common (fixed), aging was carried out under both polarities of DC voltage for 10,000 lab hours. Results revealed that the coating sample with hybrid micro/nanofillers retained the highest hydrophobicity class under both polarities. Fourier transforms infrared (FTIR) spectroscopic analysis asserted that hybrid samples showed the maximum intactness in essential chemical bonds with minor oxygen-hydrogen (OH) hydroxyl content i.e. 56.01% for positive and 26.9% for negative DC. It also measured the lowest leakage current 5.3 μA and 4.61 μA for positive and negative voltage, respectively. Weight-loss and hardness measurements depict improved performance of filled samples. Moreover, the water absorption properties of all investigated samples were assessed through water permeation tests. The study elucidated that hybrid composite performed distinctly superior showing the highest resistance against collegial stresses. As other aging parameters were common, we could single out the effect of polarity showing positive polarity to be relatively more determinantal to aging.

Investigation of high temperature vulcanized and room temperature vulcanized silicone rubber based on flexible piezo‐electric energy harvesting applications with multi‐walled carbon nanotube reinforced composites

AbstractFlexible energy harvester can be able to produce continuous voltage output under the mechanical deformations. High temperature vulcanized (HTV) and room temperature vulcanized (RTV) silicone rubbers are used for making the flexible piezo‐electric energy harvester. A total of 1 and 2 phr of multi‐walled carbon nanotube (MWCNT) are used as the electrode material mixed with the rubber solution for the preparation of flexible electrode. Cyclic loading machine is used for the application of 2 Hz of bi‐axial load and uniaxial compression load in the specimen. One centimeter depth of displacement is applied during the bi‐axial cyclic loading and 4 mm amplitude of displacement is applied during the compression loading. Tensile and compression tests are performed to determine the engineering properties of the material. Tensile load withstanding value of the silicone rubber is increasing as increasing the MWCNT filler in the rubber. Tensile value of the pure HTV silicone rubber is 10.020 N and for 2 phr MWCNT reinforced rubber is 22.106 N. Compressive withstanding load of pure HTV rubber is 189.565 N and for 2 phr MWCNT reinforced rubber is 287.066 N. HTV silicone rubber is the highly stiffness material on compares with RTV rubber based on the tensile and the compressive value. Transmission electron microscopy, optical micrographs, and scanning electron microscope show the morphology of MWCNT and surface image of specimen. A total of 2 mm substrate based 2 phr MWCNT reinforced HTV flexible energy harvester undergo decrease in voltage during the cyclic loading due to breakage of electrode. A total of 2 phr MWCNT electrode‐based sample can be able to produce more output voltage than 1 phr MWCNT electrode‐based sample during bi‐axial and compression loading. More voltage is produced in the compression specimen than bi‐axial one.

Evaluation of the Supportability and Electrical Performance of RTV Coatings Filled with Carnauba Wax under Pollution Conditions

This paper is an experimental study to evaluates the performance of Room Temperature Vulcanizing Silicone Rubber (RTV-SIR) coatings filled with carnauba wax and Alumina Trihydrate (ATH). The coatings were applied to glass insulators and subjected to pollution tests. The insulators performance was evaluated through the application of disruptive discharges and applied voltage under fog while monitoring the leakage current. The experimental results showed a reduction in leakage current and improved insulator performance for RTV-SIR coatings filled with carnauba wax under pollution conditions. The best results were achieved for coatings added with ATH and carnauba wax, indicated by the sample with the percentage composition of 75% RTV, 20% ATH and 5% carnauba wax.

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.

Analysis of Physical-Chemical Properties and Space Environment Adaptability of Two-Component RTV Silicone Rubber.

Silicone rubber (SR) has the properties of organic–inorganic materials and good adaptability to the space environment, which can be used as an atomic oxygen (AO)-resistant layer on the spacecraft surface. In this study, SR coatings were used to spray on the polyimide surface to prevent atomic oxygen erosion. Then, the physical, chemical, and AO-resistant properties of the SR were investigated. By means of laser diffraction scattering particle size distribution tests, energy-dispersive spectroscopy elemental mapping, and X-ray photoelectron spectroscopy, the fillers and matrix were confirmed as precipitated silica and phenyl SR, respectively. Through analysis of swelling behavior, greater cross-linking density and less swelling ratio were observed at higher temperature and humidity. Furthermore, after AO was exposed with an accumulated fluence of 1.2 × 1021 atoms/cm2, cracks appeared on the coating surface with the change of element content. In addition, it was found that the degree of reaction between AO and SR should not be determined based on mass loss measurements. Our work showed the practical application and great potential of SR protective coating in spacecraft.

Thermal insulation performance of silicone rubber / silica aerogel composite

Silica aerogel (SA) is considered one of the most promising thermal insulation materials due to its nano-size open pore structure. In this study, one part room temperature vulcanized silicone rubber (RTV-SiR) composite with improved thermal performance has been produced simply by incorporating SA as filler. Hydrophobic SA particles of 0.5 mm with a surface area of ∼700 m2/g and density of 0.07 g/cm3 were prepared from rice husk ash via ambient pressure drying. The RTV-SiR composite of 5.0 mm thickness was prepared by blending with 9 wt% of SA particles using a mechanical mixer and kept for vulcanization at room temperature. The properties of the RTV-SiR composite were systematically investigated using scanning electron microscopy (SEM), tensile test, surface roughness, water contact angle measurement, Fourier transform infrared spectroscopy (FTIR), hot-disk thermal conductivity analyzer, thermogravimetric analysis (TGA) and flame penetration test. Compared to pristine RTV-SiR, composite reinforced with SA particles demonstrates low density, high strength and specific modulus, low thermal conductivity, high surface hydrophobicity and excellent resistance to flame penetration test. The composite can withstand the penetration of the butane flame torch for more than 800 s and keep the unexposed side temperature (plateau of 100 °C) below the decomposition temperature of the SiR. The results suggest that the thermal performance of the composite is strongly influenced by the physical properties of the SA and the structural integrity of the SA in the composite. The SA reinforced SiR composite has a potential application prospect in building insulation and fire protection.