Mechanical Properties Of Silicone Rubber Research Articles

Morphology, thermal and mechanical performances of SR composites containing sepiolite and HGMs as binary fillers

Abstract Binary fillers-filled silicone rubber (SR) matrix composites are prepared to improve the thermal and mechanical properties of SR as a lightweight thermal insulating material. Sepiolite and hollow glass microspheres (HGMs) can be evenly dispersed in SR matrix to obtain SR/sepiolite/HGM composites with superior performances at amounts of around 7.5 parts per hundreds of rubber (phr) and 20 phr, respectively, as observed from scanning electron microscopy (SEM). The density of the composites increases slightly with the addition of sepiolite in a linear trend, while the addition of HGMs results in the abrupt reduction in density lower than 0.7 g/cm3. Sepiolite exhibits a strengthening effect in the SR matrix; however, the addition of HGMs in this matrix slightly enhances the stress of the composite; its maximum elongation at break can increase up to 300%. The addition of sepiolite and HGMs improves the initial decomposition temperatures of SR composites a little; the excellent thermal insulating effect provided by HGMs is further verified by their significant decrease in thermal conductivity at 200°C, providing the facts that these SR/sepiolite/HGM composites can be used as lightweight materials for thermal insulating purposes.

The ceramifying process and mechanical properties of silicone rubber/ ammonium polyphosphate/ aluminium hydroxide/ mica composites

The ceramifying process and mechanical properties of silicone rubber/ammonium polyphosphate/aluminium hydroxide/mica composites (hereinafter referred to as SRAAM) are investigated. The changes in microstructures and phase compositions of SRAAM during ceramifying process at different calcined temperatures are studied. At 300 °C, SRAAM residues exhibit porous structure due to gas evolution from the thermal decomposition of APP, Al(OH)3 and silicone rubber, but mica does not react with them. Although the flexural strength of SRAAM residues are low, the generation of aluminium phosphate (AlPO4) and NH4AlP2O7 improves the self-supporting. With no new phase generated, SRAAM residues maintain certain degree flexural strength due to the adhesive effection of aluminium phosphate during 300–600 °C. The reactivity of mica is increased by eliminating hydroxyl at temperature up to 800 °C, and then the chemically interactions between active mica and phosphates are able to generate Al2O3·2SiO2, and KAlP2O7 compounds improving the flexural strength. Further reactions between mica and KAlP2O7 could generate KAlSi3O8 at 1000 °C and the density of residual product is improved by low melting point phosphate filling pore to form relatively dense structure increasing the flexural strength. SRAAM with high flexural strength and good self-supporting from low to high temperatures is expected to be a kind of excellent ceramifying performance of flame retardant materials.

Improving properties of silicone rubber composites using macromolecular silane coupling agent (MMSCA)

ABSTRACTTwo types of vinyl silicone oil (VSO), allyl‐capped hyperbranched polycarbosilane (HBP), and triethoxysilane (TES) were employed to synthesize macromolecular silane coupling agent (MMSCA) by hydrosilylation. VSOs, HBP, and the hydrosilylated products were used as crosslinker, respectively, to improve weak mechanical properties of silicone rubber (SR). Structures of the crosslinkers were studied by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR). Crosslinking density test and scanning electron microscope (SEM) observation showed an increased interaction between silicone rubber and fumed silica by the use of MMSCA. Mechanical properties of the resulted composites using MMSCAs were increased to varying degrees compared with those possessing crosslinkers without ethoxy group. MMSCAs were effective for further property enhancements of composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 43415.

Preparation of CaCO3-SiO2 composite with core-shell structure and its application in silicone rubber

Abstract A new CaCO3-SiO2 composite with core-shell structure was successfully prepared by mechano-chemistry method (MCM). SEM and FTIR indicated that SiO2 particles were homogeneously immobilized on the surface of CaCO3. The well dispersion of this CaCO3-SiO2 composite into silicone rubber can not only reduce the usage amount of SiO2, but also improve the mechanical properties of silicone rubber. By the calculation, the theoretical numbers of the SiO2 particles is about 10 times as large as that of CaCO3 particles in the CaCO3-SiO2 composite. Mixing CaCO3-SiO2 composite in silicone rubber can enhance the breaking strength of the silicone rubber about 18% as high as that when mixing the pure SiO2. And the elongation at break is about 14% less than that of adding the pure SiO2 sample.

Enhancing the thermal, electrical, and mechanical properties of silicone rubber by addition of graphene nanoplatelets

Graphene nanoplatelets (GNPs)/silicone rubber composites were prepared with the assistance of the Flacktek SpeedMixer. A scanning electron microscope (SEM), transmission electron microscopy (TEM), Raman spectra, Fourier-transform infrared spectra (FTIR), and X-ray photoelectron spectra (XPS) were carried out to characterize the structure of graphene nanoplatelets. An electronic universal testing machine, laser thermal conductivity analysis (LFA), thermogravimetric analysis (TGA), and a scanning electron microscope (SEM) reveal the effects of GNP loading content on the thermal conductivity, electrical, and mechanical properties of the composites. The results show that the GNPs present a homogeneous dispersion in silicone rubber and the thermal conductivity of composites exhibits improving from 0.16 to 0.26W/(m·K) (an increase of 53.1%) and the tensile strength varies from 0.240 to 0.608MPa (an increase of 153%) with the addition of a low content (0–8%) of GNPs. In addition, the thermal stability of silicone rubber composites is significantly enhanced.

Mechanical Properties and Corrosion Resistance of Vulcanized Silicone Rubber after Exposure to Artificial Urine

Medical devices, such as Foley catheters, which are commonly fabricated from silicone rubber, need to have excellent mechanical properties and physiological inertness. This study reports the development of a facile method to prepare silicone rubber with excellent long-term performance by controlling the vulcanization procedure parameters only. Mechanical, viscoelastic, and chemical properties of vulcanized silicone rubber were investigated. The corrosion resistance of vulcanized silicone rubber was assessed by exposure to artificial body urine for a period of up to 14 days. The mechanical properties of silicone rubber were changed via adjusting the vulcanization procedure parameters. The improved mechanical properties of silicone rubber are attributed to an increase in crosslink density resulting from the proposed vulcanization technology. After 14 days of immersion in urine, no significant changes in mechanical properties and internal structure were observed. This indicated that the as-prepared rubber samples had high tear resistance and physiological inertness. These long-term properties are important for their applications as semi-permanent implant materials, such as Foley catheter balloons in clinics. Our process of vulcanization of silicone rubber may have potential for fabrication of such medical devices.

Mechanical properties of silicone rubber under high loadings of alumina trihydrate filler

It is known that Young’s modulus of elastomers increase strongly due to high filler loadings, which is critical for practical applications and processing. An experimental study was performed in order to investigate the mechanical properties of silicone rubber, which was highly filled with alumina trihydrate (ATH) under uniaxial tensile tests. Different sizes of ATH particles having different surface conditions were used. The composites were prepared in a Z-blade mixer, and the particles were partly in situ modified. In preliminary investigations, the correct amount of silane for the in situ modification was determined and the effect of the mixing time on the mechanical properties of the cured rubber was studied. Long mixing times show generally a decrease in the modulus. This is explained by the increasing formation of bound rubber. A substantial dependence of the particle size and particle surface modification on the Young’s modulus was found. This effect can be simulated using a model based on a stiff particle surrounded by a soft shell, which has a higher modulus than the polymer. Smaller particles show a stronger increase of the modulus than larger ones, which is due to (1) higher volume of interphase area and (2) shorter distance between the particles increasing the modulus of the interphase.

Adjusting the properties of silicone rubber filled with nanosilica by changing the surface organic groups of nanosilica

A series of nanosilica (denoted as nano-SiO2) surface-capped with organic modifiers hexamethyldisilazane (denoted as HMDS; molecular formula: C6H19NSi2) and KH570 (molecular formula: C10H20O5Si) containing CC double bond were prepared by in situ surface-modification method. As-obtained nano-SiO2 particles were characterized by Fourier transform infrared spectrometry and transmission electron microscopy, and they were also used to reinforce silicone rubber (denoted as SR) in order to improve the mechanical properties. Moreover, a universal material testing machine was performed to determine the mechanical properties of the SR-matrix nanocomposites. Results showed that the surface properties of nano-SiO2 can be adjusted by changing the ratio of these modifiers. The tensile strength, tear strength and elongation at break of nano-SiO2/SR nanocomposites are comparable to or even better than those of R-106/SR nanocomposite (R-106 refers to commercially obtained fumed SiO2 nanoparticles that was modified with silane coupling agent). The mechanical strength of nano-SiO2/SR nanocomposites especially for tear strength largely improve with adding a small amount of CC content of the surface-capped nano-SiO2. More importantly, it could be feasible to manipulate the mechanical properties of silicone rubber by properly adjusting the dosages of surface-modifiers HMDS and KH570 during the preparation of in situ surface-capped nanosilica, which could be of special significance to developing high performance SR-matrix nanocomposites.

Effects of multi-walled carbon nanotube structures on the electrical and mechanical properties of silicone rubber filled with multi-walled carbon nanotubes

The specific surface area is a key factor that determines both the electrical and mechanical properties of silicone rubber/MWCNTs.

Hydroxyapatite-coated sillicone rubber enhanced cell adhesion and it may be through the interaction of EF1β and γ-actin.

Silicone rubber (SR) is a common soft tissue filler material used in plastic surgery. However, it presents a poor surface for cellular adhesion and suffers from poor biocompatibility. In contrast, hydroxyapatite (HA), a prominent component of animal bone and teeth, can promote improved cell compatibility, but HA is an unsuitable filler material because of the brittleness in mechanism. In this study, using a simple and economical method, two sizes of HA was applied to coat on SR to counteract the poor biocompatibility of SR. Surface and mechanical properties of SR and HA/SRs confirmed that coating with HA changes the surface topology and material properties. Analysis of cell proliferation and adhesion as well as measurement of the expression levels of adhesion related molecules indicated that HA-coated SR significantly increased cell compatibility. Furthermore, mass spectrometry proved that the biocompatibility improvement may be related to elongation factor 1-beta (EF1β)/γ-actin adjusted cytoskeletal rearrangement.

Study of the Mechanical Properties of Ceramics Modified Composite Insulator Materials

A large number of ceramic insulators that are widely used in the power systems are returning shipment every year but there is no better processing method. Silicone rubber insulators have highly required the additive of the formulation. So this article combining the advantages of ceramic insulators and chemical composition, studies the mechanical properties of ceramics modified composite insulator materials. The measurements include the tensile strength, tear strength, hardness, SEM and Fourier transform infrared spectroscopy test of the new silicone rubber. The effects of adding different proportions of ceramic powder on the mechanical properties of silicone rubber are compared. And from the microscopic analysis the mechanism of the improved properties of the modified silicone rubber is analyzed. The results showed that a proportion of the ceramic part can replace aluminum hydroxide powder and the fumed silica powder can significantly improve the mechanical properties of the silicone rubber.

Study on Short Basalt Fiber Reinforced Silicone Rubber Composites

Silicone rubber has excellent performance, such as cold resistance, heat resistance, ozone resistance, thermal properties and insulating properties and so on. However, silicone rubber is in the state of semi-liquids and it is very soft, so the mechanical properties of silicone rubber are very poor. In order to improve its availability of silicone rubber, short basalt fiber / silicone rubber composite materials were prepared by using short basalt fiber as reinforcement, and its mechanical properties and compatibility were studied. The best formulation of short basalt fiber / silicone rubber composite materials were determined by testing Shore A hardness, tensile strength and elongation at break, and the morphology structure and compatibility of short basalt fiber / silicone rubber composite materials were discussed by scanning electron microscope and infrared spectrum, prepare excellent performance of silicone rubber composite materials.

Heat-resistant antiflaming and friction mechanisms in nano-Fe2O3-reinforced silicon rubber

Abstract A ferric oxide (Fe2O3)/silicone rubber (SR) composite was prepared to produce a magnetic rubber with good heat-resistant and friction properties: SR and nano-Fe2O3 were used as its raw materials. The heat-resistant, antiflaming, magnetic, and mechanical properties of such composites with different proportions of nano-Fe2O3 were studied. The results showed that the Fe2O3 nanoparticles were uniformly distributed throughout the composites. The physical and mechanical properties of SR were improved when Fe2O3 nanoparticles were added. The maximum elongation and tensile strength of the composites were relatively good when the ratio of Fe2O3 was 20 phr. The heat-resistance and antiflaming properties of SR were improved by adding nano-Fe2O3, which had good combined heat resistance. The friction properties of these composites were optimal at 20 phr addition of nano-Fe2O3, which laid the foundation for further applications of this type of composite in high-temperature sealing and shock absorption environments.

Mechanical and Thermal Properties of Silane Grafted Organomodified Montmorillonite Reinforced Silicone Rubber Nanocomposites

The present work deals with the preparation and characterization of silane grafted MMT (S-MMT), organomodified MMT (O-MMT) and silane grafted organomodified montmorillonite (OS-MMT) reinforced silicone rubber (SR) nanocomposites. XRD of SR filled with O-MMT (1-8 wt%), OS-MMT (1-8 wt%) and S-MMT (1-5 wt%) suggested the formation exfoliated morphology, which has also been supported by the corresponding TEM images of 3 wt% filled SR nanocomposites. TGA and DSC studies of SR/OS-MMT (3 wt%) nanocomposites have shown that the thermal stability, glass transition temperature and crystallization temperature are maximum improved with respect to neat SR by 50, 14 and 10 degrees C respectively. This is attributed to the synergistic effect of organo-modification followed by amino silane grafting of MMT on thermal properties of SR. The tensile strength of SR/S-MMT (5 wt%), SR/O-MMT (3 wt%) and SR/OS-MMT (3 wt%) relatively improved by 134, 312, and 259% respectively suggesting that the synergistic effect of OS-MMT is not effective in reinforcing the mechanical properties of SR. In all probability, the curing of SR through hydrosilylation is inhibited by the lone pair on nitrogen in NH2 group of OS-MMT.

Effects of types of fillers and filler loading on the properties of silicone rubber composites

In this study, the effects of loading levels of nano BN, nano SN and synthetic ND particles on the thermal and mechanical properties of silicone rubber were investigated. Nanoparticle-filled silicone rubber composites were prepared by cast molding process. In general, incorporation of thermally conductive nanoparticles to the silicone rubber matrix improved the thermal conductivity of the composites. BN particles have the most pronounced effect on the thermal conductivity in comparison to SN and ND particles at any given loading level. TGA studies revealed that the thermal stability of the SN/silicone rubber system increased as the filler loading level increased; however, BN and ND facilitated the thermal degradation of the silicone rubber nanocomposites. For tensile test, it is observed that the addition of nanoparticles generally increased the tensile strength of silicone rubber composites compared to the neat silicone rubber. However, for BN system, the tensile strength of the composites decreased when more than 1.5 vol.% of BN is loaded in the system. The reduction was caused by the existence of voids and agglomerations in the BN/silicone rubber system. In general, tensile modulus and strain at break of nanocomposites increased with the incorporation of nanoparticles into silicone rubber matrix.

Mechanical properties of silicone rubber composed of diverse vinyl content silicone gums blending

Silicone rubber composed of diverse vinyl content silicone gums blending were prepared and their mechanical properties were investigated. The silicone rubber composed of diverse vinyl content silicone gums blending whose crosslinking points were concentration distribution exhibited better tearing strength and higher tensile modulus in comparison with single vinyl content gums which were mean distribution. The average molecular weight (Mc) of the silicone rubber composed of diverse vinyl content blending are lower than that of single vinyl molar content 0.16% which was calculated by swelling equilibrium method. The viscoelastic behavior indicated the silicone rubber composed of 0.04% and 0.3% vinyl molar content gums blending possessed perfect flexibility at low temperature because it had the lowest glass transition temperature ( T g), and this sample had the largest storage modulus and loss modulus.

The effect of nanofiller on electrical and mechanical properties of silicone rubber

Fillers are used to enhance both electrical and mechanical properties of room temperature vulcanised (RTV) silicone rubber. Montmorillonite organoclay, MMT, was used as reinforcing filler at various contents. The X-ray diffraction predicts acceptable dispersion of organoclay in the polymer matrix and SEM images shows fairly good dispersion of the filler. Mechanical tests revealed that tensile strength and elongation at break are enhanced with organoclay. Several nonlinear elastic models were employed to represent the mechanical behaviour of the silicone composites and the best model was selected for future analysis of the composites as electro-mechanical actuators. In addition, dielectric constants were measured and compared with reference sample; therefore the best sample having desirable mechanical and electrical properties was determined.

Thermal Conductivity and Mechanical Properties of Silicone Rubber Filled with Different Particle Sized SiC

Micro- and nano- silicone carbide particles are used as heat conductive fillers of methyl vinyl silicone rubber, and the influence of filler amount, particle size and the surface treatment of filler on the thermal conductivities and mechanical properties of silicone rubber are studied. The results show that the thermal conductivities of silicone rubber are improved, but the mechanical properties are worse with the increase of the amount of fillers. The composite filled with smaller sized silicone carbide has a better thermal conductivity than that filled with large particles in a relatively high filling fraction, and composite filled with different sized silicone carbide has different mechanical properties at the same filling amount. Treatment of fillers with coupling agent (KH-560, A-171) has active impacts on the thermal conductivity but negative impacts on mechanical properties of the filled silicone rubber.

Microindentation Test for Assessing the Mechanical Properties of Silicone Rubber Exposed to a Simulated Polymer Electrolyte Membrane Fuel Cell Environment

The elastomeric materials used as seals and gaskets in polymer electrolyte membrane (PEM) fuel cells are exposed to acidic environment, humid air, and hydrogen, and subjected to mechanical compressive load. The long-term mechanical and chemical stability of these materials is critical to both sealing and the electrochemical performance of the fuel cell. In this paper, mechanical degradation of two elastomeric materials, Silicone S and Silicone G, which are potential gasket materials for PEM fuel cells, was investigated. Test samples were subjected to various compressive loads to simulate the actual loading in addition to soaking in a simulated PEM fuel cell environment. Two temperatures, 80°C and 60°C, were selected and used in this study. Mechanical properties of the samples before and after exposure to the environment were studied by microindentation. Indentation load, elastic modulus, and hardness were obtained from the loading and unloading curves. Indentation deformation was studied using Hertz contact model. Dynamic mechanical analysis was conducted to verify the elastic modulus obtained by Hertz contact model. It was found that the mechanical properties of the samples changed considerably after exposure to the simulated environment over time. The temperature and the applied compressive load play a significant role in the mechanical degradation. The microindentation method is proved to provide a simple and efficient way to evaluate the mechanical properties of gasket materials.

Preparation and characterization of γ‐irradiated crosslinked silicone rubber/organoattapulgite composites

AbstractSilicone rubber (SR)/organoattapulgite (OAT) composites were prepared with γ‐irradiation crosslinking at a dose range varied from 30 to 300 kGy. Natural fibrillar silicate attapulgite (AT) was modified by silane coupling agent, and the obtained OAT was used as reinforcing fillers in SR. The effect of irradiation doses on the degree of crosslinking of SR/OAT composites was determined by solvent swelling method. It was found that the molecular weight between crosslinks (Mc) reduced with the increase in irradiation doses. Moreover, the addition of OAT to SR matrix promoted an increase in the crosslinking density of the composites because of the presence of the active crosslinking sites of OAT. The mechanical properties of the SR/OAT composites including tensile strength, elongation at break, and Shore A hardness subjected to various irradiation doses were studied. The experimental results showed that the tensile strength, elongation at break, and Shore A hardness were all improved significantly in the presence of OAT, which indicated that OAT was an alternative reinforcing filler of SR. In addition, the effect of various irradiation doses on the mechanical properties of SR and SR/OAT composites was also investigated. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers