Silicone Rubber Samples Research Articles

Tracking and erosion resistance of LSR and HTV silicon rubber samples under acid rain conditions

Assessment of the material degradation in laboratory similar to field conditions is still a challenge. In the present work an attempt is made to study the effect of environment conditions in service life of polymeric insulators on tracking and erosion resistance. Evaluation of tracking and erosion resistance of Silicone Rubber insulating samples of high temperature vulcanized (HTV) rubber and liquid silicone rubber (LSR) are carried out under AC and positive polarity DC voltage. The samples are treated under normal contaminants as per IEC 60587 and acidic contaminant solution simulating acid rain. The conditions of pollution/ contamination severity level are taken into consideration by maintaining the conductivity approximately 2.5 mS/cm for both solution to observe the effect of acidity alone on the samples, the acidity level is varied to understand the material behavior under acidic case with AC and DC stress application. A new experimental arrangement is set up based on IEC 60587 and ASTM D-2303 standards. The constant voltage method is employed to find the relative tracking performance of silicone rubber samples for different chemical composition. Physico-chemical analysis involving SEM, EDAX and FTIR is carried out on treated samples to understand the surface morphology and chemical changes. A comparative analysis is carried out for the acid rain solution and the standard solution of NH 4 Cl. Further leakage current performance and analysis is carried under both AC and DC stress.

Unusual effect of temperature on direct fluorination of high temperature vulcanized silicone rubber and properties of the fluorinated surface layers

In order to investigate the effects of fluorination temperature on surface layer characteristics (chemical composition and structure, morphology, and thickness) and surface layer properties, high temperature vulcanized silicone rubber samples were fluorinated in a laboratory vessel using a F 2 /N 2 mixture with 12.5% F 2 by volume, at 0.1 MPa and the different temperatures of 25, 55, and 85 °C, for the same time of 30 min. ATR-IR analysis indicates that the substitution of fluorine atoms for hydrogen atoms of methyl groups is dominant for the fluorination at the different temperatures, while a substitution for methyl groups cannot be excluded. SEM cross-section and surface images show the fluorinated layers with nanostructured surfaces. The surface layer fluorinated at 55 °C appears to have the lowest degree of fluorination, but it clearly has the largest thickness and surface nanostructure size among the fluorinated layers. This unusual phenomenon is caused by two competing effects, the thermal activation of the substitution reaction and fluorine diffusion through the surface layer and the steric hindrance by the fluorinated methyl groups to the fluorination and fluorine diffusion. Contact angle measurements reveal that the fluorinated surfaces have high hydrophobicity and oleophobicity and thus an extremely low surface energy. Surface potential decay measurements show a much more rapid decay of potential on the fluorinated samples, compared to the unfluorinated sample. There is no significant difference in surface hydrophobicity or surface conduction between the fluorinated samples, due to the combined effect of compositional and structural changes. The difference in surface oleophobicity between the fluorination at 55 °C and the fluorination at 25 or 85 °C provides further evidence for the difference in their surface chemistry, because surface geometry of the fluorinated samples has little effect on the oleophobicity.

Research on Buffering Performance of Several Polymer Materials Based on Drop-weight Test

Polymer materials are widely used in vibration damping and buffering, and different materials and processing techniques would affect their buffering performance. In this study, the buffering performance of four kinds of specimens made of non-foamed polyurethane, foamed polyurethane, silicone rubber and PVC paste resin were examined by drop-weight tests. According to the drop-weight experimental principle and corresponding numerical simulation, the peak acceleration of the falling hammer could be used as the key index of buffering performance. The results show that the buffering performance of the non-foamed polyurethane and silicone rubber samples are relatively worse, while the foaming polyurethane and PVC paste resin samples have similar buffering performance.

Delay in the Freezing of Supercooled Water Drops on Superhydrophobic Surfaces of Silicone Rubber at Negative Temperatures

A method is proposed for fabricating textured superhydrophobic surfaces of silicone rubber with mechanical resistance toward liquid or freezing aqueous solutions. The anti-icing characteristics of silicone rubber samples that differ in the wetting characteristics and mechanical stability of their micro- and nanotextures are derived by analyzing the delays in the freezing of supercooled sessile water drops deposited on the sample surface. The longest delay in freezings are observed for sessile water drops on superhydrophobic surfaces prepared by laser texturing with subsequent application of a layer of a hydrophobic agent to consolidate the textural elements. Delay in freezings can be as long as tens of hours on such surfaces at T = −18°C. The prepared superhydrophobic surfaces exhibit greater anti-icing ability with respect to aqueous salt solutions than to deionized water.

Reduction of the Adhesive Friction of Elastomers through Laser Texturing of Injection Molds

It is well known that elastomers usually possess poor dry sliding friction properties due to their highly adhesive character. In order to overcome this problematic behavior in industrial applications, interfacial materials such as oils, greases, coatings, or lacks are normally used in order to separate or to functionalize the contact surfaces of elastomers. Alternatively, the high adhesion tendency of elastomers may be explicitly reduced by modifying the elastomer composition itself or by enabling a reduction of its effective contact area through, for example, surface laser texturing. This second approach, i.e., the reduction of the adhesive character of elastomers through laser structuring, will be the main topic of the present study. For this purpose, different micro-sized grooved structures were produced on flat injection molds using an ultra-short pulsed laser. The micro-structured molds were then used to produce injection molded micro-ridged Liquid Silicone Rubber (LSR) sample pads. The investigations consisted firstly of determining the degree of replication of the mold micro-structures onto the surface of the LSR pads and secondly, to ascertain the degree of reduction of the friction force (or coefficient of friction) of these micro-ridged LSR pads in comparison to the benchmark (unstructured LSR pads) when tested under dry conditions against Aluminum alloy (Al-6082) or PA6.6-GF30 plates. For this second part of the investigation, the normal force (or contact pressure) dependency of the coefficient of friction was determined through stepwise load increasing friction tests. The results of these investigations have shown that the production of micro-ridged surfaces on LSR pads through laser structuring of the injection molds could be successfully achieved and that it enables a significant reduction of the friction force for low normal forces (or contact pressures), where the component of adhesion friction is playing an important and determining role in the overall friction behavior of the LSR elastomer.

Rheological experimental properties and numerical modeling of a pressure-transmitting silicone rubber used in sheet metal flexible-die forming

In this paper, the rheological behaviors of a silicone rubber used in sheet metal flexible-die forming were analyzed experimentally and numerically. Firstly, six silicone rubber samples with different molecular weights were subjected to three tests: oscillation, creep recovery, and shear viscosity test by using dynamic shear rheometer (DSR). Then, the responses of the silicone rubber to the load were categorized into three groups as elasticity, viscoelasticity, and viscoplasticity depending on whether they were time dependent and recoverable during the unloading period. By applying Perzyna’s theory, a visco-elasto-plastic model was proposed to simulate the rheological behaviors of the silicone rubber numerically. Finally, a finite element-element-free Galerkin (FE-EFG) code was implemented on the basis of this numerical model. Employing the program into polymer extrusion and sheet metal flexible-die forming process, on the substation of parameters obtained from experiments, good matches were found between numerical results and experimental ones.

Effect of Ambient Temperature on Hydrophobic Recovery Behavior of Silicone Rubber Composites

A series of silicone rubber samples with different cyclosiloxanes contents have been successfully prepared, and their hydrophobic recovery behaviors and mechanism were investigated in detail. The gas chromatography-mass spectroscopy technique after Soxhlet extraction was utilized to examine the low molecular weight siloxanes in the sample, SEM was used to observe the surface morphology of the silicone rubber influenced by plasma treatment, and contact angle measurement was applied to probe the hydrophobic recovery of the sample surface after plasma treatment at different storage temperatures. The storage time-dependent contact angle of water can be well fitted by the diffusion model calculated from Fick’s second law. The results imply that the hydrophobic recovery of silicone rubber is related to the diffusion of low molecular weight siloxanes, while larger content or higher temperature can induce faster hydrophobic recovery.

Effect of an electric field on friction of silicone rubber against steel in the motor base oil's environment

The paper presents the experimental results of research on the effect of an external DC electric field on the coefficient of friction of silicone rubber (elastomer) during its rubbing against a steel surface in the „pin–on–disc” experimental set-up. In the tests there were used silicone rubber samples, the pure PAG and PAO synthetic base oils and their blends with an antiwear (ZDDP) additive. The coefficient of friction μ was determined under conditions with and without an external DC electric field. A DC electric field was generated between a silicone rubber sample and a rotating steel disc (a friction pair). A sample holder was electrically isolated from other metal parts of a tribometer and was connected to one of the poles of a DC power supply, while the other pole was connected by means of the carbon brushes to a rotating steel disc. The experimental results show that the external DC electric field established between the rotating steel disc and a silicone rubber sample causes the coefficient of friction to decrease. It was also found that the coefficient of friction μ depends on the steel disc's angular velocity n, the contact pressure p, and the type of base oil and its blends with the additive used.

Aging behaviors of silicone rubber composite materials under outdoor environment

We investigated the aging effect on the chemical structure of silicone rubber composite materials under outdoor environment. The variations of low molecular weight siloxanes in silicone rubber were probed by gas chromatography-mass spectrometry during the degradation process. The experimental results indicate that a series of cyclic siloxanes exist in both the virgin and aged silicone rubber samples, while the additional low molecular weight siloxanes (hexamethyl cyclotrisiloxane) only appear in the aged samples. Meanwhile, the total amounts of low molecular weight siloxanes in the aged samples are much less than those in the virgin ones. The loss of low molecular weight siloxanes is induced by the chain scission and depolymerization.

Effect of pollution severity and dry band location on the flashover characteristics of silicone rubber surfaces

This paper investigates the flashover and ageing behavior of silicone rubber insulators under various contamination and dry band conditions. Effect of pollution severity, leakage distance and dry band location on the flashover characteristics of silicone rubber insulator was investigated. Flashover voltage and electric field distribution were measured under different pollution severity levels and dry band conditions. Effect of leakage distance on flashover voltage was also studied. Tests were carried out in a climate chamber and specific values of humidity and ambient temperature were used. A commercially available simulation package, COMSOL Multiphysics, was used to validate the experimental results. Electric field and potential along a silicone rubber sample were studied under different pollution severity and dry band conditions. Fourier transform infrared spectroscopy was used to analyze the chemical changes on the insulator surface and investigate the hydrophobicity recovery property of silicone rubber after flashover tests. The results of this study will further our knowledge regarding the flashover of silicone rubber outdoor insulators under contaminated and dry band conditions and could be used to improve the existing flashover models.

The behaviour of water droplets on the silicone rubber surface in an electric field

This paper describes the influence of a water droplet placed on flat samples of silicone rubber for enhancement the local electric field and generate electrical discharges. Studies have shown a significant influence of the droplet geometry on the electric strength of the samples. For non-symmetrical arrangement of the three droplets in the inter-electrode space electrohydrodynamic phenomena was observed: a stable change in the droplets shape placed near the electrodes and stretching and tearing down of the water droplets placed far from the electrodes. Captured photos and films of the water droplets behavior placed on the surface of the samples provided data to perform the simulation of the distribution of electric field and an estimate the value of the electric field, which was followed by the development of electric surface discharges.

전극재에 의한 실리콘 고무의 C-V 특성에 관한 연구

In this study, the properties of C-V degradation for thermal conductivity silicone rubber sample which is attached by copper-copper, copper-aluminum, aluminum-aluminum on upper-side and under-side has been measured at temperature of 80 140 . The results of this study are as follows. In case the frequency is increased, it found that the electrostatic capacity increased with increasing temperature to 80 , 110 , 140 regardless of kind of electrode. It found that the electrostatic capacity increased with becoming high temperature range of frequency regardless of kind of electrode. This result is considered to be caused by thermal absorption on the thermal conductivity silicone rubber sample. It found that the electrostatic capacity decreased with increasing temperature and frequency. This result is considered to be caused by molecular motion of C-F radical or OH radical.

Use of Essential Oils for the Prevention of Biofilm Formation on Silicone Rubber High Voltage Insulators

The prevention of biofilm formation on high voltage insulators is important to avoid changes in the surface properties of the material and the subsequent failure of the application. Antimicrobial silicone rubber samples were prepared by the addition of thymol and eugenol to Sylgard 184 to determine the possibility of using natural antimicrobial agents present in essential oils in materials used for high voltage insulators. The antimicrobial effects of thymol and eugenol were studied for different fungal strains and for green algae identified in the biofilms formed on insulators in Tanzania, Sri Lanka and Sweden. It was successfully demonstrated that samples containing high amount of eugenol and different concentrations of thymol could inhibit the fungal growth of strains from Sri Lanka and Tanzania and the growth of green algae. The growth of strains from Sweden was also suppressed. The addition of eugenol to the material resulted in a non-crosslinked system and therefore, the antimicrobial effect of the additive in the material could not be assessed. The addition of thymol did not significantly influence the thermal and mechanical properties of Sylgard184. Although thermal analysis revealed that a large amount of the antimicrobial agent was lost during sample preparation, the materials were effective against microbial growth, even at low thymol concentrations.

Design, Fabrication and Testing of a Piezoresistive-Based Tactile Sensor for Minimally Invasive Surgery

Minimally invasive robotic surgery (MIRS) has become a preferred method for patients for the last two decades, thanks to its crucial advantages over classical open surgeries. Although MIRS has some advantages, it has a few drawbacks. Since MIRS technology includes performing surgery through small incisions using long slender tools, one of the main drawbacks of MIRS becomes the loss of direct contact with the patient’s body in the site of operation. Therefore, the surgeon loses the sense of touch during the operation which is one of the important tools to investigate the health condition of the treated tissue. This paper presents a novel piezoresistive-based multifunctional tactile sensor that is able to measure the contact force, relative hardness of the contact object, and the position of a hidden lump at the same time. A prototype of the designed sensor has been fabricated, simulated, analyzed, and tested numerically and experimentally. The experiments have been performed on hyperelastic materials, which are silicone rubber samples with different hardness values that resemble different biological tissues. The ability of the sensor to measure the contact force and relative hardness of the contact objects is tested with several experiments. A finite element (FE) model has been built in COMSOL Multiphysics (v3.4) environment to simulate both the mechanical behavior of the silicone rubber samples, and the interaction between the sensor and the silicone rubbers. Both numerical and experimental analysis proved the capability of the sensor to distinguish between different silicone rubber samples.

오손액 변화에 따른 실리콘 고무의 정전기 대전열화 특성

Department of Safety Engineering, Korea National University of Transportation, Chungju 380-702, Korea(Received August 16, 2015; Revised August 16, 2015; Accepted August 24, 2015)Abstract: In this study, the electrification voltage of electrostatics for silicone rubber sample(4 cm × 4 cm × 0.103 cm) following immersion with contaminants of 2 ml, 5 ml, 10 ml for six hours has been measured in through the applied voltage of 10 kV DC at temperature of 80110, humidity of 50%90%. The results of this study are as follows. In case the contaminants is constant, it found that the electrification voltage of electrostatic decreased with increasing temperature and humidity to 35, 90%. In case of 2 ml of contaminants concentration, it found that the electrification voltage of electrostatic decreased with increasing temperature and humidity to 35, 50%. In case of the sample at temperature of 15and humidity of 50%, it found that the electrification voltage of electrostatic decreased with increasing contaminants to 10 ml.Keywords: Electrostatic electrification voltage, Electrification relaxation time 실리콘 고무는 규소원자와 산소원자를 골격으로 한 실록산 결합으로 되어 있으며, 배합하는 첨가제나 충전제 등에 의해 각종 물성 및 전기 특성이 크게 변화한다. 특히 뛰어난 내열성, 발수성, 내열성과 열전도성 때문에 실리콘 고무 절연케이블의 절연 용량을 증가시킬 수 있다 [1,2]. 최근 고기능화, 고속화, 고집적화와 표면 실장(surface mount)한 반도체 디바이스를 납땜에 의한 접착 형태에서 전도성 입자를 분산시킨 필름

Gold nanorods–silicone hybrid material films and their optical limiting property

As a kind of new optical limiting materials, gold nanoparticles have optical limiting property owing to their optical nonlinearities induced by surface plasmon resonance (SPR). Gold nanorods (GNRs) possess transversal SPR absorption and tunable longitudinal SPR absorption in the visible and near-infrared region, so they can be used as potential optical limiting materials against tunable laser pulses. In this letter, GNRs were prepared using seed-mediated growth method and surface-modified by silica coating to obtain good dispersion in polydimethylsiloxane prepolymers. Then the silicone rubber films doped with GNRs were prepared after vulcanization, whose optical limiting property and optical nonlinearity were investigated. The silicone rubber samples doped with more GNRs were found to exhibit better optical limiting performance.

Fatigue fracture of composite insulator sheds utilized in strong wind areas

This paper presents the fracture failure mechanism of composite insulators that have been deployed for only one year on 750 kV transmission lines in strong wind areas. Investigations indicate that the flexible shed structure was vulnerable to flow-induced oscillation, which further brought cracking to the shed root. The interactive process of fatigue and fracture was reviewed by inspecting the failed samples to gain insight into the cracking mechanism. The fatigue theory of silicone rubber was introduced to illustrate the fatigue resistance of the material. Simulations of wind load and stress distribution were performed to demonstrate the load condition and stress concentration at the root area on sheds. Wind tunnel tests show the oscillation of two types of 750 kV insulators under strong winds of up to 60 m/s. Four samples of silicone rubber from major insulator manufacturers were tested to investigate the fatigue resistance property, and withstand limit of high- and lowperformance silicone rubbers. Results indicate that, composite insulators without specific design and wind tunnel tests were risky to apply on transmission lines in strong wind areas, which is common type of climate in northwestern China.

Effect of coldfog on the corona induced degradation of silicone rubber samples

Corona is an unavoidable phenomena in high voltage power transmission system, in spite of suitably designed insulator accessories and transmission line hardware. It is a proven fact that the continuous occurrence of corona can subject the polymeric insulator to a severe degradation. Further, moisture in the air has a positive influence on the corona activity. This paper presents the methodology to evaluate the corona performance of the silicone rubber housing material with simultaneous application of cold fog. Analysis conducted after corona treatment by the Fourier Transform Infrared Spectroscopy (FTIR) present an interesting results showing a higher hydroxylation of sample surface under the moisture application than in the normal condition for both AC and DC excitation. FTIR spectrum also indicates the presence of nitric acid on the treated surface with coldfog application. Results obtained from SEM analysis are also presented.

Research on the Piezoresistive Properties of Conductive Silicone Rubber under Water Pressure

The conductive silicon rubber samples have been prepared in different filler ingredients, the platform is builded for testing the piezoresistive characteristics of conductive silicon rubber when the material is under water pressure and the test methods are designed, the body piezoresistive properties and surface piezoresistive properties under the water pressure within a certain range are studied respectively. The results show that, the sample of 6% acetylene black/2% nanoSiO2 blends exhibit the best piezoresistive performance when the samples are under water pressure, the piezoresistive properties of the material can be improved with the increase of the thickness of the materials (2mm-4mm), and the conductive silicon rubber used for the pressure-sensitive materials of piezoresistive gauge is feasible.

Use of Shore Hardness Tests for In-Process Properties Estimation/Monitoring of Silicone Rubbers

Casting is an important rubber manufacturing process for both production and material developments. A quick and flexible way of testing the constitutive materials properties of rubber products is very important for optimising the processing parameters and quality control. In many cases, standard tests such as tensile or compression tests are time consuming and require a large volume of materials. This work reports some recent work in using a combined numerical and experimental approach to characterise the properties of rubber materials during a casting process. Durometer shore hardness is used to test silicone rubbers (as a model material) with different compositions on different moulding planes and the linear elastic property is estimated from the hardnesses. The predicted properties are systematically compared with the experimental tests on hard and soft silicone rubber samples with different compositions. The work shows that shore hardness can be used as an effective way to monitor the materials properties during amoulding process for process optimisation and quality control.