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Dielectric polymer composites with conducting fillers would have great potential for diverse applications if their severe leakage loss could be addressed. In this regard, ternary composites using both ceramic and conducting materials as fillers might be an enabler for high dielectric constant and low dielectric loss. Herein, ternary composites with both Ti3C2Tx MXene conducting nanosheets and CaCu3Ti4O12 (CCTO) dielectric particles embedded in silicone rubber were studied. It was found that a ternary composite with 1.2 wt% (0.40 vol%) Ti3C2Tx MXene and 12 wt% (2.58 vol%) CCTO could provide an overall superior performance that include a high dielectric constant of 8.8, low dielectric loss of less than 0.0015, good thermal stability up to 450 °C, and excellent mechanical properties with tensile strength of 569 kPa, elastic module of 523 kPa and elongation at break of 333%. The outstanding performance is attributed to the improved uniform dispersion and good interfacial compatibility of mixed fillers in the polymer matrix, suggesting ternary composites might be a better option over their binary counterparts in preparing high performance dielectric composites.

Due to the high-heat flux issue caused by the increasing power consumption of electronic devices in spacecraft, there is an urgent need but still a significant challenge to develop high thermal conductivity elastomeric thermal interface materials (TIMs) for spacecraft. In this study, mesophase pitch-based carbon fibers (CFs) are added as fillers on the basis of conventional alumina/silicone rubber TIMs, and the CFs are oriented in the matrix by a strong magnetic field during the preparation process. Attributed to the phonon-transport highways composed of vertically-oriented CFs and the synergistic improvement based on CFs and alumina, the through-plane thermal conductivity of the final elastomeric composite with 20 vol% CFs is increased by nearly 14 times compared with the alumina/silicone rubber composite, and it also confirms to the vacuum outgassing performance standard for spacecraft. Moreover, with the help of a verification system, the actual heat transfer capability of the composite is evaluated through the ground test and on-orbit test, and the results suggest that it has a perfect interface heat transfer capability both on the ground and in space, which reveals that this composite can potentially be applied as elastomeric TIM for spacecraft thermal control.

To address the increased demand for greater mechanical robustness of superhydrophobic and icephobic surfaces, we fabricated damage-tolerant, abrasion-insensitive, and icephobic superhydrophobic bulk nanocomposites using a facile, cost-effective, industrially applicable, and environmentally benign strategy. We prepared nanocomposites composed of high-temperature vulcanized silicone rubber through the highly controlled incorporation of nanosized fumed silica and microsized aluminum trihydrate particles. The produced nanocomposites did not require additional processing, such as sand abrasion or plasma treatment, to acquire their superhydrophobic properties. The extended roughness throughout the whole bulk of the nanocomposites imparted the volumetric superhydrophobicity and resistance to mechanical damage. The presence of micro-nanoparticles also enhanced the thermal stability and icephobic properties of the silicone rubber. The icephobic behavior of the developed nanocomposites was assessed based on freezing delay and push-off tests both of which denoted improved icephobic properties, i.e., high freezing delay time and low ice adhesion strength. We verified the extended duration of superhydrophobicity within the bulk nanocomposite using sandpaper abrasion, severe cutter scratching, tape peeling, and water-jet impacts. This study represents the first evaluation, to the best of our knowledge, of the icephobic properties of both the surface and bulk of the produced nanocomposite subjected to several cycles of sandpaper abrasion. Interestingly, even after multiple abrasion cycles, the samples demonstrated considerably low ice adhesion strength confirming their bulk icephobicity. In a nutshell, our findings are very promising for the fabrication of mechanically robust icephobic materials.

Flashover failure is a significant issue that reduces the ability to insulate the glass insulators in power transition lines. The main reason is the surface contaminates, which increases the conductivity of the surface leading to flashover occurrence. A sol-gel method was used to create a hydrophobic surface on the high voltage glass insulator, preventing dusty or salty water droplets from adhering to its surface. The cold spraying technique was utilized to build up a thin nanocomposite hydrophobic layer on the glass insulator containing different percentages of nanosilica particles, such as 23%, 33%, and 44% with the potting compound silicone substrate. The wettability test, hardness, roughness and dielectric strength of the produced nanocomposite were investigated. Furthermore, the surface morphology of the prepared silicone rubber/nanosilica hydrophobic nanocomposite was occurred using the FESEM analysis. The findings show that silicone rubber/33% nanosilica exhibits the best hydrophobic behavior, with a contact angle is more than 133.3˚. Also, the change in dielectric strength was 16.4% when adding 33% percentage of the nanosilica. The flashover test was also performed, and it was discovered that the leak current between the coated and uncoated samples were differed significantly. Using a 60 kV voltage load, the leak current of the coated sample with a hydrophobic nanocomposite was decreased to 2.4 mA, whereas the untreated sample was 3.1 mA. These findings may assist to enhance the hybrid nanocomposite as hydrophobic surface made of silica nanoparticles/silicone base preventing contaminants from adhering on the insulating glass in high voltage power transition lines.

OBJECTIVE The objective of this study was to develop a patch that can be placed on the skin during laser hair removal and similar procedures, that serves to reduce the laser-induced plume, provides a ready indicator to the laser surgeon of where pulses have been applied, and cools the skin. METHODS A two-layer patch composed of a cooling hydrogel layer and an indicator layer was optimized and tested ex vivo. The hydrogel was composed of gelatin and glycerin. The concentration of each hydrogel component was optimized to determine the minimum gelatin concentration at which the gel can be handled without breakage and the minimum glycerin concentration that allows for storage at -20°C without crystallization. This is the temperature of a conventional freezer; application of the cooling layer to the skin would help prevent epidermal injury. The indicator layer was composed of a plastic transparency sheet with small dots of black ink particles printed onto its surface. Transparency sheets were printed from templates created in Adobe Photoshop in which dots are at a specified density; additionally, Photoshop's opacity function was used to vary the opacity of the dots themselves. Performance was tested using a 755 nm alexandrite laser used clinically for hair removal by measuring light transmission through the patch and observing the sheet's ability to indicate the location of laser exposures. The transmittance of patch components across a broad spectrum was also measured using a microplate reader. Several adhesives, including a two-part epoxy, silicone rubber, and cyanoacrylate, were tested for their ability to adhere to the hydrogel and indicator layers. Assembled patches composed of the hydrogel layer, indicator layer, and adhesive were tested ex vivo for their ability to mitigate the laser hair removal plume by measuring airborne particulate matter during simulated laser hair removal. RESULTS A minimum gelatin concentration of 5% was found to enable easy handling of the hydrogel. A mixture composed of 60% water and 40% glycerin by volume consistently allowed storage at -20°C without crystallization. For the indicator layer, ink particle density of 50% and opacity of 5% provided a readily apparent indicator function following laser exposure. Transmission through the sheet measured during alexandrite laser exposures was 90% and was not different than transmission through the sheet alone without ink particles. A cyanoacrylate glue was found to adhere to the hydrogel and indicator layers, while the other adhesives proved inadequate. Measurements using a microplate reader confirmed that the reflection from the transparency sheet itself was the primary contributor to energy loss. In experiments exposing hair clippings to the laser with and without the patch, the patch allowed an increase of 5000 particles/cc relative to baseline particles in the environmental air, while the absence of the patch allowed an increase of 150,000 particles/cc relative to baseline, indicating that the patch decreased particle debris in the plume by 97%. CONCLUSIONS A two-layer patch composed of hydrogel and plastic indicator layer with cyanoacrylate adhesive can be stored in a conventional freezer without crystallization, then placed over an area of skin to be treated for laser hair removal. The patch clearly indicates the pattern and sites of laser exposure, while blocking almost all (97%) of particles in the laser-induced plume. Future work will include safety validation and in vivo testing of efficacy, as these were not undertaken in this study.

Composite insulators are widely used in high-voltage line transmission and electrical equipment due to their excellent water resistance. They are exposed to the natural environment for a long time, and they suffer from weathering corrosion of various factors and external uncertain shocks, which together lead to failure. According to the failure mechanism of composite insulators, a reliability model of the dependent competitive failure process is established. The failure thresholds of composite insulators are uncertain, and the hydrophobic performance degradation and self-healing performance are considered. According to uncertainty theory, the belief reliability and average failure time of composite insulators under three shock model patterns are calculated. The algorithm of the reliability function calculation is given. Taking the composite insulator made of silicone rubber as an example verified the effectiveness of the model.

A novel magnetic liquid silicone rubber composite core design applicable to wireless power transfer (WPT) for medical applications is presented. As a case study, the integration of WPT, including the proposed cores for the coils, with ventricular-assist devices (VADs) was investigated. This facilitates transferring 4.6 W of power wirelessly through the skin layer, which, thus, allows to disposal of the transcutaneous cable that connects the extracorporal batteries to the implanted blood pump. To enhance the coupling coefficient and consequently increase the WPT efficiency, the geometry of the cores was optimized. This reduces the temperature increase in the implant area. The field and thermal simulations were carried out with CST software. The electrical properties of the proposed design as obtained by simulation were validated by measurements. The simulation results perfectly coincide with the measured results. Finally, a new optimized design with additional high permeability core inserts is introduced to further increase the coupling coefficient. The results indicate that the coupling coefficient is increased from 0.31 to 0.52 with the optimized design compared to the case without cores. Moreover, by fixing the initial temperature as 37 °C, the maximum temperature is decreased from 38.19 °C to 37.27 °C while keeping the transferred power fixed. Its high magnetic conductivity, biocompatibility, low-loss property, flexibility, and Qi-standard compatibility make the proposed WPT design an excellent candidate for the wireless powering of heart-assist devices, such as VADs.

Some in-orbital materials of spacecraft will degas under space environments to form molecular contamination, which will be deposited on the surface of spacecraft to degrade the performance of some sensitive materials or devices. The space ultraviolet (UV) radiation may affect the deposition process of molecular contamination to cause photochemical reactions or condensation of molecular contamination on sensitive surface, and results in the enhancement of contamination effect. In this paper, a physical modeling is proposed and ground simulation test is performed to investigate the influence of UV radiation on the molecular contamination effect of spacecraft. Some physical processes such as adsorption, desorption, and photochemical reactions induced by UV radiation is comprehensively considered in modeling, the relationship between the deposition amount of contamination and the time of contamination, the temperature of the deposition surface and the dose of UV radiation have been obtained. An experimental apparatus for molecular contamination deposition under UV radiation is built, and two kinds of space organic materials are used to test their contamination with and without UV radiation. The experimental results show that UV radiation has a significant enhancement effect on the amount of contamination deposition. It is also found that this enhancement effect linearly increases with the increase of ultraviolet dose. According to the experimental data, the parameters in the physical model are determined. The maximum of UV enhancement coefficient can be up to 1.99 for silicone rubber and 4.42 for cable insulation within the experimental temperatures. The modeling and experimental results can be used as references for the design and control of spacecraft molecular contamination.

Due to the poor cell compatibility, capsular contracture is usually accompanied by the implantation of Silicone Rubber (SR). In this study, synthetical carboxyl grafted polyhedral oligomeric silses...

Novel thermoplastic vulcanizates (TPVs) based on polyoxymethylene (POM) and methyl vinyl silicone rubber (MVQ) have been prepared by dynamic vulcanization process through a batch mixer. During the preparation of TPV blends, Di-(tert butyl peroxyisopropyl) benzene (BIBP) was used as the curing agent in order to make MVQ cross-linked and TPU was used to coat MVQ for improving the compatibility of MVQ and POM. In order to understand the influence of different compositions on TPV blends, five groups of experimental processes were described in detail. During these experiments, the amount of POM was reduced from 70phr to 30phr, that of MVQ was gradually increased from 18phr to 42 phr, and TPU was increased from 12phr to 28phr. In addition, the morphology and properties of TPVs were studied by DSC, FTIR, SEM, DMA and mechanical tests. The mechanical testing results showed that with the amount of POM decreasing and the total amount of MVQ and TPU increasing, the tensile strength of the TPV blends gradually was decreased, and the elongation at break was increased accordingly from 35.2 ± 6% of pure POM to 142.8 ± 11% of sample 5#.

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.

In this study, the bending vibration characteristics of the piezoelectric composite double laminated vibrator are studied by simulation and experiment. Firstly, the bending vibration characteristics of a 2-2 piezoelectric composite double laminated vibrator under free and fixed boundary conditions are simulated by the finite element analysis software. Results show that the vibrator has a pure bending vibration mode in the frequency band of 2–4.6 kHz. Then, two types of a 2-2 piezoelectric composite double laminated vibrator are prepared by using epoxy resin and silicone rubber. The test results show that the resonance frequencies of the free and fixed boundaries are ~4.5 and 2.5 kHz, respectively. The vibrator has relatively pure bending vibration characteristics, especially the silicone rubber vibrator, which has lower resonance frequency, higher electromechanical coupling coefficient and larger bending vibration displacement; thus, the 2-2 piezoelectric composite double laminated vibrator is a better choice for the fabrication of a low-frequency transducer.

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.

Organically modified silica gels that show melting gel behavior were coated on sand-blasted steel substrates. The gel surfaces were patterned using silicone rubber molds and nickel mesh. Grooved and hexagonally imprinted surfaces were compared to an unpatterned substrate for their ability to condense water from water vapor in humid air. The patterns of vertical lines were best able to condense the vapor in a way that lead to more liquid water collection per area. The motivation for studying patterned surfaces is to find ways to extend water harvesting capabilities in regions of low humidity.

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.

Fire risk was evaluated by cone calorimeter, thermogravimetric analysis and vertical combustion tests for four common interior wallpaper species including PVC, non-woven, pure paper and silicone wallpapers. This paper compared the time to ignition, heat release rate, smoke production rate, and mass loss parameters, analyzed burning process, pyrolysis and flame propagation properties of four kinds of wallpaper. Based on observations for wallpapers, it is found that the silicone wallpaper had the longest time to ignition and was not lighted under the 15, 20 kW/m2 heat fluxes. This means that the silicone wallpaper can be ignited at a higher heat flux and will have a greater safety than other kinds of wallpaper. Under 30 kW/m2 heat flux, the smoke production of pure paper wallpaper was the lowest, the silicone wallpaper had the lower heat release rate, no smoke released and stable pyrolysis property in the first 40 s. This mean that the first 40 s of the fire of the silicone wallpaper can be used as a prime time for evacuation of people under 30 kW/m2 heat flux. The pyrolysis property and flame propagation of each wallpaper are related to its component. In addition, it is found that the "empty drum" phenomenon of the wallpapers is a prerequisite for the wallpaper used to burn, and only the silicone wallpaper among the four wallpapers has almost no flame propagation due to the thermal shrinkage phenomenon. It is concluded that the wallpaper coated with silicone rubber has a higher safety compared with the wallpapers containing PVC and synthetic fibers.

Because of considerable experimental difficulties for measuring the viscoelastic Poisson´s ratio of polymers and the scarcity of reported data of this property for most of polymers, in particular, elastomers, new measurement methods and procedures need to be developed. The aim of this article is to provide a simple, suitable and reliable procedure to allow the determination of the viscoelastic Poisson’s ratio of elastomers from simple creep strain measurements based on digital image correlation. To illustrate the proposed procedure, a silicone rubber was tested and analyzed. It consisted of performing creep tests at different stresses and temperatures for 10 min (short-term creep tests) measuring simultaneous axial and transverse strains with a DIC equipment. Creep strain functions in axial and transverse direction were obtained employing a creep model. Then, the strain functions were used to calculate the viscoelastic Poisson´s ratio through a transformation method and to obtain their long-term curves. The results obtained demonstrated significant stress and temperature dependency of the viscoelastic Poisson´s ratio for the silicone rubber. It was observed that the viscoelastic Poisson’s ratio increases with temperature but tends to a certain value, and tends to 0.5 for higher temperatures. Overall, the proposed procedure exhibited notable ease and accuracy for the assessment of viscoelastic Poisson´s ratio of elastomers. Finally, the methodology followed in this work can be a potential alternative tool for the characterization of viscoelastic Poisson´s ratio of elastomers, which is currently scarce in literature.

Cotton fabrics for outdoor use were coated with room-temperature vulcanizing silicone rubber (RTVSR) and its catalyst to obtain improved thermal stability and water repellency properties. The coated fabrics were exposed to different doses of electron beam irradiation as an extra curing step for the coating. The effect of RTVSR coating and subsequent electron beam irradiation on the cotton fabrics was then studied. The thermal stability was investigated by thermogravimetric analysis, and surface morphologies were observed by scanning electron microscopy. The mechanical properties, crease recovery, gel content, swelling property, and water repellency of the fabrics were also investigated. The results showed that the thermal stability and the water repellency of the cotton fabrics were improved as a result of the coating process. Moreover, the crease recovery and swelling properties of the fabrics were enhanced, accompanied by decreases in their gel content, as a function of the increase in the electron beam irradiation dose. These findings recommend the produced coated fabrics under the optimum conditions for use in the industrial purposes as isolation sheets through the pipes connecting points, especially those that contain hot fluids.

Graphene oxide (GO) has been widely used as a multi-functional filler in various composites. In order to improve the properties of room temperature vulcanized (RTV) silicone rubber, the functionalized GO (FGO) was used as 2-dimensional filler with short carbon fiber (SCF) and silica particle. The effects of the FGO content on the properties of the RTV silicone rubber composites were investigated. When appropriate amount of the FGOs is added in the composite, the interfacial bonding between SCFs and silicone rubber matrix could be effectively enhanced and the properties of the composites are improved. For the composite with 0.5 phr FGO, the tensile and tear strengths are about 4.7 MPa and 21.9 kN/m, respectively. Meanwhile, the corresponding values of the composite without FGO are only 4.0 MPa and 20.3 kN/m, respectively. The above said values of the composite with 1 phr FGO are 3.8 MPa and 19.8 kN/m, respectively. In addition, the onset decomposition temperature and temperature at the highest decomposition rate for the composite with 0.5 phr FGO, both remarkably increase from 493.4 to 504.2 °C and 564.4 to 613.1 °C, respectively. The carbon frameworks (dense layer and porous layer) will form during the ablation process and play the key role in protecting the RTV silicone rubber, which leads to the reduction of the ablative rate.

Nanofillers are added to polymeric insulating materials in order to modify the electrical, mechanical and thermal properties. This study investigates silicone rubber filled with hydrophilic and hydrophobic silica nanoparticles with respect to their resistance to laser ablation and to arc discharges, as well as their mechanical properties. The laser ablation is performed with single femtosecond laser pulses at wavelengths of 520 nm and 1040 nm. This way, the influence of the nanoparticles on the ablation by laser pulses with defined energy is investigated. The energy absorbed in the ablated volume is determined by taking into account the absorption for various fluences above the ablation threshold. For the silica nanocomposites, the energy specific ablation volume (ESAV), i.e., the ablated volume per absorbed energy, is significantly reduced compared to the unfilled polymer. The reduction is more pronounced for hydrophilic nanoparticles than for hydrophobic nanoparticles. Furthermore, the resistance to arc discharges and the mechanical strength of the nanocomposites are higher compared to the unfilled polymer. In particular, for nanocomposites with different types of silica filler particles the resistance to laser ablation, expressed by the ESAV, the resistance to arc discharges and the mechanical strength, expressed by Shore A hardness and the Young's modulus, show a strong correlation. From this, it is concluded that the modifications of the material properties are caused by interactions between the polymer and the nanoparticle surface, i.e., an interphase. The different extent of this interphase becomes obvious in the different degrees of impact on various electrical and mechanical properties.

Thermal and structural properties of aged silicone rubber composite insulators widely used in high-voltage transmission power systems were characterized by photothermal radiometry (PTR) to evaluate the degree of aging. A two-layer PTR theoretical model was developed to extract the thermal diffusivity and the aged layer thickness from the PTR frequency-scan data. Results show that aging generated an aged layer with a reduced thermal diffusivity at the surface of the composite insulator. Further investigation into the depth dependence of the thermal diffusivity of aged composite insulators found a monotonically increasing thermal diffusivity along the depth direction, approximating to a hyperbolic tangential profile, which indicates a spatially continuous variation from surface to bulk during the aging process. The PTR depth-profiling of thermal and structural properties provides a deeper understanding of the aging process in composite insulators.

In this paper, the electrical tree growth characteristics of silicone rubber (SiR) are studied under impulse superimposed on DC voltage and a temperature gradient (TG) field. The temperature difference between high voltage (HV) and ground (GD) electrodes varies from -90 to 90 °C resulting in a TG field in the samples. The electrical tree morphology, length and accumulated damage are discussed. Experimental results show that with the increase of absolute value of TG, the electrical tree length and accumulated damage continue to increase, and the tree morphology turns from branch-like tree to bush-branch hybrid tree. The positive TG has a more obvious acceleration effect on the tree growth than does the negative TG. Under the TG, the temperature dependent carrier transport results in space charge accumulation and electric field distortion at low temperature side, which is the main reason for the different growth characteristics of electrical tree. Besides, the accumulated damage of DC superimposed with heteropolar impulse voltage is larger than that under DC superimposed with homopolar impulse voltage. It is concluded that the temperature gradient and impulse superimposed on DC voltage promote the electrical tree growth of HVDC cable accessories insulation.

To address overheating and electromagnetic interference of integrated electronics, the design of multi-functional materials with high out-of-plane thermal conductivity and excellent electromagnetic interference shielding effectiveness is desirable. In this contribution, an anisotropy graphene/multi-walled carbon nanotubes with 3D continuous network is fabricated by KOH induced hydrothermal reaction and subsequent graphitization at 2800 °C. When the graphene oxide to multi-walled carbon nanotubes ratio is 1:3, the balance between the decline of sp2 crystallite size in horizontal direction and the enhancement of turbostratic-stacking is achieved, which facilities the phonon transfer and electron transport. The optimal thermal conductivity of composites reaches up to 1.30 W m−1 K−1 at a low loading of 2.77 wt%, which is 465% higher than that of pure silicon rubber (0.23 W m−1 K−1). Meanwhile, the composite exhibits the maximum electric conductivity and electromagnetic interference shielding effectiveness of 42 dB in K-band. Moreover, it still retains the flexibility of matrix. This work paves the way of lightweight dual-function integrated materials.

The architecture of transparent contacts is of utmost importance for creation of efficient flexible light-emitting devices (LEDs) and other deformable electronic devices. We successfully combined the newly synthesized transparent and durable silicone rubbers and the semiconductor materials with original fabrication methods to design LEDs and demonstrate their significant flexibility. We developed electrodes based on a composite GaP nanowire-phenylethyl-functionalized silicone rubber membrane, improved with single-walled carbon nanotube films for a hybrid poly(ethylene oxide)-metal-halide perovskite (CsPbBr3) flexible green LED. The proposed approach provides a novel platform for fabrication of flexible hybrid optoelectronic devices.

The accumulation of ice and contaminants on the surface of composite insulators will cause high energy consumption or even major hazards to power systems. In this work, the polydimethylsiloxane (PDMS) silicone rubber was modified by surface micropatterning and material compositing. Highly crosslinked poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) was used to directly coat ferroferric oxide (Fe3O4) nanoparticles. The obtained core-shell Fe3O4@PZS microspheres were loaded with carbon nanotubes (CNTs) to get CNTs/Fe3O4@PZS as the photothermal magnetic filler. The PDMS/CNTs/Fe3O4@PZS surfaces with micronscale truncated cones were prepared via a combined method of compression molding and magnetic attraction. The 1H,1H,2H,2H-perfluorodecyltrichlorosilane-coated template and magnetic field can increase the height of the microstructure to ∼76 μm and maintain the contact angle of microstructured PDMS/CNTs/Fe3O4@PZS surfaces at a high level (∼152°). Compared with the flat PDMS surface, the micronscale truncated cones extend the freezing time from 4.5 to 11.5 min and also undermine the ice adhesion strength from ∼25 to ∼17 kPa for the microstructured PDMS/CNTs/Fe3O4@PZS surface. The temperature of the PDMS/CNTs/Fe3O4@PZS surface molded with magnetic attraction increases linearly with time and the internal magnetic fillers and achieves 280 °C in 10 s. The efficiency of temperature rise is increased by ∼46%, and hence the entire frozen water droplet can melt within 20 s. The strategy combining active deicing with passive anti-icing undoubtedly promotes the development of high efficiency anti-icing materials and can be applied on insulators to prevent icing flashover.

Vacuum casting (VC) is a highly versatile manufacturing technique capable of producing parts in a wide range of polymers for end use plastic parts or prototypes. VC technology is ideally suited to low volume batch production compared with plastic injection molding since a silicone rubber mold (SRM) can be used to produce up to fifty to eighty parts. The main challenge of this method is that the both dimensional and form accuracies of the VC parts were affected by the fastening force of the SRM using tape due to the fastening force is inconsistent for different operators. In this study, an intelligent SRM clamping mechanism comprising a pressure sensor and Arduino pressure sensing module was developed for reducing the variations in both dimensional and form accuracies of the VC parts. It was found that the 14 kPa is the optimal clamping pressure. The angular deviation of the cuboid VC parts produced by the intelligent clamping mechanism falls within the range of one standard deviation (SD) to the average. The minimum zone circle deviation of the cylinder VC parts produced by the intelligent clamping mechanism falls within the range of − 1 to 2 SDs. In addition, the production cost of the SRM can further be reduced by about 23% using an intelligent clamping mechanism compared with that using the conventional method.

Polysilazane and platinum were adopted to enhance the thermal stability of silicone rubber. The effect and mechanism of polysilazane and platinum on enhancing thermal stability were investigated via thermogravimetry, scanning electron microscopy-energy dispersive X-ray spectrometry, thermogravimetry-Fourier transform infrared spectrometry, and Fourier transform infrared spectrometry. Remarkable synergism between polysilazane and platinum was found in enhancing thermal stability of silicone rubber. When 1.34 wt% polysilazane and 8 ppm platinum were added, the degradation temperatures were elevated. Furthermore, the thermal residues of silicone rubbers were increased from 30–45 to 66–76 wt%, and maximum degradation rates were reduced from 8.81–15.8 to 4.55–5.02 wt%/min. Besides, silicone rubber demonstrated excellent shape retention at high temperature in the presence of polysilazane and platinum. The mechanism may be that platinum cooperated with polysilazane and efficiently catalyzed radical crosslinking between polysilazane and silicone chains. As a result, a tightly crosslinked network was developed, and degradation of silicone rubber was suppressed.

Electric and magnetic properties in the frequency range (500 Hz − 2 MHz) of a composite consisting of silicone rubber and ferrofluid with magnetite particles, in a mass ratio 1/20, were investigated. Structural analysis of nanoparticles within the ferrofluid (FM sample) was performed by XRD diffraction and morphology of composite (SR-FM sample), was investigated by SEM analysis. The frequency dependence of the imaginary component, μ″, of complex magnetic permeability of composite sample exhibits two maxima. These have been associated with the Brownian relaxation process within the ferrofluid drops remained in vesicles of silicone rubber. At the same time, a dielectric relaxation process attributed to the Schwarz relaxation was also highlighted. The mechanical mobility, u, of the charge carriers, u = 1.5∙108 m/sN, from the composite sample, was computed. Based on the complex impedance measurements, the frequency dependence of the conductivity, σ(f), was determined, which respects the Jonscher universal law. The static conductivity, σdc = 2.38∙10-7 S/m, of composite sample, was determined. The results allowed the evaluation of the energy barrier of electrical conduction process, Wm = 0.353 eV and the crossover frequency, ωc = 3.39∙105 rad/s, for composite sample. The performed study is useful in manufacturing magnetic elastomeric composite materials with predetermined properties and for possible technological and biomedical applications.

The work aims to generalize the existing theoretical studies into the influence of geometrical dimensions of the Maddock element installed on the extruder screw on the mixing quality of polyethylene composition with a silicone rubber in order to establish theoretical laws of the process and to verify them experimentally. A mathematical model of the flow of polymer melts in the working gaps of a single-extruder screw with a Maddock mixing element is formulated. Numerical and simulation experiments were carried out, a technological scheme for producing a composition for an antifriction layer of protective tubes of fiber optic communication cables is proposed, and samples of the new composition were obtained.

Helical coiled heat exchangers (HCHX) are utilised to make ice slurry hygienically. The effects of four material coils was investigated: nylon, polytetrafluoroethylene (PTFE), silicon rubber and aluminium. Operation regions and ice production rate results for the materials were compared to nylon. PTFE production rates were highest at warmer refrigeration temperatures (up to -9.5 ∘ C) and a wider stable operation region at high flow rate. Silicone rubber created a wide stable operation region and used the warmest refrigeration temperatures (up to -8 ∘ C); however, ice fraction and production rate were lowest. No stable ice slurry production was achieved with aluminium. PTFE produced the lowest nucleation temperature due to its hydrophobic surface in further nucleation temperature tests; aluminium had the warmest nucleation temperatures. The duration of experiments was extended to 6000 s by (1) recirculating fluid (2) a control system for flow rate to prevent blockages and maximise ice production. PTFE and nylon produced similar amounts of ice, 1 kg and 0.96 kg respectively.

In recent years, varying degrees of surface pulverization had been found on composite insulators running for years in severe outdoor environment such as dry, high altitude, salt fog and intensive ultraviolet radiation. Research on the basic characteristics of powdered substance is essential to maintain a high reliability of the power grid. In this study, the characteristics of the powdered layer of the composite insulator sheds aged for more than 10 years under three different environmental stresses are analyzed. The results show that powdered substance of each composite insulator sample contains two parts: the organic silicon which is oxidative degradation product of the original material polydimethylsiloxane (PDMS), and the partially dehydrated and deteriorated flame retardant filler aluminum hydroxide (ATH). However, the thickness of the powdered layer, the particle size distribution of the powdered substance and the composition ratio between the two components are different. The average particle size of powdered substance is between 2–7 μm. The content of Al element is 31.8–34.5%, the content of Si element is 12.7–17.5%, and the mass fraction ratio of two types of powdered substance is about 1/2–1/3. The essence of pulverization is finally concluded that the composite insulator is severely oxidized and degraded under the effect of various aging factors. The organic component silicone rubber is decomposed to fragments, and the bonding between inorganic flame retardant filler and polymer become weak. They will be detached from the main body skeleton and lost partly, then build up at the surface, forming powdered layer.

The use of nanofillers with high surface area and extreme purity in polymer composite is an effective strategy to obtain high performance polymeric nanocomposites. Therefore, the effect of nanofillers such as carbon nanotubes (CNT), titanium dioxide (TiO2), and their hybrid on rubber-based composites was studied. In this study, rubber nanocomposites were fabricated by using room temperature vulcanized (RTV) silicone rubber matrix and nanofillers (i.e. CNT, TiO2, and CNT-TiO2) through solution casting method. Here, the purity and surface area of CNT (purity: >96% and BET surface area: 300 m2/g) and TiO2 (purity: >98% and BET surface area: 165 m2/g) were estimated by field emission scanning electron microscopy/energy dispersive X-ray (FESEM-EDX) and adsorption isotherms. The mechanical properties of the rubber nanocomposites were enhanced by incorporating nanofillers. The compressive modulus was 2.18 MPa for unfilled composites and increased to 6.8 MPa (CNT), 3.95 MPa (CNT-TiO2), and 2.44 MPa (TiO2) at 5 phr, respectively. Similarly, the tensile strength was 0.54 MPa for unfilled composites and increased to 1.37 MPa (CNT), 1.33 MPa (CNT-TiO2) and 0.61 MPa (TiO2) at 5 phr, respectively. Further, the actuation displacement was improved with increasing input voltage and it was 2 mm for CNT, 1.6 mm for CNT-TiO2 hybrid and 0.5 mm for TiO2 at 10 kV. Moreover, a series of experiments show the potential application in piezoelectric actuation.