Properties Of Silicone Rubber Composites Research Articles

Effects of High-Energy Electron Beam-Modified Fumed Silica on the Structure and Properties of Silicone Rubber Composites

Effects of High-Energy Electron Beam-Modified Fumed Silica on the Structure and Properties of Silicone Rubber Composites

Enhancing Thermal, Viscoelastic, and Mechanical Properties of Silicone Rubber Matrix through Reinforcements for Use as a Medical Implant

The use of silicone rubber as an implant is limited due to its weak properties. In this study, the impact of various reinforcements, such as TiO<sub>2</sub> or SiO<sub>2</sub> nanoparticles, carbon, or polypropylene fiber micro reinforcements, on the mechanical, thermal, and viscoelastic properties of silicone rubber composites with RTV-4125 matrix was investigated. The composites were evaluated through several tests, including tensile, compression, FTIR, TGA, DMTA, and water adsorption tests. It was found that the composites' tensile strength and compressive stress were increased by adding reinforcements, with the most significant impact on tensile strength observed for SiO<sub>2</sub> and the most notable effect on compressive stress at a strain of 0.5 observed for polypropylene fiber. Moreover, the water absorption of the matrix was increased with the addition of reinforcements, with the highest increase observed for Titania nanoparticles. TGA analysis showed that all composites had higher thermal stability than the plain matrix, with the highest degradation temperature observed for the SR-C fiber composite and the highest degradation rate observed for SR-TiO<sub>2</sub>. Additionally, DMTA analysis revealed that TiO<sub>2</sub> nanoparticles considerably decreased the glass transition temperature of the matrix (%28.5), while the other reinforcements had a negligible effect on this temperature. The introduction of reinforcements had a positive impact on the mechanical, thermal, and viscoelastic properties of silicone rubber composites, and the findings of this study can contribute to the development of new and improved silicone rubber composites for implant applications.

Effects of metal oxides on the dielectric and mechanical properties of silicone rubber composites

AbstractPolysiloxane dielectric elastomers have garnered a considerable deal of attention over the last decade due to their potential as electroactive soft materials. However, the intrinsic low dielectric constant of polysiloxanes has proven a serious limitation in their practical use. In this work, we controlled the dielectric properties of silicone rubber composites by changing the type and content of oxide fillers. The silicone‐based dielectric elastomers with a high dielectric constant (5.21@1 kHz), low modulus (1.62 MPa), and high elongation (1100%) were successfully obtained. The effects of different types of metal oxides on the dielectric properties and mechanical properties of the prepared composites are further explored. Due to their excellent comprehensive features, these types of materials are expected to be applied in capacitive sensors, actuators, generators, and beyond.

The synergistic and reinforcement mechanism of SiC nanostructures on the ablation properties of silicone rubber composites

With improvements to the performance of ramjets, the ablation environment in afterburning chambers has become more severe, leading to an urgent demand for high-performance thermal protection materials (TPMs). In this study, the reinforcing effects of silicon carbide (SiC) nanowhiskers and nanopowders on silicone rubber composites and their synergistic effects were investigated. Both SiC nanowhiskers and nanopowders improved the thermal stability of the TPMs. SiC nanowhiskers enhanced the thermal conductivity of the TPMs by forming thermal conductivity pathways. Furthermore, SiC nanofillers can reinforce the ablation resistance of the TPM. The best performance was demonstrated by the TPM formulated with five parts SiC nanowhiskers and five parts SiC nanopowders. The ablation rate was reduced by 72.7% relative to the TPM with a basic formulation, and the back temperature increased by only 27.1%. In this study, the SiC nanofiller improved the ablation resistance of composites by densifying the pore structure and strengthening the skeleton of the char layer. Furthermore, the more compact char layer improved the thermal conductivity of the composites. The increase in the thermal conductivities of the composites and the char layer led to a decrease in the thermal insulation properties of the composites.

Hydrophilic silica transformed silicone rubber into Superhydrophobic composites

AbstractSilicone rubber is widely used in medical and equipment manufacturing fields due to its excellent sealing and solvent resistance. However, the hydrophobicity of silicone rubber was unsatisfactory for many advanced engineering structures and applications. Generally, the preparation of artificial superhydrophobic materials suffered from either complicated in process or poor in environmental protection. Here, we reported a simple method to prepare silicone rubber composites with excellent superhydrophobic properties (water contact angle [WCA] = 155.2°) from low‐cost hydrophilic silica. Tests showed that the uniform micro‐nano structures were the key to the superhydrophobic properties of silicone rubber composites. The bounce test observed the rebound of water droplets with different initial velocities (0.77, 1, and 2 m/s) impacting silicone rubber surface, and verified the great advantages of silicone rubber modified by silica in hydrophobic. The modification method shown in this work provides a simple way to manufacture non‐fluorinated, robustness superhydrophobic surfaces for a wide range of potential applications.Highlights Based on the improvement of micro‐nano structure of the matrix surface by industrial silica, the preparation of superhydrophobic silicone rubber composites was realized. A process method for preparing fluorine‐free superhydrophobic silicone rubber composites from hydrophilic silica was proposed. Stretchability and robustness were the key factors for successful superhydrophobic modification of silicone rubber elastomers.

Effect of spherical alumina crystalline phase content and particle size distribution polydispersity on the properties of silicone rubber composites

High loading of thermally conductive fillers for enhancing thermal conductivity (TC) conflicts with proper rheological viscosity in excellent thermal interface materials (TIMs), which remains a significant challenge. The physical properties (crystalline phase, particle size and distribution, etc.) of thermally conductive filler are the base of the high load in the polymer. In this paper, the α-phase content of spherical aluminum (S–Al2O3) increases after calcination, leading to the viscosity of composites increasing sharply but was only slightly improved for the TC. The polydispersity of the S–Al2O3 particle size distribution was regulated to fill the silicone rubber under the premise of controlling the same average particle size, crystalline phase content and filling amount. Results indicated the viscosity of the sample with a polydispersity value of 0.74 was 41.21 Pa s at a shear rate of 10 s−1 at 66 vol%, which was 87.7% lower than that of the sample with a polydispersity value of 0.48. And the viscosity difference became more prominent with the increasing filling amount. However, the difference in TC between several groups of samples with different polydispersity is insignificant at 60–67 vol%, which provides practical, theoretical guidance for achieving controllable viscosity and developing low-viscosity TIMs in the processing process.

Effect of Modified Nanographene Oxide (mGO)/Carbon Nanotubes (CNTs) Hybrid Filler on the Cure, Mechanical and Swelling Properties of Silicone Rubber Composites

Effect of Modified Nanographene Oxide (mGO)/Carbon Nanotubes (CNTs) Hybrid Filler on the Cure, Mechanical and Swelling Properties of Silicone Rubber Composites

High ablation-resistant silicone rubber composites via nanoscale phenolic resin dispersion

High ablation-resistant silicone rubber composites exhibit significant potential for solid rocket engine ablation coating applications. However, the low char yield of silicone rubber restricts its real-world usage. Herein, silicone rubber with nanoscale dispersed Novolac-type phenolic resin particles (novolac-silicone rubber, NSR) is synthesized. The introduction of dynamic urethane bonds is crucial for achieving nanoscale dispersion of the phenolic resin, as it leads to both improved mechanical strength and enhanced char yield. In addition, the NSR-based composite materials demonstrate linear and mass ablation rates of 0.1440 mm/s and 0.0466 g/s, respectively, representing reductions of 44.19 % and 17.81 % compared with their conventional silicone rubber counterparts. Moreover, unlike the traditional physical blending approach, the nanoscale dispersion in this work is achieved by introducing a dihydroxypropyl-terminated silicone oil-novolac phenolic resin block copolymer to the silicone rubber matrix. The enhanced structural compatibility is proven to be pivotal for the improved performance of NSR. This work provides new routes for the synergistic improvement of the ablation resistance and mechanical properties of silicone rubber composites.

Synergistic Effects between Multiphase Thermal Insulation Functional Phases on the Mechanical and Heat Insulation Properties of Silicone Rubber Composites.

This work utilizes the synergistic effect between three different functional phases of thermal insulation, i.e., hollow ceramic microspheres (HCMs), hollow silica microspheres (HSMs), and hydroxy silicone oil blowing agent, to prepare a flexible and efficient thermal insulation composite with low thermal conductivity and high structural strength. First, the effects of the three phases on the mechanical and thermomechanical properties of silicon rubber (SR) were analyzed using a scanning electron microscope (SEM), a thermogravimetric (TG) analyzer, a thermal conductivity meter, and a universal testing machine, respectively. Then, the thermal insulation mechanism of multiphase thermal insulation composite materials was analyzed. The results show that the thermal stability and mechanical performance of composites were significantly enhanced, particularly for sample 18H, whose Tmax and char yield reached 621.3 °C and 77.5%, respectively, representing a respective increase of 12.1 and 35.3% compared to those of pure SR. After heat treatment at 1000 °C, the linear shrinkage of the sample diameter was about 9.4%, while the thermal conductivity was as low as 0.064 W/(m·K), which was 53.2% lower than that of the pure matrix SR. We believe that this work can serve as a reference for the preparation of heat insulation and protection materials with low thermal conductivity and high structural strength.

The Mechanical Properties of Silicone Rubber Composites with Shear Thickening Fluid Microcapsules.

In this study, Sylgard 184 silicone rubber (SylSR) matrix composites with shear thickening fluid (STF) microcapsules (SylSR/STF) were fabricated. Their mechanical behaviors were characterized by dynamic thermo-mechanical analysis (DMA) and quasi-static compression. Their damping properties increased with the addition ofSTF into the SR in DMA tests and the SylSR/STF composites presented decreased stiffness and an obvious positive strain rate effect in the quasi-static compression test. Moreover, the impact resistance behavior of the SylSR/STF composites was tested by the drop hammer impact test. The addition of STF enhanced the impact protective performance of silicone rubber, and the impact resistance increased with the increase of STF content, which should be ascribed to the shear thickening and energy absorption of STF microcapsules in the composites. Meanwhile, in another matrix, hot vulcanized silicone rubber (HTVSR) with a mechanical strength higher than Sylgard 184, the impact resistance capacity of its composite with STF (HTVSR/STF) was also examined by the drop hammer impact test. It is interesting to note that the strength of the SR matrix obviously influenced the enhancement effect of STF on the impact resistance of SR. The stronger the strength of SR, the better the effect of STF on improving the impact protective performance of SR. This study not only provides a new method for packaging STF and improving the impact resistance behavior of SR, but is also beneficial for the design of STF-related protective functional materials and structures.

Synergistic flame-retardant effect of sepiolite and magnesium hydroxide/melamine/starch on the properties of silicone rubber composites

Synergistic flame-retardant effect of sepiolite and magnesium hydroxide/melamine/starch on the properties of silicone rubber composites

Preparation of branched Al2O3 and its synergistic effect with carbon nanotubes on the enhancement of thermal conductive and electrical insulation properties of silicone rubber composites

Preparation of branched Al2O3 and its synergistic effect with carbon nanotubes on the enhancement of thermal conductive and electrical insulation properties of silicone rubber composites

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

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

Role of Liquid-Phase Amount in Ceramization of Silicone Rubber Composites and Its Controlling

The reliable mechanical properties of ceramizable silicone rubber composites during pyrolysis are necessary for their application in the fire-resistant fields. The effects of liquid-phase amount on the mechanical properties of silicone rubber composites are investigated. The results show a positive correlation between the liquid-phase amount and the flexural strength of the residual products pyrolysis below 800 °C. The nano-γ-Al2O3 in the fillers reacts with liquid B2O3 to form aluminum borate above 800 °C, which consumes the liquid phase and strengthens the residual products to a certain extent. Increasing the B2O3 addition and introducing nano-γ-Al2O3 can control the liquid-phase amount in the range of 15% to 30%, which makes the composites have better residual strength and support performance. The residual strength of composites pyrolysis at 500 °C to 1000 °C is higher than 2.50 MPa, and the maximum is up to 18.7 MPa at 1000 °C.

Investigation of Ramped Compression Effect on the Dielectric Properties of Silicone Rubber Composites for the Coating of High-Voltage Insulation.

The incorporation of inorganic oxide fillers imparts superior dielectric properties in silicone rubber for high-voltage insulation. However, the dielectric characteristics are influenced by the mechanical stress. The effects of ramped compression on the dielectric properties of neat silicone rubber (NSiR), 15% SiO2 microcomposite (SSMC), 15% alumina trihydrate (ATH) microcomposite (SAMC) and 10% ATH + 2% SiO2 hybrid composite (SMNC) are presented in this study. The dielectric constant and dissipation factor were measured before and after each compression especially in the frequency range of 50 kHz to 2MHz. Before the compression, SSMC expressed the highest dielectric constant of 4.44 followed by SMNC and SAMC. After the compression cycle, SAMC expressed a better dielectric behavior exhibiting dielectric constant of 7.19 and a dissipation factor of 0.01164. Overall, SAMC expressed better dielectric response before and after compression cycle with dielectric constant and dissipation factor in admissible ranges.

Investigation on the mechanical and tribological properties of polyethylene wax/silicone rubber composites

As an auxiliary agent for rubber processing, polyethylene wax can be used to enhance the diffusion of filler in rubber, improve the extrusion speed of rubber compound and facilitate rubber demoulding, which has good development potential in the field of rubber processing and manufacturing. At present, there is no research on the optimum amount of polyethylene wax in silicone rubber. Therefore, in this paper, we studied the influence of different amount of polyethylene wax on the mechanical and friction properties of silicone rubber. Firstly, silicone rubber composites with different polyethylene wax content were prepared by mechanical mixing and hot pressing. Then, the mechanical properties and friction and wear properties of silicone rubber composites were tested by tensile testing machine and multifunctional comprehensive tester for surface properties of materials. Finally, combined with a series of characterization methods, such as three-dimensional (3D) morphology, scanning electron microscopy (SEM), microscopic observation and energy dispersive X-ray spectroscopy (EDS), the mechanism of polyethylene wax in silicone rubber was studied. The results show that the best addition amount of polyethylene wax in silicone rubber is 0.25 phr, and the friction coefficient of polyethylene wax/silicone rubber composite is the lowest and most stable, and the wear amount is the least. In the process of friction, polyethylene wax can be separated from silicone rubber matrix and distributed on the surface of wear marks, playing a better role in lubrication and wear reduction.

Synergistic effect of diatomite and intumescent flame retardant on flame retardant properties of silicone rubber composites

Synergistic effect of diatomite and intumescent flame retardant on flame retardant properties of silicone rubber composites

Enhancement of thermal and mechanical properties of silicone rubber with γ-ray irradiation-induced polysilane-modified graphene oxide/carbon nanotube hybrid fillers.

In this study, a polysilane-modified graphene oxide (GO) and carbon nanotube (CNT) nanocomposite (GO/CNTs-Si) was prepared as a thermal conductive nanofiller to enhance the thermal and mechanical properties of silicone rubber composites. By γ-ray-radiation 3-methacryloxypropyltrimethoxy silane (MPTMS) was polymerized on the surface of GO and CNTs to improve the interfacial interaction between the GO/CNTs-Si and SR matrix. FTIR characterization results demonstrated that polysilane modified the GO/CNTs successfully. The pristine GO/CNTs and resultant GO/CNTs-Si were individually incorporated into α,ω-dihydroxypolydimethylsiloxane to vulcanize SR composites. Compared with SR–GO/CNTs, SR–GO/CNT-Si exhibited better mechanical and thermal performance. Moreover, the time-dependent complex modulus of SR–GO/CNTs-Si was much higher than that of SR–GO/CNTs, which indicates longer service time and more stable performance. In terms of electronic packaging, SR–GO/CNTs exhibited better performance than the 1180B counterpart. The low value of warpage of chip packaged by SR–GO/CNTs implied that SR–GO/CNTs-Si could have potential application as the thermal interface electronic packaging material.

Effect of hollow glass beads on density and mechanical properties of silicone rubber composites

AbstractIn this work, low density hollow glass beads (HGB)/silicon rubber (SR) composites were prepared by solution method and flocculation process. The prepared samples were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, tensile test, and friction test. The results show that the densities of SR composites decrease from 1.140 to 0.792 g/cm3 with the addition of HGB. By comparing theoretical density with true density, it can be estimated that the ratio of shattered HGB increase from 8.79% to 24.76%. Especially, the mechanical properties of SR composites were improved by surface modification of HGB. By adding surface‐modified HGB at 5 and 10 wt%, the tensile strengths of SR composites were enhanced by 17.8% and 28.2%, respectively. In addition, tear strength, shore A hardness, compression set, and friction property were significantly ameliorated. Furthermore, the mechanism of surface‐modified HGB in mechanical properties was analyzed.

Stretchable conductor based on carbon nanotube/carbon black silicone rubber nanocomposites with highly mechanical, electrical properties and strain sensitivity

Stretchable conductive polymer composites are important in the field of flexible electronic devices, in which stretchable conductive silicone rubber composites has drawn great attention. However, the poor mechanical properties of the SR composites limit their practical application. How to compensate this drawback without compromising its electrical conductivity is an issue deserved to investigate. Herein, conductive carbon black grafted with a silicone coupling agent was prepared by free radical polymerization, and further reacted with carbon nanotube to obtain a new carbon black-carbon nanotube hybrid filler. This hybrid filler can not only improve the mechanical properties of silicone rubber composites, but also greatly enhance their electrical conductivity. Consequently, a silicone rubber composite with 5.76 vol% hybrid filler has high tensile strength (4.5 MPa) and elongation at break (211%). The minimum conductive percolation threshold and maximum conductivity of the composite are 0.24 vol% and 248.8 S/m, respectively. Besides, the composite has high strain sensitivity and superior deformation recovery performance, and can be applied to detect human motion behavior under a low strain. The preparation method of the hybrid filler provides a novel approach to the preparation and production of stretchable conductive composites with good mechanical properties and potential application for flexible electronic devices.