Silicone Rubber Composites Research Articles

Enhanced fire retardancy with excellent electrical breakdown voltage, mechanical and hydrophobicity of silicone rubber/aluminium trihydroxide composites by milled glass fibres and graphene nanoplatelets

The integrity of polydimethylsiloxane (PDMS) based silicone rubber (SR) is highly critical in the electrical insulation industry during a wildfire event. In this work, SR composites are prepared with milled glass fires (MGFs) and graphene nanoplatelets (GNPs) to study the limiting oxygen index (LOI), cone calorimeter parameters, electrical breakdown voltage, mechanical and hydrophobic properties of solely aluminium trihydroxide (ATH) filled PDMS. Results exhibit that ATH could help in improving the aforementioned characteristics of pristine SR whereas, the MGFs and GNPs impart a pronounced impact on further improving the properties of solely ATH-filled SR. It is noticed that LOI improves to 35% and 36% whilst the maximum average rate of heat emission (MARHE) reduces to 78.6 kW/m2, and 69.6 kW/m2 in SR4 and SR5. In addition, the electrical breakdown voltage is slightly reduced at 24.65 kV/mm and 25.78 kV/mm in SR4 and SR5 relative to 27.47 kV/mm in SR1. GNPs and MGFs mutually render a positive impact on improving the tensile strength of SR2. Furthermore, SR composites are found with excellent hydrophobicity. The static contact angle marginally decreases in SR2 relative to SR1 whilst it is measured comparatively high at ∼115° in MGFs and GNPs-filled SR composites. SR4 and SR5 seem propitious composites comparatively with improved LOI, excellent fire retardancy, better mechanical strength and hydrophobicity whilst retaining the electrical breakdown strength.

Shear Ablation Behavior and Mechanism of Liquid Silicone Rubber Composites at Different Ablation Angles and Distances

Shear Ablation Behavior and Mechanism of Liquid Silicone Rubber Composites at Different Ablation Angles and Distances

Dielectric and Mechanical Properties of Silicone Rubber Composites Reinforced by Conductive Carbon Black and Neopentyl Glycol Diglycidyl Ether

Dielectric and Mechanical Properties of Silicone Rubber Composites Reinforced by Conductive Carbon Black and Neopentyl Glycol Diglycidyl Ether

Performance evaluation of gamma‐ray irradiated silicone rubber nano‐micro composites using electrical, thermal, physiochemical and deep learning techniques

AbstractSilicone rubber insulation used in nuclear power stations is inevitably exposed to highly energetic gamma‐ray irradiations which may lead to premature failure. Therefore, it is mandatory to develop silicone rubber composites capable of withstanding the stress posed by gamma‐ray irradiation. The present research involves the development of micro aluminum tri hydrate (ATH) and nano silica (SiO2) doped/co‐doped silicone rubber nanocomposites best suited for use in nuclear power stations. The samples were exposed to gamma‐ray irradiation of 500 kGy. Surface changes incurred were assessed using atomic force microscopy (AFM), fourier transform infrared (FTIR) spectroscopy, contact angle, surface potential/impedance, water droplet‐initiated corona inception voltage (CIV) measurements thermogravimetric analysis (TGA) was adopted to characterize the thermal stability of the specimens. Further moisture absorption behavior of the test specimens under strong electrolytic NaCl solution has been investigated. The erosion resistance of the virgin and gamma‐ray irradiated specimens has been classified using GoogLeNet convolution neural network.

Mechanical Properties of High Temperature Vulcanized Silicone Rubber Aged in the Natural Environment.

Composite insulators operate in harsh field environments all year round. Their various properties and states of aging require attention. It is important to study the performance changes of composite insulator sheds after aging to evaluate the life of insulators operating on grids. For this reason, 22 composite insulator sheds from different factories, with different voltage levels and different ages years were selected to conduct mechanical properties testing. The mechanical properties include hardness, tensile strength, and elongation at break, and were investigated by thermogravimetric (TGA) testing, surface morphology, and nuclear magnetic resonance (NMR) characterization. The changes in mechanical properties of high temperature vulcanization (HTV) composite insulator silicone rubber aged in the natural environment were analyzed, including the reasons for these changes. The results showed that the transverse relaxation time T2 of the sample was closely related to its aging state. The more serious the silicone rubber’s aging, the smaller was the T2. The state of the composite insulator can be evaluated by using T2 and aging years simultaneously. With the actual degree of aging in the silicone rubber intensified, its tensile strength and elongation at break generally showed a downward trend.

The Viability of the Filler Barrier Effect During the DC Dry-Band Arcing on Silicone Rubber

This article investigates the filler barrier effect on suppressing the erosion of silicone rubber composites during the dc dry-band arcing, by supplementing main microfillers in silicon rubber, i.e., ground silica and micro-sized alumina trihydrate, with fumed silica and nano-sized alumina trihydrate fillers. A study framework employing simultaneous thermogravimetric-differential thermal analyses (TGA-DTAs), the inclined plane tracking and erosion test, and the dry-arc test is employed. Fumed silica in silicone rubber increases the amount of the crosslinked residue and suppresses silicone rubber depolymerization, whereas nano-sized alumina trihydrate releasing water of hydration may adversely impact the residue coherence and promote combustion. The viability of the filler barrier effect is synergistically achieved by adding fumed silica to the main ground silica filler, thereby maintaining the residue integrity. The inclined plane-tracking erosion test confirms the importance of the filler barrier effect of fumed silica in supplementing the volume effect of ground silica in the suppression of the dc dry-band arcing. These filler effects appear to mainly govern the erosion resistance, with insignificant effect shown for thermal conductivity under dc. The dry-arc resistance test is shown as a useful method to simulate a stable dry-band arcing and obtain reproducible surface erosion patterns that correlate with the outcomes of the dc inclined plane tracking and erosion test.

Ti3C2Tx MXene-Ag/silicone rubber composites with enhanced dielectric properties and improved mechanical properties

Conductive filler/polymer composites were widely used in dielectric devices, but high dielectric constant was accompanied by high loss tangent. Incorporating highly conductive fillers into silicone rubber (SR) matrix may be a feasible way, since the loss tangent of SR is extremely low. In this paper, to improve the dielectric properties of polymer composites, SR composites were fabricated with Ag decorated Ti3C2Tx MXene (Ti3C2Tx MXene-Ag) as the fillers. The thermal stabilities, dielectric and mechanical behaviors of the Ti3C2Tx MXene-Ag/SR composites were investigated. Compared with Ti3C2Tx MXene/SR composites, Ti3C2Tx MXene-Ag/SR composites exhibit higher dielectric constants, due to the deposition of Ag particles on the surfaces of Ti3C2Tx MXene nanosheets. The dielectric constant of Ti3C2Tx MXene-3.2Ag/SR composites is 7.29 (17.8% higher than MXene/SR composite and 162% higher than SR), and the loss tangent is as low as 0.00114 at 1 kHz. The enhanced interfacial polarization and micro-capacitor model can be used to explain the improved dielectric properties of the composites. Furthermore, the prepared SR composites have excellent mechanical properties, with a tensile stress of 554 kPa and an elongation at break of 257%. This work illustrates a method to obtain polymer-based composites with high dielectric and mechanical performances, which can be used as dielectric elastomers in actuators, sensors, biomedicine, energy collector and so on.

Nonlinear rheology of silicone rubber composites with tailored mechanical and dielectric properties

Silicone rubber (SR) composites used in electronics demand tailored mechanical and dielectric properties. Herein cellulose nanocrystal and graphene are used as promising nanofillers for SR vulcanizates and a simple method of alignment of the fillers is explored to mediate the mechanical, dielectric and nonlinear rheological responses. The results reveal that the alignment of fillers tends to improve deformational stress and lower dielectric constant and loss, allowing preparing high-performance composites with dielectric constant being comparable with the electroinsulating SR vulcanizates. Under dynamic oscillating shear deformation, the composites demonstrate both elastic and viscous nonlinearities while the filler alignment improves the elastic and lowers the dissipation without marked influence of the relative amplitude of the Payne effect. The investigation provides a perspective for manufacturing SR composites with high elasticity and low mechanical and dielectric losses.

Improving the Heat and Ablation Resistance of Silicone Rubber Composites by Incorporating Hollow Microspheres.

For thermal protection materials (TPMs) which are used to protect space vehicles from extreme thermomechanical environments, the thermal conductivity of the original material and the char layer that has formed during ablation plays a significant role in determining the ablation performance. In order to investigate this, in this study, we introduced glass hollow microspheres (GHMs), phenolic hollow microspheres (PHMs), and acrylonitrile-methyl methacrylate copolymer hollow microspheres (AMHMs) into silicone rubber (SR), and the ablation performance of these composites was systematically studied. The thermogravimetric results showed that the residue yield of the SR composites was increased with the incorporation of the hollow microspheres. Compared to the SR composites without the hollow microspheres, the residue weight values under 800 °C (R800) of the SR composites with the 30 parts of fumed silica per hundred of the SR (phr) addition of GHMs, PHMs, and AMHMs were increased from 10.11% to 21.70%, 18.31%, and 20.83%, respectively. The ablation tests showed that the addition of the AMHMs enhanced the ablation performance of the SR composites because the linear ablation rates and the backplane temperature were clearly decreased when compared to the SR composites without the hollow microspheres. This work provides an effective and potential method for preparing thermal protection materials with an improved ablation performance.

Finite Element Analysis of Compression Behaviors of Silicone Rubber Composites Reinforced by Warp-Knitted Spacer Fabrics

In this study, the compression behaviors of silicone rubber composites reinforced by warp-knitted spacer fabrics under 20% deformation were investigated by experiment and a finite element analysis method. Based on the compression test, including the compression tests of composites and the warp-knitted spacer fabrics, the compression behaviors of composites were investigated. This revealed that the composites exhibited excellent elastic recovery abilities. Furthermore, the finite element analysis model of composites was established based on the parameters of the geometry and performance of the composites. The simulated results by the finite element analysis model were compared with the experimental ones to verify the accuracy of the model. It is obvious that the compressive finite element analysis model had good agreement with the experimental results, indicating that the compression performance of composites can be effectively simulated by the finite element analysis method. It is a useful tool for understanding the compression mechanism of composites and optimizing the composites’ parameters for cushioning applications.

Catalytic Graphitized Silicone Rubber Coatings with Highly Graphitized Ceramic Layer and Superior Ablation Resistance

AbstractThe strength of the ceramic layer formed during ablation of the silicone rubber composite is closely related to its resistance to ablation. Increasing the content of graphitic carbon in the ceramic layer plays a key role in enhancing the strength of ceramic layer. In this study, series of catalytically graphitized mesophase pitch‐modified silicone rubber composites with excellent ablation performance are prepared. And the average linear ablation rate of the composite is reduced to a maximum of 0.046 mm s‐1, which is 44.0% lower than that of the sample without catalyst named 5MP. XRD characterization proves that the addition of transition metal catalysts increases the content of graphitic carbon in the ceramic layers after ablation. The strength of ceramic layer of the 0.13Fe2O3 reached 12.09 MPa, which is 60.3% higher than that of the 5MP. The transition metal catalyst effectively increases the content of graphitic carbon in the ceramic layers, and the strengths of the ceramic layers are significantly improved, thereby greatly improving the ablation performance of the composites.

Preparation and Mechanical Properties of Thermal Insulation Silicone Rubber Composites

In this paper, three different functional phases of thermal insulation, hollow ceramic microspheres (HCM), hollow silica microspheres (HSM) and hydroxy silicone oil blowing agent (OH-3#)were selected, and a flexible and efficient thermal insulation composite with low thermal conductivity and high thermal structural strength was designed and prepared using the synergistic effect between the three. The results show that the thermal stability and mechanical performance of composites were significantly enforced.

Reversible thermochromic microencapsulated phase change materials for enhancing functionality of silicone rubber materials

The thermochromic phase change microcapsules (ETPCWs) are constructed by encapsulating ternary core composed of crystal violet lactone, bisphenol A and phase change wax into silica shell by in-situ condensation. It has good latent heat storage (∼130 J/g), high encapsulation efficiency (∼80%) and dual-output response (storage-release heat and thermochromic) produced by the solvent-modulated dissociation/aggregation mechanism. Upon heating, the ETPCWs exhibit light blue or even white, while return to dark blue when temperature decreases. Furthermore, thermochromic silicone rubber composites (TSRMs) are prepared by using ETPCWs as functional filler and silicone rubber as polymer matrix, which possess appropriate thermal regulation performance, improved thermal stability, favorable hydrophobicity, adjustable transparency and pleasurable mechanical properties. Especially, CIELAB color space values show that the TSRMs exhibit excellent thermochromic characteristics and outstanding recyclability. Therefore, this work provides a new idea for the development of functional phase change capsules, and the prepared thermochromic phase change microcapsule exhibits great application potential in security labels, intelligent electronic wearable devices as well as temperature sensors.

High-temperature behavior of silicone rubber composite with boron oxide/calcium silicate

Abstract The ceramifiable silicone rubber (SR) composite is prepared using boron oxide, calcium silicate, and kaolin as ceramifiable fillers. The effects of the content of CaSiO3/B2O3 on the high-temperature properties of composites are investigated. In the process of decomposition and oxidation of the ceramifiable SR composite in air, B2O3, and low-melting-point glass frit that participate in the formation of the residue network structure in different temperature regions, it continuously produces a liquid phase during the process of the ceramifying transformation. Microscopic images reveal that different structures are formed at different temperatures. The network structure of the ceramic residue becomes increasingly compact with the increase in temperature from 600°C to 800°C, which has a better protective effect on heat transfer and mass loss. At 900°C, with the lattice reconstruction of calcium silicate and the change of crystal structure, volume expansion occurs after cooling, alleviating the volume shrinkage caused by ceramic phase formation in the process of ablation. When the ratio of CaSiO3/B2O3 reaches 1:1 (both are 15 phr), the bending strength and linear shrinkage of the composites reach a satisfactory balance, the bending strength and the shrinkage reach 18.5 MPa and 12.1%, respectively.

Novel optical metrology for inspection of nanostructures fabricated by substrate conformal imprint lithography

Substrate conformal imprint lithography (SCIL) technology enables the fabrication of complex and non-trivial 3D nanostructures such a slanted gratings and metasurfaces with sub-10 nm resolution over large areas for industrial-scale production, which can be fabricated in a single lithography step. This technology utilizes novel composite silicone rubber stamps that provide versatility in addition to high precision. To inspect the quality and reproducibility of the nanostructures that are fabricated using SCIL, a novel optical characterization method using Fourier microscopy is proposed. In this method, nanostructures are illuminated under a microscope objective using a collimated light beam at different incident angles and the properties of the reflected and/or diffracted beams are analysed to extract the critical dimensions of the nanostructures. This fast and non-destructive method has the potential for being used as an in-line inspection technology to extract the critical dimensions of the nanostructures over large areas and improve the overall properties of nanostructured surfaces.

Enhancing thermal conductivity of silicone rubber composites by in-situ constructing SiC networks: A finite-element study based on first principles calculation

Enhancing thermal conductivity of silicone rubber composites by in-situ constructing SiC networks: A finite-element study based on first principles calculation

Bioinspired structural silicone rubber composites with high thermal conductivity based on vertically aligned hybrid filler film

To improve the capability of thermal management of thermal conductive silicone rubber (SR) composites, a novel strategy to prepare SR composites with vertically aligned graphene/silicon carbide crystal whisker (SiC) hybrid film was proposed inspired by the typical architecture of the annual rings of trees. Frist of all, a SR/graphene-SiC bilayer film was prepared through drying SR solution and aqueous filler dispersion in turn. Then the bilayer film was rolled and subsequently cured to form SR composite. Poly(ethylene glycol) grafted poly(methylhydrosiloxane-co-dimethylsiloxane) was newly synthesized and used to enhance the interfacial interaction between SR and filler film. The bioinspired structural graphene/SiC/SR composite exhibited a very high thermal conductivity of 6.72 W/(m·K). The composite was determined to be an efficient thermal interface material to reduce the working temperature of light emitting diode, clearly showing the excellent thermal management capability of the obtained SR composites.

Thermally Conductive and Electrically Insulated Silicone Rubber Composites Incorporated with Boron Nitride-Multilayer Graphene Hybrid Nanofiller.

Thermally conductive and electrically insulating composites are important for the thermal management of new generation integrated and miniaturized electronic devices. A practical and eco−friendly electrostatic self−assembly method was developed to prepare boron nitride−multilayer graphene (BN−MG) hybrid nanosheets. Then, BN−MG was filled into silicone rubber (SR) to fabricate BN−MG/SR composites. Compared with MG/SR composites with the same filler loadings, BN−MG/SR composites exhibit dramatically enhanced electrical insulation properties while still maintaining excellent thermal conductivity. The BN−MG/SR with 10 wt.% filler loading shows a thermal conductivity of 0.69 W·m−1·K−1, which is 475% higher than that of SR (0.12 W·m−1·K−1) and only 9.2% lower than that of MG/SR (0.76 W·m−1·K−1). More importantly, owing to the electron blocking effect of BN, the electron transport among MG sheets is greatly decreased, thus contributing to the high−volume resistivity of 4 × 1011 Ω cm for BN−MG/SR (10 wt.%), which is fourorders higher than that of MG/SR (2 × 107 Ω·cm). The development of BN−MG/SR composites with synergetic properties of high thermal conductivity and satisfactory electrical insulation is supposed to be a promising candidate for practical application in the electronic packaging field.

Enhancing the thermal and electrical conductivities of silicone rubber composites by constructing a 1D‐3D collaborative network

AbstractThe construction of conduction pathways is considered to be a crucial issue for the thermal and electric transfer ability improvement of silicon rubber. Fabricating three‐dimensional (3D) conductive scaffolds is attractive for rapid heat and electricity conduction in silicon composites. In the present work, carbon nanotubes (CNTs) and conductive sponges (CSs) were chosen to construct a 1D‐3D collaborative network in a silicone matrix. Novel silicone rubber composites with preferable thermal and electrical conductivity properties were fabricated. The morphology, thermostability, electroconductibility, and mechanical properties were studied. This kind of silicone‐based composite with high thermal and electrical conductivity has broad applications for thermal management in emerging electronic devices.

2D-3D collaborative network based on conductive sponge and flake graphite to design high performance silicone rubber composites

2D-3D collaborative network based on conductive sponge and flake graphite to design high performance silicone rubber composites