Silicone Grease Research Articles

Study on Reliability and Selection of Silicone Grease Used for Coating at the Interface Between Cable and Accessory

Silicone grease coated at the interface of cables and accessories performs a good role in lubricating and sealing during installation, but the swelling impact of silicone grease on rubber insulation of accessories greatly affects the long-term reliability of the interface between cable and accessory. Until recently, no standard has been proposed to guide accessory manufacturers in choosing the best silicone grease. In this study, nine different silicone greases that were widely used for accessories installation were chosen. First, three types of silicone greases with outstanding anti-swelling properties were tested using a silicone rubber (SiR) swelling experiment. The properties of the three silicone greases chosen were then investigated further, including electrical and mechanical properties, moisture resistance, and corona resistance. The results reveal that dimethyl silicone with high viscosity or by inserting phenyl side groups can minimize SiR swelling and then enhance its mechanical qualities. However, perfluoropolyether grease outperforms dimethyl silicone in terms of swelling resistance, chemical inertness, and excellent thermal stability. Thus, SiR coated with perfluoropolyether grease can maintain excellent mechanical properties after different aging. However, because of its high polarity, it can cause significant charge buildup at the interface between cables and accessories, particularly under direct current (dc) electrical stress. Consequently, perfluoropolyether grease will have a negative effect on the use in dc environment. Moreover, silicone greases after inorganic doping absorb moisture easily, resulting in a high relative dielectric constant that will have a negative effect on the use in a humid environment.

Experimental Determination of the Coefficient of Friction on a Screw Joint

This paper deals with the coefficient of determination of screw connection friction between the thread and the matrix. The coefficient of friction was measured using a laboratory device with an M20 screw connection without any grease and, subsequently, plastic grease was added (CX80 silicone, lithium, and copper grease). When grease is added, the friction in the threads and screw heads is limited and consistently retained. When tightening by torque, which represents the prevailing assembly method in standard screwing practice, only part of the torque is effectively used to create axial force and pre-stress. The rest of the torque is employed in friction suppression between threads and converted into heat. In general, the coefficient of friction depends on diverse factors such as the roughness of the thread surface, the gradient angle of the helix, and the grease properties. The tightening torque represents a primary parameter in the experimental measurements, monitored using a digital torque spanner, and generates an axial force in the screw. Based on the aforementioned parameters, the objective of this paper was to monitor changes in the coefficient of friction between the thread of the screw and the matrix in the case of different grease types. The actual coefficient of friction was calculated through the exponential equation of the torque balance. First measured was the load of the bolted joint without the use of grease, where the average value of the coefficient of friction was 0.44732; this value served as a benchmark for comparison to the measurements with the use of grease. The measurements showed that the value of the friction coefficient was reduced by 30.57% when using lithium grease, by 40.56% when using silicone grease, and by 47.64% when using copper-based grease, making the latter the most suitable for the application. Without appropriate greasing, friction suppression was accompanied by extremely high torques, which resulted in insufficient screw prolongation.

PILOT STUDY OF MODIFIED ROTATING ARM IMPACTOR FOR USE IN AEROBIOLOGICAL STUDIES

<h3>Introduction</h3> Utilized in aerobiological studies, the Rotarod Sampler (IQVIA) remains the gold standard in determining volumetric ambient airborne pollen concentration. However, utilization comes at the cost of high energy consumption, start-up and maintenance fees, and variable air patterns generated by rotating I-rods. We present a prototype to address the aforementioned issues: a battery-powered rotating arm impactor utilizing slides as opposed to rods. <h3>Methods</h3> The Rotorod Sampler Model 40 and prototype were situated in the same area and height, equipped with two rods and two slides coated with silicone grease, respectively. 7 atmospheric samples were collected and counted at various intervals over an 18-day period in June 2022, and directly compared. <h3>Results</h3> The prototype was created using 3D printing, with a 24 × 24 -millimeter exposure of each slide for sample collection. The prototype's speed was set at 10 revolutions per minute (RPM), while the Rotarod Sampler was set at 2400 rpm and utilized standard 31 × 1-millimeter sampler rods. Prototype battery needed to be replaced on days 2 and 18, and consequently may have impacted results. Mean pollen count and standard deviation of Rotarod Sampler was 124.2 and 40, and 23.4 and 10.6 for the prototype. The correlation coefficient was 0.61, signifying moderate positive association between pollen counts obtained from the Rotarod Sampler and prototype. <h3>Conclusion</h3> Though our prototype has a larger surface area, it collected significantly less pollen than the Rotarod Sampler. A moderate correlation between the two devices was observed, though increases in the RPM of the prototype should be considered for future evaluation.

Coupling Analysis on the Thermophysical Parameters and the Performance of Liquid Cooling-Based Thermal Management System for Lithium-Ion Batteries

In order to ensure the safety and extend the lifecycle of lithium-ion power batteries in electric vehicles, a battery thermal management system based on minichannel liquid cooling is proposed to cool rectangular lithium-ion batteries, and a three-dimensional cooling system model is established. The effects of the number of channels, the thickness of heat conducting silicone grease and the thermal conductivity of the battery itself on the temperature rise and voltage drop changes during the discharge process of the battery are studied. The results show that the maximum temperature of the battery decreases with the increase of the number of channels, and the voltage drop inside the channel increases with the increase of the number of channels. The maximum temperature of the battery increases with the increase of the thickness of the thermal grease, but the increase is only 1.26 K. The maximum temperature and local temperature difference of the battery change significantly with the change of the thickness of the battery and its own thermal conductivity. The simulation results will be beneficial to the design of a battery thermal management system based on minichannel liquid cooling.

Thermal Estimation and Thermal Design for Coupling Coils of 6.6 kW Wireless Electric Vehicle Charging System

Wireless electric vehicle charging technology is developing in the direction of high power levels. However, more generated heat brought by higher power will accelerate the system’s aging and can even lead to damage. An excellent thermal design for the magnetic coupler can reduce each part’s maximum temperature, ensuring long-term operation reliability. Therefore, in this article, the magnetic coupler’s thermal estimation and design are studied based on a 6.6 kW wireless electric vehicle charging system. First, the calculation method of internal resistance of a litz coil, core loss, and eddy current loss of a shielding aluminum plate are studied. Considering the influence of thermal fields on material properties, each part’s power loss calculation formula is further modified to improve the accuracy. After that, heat dissipation research is carried out. The heat dissipation measures, such as filling the surface of the shielding aluminum plate with thermal conductive silicone grease, are proposed. Finally, the effectiveness of the heat dissipation measures is verified by simulation and experiments. The experiment shows that the error between the power loss value of each part calculated by simulation and measured by the experiment is less than 15%, and the maximum temperature of the magnetic coupler is controlled below 80 °C.

Primary Factors Affecting the Efficiency of Thermoelectric Power Generation Sheets for Waste-Heat Recovery from the Ship’s Exhaust Gas

In order to investigate the effect of different influencing factors on the application of temperature differential power generation in the ship exhaust gas and to explore the potential of waste heat recovery and the utilization of exhaust gas during ship travel, an experimental system based on the temperature differential power generation of ship exhaust gas in the marine environment was established. The maximum output power and the maximum efficiency of each temperature-difference power generation module were theoretically calculated. The results showed that the insulation material and the salt water (seawater) had little effect on the efficiency of the temperature differential power generation modules. Conversely, the installation pressure, the heat transfer oil, the cooling water temperature (seawater temperature), and the heat source temperature (exhaust gas pipe temperature) had a great influence on the open-circuit voltage and the maximum output power. The thermally conductive silicone grease and the cooling water temperature of 10 °C increased the open-circuit voltage by 31.54% and 18.95%, respectively, and increased the maximum output power by 82.05% and 51.79%, respectively. The maximum output of a single temperature differential power generator reached 63.5% when using an installation pressure of 3 bar, a cooling water temperature of 20 °C, double-layer aluminum insulation, and thermally conductive silicone grease. Finally, this study provides relevant data support for using temperature differential power generation devices for ship exhaust gas.

New Interventions by silicone grease in synthesis

AbstractIn redox‐transmetallation protolysis (RTP) reactions in tetrahydrofuran (thf) between excess scandium or cerium metal, Hg(C6F5)2 and 3,5‐dimethylpyrazole (Me2pzH) in silicone greased Schlenk flasks, formation of the 3,5‐dimethyl‐1‐pyrazolyl(dimethyl)siloxide (Me2pzSiMe2O) ligand was observed. Thus the former reaction gave [Sc2(Me2pz)4(Me2pzSiMe2O)2] 1 in good yield, whilst the latter gave a mixture of [Ce4O(Me2pz)9(Me2pzSiMe2O)2] 2 a, [Ce4O(Me2pz)11] 2 b, both mixed oxidation state species, and the CeIV complex [Ce(Me2pz)4(Me2pzH)] 2 c.

Fluidic phase–change materials with continuous latent heat from theoretically tunable ternary metals for efficient thermal management

Phase-change materials (PCMs), as important energy storage materials (ESMs), have been widely used in heat dissipation for electronics. However, PCMs are encountering huge challenges since the extremely limited space in microelectronics largely suppresses the applied volume of PCMs, which demands excellent PCMs that can fully utilize the valuable latent heat. This work successfully found a universal strategy toward powerful ESMs from fluidic ternary metals (TMs, GaInSn as a representative TM in this work). TMs exhibit high thermal conductivity (20.3 W m-1 K-1) and significantly effective latent heat (115 J/cm3) and, more important, show continuous phase transition and full utilization of the valuable latent heat. Interestingly, theoretical prediction through ternary phase diagram is carried out to easily tune the melting range, latent heat, and fluidity (viscosity) of TMs to adapt with different service conditions. As a result, thermally conductive silicone grease can be conveniently fabricated via simple shear mixing of TM and polymers. Such thermally conductive TM grease inherits the merits of TM, exhibiting continuous thermal control over daily electronics according to thermal shock performance.

In situ growth of graphitic carbon nitride on multiwalled carbon nanotubes for interfacial thermal management

This work reports a facile method for in situ growth of graphitic carbon nitride (CN) on surface of multiwalled carbon nanotubes (CNTs), which was performed via the self-assembly of molecular precursors of CN on CNTs and subsequent calcination step. The self-assembly was directed by the hydrogen bonds formed between amino groups of Melamine and carboxyl units of CNTs. After polycondensation reaction, CN nanostructures grew homogeneously on surface of CNTs possibly linked by covalent bonds. The incorporation of CN improved the interfacial properties of CNTs by increasing the functional groups and wettability, which could promote the dispersion of CNTs in polymer matrix and enhance the heat conductive capacity. Accordingly, the obtained thermal conductive silicon grease involving CNTs/CN nanocomposites showed an enhancement in thermal conductivity at a loading amount of CN (~ 8%). Meanwhile, the insulation resistance of the nanocomposites increased significantly with the dose amount of CN due to its semi-conductivity. Therefore, the obtained CNTs/CN nanocomposites were suitable for interfacial thermal management that require high thermal conductivity and electrically insulative properties.

Liquid cooling system for battery modules with boron nitride based thermal conductivity silicone grease.

Heat-conductive silicone grease (HCSG), one of the most common composite thermal interface materials (TIMs) used in many advanced applications, is limited by its low thermal conductivity (TC). Different surface modification agents are required to improve the dispersion of TC additives and the interfacial compatibility with the silicone matrix. In this study, MQ silicone resin (MQ) was used to modify two kinds of self-made spherical boron nitrides (SBNs), with different particle sizes, using the sedimentation method. The amount of filler content allowed within the SBNs increased owing to the similar polarity of the MQ and the silicone matrix, and a HCSG with a TC of 1.22 W (m−1 K−1) and a thermal resistance (TR) of 0.49 °C W−1 was obtained, respectively. In addition, the TC pathway was formed more easily with the 15 μm SBNs than with the 5 μm SBNs. In order to verify its potential application in battery thermal management, the HCSG was assembled on the surface of the liquid-cooling plate in the 18 650-battery module, and it was found that the maximum temperature of the battery module could be maintained below 42 °C, and the temperature difference could be controlled within 5 °C. Thus, with these excellent performances, the MQ silicone resin reported here, with respect to the assembly methods, will provide insights into the thermal management and energy storage fields.

Flexible and insulating silicone rubber composites with sandwich structure for thermal management and electromagnetic interference shielding

High integration development of electronics requires materials possessing excellent thermal conductivity, electromagnetic interference (EMI) shielding, and electrical insulation. In this work, Fe2O3 particles are deposited on carbon fibers (CF) and then utilized as fillers (CF@Fe2O3) in boron nitride/silicone rubber (BN/SR) to fabricate sandwich structured CF@Fe2O3/(BN/SR) composites, herein, BN/SR as top & substrate layer, and CF@Fe2O3 as middle layer. Orientation of BN in CF@Fe2O3/(BN/SR) composites realizes excellent in-plane thermal conductivity coefficient (λ∥), and the core-sheath structure of CF@Fe2O3 achieves good EMI shielding performance by the “absorption-reflection (transmittance)-reabsorption” process of electromagnetic waves, insulation modification of CF and the sandwich structure strengthen the electrical insulation. When the amount of BN and CF@Fe2O3 are 20.6 wt% and 45.5 wt%, respectively, the λ∥, EMI shielding effectiveness, volume resistance and breakdown strength of CF@Fe2O3/(BN/SR) composites reach 3.86 W/(m·K), 37.7 dB, 6.2 × 1014 Ω cm and 26.8 kV/mm, respectively, which are all higher than those of commonly fabricated CF/(BN/SR) composites with same amount of BN and CF (3.83 W/(m·K), 19.4 dB, 8.6 × 1013 Ω cm and 21.4 kV/mm). CF@Fe2O3/(BN/SR) composites possess better cooling effect (5.6 °C) than that of commercial silicon grease (QM850) on the testing platform of computer's central processing unit, whose functions are more abundant and have wide application prospects in electronics.

Electronic cooling using Thermal Interface material

Present work is an experimental investigation, carried on metallic contacts in order to enhance the thermal contact conductance and hence heat dissipation by applying Thermal Interface Materials. The steady state experiments have been performed under an atmospheric environment on Copper-Aluminum contacts for selected range of contact pressure and temperatures in order to suit the specifications of electronic industry. Here, Graphene paste has been evaluated as thermal interface material against the bare metallic contacts for a range of interface pressure and heating conditions. Error analysis has also been carried out for the present experimental analysis. A very good improvement in TCC has been observed using graphene paste as Thermal Interface Material, which leads to better heat dissipation. TCC has been compared with the silicon grease results also provided in the literature. Therefore, the present results show the application and suitability of the chosen Thermal Interface Materials and will be relevant in thermal management applications for the selected range of interface pressure and temperature conditions.

Design and Development of a New Rotating Electromagnetic Field Generation System for Driving Microrobots

This article presents the design, optimization, and testing of a new rotating electromagnetic field generation system for actuating magnetic microrobots. Its unique feature lies in that the proposed six-coil electromagnetic actuation system produces a uniform rotating magnetic field with a large 3-D workspace, which is enabled by conducting an architectural optimization of the system in consideration of both electric issues and geometry constraints. To maintain a low working temperature, each coil is fabricated with silicone grease for filling the gap among the copper wires and integrated with a water cooling fan for reducing the effect of coil heating. An analytical model is established to determine the dominant structural parameters, which are optimally tuned by resorting to genetic algorithm (GA) to achieve the best actuation performance. A prototype magnetic field generation system is developed for experimental testing. Experimental studies are carried out by driving various magnetic microrobots, including helical microswimmers and microparticles. Results indicate that the developed system can effectively actuate the microrobots with precision motion tracking, validating the effectiveness of the developed rotating magnetic field generation system.

Morphology evolution and breakdown mechanism of cross‐linked polyethylene (XLPE)–silicone rubber (SiR) interface induced by silicone grease diffusion

Silicone grease (SG) is used for lubrication during cable accessory installation and can penetrate into the silicone rubber (SiR), leading to properties deterioration of the SiR. In this study, the effects of SG on the breakdown characteristics of the cross-linked polyethylene (XLPE)–SiR interface are investigated. First, the variation of the XLPE–SiR interface breakdown voltage with SG coating time is experimentally explored. The interface breakdown voltage significantly increases after SG is applied, remains stable for coating times of up to approximately 144 h and then rapidly decreases; the minimum interface breakdown voltage is lower than that without the SG coating. Next, the effects of SG on the chemical composition and surface topography of the SiR are examined by infrared spectroscopy and optical profilometry, respectively. The SG penetration does not change the functional groups of the SiR but significantly increases its surface roughness. Finally, the interface electric-field distribution after coating with SG is analysed by finite-element simulation, revealing that the residual SG at the interface distorts the interface electric field after a long coating time. The increase in the SiR surface roughness caused by SG diffusion and the interface electric-field distortion caused by the residual SG together lead to the decrease of the interface breakdown voltage.

Stable magic angle spinning with Low-Cost 3D-Printed parts

A 3D-printed double-bearing magic angle spinning (MAS) system was developed with a home-built 4.0 mm MAS nuclear magnetic resonance (NMR) probe at 7 T. Various fused deposition modelling 3D printers were used to produce spinning modules of ignorable materials costs for rotors with a diameter of 7.0, 4.0, and 3.5 mm. High-performance MAS experiments on the 4.0 mm-diameter model using a pencil-type ceramic rotor and 3D-printed drive cap resulted in a high-resolution 1H NMR signal of silicone grease. The 3.5 mm-diameter MAS system reached a spinning frequency of 23 kHz. Furthermore, 3D-printed inserts were designed for various rotor sizes which can isolate the sample from humidity for a duration of more than a week. Single crystal inserts for MAS rotors of commercial probes can readily be printed using two-color printers. Those developments enable customized low-cost MAS NMR for both adapting existing and manufacturing new probes, respectively.

Effect of ionic liquids modified nano-TiO2 as additive on tribological properties of silicone grease

A series of silicon greases were fabricated by using polytetrafluoroethylene as thickening agent and polydimethylsiloxane as base oil. Four kinds of ionic liquids modified nano-titanium dioxide were employed as solid additives with different concentrations of 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 wt%. The chemical composition and thermal stability of the additives were explored by a Fourier transform infrared spectroscopy and a thermal gravimetric analyzer at a heating rate of 10 °C min−1 under a flow of nitrogen, respectively. The volume resistivity of greases was measured by a volume surface resistance tester in the room temperature of 25 °C. The tribological properties were investigated using a ball-on-disc tribometer under a stroke of 5 mm, a frequency of 5 Hz and different applied loads of 50, 100, 150 and 200 N. After tribological tests, a scanning electron microscopy and x-ray photoelectron spectroscopy were used to probe the lubrication mechanisms. Results showed that nano-titanium dioxide were successfully modified by ionic liquids and their decomposition temperatures were all higher than 300 °C. Meanwhile, the addition of additives had a significant influence on the conductivity and tribological properties of the greases. Specially, the grease containing 1.5 wt% additives exhibited good friction reduction and anti-wear abilities. The analysis of the worn surfaces indicated that the reasons for raising the anti-friction and anti-wear abilities were attributed to the synergistic effects of ionic liquids and solid additives which promoted the formation of lubricating films on the worn surfaces.

A Greasing Method for Improving The Performances of Polluted Insulators.(Dept.E)

The present experimental work reports an investigation of the effect of artificial pollution on the performance of suspension ingulators. It was found experimentally that the greasing of suspension insulators by silicone grease improve their performancos oven undor heavy pollution conditions. A silicono grease layer of comparatively small thickness reduces the effect of dirt accumulation and increase the flashover voltage. The leakage current of greased insulators is very lower than that of ungreased insulators. It was found also that the flashover mschanism of polluted insulators under both d.c. and a.c. voltagos depends mainly on the formation of dry-bands, formed by the leakage current. As the applied voltage is increase, these bands extend in width causing partial sparkings across them and leading finally to a totally flashover over the insulator.

Systematic Research on the Heat Dissipation Channel of High Power LED Street Lamps

This article mainly studies the thermal characteristics of light source of the street lamp, and systematically analyzes the effective ways of heat transfer and heat dissipation of street lamp. Based on experiments and finite element simulations, the heat dissipation channels of street lights were studied, and the weak links of heat transfer and heat dissipation were analyzed, and the heat dissipation structure of street lamp was optimized. The experimental results show that the junction temperature of the chip is lower than 90 °C in the steady state, and the luminous efficiency decreases by 5.93%. In order to ensure the efficiency and reliability of the street lamp, it is recommended that the junction temperature of the street lamp be controlled below 85 °C. After analyzing the arrangement of the chips, silicone grease with different thermal conductivity and aluminum substrate, it is found that the substrate is the bottleneck affecting effective heat transfer, and the use of diamond like carbon metal core printed circuit board (DLC-MCPCB) can reduce the junction temperature by 17.04 °C. Through the grid design of shell of the street lamp, the heat dissipation effect of the street lamp surface can be enhanced, and the junction temperature can be reduced by 7.04 °C. Based on these studies, the optimal design model of street lamp was obtained, which provides guidance for practical applications.

Compatibility and Interaction Mechanism between EPDM Rubber and a SF6 Alternative Gas-C4F7N/CO2/O2.

Among the numerous novel eco-friendly insulating gases, C4F7N has attracted much attention due to its excellent electrical performance. However, except for the electrical perfomance, the compatibility between the gas medium and the sealing materials is equally important for gas-insulated equipment. At present, studies about the compatibility between C4F7N and EPDM, a widely used sealing material in power systems, are available in some previous works, but few focused on the compatibility comparison between C4F7N gas mixtures and EPDM with different third monomers. In this paper, we carried out the thermal aging test on ENB-EPDM, DCPD-EPDM, and C4F7N gas mixture to perfect the compatibility mechanism between EPDM and C4F7N. It was found that both of the EPDM reacted with the gas mixture and led to the property changes in the solid samples and the decomposition of C4F7N. On the other hand, by coating silicone grease, the contact between gas and rubber was effectively blocked and the concentration of the decomposition product was significantly reduced. The performance comparison indicates that ENB-EPDM is more suitable for sealing the C4F7N gas mixture, which is due to the superior thermal stability of ENB.

Machinability improvement of Inconel 718 through mechanochemical and heat transfer effects of coated surface-active thermal conductive mediums

Low thermal conductivity usually leads to workpiece materials machine poorly and difficultly. Surface-active media has been proven to improve the machinability of workpiece materials. However, the non-thermal-conductive films have been selected in previous research as the surface-active medias, which are hard to improve machinability of workpiece materials with low thermal conductivity such as Inconel 718. This paper presents a novel technique to improve the machinability of Inconel 718 by applying surface-active thermal conductive medium (SACM) on the surface of workpiece before machining. The SACM can improve the heat dissipation and reduce the cutting temperature. Three SACMs including thermal conductive silicone grease (SG), glue (GL) and liquid graphene (GR) are recommended and applied on Inconel 718 surface. The effects of SACMs on the Inconel 718 machinability improvement are verified through machining experiments. The cutting temperature, surface roughness, and cutting force with and without SACMs are measured and analyzed. The results show that the minimum cutting force, cutting temperature and machined surface roughness under using GR SACM, which are reduced by 11%, 12% and 23% respectively compared with that without SACM. It is found that the improvement of Inconel 718 machinability is attributed to the coupling effect of mechanochemical and heat transfer effects of GR SACM.