Liquid Silicone Rubber Research Articles

Mechanical, Electrical and Thermal Behavior of Liquid Silicone Rubber Based Composites

Manufacturers' primary emphasis in diversifying sectors is on environmentally friendly materials. It aims to produce electrical and electronic appliances. These material solutions are necessary to improve insulator performance and functioning as they get smaller, lighter, and more dependable. High-voltage devices, transformers, and other electrical components are well-insulated by silicone rubber. Silicone rubber not only retains its electrical qualities when exposed to external conditions such as moisture and temperature variations, but it is also safer and cleaner than its competitors. This paper primarily focuses on comparative analysis of the mechanical, electrical, and thermal characteristics of adding several ceramic nano-fillers, such Al2O3, Mullite, and Cordierite, to a liquid silicone rubber (LSR) matrix for suggested electrical insulation applications.

UVC Irradiation as a Surface Treatment of Polycarbonate to Generate Adhesion to Liquid Silicone Rubber in an Overmolding Process.

This study investigates the adhesion properties of polycarbonate (PC) and liquid silicone rubbers (LSR) through surface activation using ultraviolet C (UVC) radiation. While self-adhesive LSRs adhere easily to certain thermoplastic composites such as polybutylene terephthalate (PBT) and polyamides (PAs), bonding to PC typically requires surface treatment due to the lack of compatible functional groups. Previous methods like plasma or flame treatment have been effective, but the use of UVC radiation for surface activation remains unexplored. Through experiments, it was found that UVC surface activation, particularly with ozone-generating lamps, significantly enhances the peel strength between PC and self-adhesive LSRs. The study evaluates the impact of different irradiation times and lamp configurations on peel resistance, surface energy, and composite stability. Results show that UVC/ozone (wavelengths 254 nm and 185 nm) activation increases peel resistance, with distinct differences observed between LSR types. Additionally, the study examines the stability of UVC activation over time and under various storage conditions, highlighting its effectiveness for up to 36 months at room temperature. Furthermore, the relationship between surface energy and peel strength is analyzed, finding that UVC/ozone activation increases surface energy but does not consistently correlate with improved adhesion. The study concludes with a comparison of UVC/ozone activation to alternative surface treatment methods, emphasizing its advantages such as cost-effectiveness and stability while considering limitations regarding substrate compatibility and occupational safety aspects. Overall, UVC/ozone surface activation presents a promising approach for enhancing adhesion in PC-LSR composite systems and holds potential for applications across various industries.

Effects of Carbon Black on Mechanical Properties and Oil Resistance of Liquid Silicone Rubber.

Liquid silicone rubber (LSR) garners attention across a diverse range of industries owing to its commendable fluidity and heat resistance. Nonetheless, its mechanical strength and oil resistance fall short compared to other rubbers, necessitating enhancement through the incorporation of a suitable filler. This research focuses on reinforcing LSR using carbon black (CB) particles as a filler, evaluating the mechanical properties and oil resistance of neat LSR, and LSR containing up to 3 wt% of CB filler. CB was added in powder form to investigate its effect on LSR. When LSR was impregnated with oil, the deterioration of rubber was noticeably observed under high-temperature conditions compared to room-temperature conditions. Consequently, the mechanical properties and oil resistance, excluding the permanent compression reduction rate, tended to increase as the filling content of CB increased compared to the unfilled state. Notably, in the specimen with 2 wt% CB filler, the tensile modulus increased significantly by 48% and the deterioration rate was reduced by about 50% under accelerated deterioration conditions. Additionally, the swelling rate in oil decreased by around 14%. This validates a notable improvement in both mechanical properties and oil resistance. Based on the identified mechanism for properties enhancement in this study, CB/LSR composite is expected to have a wide range of applications in fields such as gaskets, oil seals, and flexible sensors.

Effect of Methyl Hydro-Silicone Oil Content and Aging Time on Compression Modulus and Breakdown Strength of Additional Liquid Silicone Rubber Gel.

The performance of silicone rubber gel elastomers is affected by the composition and structure of the crosslinker. In this work, a two-component addition liquid silicone rubber gel material was developed, and the effects of the contents of two methyl hydro-silicone oils on the compression modulus and breakdown strength of the silicone rubber gel insulating material, as well as the performance change after hot air aging at different times (24 h, 48 h, 72 h, 96 h, 120 h, 144 h, 168 h), were studied. The results showed that the breakdown strength and compression modulus exhibited an upward trend with the increase in the hydrogen silicone oil content. The best performance was achieved in the silicone rubber gel with Si-H:Si-Vi = 1.4:1. Moreover, with the increase in aging time, the breakdown strength decreased and the compression modulus increased.

Porous structures design in liquid silicone rubber foams through CO2 controlled molecular crosslinking

During CO2 foaming, molecular crosslinking plays an important role on cell structure of rubber foam. In this work, effects of CO2 on crosslinking reaction of liquid silicone rubber (LSR) were investigated according to viscoelasticity and reaction activation energy. It was found that CO2 facilitates formation of local primary crosslinking structure in LSR, while inhibiting creation of crosslinking network. When saturation pressure was lower than 13 MPa, LSR foam can obtain uniform cells only under a narrow saturation time. After increasing CO2 pressure higher than 13 MPa, cell structure was less affected by saturation time and time window for preparing uniform cell structure was extended. LSR foam was prepared with minimum cell size of 22.1 µm as well as maximum expansion ratio of 4.9. This work demonstrates CO2 controlled molecular crosslinking is key to porous design of LSR, which exhibits good theoretical exploration and application value in preparation of LSR foam.

Network Structure and Mechanical Properties of Flexible Electronic Interconnects based on Linear Low-Density Polyethylene (LLDPE) and Liquid Silicone Rubber (LSR) Conductive Polymer Composites

Network Structure and Mechanical Properties of Flexible Electronic Interconnects based on Linear Low-Density Polyethylene (LLDPE) and Liquid Silicone Rubber (LSR) Conductive Polymer Composites

Improvement of the Cell Structure of Water‐Foamed Liquid Silicone Rubber

This article shows three different water‐based physical blowing agents for liquid silicone rubber (LSR) in terms of physical, mechanical, and morphological properties depending on the manufacturing parameters and amounts of blowing agents. The compositions consist of common LSRs added with pure water, water–silicone oil emulsion, and aqueous silicone. The foaming process is initiated in an injection molding process. By subvolumetrically filling the mold, it is possible to foam the LSR during the injection molding process. This publication aims to compare different, water‐based blowing agents for LSR in the injection molding process. The results show that for all foams porosities between 0.25 and 0.4 are possible. An analysis of the foam structure shows that the aqueous silicone produces a significantly more homogeneous structure than the other two blowing agents. In addition, the mechanical properties are analyzed. For this purpose, tensile tests are carried out and the Shore hardness is determined. The elasticity and mechanical properties decrease slightly. The specific tensile strength also shows a small decrease, although this may be due to either the gradient of the foam structure or chemical reactions between the blowing agents and the LSR.

Development of Lead-Free Radiation Shielding Material Utilizing Barium Sulfate and Magnesium Oxide as Fillers in Addition Cure Liquid Silicone Rubber.

The radiological protection has the purpose of safeguarding the physical well-being of the user, preventing exposure to detrimental levels of ionizing radiation. This study introduces a novel, cost-effective category of lead-free elastomeric material designed for radiation shielding. The filler compounds utilized are notably lighter than conventional lead-based materials, enhancing user ergonomics during application. They comprise of a blend of barium sulfate combined or not with magnesium oxide with addition-cure liquid silicone rubber. To ensure the effectiveness of the radiation shielding, X-ray transmission measurements were performed for the different thicknesses of the materials and the results compared with Monte Carlo simulations. Additionally, the physical properties of the new materials, such as density, homogeneity, tensile strength, viscosity, and wettability, were also evaluated. The findings indicate that both materials fulfill the requirement for application in radiation protection garments.

Liquid Silicone Rubber Headlamp Lens Injection Molding Process Optimization Based on Tie Bar Elongation and NSGA III.

This study aimed to improve the injection molding quality of LSR material lenses by optimizing the process parameters. To achieve this goal, we employed the population-based optimization algorithm NSGA-III, which can simultaneously optimize multiple objective functions and identify an equilibrium point among them, thereby reducing the time required to find the optimal process parameters. We utilized analysis software to simulate the injection molding process of LSR material lenses, with a specific focus on examining the relationship between tie bar elongation and the optimized process parameters. During the study, we intentionally varied key process parameters, including the melt temperature, holding pressure, and holding time, to analyze their impact on the residual stress of the final product. In order to investigate the intricate relationship between the tie bar yield, injection molding process parameters, and lens residual stress, we installed strain sensors on the tie bar to continuously monitor changes in clamping force throughout the injection molding process. The experimental results showed that both the tie bar force and mold cavity pressure exerted significant influence on residual stresses. By applying the NSGA-III algorithm for optimization, we successfully determined the optimal process parameters, which included a melt temperature of 34.92 °C, a holding pressure of 33.97 MPa, and a holding time of 9.96 s. In comparison to the initially recommended process parameters during the design phase, the optimized parameters led to reductions of 12.98% in clamping force and 47.14% in residual stress. Furthermore, the average transmittance of the actual product remained within the range of 95-98%. In summary, this approach not only enables the prediction of the lens's residual stress trends based on the tie bar elongation, but also leads to a substantial enhancement of lens quality, characterized by reduced residual stress and improved transmittance through the optimization of process parameters. This methodology can serve as a valuable guide for optimizing real-world injection molding processes.

Improving the transient thermal response and ablation properties of epoxy‐modified silicone rubber composites by adding fluxing agent

AbstractIn this work, transient thermal response and ablation behavior of liquid silicone rubber composites containing fluxing/ceramic forming fillers were investigated under different heat flows using an oxyacetylene flame. The results indicated that the introduction of zinc borate (ZB) and aluminum oxide (Al2O3) effectively reduced the temperature at various depths of the samples, and they improved the thermal insulation properties and lowered pyrolysis rates. The above finding was attributed to the heat absorption arising from water release and melt filling as well as the vitrified reaction of solid melt due to the decomposition of ZB. Besides, the melting and exfoliation of Al2O3 and the formation of aluminum silicate (Al2SiO5) caused heat absorption effect. Additionally, the mass ablation rates and line ablation rates increased with rising heat flows coupling with a decrease of compressive strength of the char layers. In a nutshell, the effect of adding ZB/Al2O3 on the thermal insulation behavior of epoxy‐modified vinyl silicone rubber (EMVSR) composites under different heat flows was elucidtaed. This work served as a reference for the design and preparation of flexible ablative materials for thermal protection applications.

MC-Injection Molding with Liquid Silicone Rubber (LSR) and Acrylonitrile Butadiene Styrene (ABS) for Medical Technology.

The multicomponent injection molding of liquid silicone rubbers (LSR) with thermoplastics, such as polybutylene terephthalate (PBT) or polyamide (PA), is a state-of-the-art technique and is used in the manufacturing process for many components in the automotive industry and in the field of sanitary engineering. Standard thermoplastics, such as acrylonitrile butadiene styrene (ABS), cannot be bonded with silicone rubbers in injection molding because of their low heat deflection temperature. In this study, we investigated ABS grades approved for medical applications to show how dynamic mold heating and various pretreatment methods for thermoplastic surfaces can be used to produce ABS-LSR test specimens. In addition, such components' sterilization effect on the adhesive bond will be shown.

The role of cordierite nano filler on the electrical, mechanical, thermal, and chemical properties of liquid silicone rubber used in composite insulators

The role of cordierite nano filler on the electrical, mechanical, thermal, and chemical properties of liquid silicone rubber used in composite insulators

FEA Assessment of Contact Pressure and Von Mises Stress in Gasket Material Suitability for PEMFCs in Electric Vehicles

Ensuring the safety of electric vehicles is paramount, and one critical concern is the potential for hazardous hydrogen fuel leaks caused by the degradation of Proton-Exchange Membrane Fuel Cell (PEMFC) gasket materials. This study employs advanced techniques to address this issue. We leverage Finite Element Analysis (FEA) to rigorously assess the suitability of gasket materials for PEMFC applications, focusing on two crucial conditions: ageing and tensile stress. To achieve this, we introduce a comprehensive “dual degradation framework” that considers the effects of contact pressure and von Mises stress. These factors are instrumental in evaluating the performance and durability of Liquid Silicon Rubber (LSR) and Ethylene Propylene Diene Monomer (EPDM) materials. Our findings reveal the Yeoh model as the most accurate and efficient choice for ageing simulations, boasting a minimal Mean Absolute Percentage Error (MAPE) and computational time of just 0.27 s. In contrast, the Ogden model, while accurate, requires more computational resources. In assessing overall model performance using MAE, Root Mean Square Error (RMSE), and R-squared metrics, both LSR and EPDM materials proved promising, with LSR exhibiting superior performance in most areas. Furthermore, our study incorporates uniaxial tensile testing, which yields RMSE and MAE values of 0.30% and 0.40%, respectively. These results provide valuable insights into material behaviour under tensile stress. Our research underscores the pivotal role of FEA in identifying optimal gasket materials for PEMFC applications. Notably, LSR is a superior choice, demonstrating enhanced FEA modelling performance under ageing and tensile conditions. These findings promise to significantly contribute to developing safer and more reliable electric vehicles by advancing gasket material design.

Multi-scale-filler reinforcement strategy enabled stretchable silicone elastomer with synergistically enhanced thermal conductivity and mechanical strength

As soft electronic devices and robotics advance towards high power density and miniaturization, integrating superior thermal and mechanical properties has become a big challenge for functional elastomers. Herein, a multi-scale-filler reinforcement strategy was reported for constructing stretchable, mechanically strengthened and thermally conductive silicone elastomers. The multi-scaled Al2O3/vinyl and methyl co-modified fumed SiO2 (VM-SiO2) co-filled liquid silicone rubber composite exhibited a high thermal conductivity of 1.25 W m−1 K−1 at ∼55 vol% filler loading, 555.7% higher than that of the matrix. The finite element simulation demonstrated that the “bridging” effect of small-scaled fillers between gaps of large-scaled spheres in the matrix lowered the interfacial thermal resistance. Meanwhile, stemming from the strong interfacial interactions between the VM-SiO2 and matrix, up to 12.4 times higher elongation at break (7.17%) and 317.7% increase of tensile strength (3.00 MPa) were reached. We further demonstrated the potential application of the multi-scaled Al2O3/VM-SiO2 co-filled LSR composites for thermal management materials.

Enhancing Surface Temperature Uniformity in a Liquid Silicone Rubber Injection Mold with Conformal Heating Channels.

To enhance the productivity and quality of optical-grade liquid silicone rubber (LSR) and an optical convex lens simultaneously, uniform vulcanization of the molding material is required. However, little has been reported on the uniform vulcanization of LSR in the heated cavity. This paper presents a conformal heating channel to enhance the temperature uniformity of the mold surface in the LSR injection molding. The curing rate of an optical convex lens was numerically investigated using Moldex3D molding simulation software. Two different sets of soft tooling inserts, injection mold inserts with conventional and conformal heating channels, were fabricated to validate the simulation results. The mold surface temperature uniformity was investigated by both numerical simulation and experiment. In particular, both a thermal camera and thermocouples were employed to measure the mold surface temperature after LSR injecting molding. It was found that the uniformity of the mold surface for LSR injection mold with the conformal heating channel was better. The average temperature of the mold surface could be predicted by the heating oil temperature according to the proposed prediction equation. The experimental results showed that the trend of the average temperature of five sensor modes was consistent with the simulation results. The error rate of the simulation results was about 8.31% based on the experimental result for the LSR injection mold with the conformal heating channel.

Gel point investigation of liquid silicone rubber using rheological approaches

Liquid silicone rubber (LSR) is becoming increasingly popular due to its chemical, UV, and heat resistance as well as its excellent optical properties. However, there is currently a lack of research and understanding of the rheological properties of the material. During the processing of liquid silicone rubber, the material can assume different rheological states. In the present work, both the physical and the chemical gel behavior are investigated rheologically. For this purpose, measurements are carried out with a rotational rheometer and a high-pressure capillary rheometer. Depending on the temperature and pre-shear rate, times are given for the physical gel point, after which a significantly destroyed physical network is recovered. Investigations at higher temperatures, which lead to chemical crosslinking and, therefore, to a chemical gel point, resulted in a representation of the temperature-dependent chemical gel point. The presented results serve as a material database for reliable simulations.

Al2O3 Nano filler’s impact on electrical, mechanical, thermal, microstructural and the chemical characteristics of liquid silicone rubber for composite insulators

This study examines the function of Al2O3 nanofiller in liquid silicone rubber (LSR) for the purpose of outdoor insulation. Several characteristics, including structural (Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), physical (density), mechanical (tensile, tear, percentage elongation at break, and shore A hardness), thermal (thermal conductivity, thermo gravimetric analysis (TGA)), electrical (dielectric constant, dielectric breakdown strength, DC volume resistivity, arc resistance, and recovery of hydrophobicity), although chemical (immersion of samples for 72 h in NaCl, HCl, and H2SO4 solutions and measurement of sample weight and PH of the solution before and after immersion) were investigated after the addition of Al2O3 nanofiller with different compositions, such as 5, 10, and 15 weight percentages. In comparison to pure LSR, it was discovered that the inclusion of nano Al2O3 particles enhanced the material’s density by 11%, thermal conductivity by 12%, dielectric constant by 24%, DC volume resistivity by 2%, arc resistance by significantly 1205%, dielectric breakdown strength by 54%, and hydrophobicity. Other improvements include a 7% rise in tensile strength, a 23% rise in tear strength, a 17% rise in hardness, and an 18% reduction in percentage elongation at break when compared to pure LSR for the composite samples. Mechanical qualities are affected by the curing process duration. More specifically, we discovered there is a proportionality relationship between the tensile strength and the elastic modulus. Findings of the chemical examination revealed that the composites have corrosion resistance in the form of negligible weight change in the sample when exposed to salt and acid solutions. The combination of these exceptional qualities makes Al2O3 composites appealing within an insulating materials realm.

Facile preparation of smart nanocomposite adhesive with superhydrophobicity and photoluminescence

Smart photoluminescent nanocomposite adhesive was developed toward simple commercial manufacturing of long-persistent luminescent and hydrophobic applications. The prepared photoluminescent glue was able to continue emitting light after turning the illumination source off even after being in the dark for up to 1.5 h. Lanthanide-doped strontium aluminum oxide (LSAO) nanoparticles (NPs) dispersed in liquid silicone rubber (SR) was prepared to function as nanocomposite glue for various surfaces. Using nano-scaled particles, LSAO was uniformly disseminated without agglomeration in the silicone rubber matrix, enabling the produced nanocomposite glue to transmit light. For the applied glues, there is an excitation peak determined at 365 nm, and an emission peak determined at 518 nm. Depending on the LSAO ratio, the photoluminescence spectra displayed either afterglow phosphorescence or fluorescence. Photochromism was monitored from transparent to greenish under UV irradiation and greenish-yellow in darkness. The glued samples benefit from enhanced superhydrophobicity and scratch resistance due to LSAO NPs embedded in the silicone rubber matrix. The glueed LSAO@SR nanocomposite showed high durability and resistance to light damages. This research established the feasibility of mass-producing smart glue for various uses such as building safety directed signs and smart windows.

Particle-reinforced elastomer model to analyse viscoelastic properties of flake-shaped electrolyte iron particle-based magnetorheological elastomer

This paper uses parallel-plate-plate rheometry to focus on the magnetic field-dependent nonlinear viscoelastic behaviour of flake-shaped electrolyte iron powder-based magnetorheological elastomer (MRE). MRE was prepared using liquid silicon rubber as a base, a curing agent and electrolyte iron particles as fillers. Three MRE samples having 60%, 40%, and 0% filler weight fractions were prepared. The curing was carried out at 300 K. The thickness of the sample was 1.00 ± 0.04 mm. Scanning electron microscopy results showed uniform dispersal of particles within a matrix. The swelling measurement technique was used to confirm the enhanced reinforced properties of elastomer by calculating the cross-link density. The magnetic volume fraction evaluated from magnetisation measurements yields values of 18.7% for MRE-60 and 8.7% for MRE-40. Both moduli’s field-induced linear and nonlinear amplitude dependence were analysed using the modified particle-reinforced elastomer model. The result indicates that filler particles adsorbed on polymer chains were essential in determining the reinforcing properties of MRE. The improved cross-link density and particle morphology were responsible for the enhanced field-induced magnetorheological effect (277%). This value is nearly three times greater than that observed in spherical particles-based MRE.

Preparation and characterization of red mud/liquid silicon rubber with good thermal‐stability and processability

AbstractAs reported herein, a novel addition‐type liquid silicone rubber (LSR)/red mud (RM) composite has been synthesized. Triethoxyvinylsilane (KH151) was used as a surface modification agent to treat RM and form hydrophobic surfaces. The optimal formulation of the composite was determined by the mechanical properties of the LSR that were prepared at different crosslinker and filler contents. The reinforcement mechanism of modified RM on LSR was revealed by combining Fourier transform infrared (FTIR) spectroscopy, x‐ray photoelectron spectroscopy and mechanical property tests. Thermal degradation behavior of RM/LSR at elevated temperature was investigated by the thermogravimetric analysis (TG), TG‐FTIR and alteration of mechanical properties after thermal aging. The results of the experiment indicate that modified RM increased the tensile strength and Young's modulus of LSR dramatically and provides superior thermal stability to the LSR. With 100 phr RM added, the tensile strength of RM/LSR composite was almost 12 times greater than that of pure LSR, and pure LSR degrades completely after aging at 300°C for 24 h while RM/LSR retains its mechanical properties.