Phenyl Silicone Rubber Research Articles

Enhancing the damping and mechanical properties of phenyl silicone rubber by introducing phenyl MQ silicone resins as molecular fillers

Silicone rubber features excellent thermal stability, outstanding low-temperature performance, and superb processability, however, the poor damping property and low mechanical strength limit its applications. In this work, we synthesized two types of phenyl MQ resins as molecular fillers and incorporated them into phenyl silicone rubber to prepare damping composites. The effects of both the phenyl MQ resin structures and contents on the damping properties and mechanical performances were investigated. The results showed that phenyl MQ resins exhibit multiscale damping effects with temperature rising, and phenyl MQ resins are distributed in silicone rubber with a "sea-island" structure, which strengthen the mechanical property. The composite exhibit optimal performance with incorporating 30phr diphenyl MQ resins: the damping factor at 150 °C increased from 0.1 to 0.18, the temperature range for tan δ > 0.3 expanded by 115.2 %, and maintained a tensile strength of 6.3 MPa. This study paves a new path to design and prepare silicone rubber composite that balance high damping performances with better mechanical strength.

Synthesis, characterization and properties of vinyl-terminated poly[dimethylsiloxane-co-methyl(phenyl)siloxane]

Phenyl-containing polysiloxanes have better thermal stability, low-temperature flexibility, and room-temperature damping performance than polydimethylsiloxanes. Poly [dimethylsiloxane-co-methyl (phenyl)siloxane] and poly (dimethylsiloxane-co-diphenylsiloxane) were synthesized through a bulk copolymerization of octamethylcyclotetrasiloxane and methylphenylcyclosiloxane mixture or octaphenylcyclotetrasiloxane, and the structure and properties of the copolysiloxanes were comparatively studied. The phenyl content in poly [dimethylsiloxane-co-methyl (phenyl)siloxane] can be as high as 50 mol%. With the increment of the phenyl content, the thermal stability of the copolysiloxanes is dramatically improved as evaluated by thermal gravimetric analysis. At a given phenyl content, poly [dimethylsiloxane-co-methyl (phenyl)siloxane] has higher thermal stability than poly (dimethylsiloxane-co-diphenylsiloxane). The former is more difficult to crystalline at low temperatures and has lower room temperature viscosity than the latter as confirmed by differential scanning calorimetry and rotational rheometer. The copolysiloxanes is mixed with hydrogen-containing polysiloxane and silica, and vulcanized at elevated temperature to get copolysiloxane composites with good damping properties, oil resistance, and low-temperature resistance. This study not only enriches the fundamental academic research on functional polysiloxanes, but also provides useful technical references for practical applications of phenyl silicone rubber.

개질된 Nanographene Oxide기반의 실리콘 고무 복합체의 기계적 물성 및 Swelling 거동 연구

Nanocomposites were created by using nanographene oxide (GO) as a reinforcing filler into silicone rubber and evaluating the materials’ mechanical and abrasion resistance properties. GO was treated with 4,4’-diphenylmethane diisocyanate (MDI), then mixed with phenyl silicone rubber (PSR) at different concentrations (2-10 phr) and vulcanised. It was investigated the impact of MDI modified GO concentration on the morphology of PSR nanocomposites. The swelling properties of silicone rubber/MDI modified GO nanocomposites were also investigated in relation to penetrants (aromatic, aliphatic, and chlorinated solvents) and nanofiller concentrations (0-10 phr). Due to greater dispersion and reinforcing impact, mechanical parameters (tensile strength and modulus), and swelling resistance of silicone nanocomposites improve with MDI-GO concentration. The rate of rise is constant up to a concentration of 6 phr MDI-GO, after which it drops, confirming the formation of agglomeration. The MDI modification of GO improves the dispersion of MDI-GO in silicone rubber considerably, according to FESEM analysis. Because of its strong contact with the polymer matrix, GO serves as reinforcement. This research expands the range of applications for GO in the silicone rubber sector.

Impact of Raw Phenyl Silicone Rubber Parameters on ethod Vulcanized Phenyl Silicone Rubber

Based on the structure of raw phenyl silicone rubber and performance of vulcanized rubber, the properties of raw and vulcanized phenyl silicone rubber are tested in this study. The relationship between raw rubber parameters and the influence of raw rubber properties on the performance of vulcanized rubber are also analyzed. Conclusions are as follows: (1) The viscosity average molecular weight of the raw silicone rubber measured by Ubbelohde viscometer and gel permeation chromatography (GPC) mdiffers relatively greatly, with the result of Ubbelohde viscometer higher than that of GPC. (2) The glass transition temperature of raw silicone rubber is significantly affected by the molar content of phenyl chain (phenyl content) in its structure. In a good linear relationship with phenyl content, it increases as the phenyl content increases. (3) The static glass transition temperature of raw rubber measured by differential scanning calorimetry (DSC) is 0-15 °C lower than the dynamic glass transition temperature measured by dynamic thermo-mechanical analyzer (DMA). (4) Mooney viscosity increases with the increase of the viscosity average molecular weight of raw rubber. (5) As phenyl content rises from 20 % to 40 %, the damping peak loss factor of vulcanized rubber increases from 0.4 to 0.7 and the damping peak temperature increases from -90 °C to -40 °C. (6) As the molar content of vinyl chain (vinyl content) is raised from 0.1 % to 0.6 %, the hardness of vulcanized rubber is boosted from 45 to 65, and the tensile strength decreases from 12 MPa to 6 MPa. (7) With the increase of vinyl content from 0.1 % to 0.4 %, the tear strength of vulcanized rubber decreases from 45 kN/m to 25 kN/m. (8) The vinyl content has an obvious impact on the damping performance of vulcanized rubber at high temperatures. When vinyl content increases from 0.1 % to 0.5 %, the damping property of the vulcanized rubber under high temperature drops from 0.25 to 0.1. (9) The compression set of vulcanized rubber decreases with the increase of vinyl content of raw rubber.

Progress in the Preparation and Application of Arylsilane

Abstract: Arylsilanes are the basic raw material for the synthesis of advanced silicone new materials such as phenylsilicone resin, phenylsilicone oil and phenyl silicone rubber, etc. The silicone polymers containing aryl groups were applied widely in the fields including electronics, and aerospace. In the past decades, arylsilanes have been widely used in organic synthesis, such as Hiyama coupling, C-N bond formation, synthesis of biaryl, polyketone polymer, and so on. Therefore, synthetic research on arylsilanes has also received wide attention. In this paper, the research progress of the synthesis and applications of arylsilanes in the past decades has been reviewed.

Structural analyses of the bound rubber in silica-filled silicone rubber nanocomposites reveal mechanisms of filler-rubber interaction

Although the reinforcing effect of fumed silica on silicone rubber is always better than that of precipitated silica, their enhancement mechanism is still controversial due to the cognitive defects of the interface effect and filler network effect of polymer nanocomposites with the limited experimental study. Herein, significant entanglement network structure differences were revealed in the fumed and precipitated silica-filled phenyl silicone rubber by removing the physisorbed rubber gradually via 90 °C-ultrasonic solvent extraction method, which eventually obtained tightly bound rubber to explain filler-rubber interaction. The silica wrapped by tightly bound rubber was observed by SEM and TEM, where fumed silica is entangled with tightly bound rubber to robust dendritic structure, while precipitated silica is entangled with tightly bound rubber to the irregular agglomerate structure. Low-field 1H NMR confirmed that the mobility of the tightly bound rubber was significantly lower than loosely bound and free rubber. Furthermore, during the US treatment, the Si–O–Si infrared peaks of fumed silica-filled rubber exhibited "blueshift-redshift-blueshift" while the precipitated silica one only "blueshift" appears, which directly confirmed that different nanoporous structures of nanofiller induced diversity of filler-rubber entanglement network. The tightly bound rubber of precipitated silica (16.71%) was much more than that of fumed silica (3.72%) (40 phr). Although fumed silica adsorbs less tightly bound rubber than precipitated silica, the prominent nanofiller networks formed by fumed silica-rubber greatly enhanced the Payne effect and damping properties. This work can help to deeper understand the formation of the filler-rubber entanglement network and its contribution to the physical properties.

Influence of Curing Agent Amount on Properties of Dynamic Vulcanized Phenyl Silicone Rubber-SEBS-SBS System.

In this paper, we prepared a new type of thermoplastic vulcanizate (TPV) by melt blending methyl vinyl phenyl silicone rubber (PSR), styrene butylene copolymer (SBS), and hydrogenated SBS (SEBS) and then dynamically vulcanizing it. At the same time, we studied the influence of the content of the vulcanizing agent on the properties. The corresponding backscattered electron images were obtained by a scanning electron microscope (SEM) test of each group of samples, as well as the distribution of the PSR phase and the SEBS-SBS phase, and the vulcanization process of the samples with a vulcanizing agent content of 1 phr were characterized. According to the imaging principle of the backscattered electron signal, we found that the atomic number contrast can be clearly reflected in the backscattered image. From the obtained images, we found that PSR is a dispersed phase, while SEBS and SBS are continuous phases, that is, they had a "Sea-Island" structure. In the first 30 s of the vulcanization reaction, the "Sea-Island" structure is formed, and then the vulcanization reaction rate gradually slows down. We then printed the images and analyzed them using a colorimeter and found that it was feasible to quantitatively characterize the size of the compatible layer between the continuous and dispersed phases. According to the quantitative characterization results, we found that the silane coupling agent KH-172 can increase the thickness of the compatible layer by nearly 35%. In addition, we also tested the mechanical properties and low-temperature elastic properties of the material. Finally, we found that when the content of the vulcanizing agent was 1 phr, the elastic properties and tensile properties were the best, and when the content of the vulcanizing agent was more than 1 phr, the tensile and elastic properties of the material decreased significantly. At the same time, we also found that the addition of the silane coupling agent KH-172 can also significantly improve the tensile properties and elastic properties of TPV, which we believe is related to the increase in the thickness of the compatible layer. The test results of dynamic mechanics show that PSR has good compatibility with SEBS-SBS. When the vulcanizing agent content is less than or equal to 1 phr, the material exhibits good low-temperature resistance. In addition, through the test of the melt index of each group, it was also found that the addition of the vulcanizing agent will affect the fluidity of the melt to a certain extent. When the content of the vulcanizing agent is greater than 1 phr, the melt fluidity decreases more obviously.

Optimization of silicone rubber materials for high voltage switchgear and study on characteristic gas of thermal decomposition

In this paper, three kinds of silicone rubber materials, methyl silicone rubber, phenyl silicone rubber and fluorosilicone rubber, are used as the research object, contact angle tester, thermal conductivity tester, insulation resistance tester, differential scanning calorimeter and thermogravimetric analyzer to explore the effect of side groups on the properties of silicone rubber. The results show that the thermal conductivity of three kinds of silicone rubber materials is poor, but they all have good hydrophobicity, insulation and thermal stability. Among them, phenyl silicone rubber shows better hydrophobicity and thermal stability. In addition, the type and relative content of characteristic gases of thermal decomposition of silicone rubber materials at different temperatures are analyzed in detail by gas chromatography mass spectrometer. The results show that C6H18O3Si3 and C8H24O4Si4 are the common characteristic gases of thermal decomposition of three kinds of silicone rubber.

Enhancing the thermal stability and mechanical properties of phenyl silicone rubbers by controlling BN addition and phenyl content

Silicone rubber matrix composites with high thermal stability and flexibility are widely used in electronics and aerospace industries. In this work, boron nitride (BN) was added into the phenyl silicone rubber matrix as the reinforcement, and the influence of both the BN content and phenyl content on the thermal stability and mechanical properties of as-prepared composites was studied. The results showed that the thermal stability and mechanical properties were efficiently enhanced by BN addition, regardless of the phenyl content in the matrix. When the filler content was fixed at 40 wt%, the composite with 20 mol% phenyl showed the highest initial decomposition temperature (T5%) of 454 °C and good flexibility (tensile strength, elongation at break and hardness reached 3.10 MPa, 145% and 56 A). However, the decomposition temperature of 30% weight loss, mass retention rate at 800 °C and mechanical properties were improved for the composite with 50 mol% phenyl. The enhancement in thermal stability and mechanical properties was ascribed to the coupled effects of the interfacial force between the matrix and BN particles as well as the pores inside the composite, which was verified by Fourier transform infrared spectroscopy and scanning electron microscopy.

Effects of scCO2 foaming process and post‐vulcanization method on cellular structure, mechanical properties, and thermal stability of PMVQ foams

AbstractIn this paper, the microcellular foam materials of methyl vinyl phenyl silicone rubber (PVMQ) were prepared by supercritical foaming technology (SFT) and high temperature compression molding. The effect of supercritical carbon dioxide (scCO2) on the vulcanizing properties of PVMQ composite was investigated because vulcanization of microcellular PVMQ foams played an important role on the cellular structure and mechanical properties. It was found that the sulfurization reaction of PVMQ composite was inhibited by scCO2, which led to reduction of apparent activation energy (Ea) of PVMQ composite. Compared with the existing post‐vulcanization process, the introduction of the high temperature molding can effectively improve the degree of vulcanization of microcellular PVMQ foams, which can solve the problem that the cellular structure will be destroyed during the application of external force. What's more, the mechanical properties of microcellular PVMQ foam were obviously improved. The maximum value of tensile strength and the compressive strength of microcellular PVMQ foam with the high temperature molding respectively increase by 34.7% and 133.3% compared with that of microcellular PVMQ foams with existing post‐vulcanization.

The microwave-absorption properties and mechanism of phenyl silicone rubber/CIPs/graphene composites after thermal-aging in an elevated temperature

Recently, the application and development of flexible microwave-absorption composites based on silicone rubber have gradually become a research hot spot. In this study, methyl vinyl phenyl silicone rubber (MPVQ)/carbonyl iron particles (CIPs)/graphene (GR) composites were prepared by mechanical blending, and the effects of thermal-ageing temperature on the microwave-absorption properties of the composites were investigated. The mechanism of the thermal-ageing temperature’s effects on microwave-absorption behaviour was identified. The results show that unaged composites have superior microwave-absorption properties, with a minimum reflection loss (RLmin) of − 87.73 dB, a lowest thickness of 1.46 mm, and an effective absorption bandwidth (EAB, RL < − 10 dB) reaching 5.8 GHz (9.9–15.7 GHz). With ageing at 240 °C for 24 h, the RLmin at a frequency of 5.48 GHz is − 45.55 dB with a thickness of 2.55 mm, and the EAB value reaches 2 GHz (range 4.6–6.6 GHz). In the thermal-ageing process, a crosslinking reaction occurs in MPVQ with an increase in crosslinking density from 5.88 × 10−5 mol g−1 (unaged) to 4.69 × 10−4 mol g−1 (aged at 240 °C). Simultaneously, thermal degradation of the composites leads to a reduction in the rubber concentration. In addition, a small amount of CIPs are oxidized to Fe3O4, and the remaining CIPs aggregate to generate more electrically conductive pathways. Consequently, the dielectric loss of the composites will be significantly improved, resulting in poor impedance matching. The microwave-absorption properties of the composites gradually decrease with increasing thermal-ageing temperature from 200 to 240 °C.

The Effect of Phenyl Content on the Liquid Crystal-Based Organosilicone Elastomers with Mechanical Adaptability.

An elastomer with mechanical adaptability is a new kind of polymer material in which the increasing stress under continuous deformation is significantly inhibited in a large deformation area. Liquid crystal-based organosilicone elastomers, which can dissipate energy through reversible internal phase transition under external stimulation and have recoverable large deformation capacity, have drawn much interest as mechanical adaptability materials. However, there is no good way to control the mechanical adaptability at present. For this purpose, we prepared a new liquid crystal-based phenyl silicone rubber (LCMVPQ) using two-step click reactions and systematically explored the effect of phenyl content on its mechanical adaptability to achieve the regulation of mechanical adaptability. With an increase in phenyl content in the LCMVPQs, phenyl can hinder the rearrangement of the mesogenic units along the applied stress direction, which enables the adjustment of mechanical adaptability to meet the needs of different situations. In addition, the introduction of the liquid crystal phase impedes the internal friction of the molecular chain movement of the LCMVPQs and reduces the damping performance of silicone rubber. This research achieves the regulation of elastomers with mechanical adaptability and is expected to be applied in practical application fields.

Analysis of Physical-Chemical Properties and Space Environment Adaptability of Two-Component RTV Silicone Rubber.

Silicone rubber (SR) has the properties of organic–inorganic materials and good adaptability to the space environment, which can be used as an atomic oxygen (AO)-resistant layer on the spacecraft surface. In this study, SR coatings were used to spray on the polyimide surface to prevent atomic oxygen erosion. Then, the physical, chemical, and AO-resistant properties of the SR were investigated. By means of laser diffraction scattering particle size distribution tests, energy-dispersive spectroscopy elemental mapping, and X-ray photoelectron spectroscopy, the fillers and matrix were confirmed as precipitated silica and phenyl SR, respectively. Through analysis of swelling behavior, greater cross-linking density and less swelling ratio were observed at higher temperature and humidity. Furthermore, after AO was exposed with an accumulated fluence of 1.2 × 1021 atoms/cm2, cracks appeared on the coating surface with the change of element content. In addition, it was found that the degree of reaction between AO and SR should not be determined based on mass loss measurements. Our work showed the practical application and great potential of SR protective coating in spacecraft.

Tetraphenylphenyl-modified damping additives for silicone rubber: Experimental and molecular simulation investigation

The incorporation of additive into rubber matrix is a promising approach toward desirable damping materials. However, the design and selection of additives remain a challenge. Herein, tetraphenylphenyl-modified damping additives were synthesized by Diels-Alder chemistry. The effects of additives on the mechanical and morphological properties of phenyl silicone rubber were investigated experimentally and computationally. Experimental results showed that the addition of additives substantially improved the damping while preserving excellent mechanical properties. The composite with 15 phr tetraphenylphenyl-modified dimethylpolysiloxane (TPP-VMPS-3) exhibited a broad plateau of loss factor (tanδ >0.25) from −50 to 30 °C, effectively expanding the damping temperature range. When the composite incorporated 15 phr tetraphenylphenyl-modified methylphenylpolysiloxane (TPP-VPMPS), the tanδ increased from 0.09 to 0.21 at 150 °C, showing excellent high-temperature damping performance. Furthermore, molecular dynamics (MD) simulation provided mechanistic insights into the phase separation and relaxation behavior of composites by studying the compatibility, interaction mechanism, and diffusion characteristic. The results demonstrated that the enhanced intermolecular interactions and steric hindrance were the crucial reason for the improvement of damping. This work shed light on the relationship among composition, structure and property, which may provide a framework for preparing high-performance silicone composites via the synergistic experimental and computational method.

High and Low Temperature Resistance of Phenyl silicone rubber

Methyl Phenyl and diphenyl silicone rubbers were synthesized from octamethyl cyclotetrasiloxane (D4), methylphenyl cyclosiloxane, octaphenyl cyclotetrasiloxane, etc. Compared with the commercial methylvinyl silicone rubber, the high and low temperature resistances of methyl vinyl silicone rubber were studied in this paper. The results showed that the introduction of phenyl groups can improve the thermal properties of silicone rubber, and the thermal stability of diphenyl silicone rubber is better than that of methyl phenyl silicone rubber. But there is little difference of mechanical properties in high temperature environment for three silicone rubber. DMTA analysis showed that there were still a small amount of crystals in diphenyl silicone rubber, while methylphenyl silicone rubber was amorphous rubber. The mechanical properties at low temperature indicated that the tensile strength of diphenyl silicone rubber was 4.1Mpa higher than that of methylphenyl silicone rubber at -70 °C due to the existence of low-temperature crystallization.

Effects of chain structure on damping property and local dynamics of phenyl silicone rubber: Insights from experiment and molecular simulation

The dynamic mechanical property of silicone rubbers with different phenyl units and phenyl contents were comprehensively investigated by means of experiments combined with molecular dynamics (MD) simulation. Experimentally, the results indicate that the phenyl units are randomly distributed in the polymer chains and the damping capacity is considerably improved with the augment of phenyl contents. Compared with methylphenyl units, diphenyl units endow the silicone rubber with enhanced mechanical stability, which leads to a wider glass transition region and effective damping temperature range. Furthermore, the MD simulation reveals the equilibrium structures and local dynamics by monitoring the changes of molecular interactions, bond rotation, conformational transition and molecular diffusion during the cooling process, which correlates the dynamic mechanical response to the molecular relaxation behavior. This work provides a deeper insight into the relationship among the composition, microstructure and damping property, which may promote theoretical predictions and scientific basis for the designs of silicone rubber with desired performances.

Tribological properties of phenyl-silicone rubber composites with nano-CeO2 and graphene under thermal-oxidative aging

Phenyl-silicone rubber composite components have been used in the sealing field under various working conditions. However, research on friction behavior during service is somewhat lacking. Thermal-oxidative aging’s effects on the tribological properties of phenyl-silicone rubber composites are investigated in this work. With the addition of nano-CeO2 and graphene, the coefficient of friction (COF) gradually decreases between the GCr15 steel ball and phenyl-silicone rubber composites, which can be attributed to nano-CeO2’s and graphene’s protection of surface matrices during aging and friction-heat generating processes. The results of this study indicate that the COF gradually decreases as the load increases because frictional heat generation increases with loads, resulting in softening the matrix and decreasing friction resistance. When the graphene content increases (0.8–1.5 phr), the wear rate (Ws) of phenyl-silicone rubber composites increases due to the destruction of graphene transfer films and severe fatigue wear. This study provides new ideas for improving the friction and wear properties of phenyl-silicone rubber composites before and after thermal-oxidative aging.

Design and synthesis of phenyl silicone rubber with functional epoxy groups through anionic copolymerization and subsequent epoxidation

In this paper, we have developed epoxidized phenyl silicone rubber (EMVPQ) with good oil and radiation resistance by anionic ring-opening copolymerization and further epoxidation modification. Silicone rubbers with both phenyl and epoxy groups were firstly synthesized and main properties of the material were characterized. When the phenyl content in EMVPQ was increased from 5% to 20%, the damping loss peak shifted to the high temperature by 36 °C and the effective damping temperature range was widened by 3 °C. The tensile strength of EMVPQ with 20% phenyl content did not change before and after irradiation. When the epoxy content is only 13%, the EMVPQ retained mechanical properties after immersion at 25 °C or 100 °C for 72 h, but a commercial sample substantially lost its mechanical properties. This work not only promotes the research of epoxidized phenyl silicone rubber, but also opens an effective way for the preparation of high-performance aerospace materials.

Effect of phenyl content, sample thickness and compression on damping performances of silicone rubber: A study by dynamic mechanical analysis and impact damping test

The relaxation behaviors and impact damping effects of phenyl silicone rubber were investigated using dynamic mechanical analysis (DMA) and a home-designed impact damping test. The effects of rubber phenyl content, sample thickness and compression on the damping performance were evaluated. DMA results over a broad temperature and frequency range indicate that silicone rubber with higher phenyl content would overall exhibit better damping capacity owing to the increase in friction between molecular chains, and the impact damping performances agree well with the relaxation results. Besides, sample thickness and compression will also strongly influence the damping performances as directly evidenced by the impact damping tests. It is demonstrated that a combination of DMA and impact damping test is of critical use for designing rubber damping devices according to the frequency range of interest. This work will provide deeper insight into damping performances of rubbers and practical guidance for their engineering applications.

Improved adhesion, heat resistance, anticorrosion properties of epoxy resins/POSS/methyl phenyl silicone coatings

A series of coatings composed of hydroxyl-terminated methyl phenyl silicone rubber (PSi) and silanized epoxy resins (SERs) were prepared in a facile way. Four kinds of SERs with different structures and degree of functionality were synthesized successfully and used to modify the silicone coating. The obtained room temperature vulcanized (RTV) silicone coatings showed excellent adhesion, great heat resistance and anticorrosion properties. Compared with pure PSi, the coatings containing 25 wt% SERs showed better thermal properties, manifested as delayed degradation temperature and greatly increased char yield at 800℃. The adhesion of coatings all reached the highest level (degree 0) which exceeded that of pure PSi coating (degree 2). Furthermore, the anticorrosion property of the coatings in 5 wt% acid, alkaline, and saline environments was all improved. The incorporation of SERs improved the compatibility between the silicone rubber and epoxy resins, in which the epoxy group created more adhesion of cured blended coating and POSS led a significant enhancement in thermal and anticorrosive properties. Their combined effect endowed silicone coatings with more application prospects.