Silicone Rubber Composite Materials Research Articles

Study on the Effect of Cleaning and Swelling Action of Cleaning and Repairing Agents on the Properties of Silicone Rubber

Silicone rubber composite materials are prone to fouling under outdoor conditions for a long time, leading to a decrease in hydrophobicity and even the occurrence of pollution flashover. Generally, the silicone rubber surface is cleaned and repaired with cleaning and repair agents, which can quickly restore its hydrophobicity to the factory state and even reach HC1. Under the action of cleaning and repairing agents, silicone rubber will undergo a certain swelling effect. This article conducts in-depth research on the impact of the cleaning and swelling effect of cleaning and repairing agents on the performance of silicone rubber. Research has found that this cleaning and repairing agent can significantly improve the surface hydrophobicity of silicone rubber. When silicone rubber is immersed in the cleaning and repairing agent for up to 10 hours, its surface undergoes swelling equilibrium, where the evaporation volume and swelling index remain unchanged. Through testing its mechanical properties, it was found that its tear resistance and fracture performance have been improved to a certain extent, with growth rates of 23.36% and 2.55%, respectively; Through electrical performance testing, it was found that its volume resistivity and dielectric strength were both improved to a certain extent, with volume resistivity and dielectric strength increased by 16.5% and 14.3%, respectively. Moreover, after reaching swelling equilibrium in the cleaning and repairing agent, the hydrophobicity of silicone rubber did not decrease, and it can still maintain HC1 for a long time, exhibiting good hydrophobicity.

Enhancing thermal conductivity of spherical boron nitride/silicone rubber composites by matching interfacial modulus

ABSTRACT Lightweight, electrically insulating and high thermally conductive materials are highly desirable in electronic and power systems because they can effectively transfer heat and avoid temperature rise of the equipment and devices, thus guaranteeing normal operation. In this work, silica-coated spherical boron nitride (SiO2@s-BN) was successfully fabricated and prepared as a thermally conductive composite by blending with silicone rubber (SR). Due to the modulus matching, SiO2@BN could decrease the thermal resistance between the SR matrices and the thermally conductive fillers, thus achieving higher thermal conductivity compared with the original BN at the same filler loading. When the SR composite is filled with 40 wt% SiO2@BN, the thermal conductivity can reach 1.2 W m−1 K−1, which is 16.5% higher than that of the 40 wt% s-BN/SR composite. Simultaneously, the 40 wt% SiO2@BN/SR composite material not only exhibits excellent dielectric, thermal, and mechanical properties but also demonstrates outstanding processability, maintaining a low precursor viscosity of only 14.5 Pa·s. Overall, this work provides a novel strategy for developing high thermally conductive SR composites with good processability.

Investigations of Shape Deformation Behaviors of the Ferromagnetic Ni-Mn-Ga Alloy/Porous Silicone Rubber Composite towards Actuator Applications.

Ferromagnetic shape memory alloys (FSMAs), which are potential candidates for future technologies (i.e., actuators in robots), have been paid much attention for their high work per volume and rapid response as external stimulation, such as a magnetic field, is imposed. Among all the FSMAs, the Ni-Mn-Ga-based alloys were considered promising materials due to their appropriate phase transformation temperatures and ferromagnetism. Nevertheless, their intrinsic embrittlement issue and sluggish twin motion due to the inhibition of grain boundaries restrict their practicability. This study took advantage of the single-crystal Ni-Mn-Ga cube/silicone rubber composite materials to solve the two aforementioned difficulties. The single-crystal Ni-Mn-Ga cube was prepared by using a high-temperature alloying procedure and a floating-zone (FZ) method, and the cubes were verified to be the near-{100}p Ni-Mn-Ga alloy. Various room temperature (RT) curing silicone rubbers were utilized as matrix materials. Furthermore, polystyrene foam particles (PFP) were used to provide pores, allowing a porous silicone rubber matrix. It was found that the elastic modulus of the silicone rubber was successfully reduced by introducing the PFP. Additionally, the magnetic field-induced martensite variant reorientation (MVR) was greatly enhanced by introducing a porous structure into the silicone rubber. The single-crystal Ni-Mn-Ga cube/porous silicone rubber composite materials are considered to be promising materials for applications in actuators.

Mesophase pitch modified silicone rubber coatings with fence-like ceramic layer structures and excellent ablation resistance performance

For ablation resistant silicone rubber composite materials, the strength of the ceramic layer is closely related to the ablation resistance of the composites. In this study, a series of mesophase pitch (MP) modified silicone rubber composites with superior ablation resistance performance were prepared. The ceramic layers of these composites have unique fence-like structures with good compressive strength. Characterization of ablation performance shown that the 20MP composite exhibited the best ablation resistance performance: a linear ablation rate of 0.072 mm/s and a mass ablation rate of 0.030 g/s. SEM and mercury intrusion measurements indicated that the ceramic layers of the composites formed porous and regular fence-like structures, which helped to resist flame ablation. The characterization of the compressive properties shows that the ceramic layers had excellent compressive strengths, and the compressive strength of the ceramic layer of the 20MP sample can reach 13.390 MPa. Observation by polarizing microscope shows that mesophase pitch left much ordered graphitic carbon in the ceramic layers, which helped to improve the strengths of the ceramic layers. XRD measurement confirmed that the ceramization reaction occurred and the ceramic substance SiC was produced during the ablation process. Mesophase pitch was proven to be a material that can improve the ablation performance of silicone rubber composites by increasing the ordered carbon content and strengths of the ceramic layers. These silicone rubber composites have the potential to be applied to ablation-resistant coatings on aircraft surfaces.

Anti-icing capability of textured silicone rubber surfaces via laser processing

ABSTRACT It is an undisputable fact that surface texture has a profound influence on the functional behavior of products. A method is proposed for manufacturing an anti-icing surface on silicone rubber composite material. Using a multi-function laser engraving machine, cylindrical micro-textures with different size and depth parameters are processed on the umbrella skirt surface of composite insulator samples. The optimal dimensional parameter of the surface micro-texture was determined by the best superhydrophobic property. By analyzing the freezing time of droplets, the influence of texture depth parameters on the anti-icing performance of the silicone rubber surface was investigated, which clearly confirmed that the contact angle affected anti-icing performance. Studying on adhesion of the ice on the sample surface and changing of the water contact angle after ice coating demonstrated the influence of texture-depth parameter on the deicing performance of silicone rubber surface. Thus, the characteristics and optimality of the texture specimen were obtained.

Preparation of Boron Nitride and Silicone Rubber Composite Material for Application in Lithium Batteries

Hexagonal boron nitride and silicone rubber (h-BN/SR) composites were prepared by the mechanical stirring method, and their crystal morphology, chemical structure, thermal properties, and compression stress–strain performance were investigated. The experimental results suggest that silicone rubber combined with h-BN exhibits better thermal conductivity and mechanical properties. When the proportion of h-BN is 30 wt%, the thermal conductivity of the h-BN/SR composite material is 0.58 W/m∙K, which is 3.4 times that of pure silicone rubber. At the same time, the compressive strength of h-BN/SR is 4.27 MPa, which is 6.7 times that of pure silicone rubber. Furthermore, the finite element model was employed to numerically analyze the thermal behavior of a battery with a h-BN/SR composite as the thermal interface material. The analytical results show that the highest temperature of the battery decreased when using h-BN/SR as the thermal interface material in the battery thermal management system. The h-BN/SR composite can thus effectively improve the safety properties of batteries.

Research on Tracking Resistance of Silicone Rubber Based on Laser-induced Breakdown Spectroscopy

Silicone rubber composite materials are widely used in the external insulation equipment of power systems, and the tracking resistance grade is one of the indicators used for evaluating the performance of silicone rubber. It is of great significance to quickly detect the tracking resistance of insulator materials on site. The existing tracking resistance tests are all laboratory tests performed after sample preparation, and there is a lack of on-site detection methods. The laser-induced breakdown spectroscopy (LIBS) method was used to establish the linear relationship between the amount of ablation due to tracking and the background radiation intensity of the experimental LIBS spectrum, and the influence of silica and alumina trihydrate (ATH) fillers on the material’s tracking resistance was studied. This study showed that the LIBS technology can be used to detect the tracking resistance of silicone rubber materials.

Enhanced mechanical, thermal and solvent resistance of silicone rubber reinforced by organosilica nanoparticles modified graphene oxide

To improve the mechanical and solvent resistance of silicone rubber (SR), the graphene oxide (GO) was proposed to reinforce the SR. GO was modified with organosilica nanoparticles which were synthesized by hydrolysis condensation of triethoxyvinylsilane (TEVS) to improve compatibility and interface interaction with matrix. The structure and morphologies of the organosilica-modified graphene oxide (MGO) was fully characterized by Fourier-transform infrared (FTIR), Raman, transmission electron microscopy (TEM) and thermal analysis (TGA) methods. It was found that TEVS was successfully hydrolysis condensation and organosilica nanoparticles with narrow size distribution were formed on the surface of graphene oxide nanosheets. The MGO was adopted to reinforce SR composites through physical mixing method. Raman mapping images confirmed that the improved distribution of MGO nanosheets than neat GO in SR. The mechanical, thermal and solvent resistance of MGO/SR composite was thoroughly studied. Compared with neat silicone rubber, the tensile strength of the silicone rubber composite material was improved by 2.1 MPa when the packing content was 20phr. Also, solvent resistance, the thermal stability and thermal conductivity of the MGO reinforced SR were increased by a certain margin. The mechanism of the improved mechanical and solvent resistance was also studied.

Preparation and Properties of Hollow Glass Microsphere/Silicone Rubber Composite Material with the Transition Layer of Silicone Resin

Hollow glass microsphere (HGM)/silicone rubber composite material was prepared by using silicone resin as the transition layer between silicone rubber and HGM. Silane coupling agent was hydrolyzed on the surface of HGM by in-situ polymerization to form the silicone resin layer. And then such modified HGM was added to the silicone rubber to prepare HGM/silicone rubber composite material. The curing process, mechanical property, morphology, thermal stability, and electrical property were studied. It is found that the transition layer of silicone resin can speed up the curing reaction. And the curing time becomes longer with the increase of HGM. The transition layer of silicone resin also improves the compatibility between HGM and silicone rubber. And the mechanical properties of the silicone rubber are reduced with the increase of HGM. The introduction of HGM can improve the thermostability of the silicone rubber. And HGM can obviously reduce the dielectric constant (from 3.4 to 2.6) and increase the dielectric breakdown strength (from 14.78 kV/mm to 16.71 kV/mm) of the samples.

A Quick Classifying Method for Tracking and Erosion Resistance of HTV Silicone Rubber Material via Laser-Induced Breakdown Spectroscopy.

Silicone rubber material is widely used in high-voltage external insulation systems due to its excellent hydrophobicity and hydrophobicity transfer performance. However, silicone rubber is a polymeric material with a poor ability to resist electrical tracking and erosion; therefore, some fillers must be added to the material for performance enhancement. The inclined plane test is a standard method used for evaluating the tracking and erosion resistance by subjecting the materials to a combination of voltage stress and contaminate droplets to produce failure. This test is time-consuming and difficult to apply in field inspection. In this paper, a new and faster way to evaluate the tracking and erosion resistance performance is proposed using laser-induced breakdown spectroscopy (LIBS). The influence of filler content on the tracking and erosion resistance performance was studied, and the filler content was characterized by thermogravimetric analysis and the LIBS technique. In this paper, the tracking and erosion resistance of silicone rubber samples was correctly classified using principal component analysis (PCA) and neural network algorithms based on LIBS spectra. The conclusions of this work are of great significance to the performance characterization of silicone rubber composite materials.

Surface Hardness Analysis of Aged Composite Insulators via Laser-Induced Plasma Spectra Characterization

Silicone rubber composite materials, especially high-temperature vulcanized (HTV) insulators, are widely used in high-voltage transmission lines. Previous studies have shown that the degree of aging of an HTV material is approximately linear with its hardness. The hardness measurement relies on laboratory analysis after sampling, and there is no alternative hardness test available for on-site application. In this paper, the ablation characteristics of HTV materials and the spectral and temperature characteristics of the corresponding plasmas were investigated via laser-induced breakdown spectroscopy (LIBS), thereby laying the foundation for the subsequent use of LIBS technology for on-site hardness characterization. A linear relationship was found between the hardness (either macroscopic or microscopic) of an HTV material and the intensity ratio of the ion line to the atomic line in the spectral data as well as a linear relationship between the hardness and the average plasma temperature corresponding to the aging layer. The results show that LIBS can serve as an effective source of hardness information for an HTV material and is therefore helpful for maintaining the safety of transmission lines.

Analysis of the silicone polymer surface aging profile with laser-induced breakdown spectroscopy

Silicone rubber composite materials have been widely used in high voltage transmission lines for anti-pollution flashover. The aging surface of silicone rubber materials decreases service properties, causing loss of the anti-pollution ability. In this paper, as an analysis method requiring no sample preparation that is able to be conducted on site and suitable for nearly all types of materials, laser-induced breakdown spectroscopy (LIBS) was used for the analysis of newly prepared and aging (out of service) silicone rubber composites. With scanning electron microscopy (SEM) and hydrophobicity test, LIBS was proven to be nearly non-destructive for silicone rubber. Under the same LIBS testing parameters, a linear relationship was observed between ablation depth and laser pulses number. With the emission spectra, all types of elements and their distribution in samples along the depth direction from the surface to the inner part were acquired and verified with EDS results. This research showed that LIBS was suitable to detect the aging layer depth and element distribution of the silicone rubber surface.

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.

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.

Effects of Oil Palm Empty Fruit Bunch Filler on the Electrical Tree Propagation in Silicone Rubber

This paper presents the study on the effects of oil palm empty fruit bunch (OPEFB) micro-filler on electrical tree propagation in silicone rubber composite material. In this study, the oil palm empty fruit bunch (OPEFB) filler with mean size of 32μm was employed as an electrical tree inhibitor. The sample for this electrical tree experiment was in the form of leaf-like specimen which was characterized as filled sample and non-filled sample. The filled sample contained 1 wt% of OPEFB filler while the non-filled specimen contained no fillers. Obtained results show that the lengths of electrical trees in filled silicone rubber were shorter than tree length of non-filled silicone rubber for 60minutes propagation time. This tree length difference shows that the OPEFB micro-filler helped to retard the growth of electrical tree. Therefore, this new organic filler is found to be useful for electrical tree inhibitor in high voltage insulation.