Vinyl Silicone Research Articles

Effect and mechanism of phenyl content on the electrical insulation properties of silicone rubber

AbstractSilicone rubber is widely used in reinforced insulation of cable accessories due to its good electrical insulation and weather resistance. With the continuous improvement of high voltage transmission grade, higher requirements are put forward for the electrical insulation performance. The effect and mechanism of phenyl content on the electrical insulation properties of silicone rubber are investigated by the method of combination of experiments and molecular simulations. The experimental results show that the properties of silicone rubber are improved with the increase of phenyl content. Among them, the silicone rubber composite with phenyl content of 20 wt% has the best comprehensive performance. Compared with vinyl silicone rubber, the dielectric constant at 50 Hz decreases from 3.50 to 2.95, and the breakdown strength increases by 38.03%, from 56.59 to 78.11 kV/mm. In addition, the tensile strength and elongation at break are 5.44 MPa and 456%, respectively. The molecular simulation results show that with the increase of phenyl content, the glass transition temperature increases, the mean square displacement decreases, and the free volume decreases, which macroscopically leads to the change of electrical properties of the silicone rubber material. This work has a certain guiding significance for improving the electrical properties of silicone rubber for cable accessories.

Improving the ablative properties of silicone rubber by adding aluminum foil/expanded perlite

In this study, aluminum foil (AF) and expanded perlite (EP) were used as the reinforcing fillers to improve the ablation properties of phenyl methyl vinyl silicone rubber composites. The expansion and caramelization of char layer enhanced the ablation and thermal insulation performance of silicone rubber-based composites. The improved bonding of char layer provided a good basis for enhancing ablative properties. The presence of EP increased the emissivity of the char layer which improved the heat radiation properties during ablation process, and it was advantageous to lower surface temperature and reduce thermal erosion. The graphitic degree of char layer was increased which improved high-temperature and oxidative resistance. SEM observations revealed that the surface and cross-section of the char layer were densified, as characterized by the pore size distribution analysis. The above results indicated that the ablation and anti-erosion resistance as well as thermal insulation behavior of silicone rubbers were significantly improved by implementing the expansion and caramelization strategy, which exhibit promising applications as flexible anti-ablation materials for thermal protection purposes.

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.

Improvement of shoulder peak effect in graphene/silicone rubber strain sensors by nanosilica

Conducting polymer composites (CPCs) typically exhibit shoulder peak phenomena in their resistive response signals, which greatly limits their practical application as strain sensors in the field of vibration damping. In this paper, nanosilica (SiO2) nanoparticles were incorporated into graphene (GR)/methyl vinyl silicone rubber (VMQ) composites to obtain the optimum content of SiO2 to eliminate the shoulder peak phenomenon. The results showed that the shoulder peak phenomenon of the resistance response signal of the composites disappeared after the addition of 30 % SiO2, which explained the mechanism of eliminating the shoulder peak phenomenon. Meanwhile, the tensile strength and Young's modulus of the composites were improved, and excellent resistance-strain response properties were obtained, including a wide sensing range (＞200 %), high sensitivity (GF = 839.02), fast response time (37 ms), and good durability and stability (9000 cycles at 50 % strain). It shows that the strain sensor has great potential for health monitoring in the field of vibration damping.

Silicone elastomer dielectric composites by introducing novel O-MMT@TiO2 nanoparticles for energy harvesting application

Dielectric elastomers have attracted attention in emerging advanced electromechanical applications. However, how to simultaneously improve the dielectric constant and the breakdown strength of dielectric composite needs to be solved. In this paper, we propose a new strategy to anchor TiO2 nanoparticles onto organically modified montmorillonite (O-MMT) nanoplatelets through dehydration reaction to synthesize a novel filler O-MMT@TiO2. Then, the O-MMT@TiO2 is incorporated into methyl vinyl silicone rubber (MVSR) matrix to obtain O-MMT@TiO2/MVSR dielectric composites. Comparing with the composites by direct mixing of TiO2 and O-MMT in MVSR (O-MMT/TiO2/MVSR), O-MMT@TiO2/MVSR composites significantly increase mechanical and dielectric and energy storage properties. 30 wt% O-MMT@TiO2/MVSR composite achieves the highest energy storage density of 118.65 kJ/m3, which is 142.9 % higher than that of 15 wt%O-MMT/15 wt%TiO2/MVSR (48.84 kJ/m3). This study offers an effective method for the preparation of high-performance dielectric elastomer materials, which can be exploited for the energy harvesting application.

Enhancement of the Electric-Force Response of Carbon Black/Silicone Rubber Composites by Silane Coupling Agents.

Flexible strain sensors have a wide range of applications in the field of health monitoring of seismic isolation bearings. However, the nonmonotonic response with shoulder peaks limits their application in practical engineering. Here we eliminate the shoulder peak phenomenon during the resistive-strain response by adjusting the dispersion of conductive nanofillers. In this paper, carbon black (CB)/methyl vinyl silicone rubber (VMQ) composites were modified by adding a silane coupling agent (KH550). The results show that the addition of KH550 eliminates the shoulder peak phenomenon in the resistive response signal of the composites. The reason for the disappearance of the shoulder peak phenomenon was explained, and at the same time, the mechanical properties of the composites were enhanced, the percolation threshold was reduced, and they had excellent strain-sensing properties. It also exhibited excellent stability and repeatability during 18,000 cycles of loading-unloading. The resistance-strain response mechanism was explained by the tunneling effect theoretical model analysis. It was shown that the sensor has a promising application in the health monitoring of seismic isolation bearings.

Improvement of heat resistance in silicone rubber by Fe-doped TiO2 nanoparticles prepared via flame spray pyrolysis

In recent years, the development of heat-resistant silicone rubber has been a research hotspot. In this paper, a kind of Fe doped TiO2 nanoparticles (Fe-TiO2) was prepared via flame spray pyrolysis, which can significantly improve the high temperature resistance of silicone rubber. The results show that, on the one hand, the prepared Fe-TiO2 can inhibit the breakage of Si-O main chain; on the other hand, because Fe is doped into the lattice of TiO2, it causes the change of TiO2 crystal phase and produces more oxygen vacancies, which is more beneficial to capture free radicals in silicone rubber matrix, so that Fe-TiO2 can effectively inhibit the excessive cross-linking of silicone chain caused by methyl oxidation on the side of silicone rubber. TGA results showed that after adding Fe-TiO2, the 5 % thermal weight loss temperature of methyl vinyl silicone rubber increased from 392.8 °C to 435.6 °C.

Fluorination Modification of Methyl Vinyl Silicone Rubber and Its Compatibilization Effect on Fluorine/Silicone Rubber Composites.

Among numerous rubbers, high-performance rubber composites can be obtained by mixing fluororubber (FKM) with excellent oil resistance and silicone rubber (SiR) with excellent low-temperature resistance. While the difference in polarity between these two kinds of rubbers leads to a reduction in the properties of the composites. To solve the compatibility problem between the two-phase interfaces in FKM/SiR composites, in this research, fluorinated silicone rubbers (MVQ-g-PFDT) of methyl vinyl silicone rubber (MVQ) grafted with 1H,1H,2H,2H-perfluorodecanethiol (PFDT) were prepared via a facile and efficient thiol-ene click reaction, which was then added into FKM/SiR composites. The results showed that the fluorine-containing side chains could effectively inhibit the low-temperature crystallization phenomenon of silicone rubber and further broaden its application ranges in low-temperature environments. The properties of FKM/SiR composites with the addition of MVQ-g-PFDT were significantly improved, with the highest tensile strength of 14.1 MPa and the lowest mass change rate of 6.71% after 48h immersion at 200 °C in IRM903 oil. Additionally, the hydroxyl groups between the fluorine-containing side chains of MVQ-g-PFDT and the surface of silica facilitate the enhancement of the uniform dispersion of fillers. Atomic force microscopy (AFM) characterization results showed a distinct enhancement of the compatibility between the two phases of FKM and SiR. This work would provide further insight into efforts to improve compatibility between rubbers with widely different polarities.

Preparation and application research of composites with low vacuum outgassing and excellent electromagnetic sealing performance

Abstract Electromagnetic interference (EMI) shielding rubber effectively fills gaps in electronic devices to prevent electromagnetic (EM) leakage. However, research on the potential application of EMI shielding rubber in the field of space is limited. This study explores the optimal amount of silver-coated aluminum powder (SCA) in SCA/ methyl vinyl silicone rubber (MVQ) composites to balance the electrical and mechanical properties of EMI shielding rubber. The EMI shielding effectiveness (SE) of 41.8 vol% SCA/MVQ composite exceeded 90 dB in the frequency range between 100 and 1,200 MHz with a compression set of only 14%. To address the outgassing characteristics of silicone rubber in a vacuum environment, both pre-heating and post-heating treatments for reducing rubber volatility are explored, proving that silicone rubber followed by 4 h of post-heating treatment at 200°C, is an appropriate solution to reduce silicone rubber volatility, leading to the SCA/MVQ composite with a total mass loss of only 0.2%, and a collected volatile condensable material of only 0.02%. In addition, high reliability is crucial for EMI shielding materials. SCA/MVQ composite exhibits excellent adaptability to vacuum temperature cycles, with the EMI SE maintained at 90 dB after cycles. At room temperature, after 30 days of storage, the EMI SE of the composite remains at 90 dB. These findings indicate that SCA/MVQ composites exhibit broad potential applications in the field of EM sealing for aerospace electronic devices.

Improving the stability of multiwalled carbon nanotube/silicone rubber composites strain sensors by nanosilica

AbstractConductive polymer composites use elastomers as a matrix for strain sensors. However, elastic polymer composites usually exhibit shoulder peak effects in their resistance response signals, limiting their applicability as strain sensors. In this study, we modified multiwalled carbon nanotubes (MWCNTs)/methyl vinyl silicone rubber (VMQ) by incorporating nanosilica (NSD) to eliminate the shoulder peak effect. The results showed that the addition of a suitable amount of NSD can improve the reconstruction of the conductive network of composite material and eliminated the shoulder peak effect of the composite material in the resistive response signal. The mechanism of eliminating the shoulder peak effect was elucidated, while the mechanical properties of the composite material were improved, which endowed the composite material with excellent strain sensing properties, including sensitivity (GF = 127) and response time (270 ms), and maintained excellent stability and recovery even in 15,000 cycles. These findings highlight the potential of our strain sensor for the real‐time strain monitoring of large‐deformation isolation bearings.Highlights NSD eliminates shoulder peak effect in MWCNT/VMQ composites. Explained the shoulder peak effect elimination mechanism. NSD enhanced mechanical properties of MWCNT/VMQ composites. MWCNT‐NSD20/VMQ composites have stable resistive strain response properties.

Improving the ablative performance of epoxy‐modified vinyl silicone rubber composites by incorporating different types of reinforcing fibers

AbstractIn this study, ablative resistance of single fiber‐ and hybrid fiber‐reinforced epoxy‐modified vinyl silicone rubber (EMVSR) composites was systematically studied. Three types of fibers, namely aramid fiber (AF), basalt fiber (BF), and carbon fiber (CF), were employed as the reinforcements. The results indicated that the incorporation of fiber reinforcements effectively suppressed the expansion and strengthened the char layer. Besides, the quality of char layer was quite different when different types of fibers were used. The char layer of AF‐modified samples had more surface defects, BF‐modified samples were brittle, and CF‐filled samples were dense and flat. The use of hybrid AF/BF fibers improved the ablation and anti‐erosion performance of EMVSR. Meanwhile, the thermal insulation performance was enhanced because the back‐face temperature was the lowest with the addition of 1 phr AF and 5 phr CF. The above results indicated that the ablation and anti‐erosion resistance and the quality of char layer as well as the thermal insulation behavior of EMVSR were significantly improved by incorporating fibrillar fillers, which demonstrate practical applications as flexible anti‐ablation materials for thermal protection systems.Highlights Epoxy‐modified vinyl silicone rubber was used for preparing ablative composites. The effect of adding different fibers on the ablation properties was studied. The presence of single fibers improved the strength of char layer. The use of hybrid fibers was found effective in enhancing the ablative properties. The intrinsic property and entanglement of fibers affected the ablative properties.

Marginal fit of 3D printed interim crowns fabricated with intraoral scanners over conventional and reverse-tapered preparations

Background/Aim: 3D printing technology has become increasingly prevalent in the field of dentistry. Research is ongoing regarding the usability of resin-based 3D printed temporary crowns in clinical applications. Marginal fit of 3D printed interim restorations produced from digital impressions obtained with intraoral scanners may vary according to the geometry and inclination of the axial walls of the abutment tooth. The purpose of this in vitro study was to evaluate the marginal fit of 3D printed interim crowns fabricated over conventional and reverse-tapered preparations. Material and Methods: Crown preparations with known total occlusal convergence (TOC) angles (-8°,-4°, 0°, 8°, 12°, 16°, and 22°) were digitally created from a maxillary central incisor and printed in acrylic resin. Then, prepared tooth models (n=7) were scanned 10 times with an intraoral scanner (TRIOS3, 3Shape Inc, Denmark). Each experimental scan was used to design and fabricate a 3D printed interim anatomically contoured crown. Vinyl polyether silicone was used three times to assess the marginal discrepancy of the specimens by measuring five marginal points on digital photographs for each surfaces (buccal, mesial, distal, lingual). Marginal fit measured values did not follow a normal distribution; therefore, the Kruskal-Wallis and the Dunn/Bonferroni multiple comparison tests were applied (p = 0.05). Results: Marginal gap values were found significantly higher (p<0.05) in crowns produced for specimens with-8 and-4 degrees axial wall than other specimens. Conclusions: Negative inclination of the axial walls adversely affects the marginal fit of crowns produced with 3D printing technology.

A stable amphiphilic hybrid nanoparticle compatibilizer constructed from polyhedral oligomeric silsesquioxane (POSS) for immiscible thermoplastic polyurethane/methyl vinyl silicone elastomer (TPU/MVQ) blends

A series of amphiphilic hybrid POSS particles grafted with PDMS chains and PU analogue chains (PUA-POSS-PDMS) were prepared by a grafting-from method, and can be used as compatibilizers for TPU/MVQ blends.

Molecular dynamics simulation and experimental verification of the effects of vinyl silicone oil viscosity on the mechanical properties of silicone rubber foam.

The molecular motion trajectories of silicone rubber foam (SRF) at various vinyl silicone oil viscosities were studied via molecular dynamics (MD) simulation from the perspective of all atomic molecules. The influence of different viscosities of vinyl silicone oil on interaction, compatibility, and aggregation degree of molecules was determined based on the mean square displacement, diffusion coefficient, binding energy, solubility parameter, radial distribution function, and radius of gyration. The mechanical properties of the SRF were also experimentally verified. Results revealed that as the viscosity of vinyl silicone oil increased, the mean square displacement, fractional free volume, diffusion coefficient, and solubility parameter of the system decreased, whereas its larger radius of gyration increased. Moreover, the radial distribution function showed a weaker relative interaction between molecular chains. The calculated binding energy demonstrated that the system had better compatibility at a viscosity of 0.45 Pa s. This study provided a deeper insight into the relation between the viscosity of vinyl silicone oil and mechanical properties of the SRF. As the viscosity of vinyl silicone oil increased, the changing trend in MD simulation results of elastic modulus, shear modulus, bulk modulus, and Poisson's ratio was consistent with the experimental results. The MD simulations can promote theoretical predictions and scientific basis for the design of the SRF with desired performances.

Super-tough poly(lactic acid)/silicone rubber thermoplastic vulcanizates: The organic and inorganic synergistic interfacial compatibilization

Polymer modification using silicone rubber represents a promising avenue for enhancing physico-mechanical properties. However, achieving optimal performance through direct blending is hindered by the poor interface compatibility between silicone rubber and the matrix. In this study, we prepared super-tough thermoplastic vulcanizates (TPVs) of polylactic acid/silicone rubber through dynamic vulcanization with PLA, methyl vinyl silicone rubber (MVQ), glycidyl methacrylate grafted MVQ (MVQ-g-GMA), and fumed silica nanoparticles (SiO2). The impact of the SiO2 addition in MVQ on the morphology, mechanical properties, crystallization, and thermal properties of the TPVs was investigated. The results showed that MVQ-g-GMA and SiO2 exhibited a synergistic compatibilization effect significantly improving the interfacial adhesion between PLA and MVQ. Therefore, the impact and tensile strength of the TPVs increased from 8.0 kJ/m2 and 22.2 MPa to 62.6 kJ/m2 and 36.7 MPa, respectively. Moreover, the TPVs also presented good low-temperature toughness with a maximum impact strength of 40.4 kJ/m2 at −20 °C. Additionally, improvements in thermal stability and crystallization rate were also observed. Overall, combining organic and inorganic synergistic compatibilization is a feasible and effective method to fabricate outstanding low-temperature toughness to PLA.

Effect of adding (ZrO2-ZnO) nanopowder on the polymer blend (lamination and methyl vinyl silicone) in a hybrid nanocomposite material

A polymeric blend combines two or more polymers to form a new material with different physical properties. In this work, a base material consisting of a polymeric mixture was manufactured to improve its properties and then strengthened with nanoparticles (ZrO2-ZnO) to develop a hybrid nanocomposite material, which has better properties than its constituent materials. Reinforcement material, i.e., (ZrO2-ZnO) nanoparticles, were prepared using relaxation method. A polymeric resin mixture (lamination and methyl vinyl silicone) was prepared by adding methyl vinyl silicone to the lamination resin in different ratios (4 %, 8 %, 12 %, and 16 %). The mixture properties were studied through tensile, bending, shock, and hardness tests, and the optimal results were achieved for the 12 % ratio. The resulting composite nanoparticles and their properties were studied using EDX, X-Ray, SEM, and PSA techniques. Finally, the nano-hybrid composite material was manufactured by choosing the optimal blend (i.e., 12 %). It had the highest polymeric base material properties, and nanoparticles were added at different dosages (3 %, 6 %, 9 %, and 12 %). The resulting hybrid composite material properties were studied through different tests (tensile, flexural, impact, and hardness). The results showed that the binary composite nanoparticles improved the properties of the mixture for both sizes (30 nm and 89 nm) at all mixing ratios, compared to the control specimens (i.e., without any addition). The optimal results were obtained when 30 nm particles were added and for all tests compared to samples reinforced with 89 nm particles. The optimal ratio of (ZrO2-ZnO) was 9 % wt 30 nm size, representing the best sample in terms of the resulting properties. It is recommended to use the sample with the 9 % addition of (ZrO2 - ZnO) wt with a granular size of (30 nm) in essential applications, including prosthetics (foot).

Foaming behavior regulation of silicone rubber via evolution of crosslinked structure

The cellular structure and foam density of silicone rubber foam are known to be influenced by its rheological behavior, which could be adjusted by crosslinked density and crosslinked structure. However, the effect of the crosslinked structure evolution in methyl vinyl silicone rubber (MVQ) on the supercritical foaming behavior has never been investigated. In this research, the crosslinked density and T2 relaxation time of MVQ were charactered by low-field nuclear magnetic resonance (LF-NMR), which revealed the evolution of crosslinked structures and change of the crosslinked density under different vinyl group contents and pre-cure time in MVQ. In addition, a processing strategy which utilized conjunctively crosslinked structure and crosslinked density of MVQ was used to design the cellular structure and prepare low density foam. The resulting MVQ foam had an adjustable density range from 1.12 g/cm3 to 0.08 g/cm3 and different cellular structures. In this study, the effective control of foaming behavior was realized by manipulating the crosslinked density and crosslinked structure, and this approach would pave a new possibility to obtain desired cellular structures.

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.

Optical Properties of PVA Silicon Carbide Nano Composites Films Synthesized Via Laser Ablation

Background: Enhancing the optical characteristics of nano-silicon carbide and polyvinyl alcohol films is thought to be crucial for obtaining the semiconductor with the lowest energy gap for applications in electrical devices, digital displays, and sensors.
 Materials and Methods: Poly vinyl alcohol and silicon carbide's optical properties were examined. A pulsed laser with a 532 nm wavelength is used to create these nanoparticles into widespread nanoparticles in two environments (water and vinyl alcohol). Polyvinyl alcohol nanocomposite was created by spin coating silicon carbide particles with the weight fractions 0.90%, 0.91%, 0.93%, and 0.95%. Fourier spectroscopy was used to locate the functional groups based. Techniques FESEM were used to analyze the surface composition and nanoparticle dispersion on the membrane-surface of the nanocomposite. using spectroscopy UV-Vis used to record the absorbance spectrum in the range of (200-800) nm for ultraviolet radiation.
 Results: The direct energy gap (5.585, 5.310, 5.480, 4.986, 4.800) eV and the indirect (5.006, 4.880, 4.916, 4.683, 4.490) eV and Urbach energy (2.38, 2.45, 2.94, 2.74, 3.67) eV were calculated.for the samples by ratio, as shown in Table No. 1.
 Conclusion: By investigating the optical characteristics of nanoparticles, such as their extinction and absorption coefficients, direct and indirect optical energy gaps, and Urbach energies .increase in extinction and absorption coefficients Urbach energy when adding nano carbide to polyvinyl alcohol, results show narrowing of the direct and indirect energy gaps. This suggests that the nanocomposite's optical characteristics have improved.

UV-curable silicone pressure-sensitive adhesive based on thiol-ene reaction

In order to improve the curing efficiency and reduce energy consumption of silicone pressure-sensitive adhesive (SiPSA), a kind of UV-curable SiPSA based on thiol-ene reaction was prepared with methyl vinyl MQ resin as hard segment, methyl vinyl silicone rubber (110-2S) as soft segment and mercaptyl silicone oil as cross-linker. The UV-cured SiPSA exhibited excellent thermal stability and water resistance. Its physical features such as chemical composition, cross-linking extent and dispersion of MQ resin in silicone rubber were directly related to the vinyl content in MQ resin, the thiol/ene ratio and the resin/rubber ratio, which further affected mechanical properties and adhesive properties of SiPSA. With the vinyl content in MQ resin of 56 mmol/100 g, the thiol/ene molar ratio of 0.8 and the resin/rubber mass ratio of 1.4, the UV-cured SiPSA-B1.4–0.8 had better mechanical properties, moreover it had higher tensile shear strength of >2.0 MPa and showed interface failure on the surface of substrates, indicating that it had great potential applications as PSA.