Silicone Fluid Research Articles

Machine Learning Analysis of Low-Frequency Impedance Spectra of Binary Mixtures of Polar and Non Polar Liquids

The complex dielectric permittivities were determined using a precision LCR meter of the binary mixtures of a polar liquid (methyl ethyl ketone, or MEK) and a non-polar liquid (dimethyl silicone fluid, or DMSF) at 303.15 K temperature. After determining the complex impedance (Z* (ω)) using the complex permittivity portion (ɛ* (ω)) of polar and nonpolar liquids, the complex impedance data (Z* (ω)) was fitted to the Nyquist Plot. Our research described here investigated the impact of ionic impurities in the pure MEK, DMSF and in their mixed state. The established parameters provided information on the impact of concentration changes on the electrical characteristics of the binary mixtures. Our research delved into utilizing machine learning (ML) techniques, such as random forest (RF), LightGBM, and XGBoost regressors, to improve the material design and prediction modeling. The main objective was to assess the efficacy of various regression techniques in evaluating the material characteristics performance. Experiments spanning from 30% to 50% of the data set were carried out, with performance metrics, like, R2 score and MAE, being utilized. Notably, the RF regressor demonstrated outstanding performance in these evaluations with an R2 score of 0.9999. The simulation results indicated that the ML-based techniques offer resource and time savings, serving as effective tools for predicting material performance at intermediate frequencies.

Design and Development of a Heating System to Control Windshield Fog

Road visibility in passenger vehicle is of major concern for the car manufacturers and safety design engineers. Water film (Fog) that forms on the windshield during winter times would reduce and disturb the driver’s visibility. Extreme weather condition can make a difference while driving. One may experience the wide range of challenges during driving. The factors which mostly affected the visibility can be rain, fog, ice, snow, dust, etc. Due to such factors, it becomes very tough for driver to have a clear view of front side. Rear view is possible with the help of left and right view mirror fitted outside the front doors. Visibility of rear view mirror depends upon the visibility of the front side window glasses. Driving through rain, produces more challenging situation when water droplets on outsides surface of front window glass obstruct the vision. This problem becomes more dangerous when light gets scattered through water droplets and obstruct the vision during rainy night. The main objective of this work is to find the possible solution for removing the fog from a specific area of front and rear windshield to have a clear view to avoid the accidents. In the present work, hot water and silicon fluid utilized to impinge on the front and rear glasses with the help of converging nozzle and fluid inside the two windshields. The various combination of outlet water and silicon temperature is used for obtaining maximum clearing area. Computer simulated results are verified with the experimental results.

Saffman–Taylor instability in eccentric cylinders at gaseous cavitation

A flow of silicon fluid in the gap between eccentric cylinders was studied experimentally. The condition of gaseous cavitation inception during the rotation of internal cylinder was considered. It was shown that at reduction of the gap between cylinders Saffman–Taylor instability appeared on surface of the internal cylinder and then gaseous cavitation was observed. Possibility of one uniform gas formation appearance under this type of instability was demonstrated.

Impedance Spectroscopy of Binary Mixtures of Dimethyl Silicone Fluid and Methyl Iso Butyl Ketone

A precision LCR metre was used to measure the parallel resistance (RP) and parallel capacitance (CP) of a capacitive cell filled with samples of binary mixes of methyl isobutyl ketone (MIBK) and dimethyl silicone fluid (DMSF), over the frequency range of 100 Hz to 2 MHz, at a temperature of 303.15 K. Using RP and CP, complex impedance Z*(ω) was computed. A four-element equivalent circuit model was used to fit the complex impedance data. The fitting provided the values of various circuit elements representing various electrical processes occurring in the capacitive measurement cell under the influence of an applied ac field. The Bode plot presentation of the complex impedance data confirmed the values of various circuit elements determined using the fitting process. Complex impedance formalism supports the observation of the electronic double-layer capacitance (EDLC) phenomena and ionic conduction relaxation phenomena.

Preparation of Monotrimethoxylsilylethyl-Terminated Polysiloxane Fluids and Their Application in Thermal Interface Materials.

In this study, α-Trimethylsilylmethyl-ω-dimethylsilyl-terminated polydimethylsiloxane, polydiethylsiloxane and poly[2,2,2-trifluoropropyl(methyl)siloxane] are synthesized using an anion catalyzed nonequilibrium polymerization reaction with trimethylsilylmethyl lithium as the initiator; hexamethylcyclotrisiloxane, hexaethylcyclotrisiloxane or 1,3,5-trimethyl-1,3,5-trifluoropropylcyclotrisiloxane as the monomer; and dimethylchlorosilane as an end-capping agent. Three kinds of α-trimethylsilylmethyl-ω-trimethoxylsilylethyl-terminated polysiloxanes are further prepared by hydrosilylation reaction of α-trimethylsilylmethyl-ω-dimethylsilyl-terminated polysiloxanes with vinyltrimethoxysilane using Karstedt's catalyst. These α-trimethylsilylmethyl-ω-trimethoxylsilylethyl-terminated polysiloxanes are functionalized as in situ surface treatment agents for AlN particles. The effects of the structure of these polysiloxanes on the dispersion of AlN in the polysiloxane matrix and on the heat transfer performance of silicone pastes and silicone rubbers are investigated. A possible mechanism of surface treatment of AlN fillers by these novel silicone fluids is also discussed.

Physicochemical considerations in the formulation development of silicone elastomer vaginal rings releasing 5-nitroimidazole drugs for the treatment of bacterial vaginosis

Bacterial vaginosis (BV) is a common dysbiosis of the human vaginal microbiota characterized by depletion of hydrogen peroxide and lactic acid-producing Lactobacillus bacteria and an overgrowth of certain facultative anaerobic bacteria. Although short-term cure rates following treatment with frontline antibiotics (most notably oral metronidazole (MNZ), clindamycin vaginal cream, and MNZ vaginal gel) are generally high, longer-term recurrence rates are an issue. The development of vaginal formulations offering continuous/sustained administration of antibiotic drugs over one or more weeks might prove useful in reducing recurrence. Here, we report the manufacture and preclinical testing of matrix-type vaginal rings offering sustained release of four 5-nitroimidazole antimicrobial drugs either being used clinically or having potential in treatment of BV – MNZ, tinidazole (TNZ), secnidazole (SNZ) and ornidazole (ONZ). All four drugs showed good compatibility with a medical-grade addition-cure silicone elastomer based upon thermal analysis experiments, and matrix-type rings containing 250 mg (3.125 %w/w) of each drug were successfully manufactured by reaction injection molding. 28-day in vitro drug release studies demonstrated root-time kinetics, with daily release rates of 25, 22, 9 and 6 mg/day½ for SNZ, ONZ, MNZ and TNZ, respectively. The rank order of drug release from rings correlated with the simple molecular permeability parameter S/V, where S is the measured drug solubility in silicone fluid and V is the drug molecular volume. The relative merits of SNZ and ONZ over MNZ (the current reference treatment) are discussed. The data support development of vaginal rings for sustained release of 5-nitroimidazole compounds for treatment of BV.

Starch/Silicone Elastomers and Foams

While the beneficial physical properties of silicone polymers are exploited in many sustainable applications, the high energy requirement for their synthesis compromises to a degree their sustainability. We report a strategy to mitigate this issue by filling the silicone with inexpensive and renewable starch. Elastomeric materials with covalently grafted starch, utilizing anhydride-modified silicones, permits loading of up to about 75% starch while maintaining many of the properties of the silicone. Alternatively, 50 wt.% starch-filled silicone foams can be prepared simply by mixing powdered starch with a mixture of HSi-functional silicone fluids in the presence of B(C6F5)3. The physical properties of the resulting foams are determined by the quantity of SiH, which controls the final density of the foams (ranging from 0.258–0.875 g mL−1), their Young’s modulus, and their degree of elasticity; both rigid and flexible foams were prepared. Materials with a high natural and renewable material content better adhere to green chemistry principle 7, should enhance the ease of degradation at end of life, and augment the sustainability of these silicone composites.

Synthesis and Properties of Polyurea Greases Based on Silicone Fluids and Poly-α-olefin Oils

The paper describes an investigation of lubricants synthesized by thickening a dispersion medium consisting of silicone oil (PES-5) and poly-α-olefin oil (PAOM-12) with diureas of different compositions. The study revealed the effects of the compositions both of the dispersion medium and urea thickener, as well as their ratio in the lubricating formulation, on the major physicochemical properties of resultant greases. Increasing the content of the hydrocarbon component of the grease was shown to improve the physicochemical properties. Finally, the optimum grease composition was identified: introducing a polyurea thickener that contained diphenylmethane-4,4'-diisocyanate resulted in the synthesis of greases that had adequate operating characteristics and an improved wear performance.

Application of Transformer Oil and Biodegradable Ester Mixtures as Insulation for High-Voltage Equipment

Synthetic and natural esters as insulating fluids for high voltage equipment have been a focus of much research, especially in the last two decades. This is due to the fact that, unlike mineral oil, ester fluids are biodegradable, non-toxic, safe for the environment and human health, produced from renewable raw materials, and feature high fire resistance. Despite the fact that commercially available ester fluids having excellent insulating properties are offered in the market, both transformer manufacturers and operators are not yet ready for mass-scale transition to the use of biodegradable ester dielectric fluids. In addition, since there is a huge amount of electrical equipment filled with mineral oil, mass-scale replacement of this oil with ester dielectric fluids will be extremely expensive for power companies. A suitable way for making a shift from oil to esters can be partial replacement of mineral oil with ester fluids (for example, topping up during repairs) or complete replacement of mineral oil with biodegradable esters. Whatever of these options is implemented, there will be a mixture of two insulating fluids inside of the equipment. Therefore, specialists intensely study the characteristics and behavior of insulating mixtures based on mineral oil and other dielectric fluid (synthetic ester, natural ester or silicone fluid). The article presents a review of the latest advances in the investigations of mixtures consisting of mineral oil and other dielectric fluids, including the studies of their properties. Problems associated with the operation of equipment in the case of its filling with mixed liquids are discussed.

Synthesis and Properties of Polyurea Greases Based on Silicone Fluids and Poly-α-olefin Oils

The paper describes an investigation of lubricants synthesized by thickening a dispersion medium consisting of silicone oil (PES-5) and poly-α-olefin oil (PAOM-12) with diureas of different compositions. The study revealed the effects of the compositions both of the dispersion medium and urea thickener, as well as their ratio in the lubricating formulation, on the major physicochemical properties of resultant greases. Increasing the content of the hydrocarbon component of the grease was shown to improve the physicochemical properties. Finally, the optimum grease composition was identified: introducing a polyurea thickener that contained diphenylmethane-4,4'-diisocyanate resulted in the synthesis of greases that had adequate operating characteristics and an improved wear performance.

A Cobalt-Containing Polysilane as an Effective Solid-State Catalyst for the Hydrosilylation of Alkenes

A cobalt-containing polysilane was readily obtained from the treatment of poly(monohydro)silane with Co2(CO)8 at 60 °C. The resulting polysilane-supported cobalt catalyst (Co/Si catalyst) acts as a solid-state catalyst that exhibits good catalytic performance toward the hydrosilylation of various alkenes with hydrosiloxanes, such as 1,1,1,3,3-pentamethyldisiloxane. Suitable alkenes for this catalysis include functionalized alkenes such as allyl glycidyl ether and vinylsiloxanes as well as multiply functionalized alkenes such as triallylisocyanurate. The Co/Si catalyst can be recycled multiple times, and recycling is accomplished by simple centrifugation. It is noteworthy that this Co/Si system also catalyzes the modification of a silicone fluid and cross-linking between poly(monohydro)siloxanes and polysiloxanes that bear vinyl functionalities to afford silicone polymers, which are industrially important reactions.

United atom and coarse grained models for crosslinked polydimethylsiloxane with applications to the rheology of silicone fluids.

Siloxane systems consisting primarily of polydimethylsiloxane (PDMS) are versatile, multifaceted materials that play a key role in diverse applications. However, open questions exist regarding the correlation between their varied atomic-level properties and observed macroscale features. To this effect, we have created a systematic workflow to determine coarse-grained simulation models for crosslinked PDMS in order to further elucidate the effects of network changes on the system's rheological properties below the gel point. Our approach leverages a fine-grained united atom model for linear PDMS, which we extend to include crosslinking terms, and applies iterative Boltzmann inversion to obtain a coarse-grain "bead-spring-type" model. We then perform extensive molecular dynamics simulations to explore the effect of crosslinking on the rheology of silicone fluids, where we compute systematic increases in both density and shear viscosity that compare favorably to experiments that we conduct here. The kinematic viscosity of partially crosslinked fluids follows an empirical linear relationship that is surprisingly consistent with Rouse theory, which was originally derived for systems comprised of a uniform distribution of linear chains. The models developed here serve to enable quantitative bottom-up predictions for curing- and age-induced effects on macroscale rheological properties, allowing for accurate prediction of material properties based on fundamental chemical data.

Chemically Modified Silicone Oil with Enhanced Tribological and Anti-Foaming Properties

Two kinds of chemically modified silicone oil, diisooctyl phosphate-terminated silicone oil (UCP204) and dioctyl dithiophosphate-terminated silicone oil (UCT2003), were synthesized. The tribological properties of silicone oil were evaluated using an SRV tribometer, and the worn surface and chemical composition were examined by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). The friction coefficients of UCP204 and UCT2003 were reduced by approximately 62.7% and 56.7% compared with untreated silicone oil. The results indicated that the incorporation of phosphorus and/or sulfur could significantly enhance the tribological performance of modified silicone oil. Benefiting from their unique chemical structure, chemically modified silicone fluids also exhibit good dispersion stability and excellent anti-foaming properties, which are mainly attributed to the low surface tension properties imparted by the silicone backbone and the better dispersion stability provided by the dialkyl dithiophosphate group in chemically modified silicone fluids. It is also found that lubricants containing modified silicone oil remain clear after three months of storage and still maintain good anti-foaming properties.

Investigation of the interface behavior of a viscous fluid under free surface shear flow using an eccentric transparent Couette cell

Abstract In the present work, a prototype was developed to observe the flow behavior of viscous fluids under free surface shear and determine an adhesion energy in this flow geometry. The geometry consists of an eccentric Couette cell (outer cylinder radius of 89.5 mm, inner cylinder radius of 43.75 mm and minimal gap of 3 mm) that can be used in two modes, where both cylinders can respectively rotate in the same or opposite directions. Cylinders are horizontal and short relatively to their diameters (30 mm long). Transparent windows allow in-situ flow observations. The design, development, and testing of the prototype with a model viscous fluid (silicone fluid with a 2.2 104 Pa.s Newtonian viscosity) are reported in this paper. The flow behavior of small fluid volumes (fill factor smaller than 15%) was investigated under co- and counter-rotating configurations to determine steady-state flow conditions. Stationary conditions were identified in the counter-rotating mode. The velocity conditions and resulting observations are studied and analysed. However, for the used silicone fluid, the bulk dissipative energy is much larger than the work of adhesive forces in the investigated regimes. The adhesion energy contribution could not be detected for this fluid.

Realizing Vat-Photocycloaddition 3D Printing with Recyclable Synthetic Photorheological Silicone Fluids.

Synthetic silicone rubbers are finding a broad spectrum of applications, yet there is a demand for developing greener silicone rubbers with processability, recyclability, and reversible tunability in their mechanical properties. Here, a recyclable photorheological silicone fluid (RPSF) is developed, which realizes completely reversible wavelength-selective liquid-rubber conversion upon photoirradiation, relying on the reversible photocycloaddition of coumarin upon alternating irradiation of light with wavelengths of 365 (UV365 ) and 254nm (UV254 ). Rheological studies demonstrate that the storage modulus of the developed RPSF increases by a factor of more than 100 000 upon UV365 irradiation to reach 20-50kPa, while it decreases to ≈0.01kPa upon UV254 irradiation. The reversibility of the photocycloaddition of coumarin enables the application of RPSF as a photodismantlable adhesive. Furthermore, unprecedented vat-photocycloaddition 3D printing of silicone rubber is realized by taking advantage of the excellent photocurability, that is, the dramatic increase in viscoelasticity upon UV365 irradiation.

Анализ работоспособности силиконовых демпферов крутильных колебаний судовых двигателей внутреннего сгорания на основе результатов испытательного центра Marine Technology Service

The article presents the analysis results of changes in the operability of silicone dampers of torsional vibrations of marine diesel engines on the basis of practical measurements carried out by the Testing Center Marine Technology Service under the Astrakhan State Technical University (TC MTS). TC MTS is accredited by the Russian classification society - the Russian Maritime Register of Shipping (RMRS) in the field of calculation and measurement of torsional vibrations. During its functioning (2001 – to date) the TC MTS has conducted torsiographing procedures of the machine-propulsion systems (MPS) of more than 200 vessels. The large amount of data obtained makes it possible to assess the dynamics of changes in the parameters of torsional vibrations, including amplitude and frequency, according to the results of periodic torsiographing the ship MPS. A change in the technical condition of the torsional vibration damper (a decrease in the efficiency of its operation) and the lack of its constant monitoring lead to the increasing stresses in the ship shaft line and, as a result, to a growing risk of its breakdown, which confirms the urgency of the study. There are given the images as real examples of ship operation failure: Aratere ship shaft fracture, damper mass wedging due to silicone fluid leakage, silicone fluid viscosity increasing to suspension state due to wear products, wear of silicone damper flyweight surfaces, silicone damper body wear. The Hasse & Wrede damper cap fastening with bolts is illustrated.

Anthropomorphic Polydimethylsiloxane silicone-based phantom for Diffuse Optical Imaging

This work presents a method for constructing phantoms suitable for diffuse optical mammography. They are based on Polydimethylsiloxane silicones, with the characteristic of being anthropomorphic, and having similar mechanical and optical properties as a real breast. These phantoms are useful for testing the performance of diffuse optical imaging devices in the near infrared, both in transmittance and reflectance geometries, since they can be constructed containing inclusions, to simulate breast tumors. An alternative component to be used as scattering agent, that is easier to handle than traditional scattering agents, is also studied.The optical properties of the phantoms were tested varying the concentration of scattering and absorbing agents, while their mechanical properties were modified by adding a silicone fluid to the basic mixture.Finally, the phantoms were tested by Diffuse Optical Imaging experiments, and these images were compared to the ones obtained by conventional ultrasound techniques.Results show that the constructed anthropomorphic phantoms properly reproduce the optical and mechanical characteristics of human breasts, and are suitable to be used in Diffuse Optical Imaging.

Gelation of highly entangled hydrophobic macromolecular fluid for ultrastrong underwater in situ fast tissue adhesion.

Although strong underwater bioadhesion is important for many biomedical applications, designing adhesives to perform in the presence of body fluids proves to be a challenge. To address this, we propose an underwater and in situ applicable hydrophobic adhesive (UIHA) composed of polydimethylsiloxane, entangled macromolecular silicone fluid, and a reactive silane. The hydrophobic fluid displaced the boundary water, formed an in situ gel, bonded to tissues, and achieved exceptional underwater adhesion strength. Its underwater lap shear adhesion on porcine skin was significantly higher than that of cyanoacrylate and fibrin glues, demonstrating excellent water resistance. The burst pressure of UIHA on porcine skin was 10 times higher than that of fibrin glue. The cytocompatible UIHA successfully sealed ruptured arteries, skin, and lungs in rats, pigs, rabbits, and dogs. Together, the gelation of highly entangled hydrophobic macromolecular fluid provided a means to prepare underwater bioadhesives with strong bonding to tissues and excellent water resistance.

Shin-Etsu to invest big in silicones

Shin-Etsu Chemical will spend close to $700 million to raise output of silicone fluids, resins, and rubber at three plants in Japan. The firm says the expansion complements a $1 billion project it started in 2018 that increased capacity to make silicone monomers by 50%. Shin-Etsu says the new investment will also help it further novel technologies such as molded silicone rubbers that don’t require a cure step and silicones for microLED display products.

A novel method of cooling a semiconductor device through a jet impingement thermal management system: CFD modeling and experimental evaluation

This study investigates the viability of a liquid jet-impingement (JI) thermal management system (TMS). The JI-TMS was used as a heat dissipation tactic to ensure a silicon semiconductor-based pulse-power device’s temperature was maintained below 80 °C during operation. The JI-TMS’s design, which is comprised of 27 nozzles (1 mm nozzle diameter), is analyzed by computational fluid dynamics (CFD) modeling, with 100 W of average power (i.e., heat generation rate). The heat transfer fluid (HTF) is pure silicone fluid with a viscosity of 20 cSt. The selected HTF has the dielectric constant which provides better electrical insulation than other common HTFs (water, water–glycol, etc.). Validation of the model was performed experimentally to ensure the accuracy of the CFD results. The results show that device’s temperature is maintained well below the maximum desired operating temperature (57.5 °C when using 0.06 kgs), showing average difference of 5.89% between numerical and experimental data. To better understand the achieved error, heat capacity analysis of the HTF was investigated with differential scanning calorimeter which shows an average deviation of 13.12% with the reported vendor value. The results from this study can be a benchmark for cooling purposes of semiconductor devices in high power densities.