Silicone Rubber Research Articles

Study on the Relationship between Electron Transfer and Electrical Properties of XLPE/Modification SR under Polarity Reversal.

The insulation of high-voltage direct-current (HVDC) cables experiences a short period of voltage polarity reversal when the power flow is adjusted, leading to sever field distortion in this situation. Consequently, improving the insulation performance of the composite insulation structure in these cables has become an urgent challenge. In this paper, SiC-SR (silicone rubber) and TiO2-SR nanocomposites were chosen for fabricating HVDC cable accessories. These nanocomposites were prepared using the solution blending method, and an electro-acoustic pulse (PEA) space charge test platform was established to explore the electron transfer mechanism. The space charge characteristics and field strength distribution of a double-layer dielectric composed of cross-linked polyethylene (XLPE) and nano-composite SR at different concentrations were studied during voltage polarity reversal. Additionally, a self-built breakdown platform for flake samples was established to explore the effect of the nanoparticle doping concentration on the breakdown field strength of double-layer composite media under polarity reversal. Therefore, a correlation was established between the micro electron transfer process and the macro electrical properties of polymers (XLPE/SR). The results show that optimal concentrations of nano-SiC and TiO2 particles introduce deep traps in the SR matrix, significantly inhibiting charge accumulation and electric field distortion at the interface, thereby effectively improving the dielectric strength of the double-layer polymers (XLPE/SR).

Preparation of Stable Superhydrophobic Anti-icing Coating on the Surface of Silicone Rubber Insulators

Preparation of Stable Superhydrophobic Anti-icing Coating on the Surface of Silicone Rubber Insulators

Aging assessment of silicone rubber materials under corona discharge accompanied by humidity and UV radiation

Abstract High voltage (HV) outdoor insulators are subjected to both electrical and environmental stresses, which may lead to their failure. Among the causes, corona discharge, humidity and UV radiation are considered to be the most damaging factors. Efforts are therefore underway to investigate new materials for improving the performance of insulating systems. In this research work, silicone-based room temperature vulcanized samples filled with alumina trihydrate (ATH), silicon dioxide and magnesium hydroxide (MH) were prepared and exposed to AC corona discharge for a duration of 110 h. The electric discharge was also accompanied by UV radiation and two different humidity levels. Following aging of the test samples, diagnosis was conducted to assess their integrity. Measurements based on determining the static contact angle demonstrated the loss of hydrophobicity of all the materials, while hydrophobicity recovery phenomena revealed that ATH-doped materials demonstrated a comparatively higher increase in the contact angle than in samples filled with silicone dioxide (silica) and MH. Scanning electron microscopy analysis revealed deep cracks and block-like structures on their surfaces. Similarly, energy-dispersive X-ray analysis indicated the signs of surface oxidation of the aged samples. However, the data of elemental composition exhibited the loss of filler contents as well as that of carbon from the base matrix. The overall assessment showed that resistance to suppress aging is influenced by both the filler type and its concentration in the investigated composites. The ATH-filled composites exhibited outstanding performance when exposed to the rigors of corona discharge and other environmental stresses. This research contributes to materials science and HV engineering by addressing the development of composites for enhanced insulator performance, with future aspects lying in the utilization of nano-composites for advanced functionality and durability.

Mechanical Characteristics of Multi-Level 3D-Printed Silicone Foams.

Three-dimensional-printed silicone rubber foams, with their designable and highly ordered pore structures, have shown exceptional potential for engineering applications, particularly in areas requiring energy absorption and cushioning. However, optimizing the mechanical properties of these foams through structural design remains a significant challenge. This study addresses this challenge by formulating the research question: How do different 3D-printed topologies and printing parameters affect the mechanical properties of silicone rubber foams, and how can we design a novel topological structure? To answer this, we explored the mechanical behavior of two common structures-simple cubic (SC) and face-centered tetragonal (FCT)-by varying printing parameters such as filament spacing, filament diameter, and layer height. Furthermore, we proposed a novel two-level 3D-printed structure, combining SC and FCT configurations to enhance performance. The results demonstrated that the two-level SC-SC structure exhibited a specific energy absorption of 8.2 to 21.0 times greater than the SC structure and 2.3 to 7.2 times greater than the FCT structure. In conclusion, this study provides new insights into the design of 3D-printed silicone rubber foams, offering a promising approach to developing advanced cushioning materials with superior energy absorption capabilities.

Rate-dependent and delayed snap-through behaviors of viscoelastic metamaterials

Snap-through instability can occur after a significant time delay for some viscoelastic structures under certain loading history; the mechanisms of this phenomenon in viscoelastic metamaterials are still unrevealed. This work uses a combined method of experiments, finite element analysis (FEA), and analytical modeling to investigate the rate-dependent and delayed snap-through behavior of viscoelastic metamaterials. The load-displacement responses under different loading-rates and viscoelastic parameters are illustrated with an emphasis on the programable load capacity and stability via FEA. Experimentally, a viscoelastic metamaterial made of silicone rubber is fabricated through 3D printed molds, and demonstrated for delayed snap-through after creeping under a constant force. The sensitivity of the delayed time to the applied force is presented. A phase diagram with respect to the applied force and material viscoelasticity is constructed to demonstrate different snapping behaviors, including near-instantaneous snapping, delayed snapping at finite time, and no snapping. A discrete model that can capture different snapping modes is developed to provide straightforward understanding of the underlying mechanisms. This work can open up potential novel applications of the tunable delayed snap-through behavior of viscoelastic metamaterials.

Flexible composite films with ultrahigh through-plane thermal conductivity yet low graphene content

Graphene-based polymeric composites have become one of the promising thermal interface materials (TIMs) for the high integration electronic devices due to the excellent intrinsic thermal conductivity of graphene. However, the challenges still remain, such as ordered alignment of graphene in elastic polymer and regulation of phonon scattering at graphene/graphene interface. In this study, a vertically oriented graphene framework within a flexible silicone rubber matrix was fabricated by non-solvent induced phase separation (NIPs) coupled with an in in-situ welding technique. The as-prepared film exhibits an outstanding through-plane thermal conductivity of 29.5W/mK at low graphene loading of 7.5 wt%, which indicates an exceptionally high thermal conductivity enhancement per 1 wt% graphene content (specific TCE) over 1950 %/wt%. Furthermore, the composite films demonstrate excellent conformability inherited from the silicone rubber matrix and achieves low contact resistance of 40–70 Kmm2W−1 under various pressure and interfacial conditions. This study contributes to a deeper insight into the development of the high-performance graphene-based polymeric TIMs.

Color Modifications of a Maxillofacial Silicone Elastomer under the Effect of Cigarette Smoke.

Although it is known (from the observations of medical professionals) that cigarette smoke negatively affects maxillofacial prostheses, especially through staining/discoloration, systematic research in this regard is limited. Herein, the color modifications of M511 maxillofacial silicone, unpigmented and pigmented with red or skin tone pigments, covered with mattifiers, or with makeup and mattifiers, and directly exposed to cigarette smoke, were investigated by spectrophotometric measurements in the CIELab and RGB color systems. The changes in color parameters are comparatively discussed, showing that the base silicone material without pigmentation and coating undergoes the most significant modifications. Visible and clinically unacceptable changes occurred after direct exposure to only 20 cigarettes. By coating and application of makeup, the material is more resistant to color changes, which suggests that surface treatments provide increased protection to adsorption of the smoke components. The dynamic water vapor sorption (DVS) measurements indicate a decrease of the sorption capacity in pigmented versus unpigmented elastomers, in line with the changes in color parameters.

Physicochemical characterization of the metamorphosis of film-forming formulations of betamethasone-17-valerate

Following topical application of a dermatological product, the loss (by evaporation and/or absorption through the skin) of volatile excipients will alter the composition of the formulation remaining on the tissue. This so-called metamorphosis impacts the concentration of the drug in the residual vehicle, (potentially) its physical form therein and, as a result, its uptake into and subsequent permeation through the skin. This research aimed to characterise – using primarily confocal Raman microspectroscopy – the metamorphosis of film-forming formulations of betamethasone-17-valerate (at different loadings) comprised of hydroxypropyl cellulose (film-forming agent), triethyl citrate (plasticizer) and ethanol (solvent). Dissolved and crystalline drug in the films were identified separately by their different characteristic Raman frequencies (1666 cm−1 and 1659 cm−1, respectively). These Raman measurements, as well as optical imaging, confirmed corticosteroid crystallisation in the residual films left after ethanol evaporation when drug concentration exceeded the saturation limit. In vitro release tests of either sprayed or pipette-deposited films into either aqueous or ethanolic receptor solutions revealed drug release kinetics dominated by the residual film post-metamorphosis. In particular, the rate and extent of drug release depends on the concentration of dissolved drug in the residual film, which is limited by drug saturation unless supersaturation occurs. For the simple films examined here, supersaturation was not detected and the solubility limit of drug in the films was sufficient to sustain drug release at a constant flux from the saturated films through a thin silicone elastomer membrane into an aqueous receptor solution for 30 h. Flux values were ∼ 1 μg cm–2h−1 from saturated residual films independent of the amount of crystallized drug present. Flux from subsaturated films was reduced by an amount that was consistent with the lower degree of saturation.

Modulation of Mechanical Properties of Silica-Filled Silicone Rubber by Cross-Linked Network Structure.

Associating molecular structure and mechanical properties is important for silicone rubber design. Although silicone rubbers are widely used due to their odourless, non-toxic, and high- and low-temperature resistance advantages, their application and development are still limited by their poor mechanical properties. The mechanical properties of silicone rubbers can be regulated by designing the cross-link density and cross-linking structure, and altering the molar contents of vinyl in the side groups of methyl vinyl silicone rubber (MVQ) leads to different cross-linking structures and cross-linking densities in the vulcanized rubber. Therefore, this study investigated the differences in molecular parameters and molecular chain structures of unprocessed MVQ rubbers with different vinyl contents. The results showed that MVQ rubbers with high vinyl contents were branched polymers, better facilitating the cross-linking reaction than MVQ rubbers with low vinyl contents. In addition, silicone rubbers with different vinyl contents were co-cross-linked to introduce an inhomogeneous cross-linked network in the silicone rubber to improve its mechanical properties. The cross-linked network properties were analysed by the Flory-Rehner model and Mooney-Rivlin plots, and it was found that the long chains in the sparsely cross-linked domains of the network favoured high elongation at break and the short chains in the densely cross-linked domains contributed to high modulus, which could satisfy the functions of reinforcing and toughening the rubber materials at the same time. It was also found by analysing the filler network and aggregate morphology that the inhomogeneous cross-linked network led to an improvement in the dispersion of silica in the rubber and a significant improvement in the mechanical properties of silicone rubber.

A manual operated and eco-friendly plasma-assisted polymerization method for enhancing surface weather resistance of insulation

With the increasing demand for high-voltage long-distance power transmission, insulation as the first protection of power system, faces serious challenges from material degradation caused by moisture invading, surface contamination and pollution flashover. Addressing the issue requires significant effort and may cause harmful by-product emission from large-scale wet type material processing. In this work, a novel eco-friendly dry treatment method based on manual operated Air/Alkoxysilane(PMDMS)/plasma is developed to enhance weather resistance and electrical performances of contaminated insulation. Tiny amounts of harmless reaction medium are transmitted to plasma through controllable air bubbling, and it implements precise dry type processing on material surface. Plasma pulverizes pre-existing contamination and synchronously activates hydrolysis-polymerization of PMDMS to deposit Si-containing protection layer (Si-O2, Si-CH3) on surface. It is demonstrated that the plasma treatment inhibits dirt pollution and electrical erosion of on-site 110 kV silicone rubber (SIR), and the electrical and hydrophobicity properties are both promoted. Flashover voltage increases from 4.65 to 8.71 kV, and water contact angle increases from 138.27° to 146.41°. Overall, this newly-developed dry portable plasma treatment strategy for insulation enhancement avoids environment pollution and economic losses, and provides a scalable avenue for on-site insulation recovery and service life prolonging.

Super anti‐impact silicone elastomer with shell‐less shear thickening fluid droplets in matrix

AbstractA soft and stretchable safeguarding silicone rubber is obtained by embedding large amount of shell‐less shear thickening fluid (STF) droplets into polydimethylsiloxane (PDMS) matrix through the synergistic process of emulsification and polymerization. Feeding time and temperature are optimized to generate the efficient STFs with 72.2 wt% SiO2 and high thickening viscosity of 6340 Pa·s. The embedding process and the evolution of the shell‐less STF droplets in PDMS matrix are explored by both optical and scanning electronic microscopes. The influence of the STF content on the mechanical and anti‐impact performance of the composites is explored through tensile tests and drop hammer tests. The STF content could be as much as 75 wt%, which enhances not only the softness and stretchability (elongation at break >200%) but also the impact‐protective performance of the silicone rubber. The STF/PDMS composites covering on planar and nonplanar glass substrates demonstrate self‐adaptive protection effect by reducing the force impact peak by 35%, due to the shear thickening and energy absorption of STF in the composites. This study develops a facile and scalable method for the implantation of the STF into polymer matrix, extending the applications of STF/PDMS composites in varied fields.

Preparation and properties of an anti-icing and de-icing emulsified asphalt coating containing RTV and CNTs

In regions experiencing cold weather, road icing poses significant challenges to transportation safety. Traditional anti-icing or de-icing methods, such as salt spraying, have raised environmental concerns, prompting the exploration of more sustainable alternatives. This study introduces a novel approach by developing a hydrophobic coating for road surfaces. This method involves using room-temperature vulcanized silicone rubber (RTV) and carbon nanotubes (CNTs) for the hydrophobic modification of emulsified asphalt (EA), resulting in the preparation of modified emulsified asphalt (RCEA). This method does not cause environmental pollution and makes the road surface highly hydrophobic and effective at preventing ice formation. When the dosages of RTV and CNTs are 20 wt% and 4 wt%, respectively, the contact angle of RCEA reaches 118.6°, showing a significant increase of 73.4 % compared to EA. Comparative tests have revealed that RCEA extends the freezing time of water droplets by 66.7 % at −10 °C compared to traditional emulsified asphalt (EA). Furthermore, the adhesion force of ice on the RCEA surface is 58.2 % lower than on EA, indicating significantly improved de-icing efficiency. The results of ultraviolet aging and freeze-thaw cycle tests show that RCEA maintains its hydrophobicity, evidenced by only a slight reduction in the contact angle. Additionally, water seepage coefficient tests and anti-skid performance assessments confirm that RCEA meets the requisite standards for road performance. In summary, RCEA emerges as a promising anti-icing and de-icing material for asphalt roads, offering an environmentally friendly alternative to traditional de-icing methods.

Empowering Particle Jamming Soft Gripper with Tactility via Stretchable Optoelectronic Sensing Skin

Particle‐jamming soft grippers demonstrate notable shape adaptability and adjustable stiffness, which improve their grasping efficiency. However, integrating tactile sensing into these grippers presents challenges due to the specific properties of the particle jamming mechanism. This study introduces a parallel particle jamming soft gripper equipped with tactile sensing capabilities. The gripper consists of two tactile sensing particle jamming pads (TSPJPs) that are integrated with flexible optoelectronic skins. These skins are made of silicone rubber membranes and are embedded with a 3 × 3 array of stretchable optical waveguide arrays (SOWAs). Testing indicates that incorporating these sensors enhances the gripper's tactile sensing capabilities, with minimal impact on its particle jamming‐based grasping function. A single TSPJP can accurately detect various contact points and estimate the contract forces. The proposed soft gripper can reliably grasp a wide range of objects, varying in shape, hardness, and weight, and it provides detailed tactile feedback on contact locations and the intensity of the grasping through the SOWA sensor. It can precisely distinguish between different grasping postures using a light gradient boosting machine (LightGBM) learning model. Furthermore, it can effectively detect the slippage of grasped objects, facilitating accurate closed‐loop control for secure manipulation.

Synergistically Improving Tracking Resistance of Addition-Cure Liquid Silicone Rubber with Aminepropyltriethoxysilane-Immobilized Silica and Platinum Catalyst

Synergistically Improving Tracking Resistance of Addition-Cure Liquid Silicone Rubber with Aminepropyltriethoxysilane-Immobilized Silica and Platinum Catalyst

Formulation of optimized TCA using PDMS epoxy and Ag-coated PMMA for high-efficiency Si tandem solar cell applications

In this study, we aimed to develop and characterize Transparent Conductive Adhesive (TCA) materials for mechanically stacked tandem solar cell applications. The research objectives were to enhance the transparency, conductivity, and adhesive strength of TCAs to improve the efficiency and practicality of tandem solar cells. The TCA formulation comprises a combination of polymers and Ag-coated particles, with flexible poly-methyl methacrylate (PMMA) micro-spheres serving as conductive particles and SYLGARD 184 silicon elastomer poly-di-methyl-siloxane (PDMS), mixed in a 10:1 ratio of base to curing agent, serving as the transparent adhesive. We conducted systematic experiments with Ag-particle coverage areas ranging from 0.34 % to 21.61 % at temperatures of 80 °C and 100 °C, under 500 mb pressure. The optimal conductivity was achieved at 2 wt% Ag-particle coverage, measuring 5.26 × 10⁷ S/m, with over 93 % transparency. These key results indicate the significant potential of the optimized TCA in enhancing the performance of mechanically stacked tandem solar cells, thus contributing to the advancement of renewable energy technologies.

Correlations between the Aging Behavior and Finite Element Method Simulation of Three Silicone Elastomers.

The material parameters required to describe material behavior can change with the age of the components due to chemical and physical aging processes. The finite element method (FEM) is a tool for designing components for later use. The aim of this study is to correlate the change in the mechanical properties of silicone elastomers from standard tests over a longer period of time with the parameters of the Mooney-Rivlin model. To date, there are no publications on the development of the Mooney-Rivlin parameters of silicone elastomers over a storage period. For this purpose, the Shore A hardness, rebound elasticity, compression set and tensile properties were investigated over an aging period of approx. 200 days on two liquid silicone rubbers (LSRs) and one room-temperature-vulcanizing (RTV) silicone rubber. Depending on the silicone elastomer used, different trends in the characteristic values can be observed over the storage period. In general, increases in the Shore A hardness, rebound resilience and stress at a 100% strain with a decrease in the compression set can be determined. In addition to standard tensile tests, the material's multiaxial behavior under tension was probed, and it was found that the similarly stress at a 100% strain increased. Finite element simulations verified the standard tensile test and corresponding Mooney-Rivlin model parameters. These parameters from the uniaxial tensile were validated in the multiaxial behavior, and the model's accuracy in representing material properties and the influence of aging on the FEM simulation were affirmed.

Prediction of thermo-physical properties and evaluation of thermal energy storage performance of phase change materials based on silicone rubber/graphite (Q/G) composites

ABSTRACT Phase change composite materials (PCCMs) are a type of thermal energy storage system known for their high latent heat of fusion. In this study, PCCM samples based on peroxide-cured silicone rubber (Q) were prepared using a simple soaking procedure in molten Paraffin Wax (PW). At any fixed amount of peroxide, the rubber base samples were filled with varying amounts of graphite powder (G), 4 to 8 Wt.%, to improve the thermo-physical properties. The effect of peroxide and graphite content was then evaluated on the PW loading, PW leakage, and thermal storage performance of the resulting Q/G/PW composites. It was found that the highest ratio of the PW loading to PW leakage occurs at a peroxide content of 6 Wt.%. Moreover, the graphite particles demonstrate a significant role in PW trapping inside the rubber structure and lowering the PW leakage. Finally, the thermal studies showed that the Q/G/PW composite containing 6 wt.% of peroxide and 4 wt.% of graphite has the highest latent heat of 111.5 J/g with a PW loading of 15.2%. This sample also had the lowest thermal diffusivity and the slowest cooling and heating rate.

Fabrication of CoFe‐layered double hydroxide for flame retardant and smoke suppression of silicone rubber foam

AbstractIn order to improve the flame retardancy and smoke suppression of silicone rubber foam (SRF), the CoFe‐LDH was fabricated by coprecipitation method and used as flame‐retardant ingredient in SRF. The influence of CoFe‐LDH on the flame retardancy, combustion behavior, and thermal stability of SRF was investigated. The results demonstrate that SRF containing only 1.0 phr CoFe‐LDH can pass V‐0 rating in the vertical combustion test, with a limiting oxygen index of 28.6%. The total heat release and total smoke production are 22.2% and 61.1% lower than that of SRF, respectively. Moreover, CoFe‐LDH can improve the thermal stability of SRF in the high temperature range, and the char residue at 900°C of SRF/LDH composite is obviously higher than that of pure SRF. In addition, to further understand the flame‐retardant mechanism of CoFe‐LDH, the micromorphology of the char residue and the gaseous products during heating for SRF and SRF/LDH composite were analyzed. The results indicate that CoFe‐LDH exhibits excellent flame‐retardant effects in both condensed and gaseous phases for its functions of catalysis, carbonization, and nonflammable gas release. This study provides a more efficient and convenient strategy for the flame retardant and smoke suppression research of SRF.

Self‐healing, low oil leakage and recyclable thermally conductive Al2O3/boron nitride@siloxane composites based on reversible dynamic network

AbstractIn order to overcome the commercialized silicone‐based thermal interface materials' issues such as oil leakage and mechanical damage, we developed a thermoset silicone rubber matrix (SR) achieved through the condensation reaction of hydroxyl silicone oil and tetraethyl silicate. Additionally, we constructed a self‐healing and recyclable silicone rubber matrix (SCNR) by incorporating heat reversible ionic and hydrogen bonds between carboxyl and amino functionalized polydimethylsiloxane. Finally, the flexible, low oil leakage, self‐healing, and recyclable composites Al2O3/BN@SR/SCNR was prepared by adjusting the ratio of SR/SCNR and the spherical alumina and boron nitride (BN) fillers. The results indicated that with SR/SCNR mass ratio of 1/0.075 and filler content of 70 wt%, the thermal conductivity of the composite reaches 1.866 W m−1 K−1, 646% increasing over the SR/SCNR matrix. The self‐healing efficiency reaches 97% and the thermal conductivity remains essentially unchanged after being recycled for three times. The composites can be bent and twisted multiple times and still return to their original shape. Notably, the oil leakage of the Al2O3/BN@SR/SCNR composites is significantly lower than that of additive silicone composites. Therefore, the recyclable thermal conductivity composite developed in this study provides a promising solution for improving the durability of heat dissipation materials in electronic devices.

Study on hemostatic and antibacterial properties of modified silicone rubber sponge

At present, gauze compression and hemostatic powder are commonly used in first aid to stop bleeding. However, the hemostatic effect of gauze compression is poor, and the hemostatic powder is easy to block blood vessels and causes thrombosis. Therefore, developing hemostatic materials with rapid hemostatic function and biosafety remains a challenge. In this article, a double layer hemostatic dressing based on silicone rubber (SR) was prepared. Among them, sponge layer was modified with polydopamine (PDA), and connected to the hydrophilic polymer polyvinylpyrrolidone (PVP) by strong hydrogen bonding. The synergistic synergy of the blood cell affinity of the catechol group and the water absorption of sponge enhanced the hemostatic ability. For the SR layer, ZnO was grown in situ by hydrothermal method as an antimicrobial layer (SRZ). SRZ/PDA-PVP dressing has good mechanical properties, antibacterial properties, coagulation ability and excellent biocompatibility, providing a new idea for the development of hemostatic materials.