High Viscosity Silicone Research Articles

Optical and mechanical testing of 3D printed parts made of high-viscosity silicone to identify process parameters and design advice for 3D printing and printer development

AbstractThe additive manufacturing of parts made from close-to-production materials poses a great challenge. One example are highly viscous silicones, as used in injection moulding. For small production quantities, the manufacturing of injection moulds is uneconomical. This paper presents tensile specimens printed with an in-house developed dispensing system, which are analysed for air cavities (micro-CT scans) and mechanical properties. Based on the results, advice for the design and slicing parameters of parts using high-viscosity silicones in AM by means of material extrusion are developed.

Development of a 2-dimensional thermal calculation method to estimate silicone oil's temperature distribution in viscous torsional vibration dampers

AbstractHigh-performance internal combustion engines are subject to severe torsional vibrations which result from uneven gas and inertial loads. Fatigue damage occurs if the frequency of these undesired oscillations matches the resonance frequency of the crankshaft and the driven engine elements. This phenomenon can be avoided by the application of visco-dampers whose working fluid is high-viscosity silicone oil. Since silicone oil is exposed to a significant amount of heat load during operation, it is essential to calculate the temperature distribution in a relatively easy, quick, and cost-efficient way for lifetime estimation purposes. The aim of this article is to develop a reliable, fast, and accurate finite difference-based numerical method for steady-state thermal calculations for arbitrary damper sections. The developed MATLAB code calculates the temperature field of the damping fluid together with all components in a radial cross-section at given operational conditions. The accuracy of the developed thermal calculation method has been tested in a 3-dimensional – 2-dimensional two-step verification process by finite element and finite volume-based advanced engineering software in ANSYS environment. Furthermore, the original Iwamoto equation available in the literature has been updated to provide more accurate surface temperature results based on the simulations' outcome gained by the finite volume method.

Performance evaluation and optimization of data center servers using single-phase immersion cooling

This paper conducts a comprehensive performance evaluation and optimization of single-phase immersion cooling (SPIC) systems to address challenges in data center server cooling. A three-dimensional model of blade servers with different cooling methods is constructed and numerically solved to compare thermal transport performance, flow characteristics, and energy consumption performance. Furthermore, the influence mechanisms of different oil coolants and operating conditions on SPIC system performance are studied. The results indicate that the SPIC scheme exhibits significant advantages in terms of heat transfer capability, heat transfer uniformity, and flow resistance loss. Moreover, the power usage effectiveness (PUE) of SPIC systems decreases by 20.8 % and 17.6 % compared to forced air cooling and water cooling plate solutions, respectively. The dynamic viscosity of oil coolants has the greatest impact on the SPIC performance. Moreover, high-viscosity silicone oil increases the flow resistance of SPIC systems and weakens the convective heat transfer capability between the coolant and components. By ensuring safe operation, increasing the inlet temperature of oil coolants reduces flow resistance losses and enhances heat transfer capacity. Additionally, initially increasing the mass flow rate improves convective heat transfer capacity. However, the heat transfer improvement gradually diminished beyond a certain threshold while flow resistance losses increased significantly.

New approaches to explanting high-viscosity silicone oil in retinal surgery—polyimide cannulas vs extraction sleeves vs a luer-trocar

BackgroundThe removal of high-viscosity silicone oil in retinal surgery is time-intensive. In this laboratory and porcine eye study, we evaluated the efficiency of novel extraction techniques, namely shortened polyimide-cannulas, an extraction sleeve and an experimental luer-trocar system, for commercially available silicone oils.MethodsThe volume of silicone oil after a 5-min removal time was quantified. The feasibility of all studied techniques was additionally tested in vitrectomized porcine eyes. Siluron 1000, 2000, 5000 and Xtra, as well as Densiron 68 and Densiron Xtra were examined.ResultsShortening the 23G-polyimide-cannula from 6 mm up to 1.5 mm led to a significantly higher mean aspirated volume (e.g., 1 ml/min to 1.7 ml/min for Siluron Xtra). The extraction sleeve and luer-trocar increased the flow threefold compared to the shortest polyimide cannulas at 23G (5.2 ml/min and 5.2 ml/min vs 1.7 ml/min for Siluron Xtra, respectively). The extraction sleeve and luer-trocar system reached a similar flow at 27G as the best performing 23G-cannula. Angulation and movement of the eye was possible with the 2 mm-cannula, no angulation was possible when using the extraction sleeve. Stability and control were not impaired with the experimental luer-trocar setup.ConclusionShorter polyimide-cannulas and extraction sleeves increase the extraction flow but may decrease stability during surgery. The luer-trocar system facilitates rapid removal while offering great stability and control. Small 27G silicone oil removal is possible and time efficient.

Evaporative drying of a water droplet on liquid infused sticky surfaces

We report the evaporation dynamics of water droplets over liquid infused slippery surfaces fabricated by dispensing high viscosity silicone oil over topographically patterned substrates obtained by replication of rose petals. These replicated surfaces also exhibit sticky hydrophobicity, similar to that observed in actual rose petals due to the presence of secondary nano-folds that decorate the primary conical micro-pillars. We first show that such a surface imparts stickiness to a high viscosity slip enhancing oil layer dispensed over it, thereby suppressing hemi-wicking even at low oil layer thickness (hE). Subsequently we show that hE strongly influences the dynamics as well as morphological evolution of an evaporating water drop dispensed over such slippery surfaces, particularly in terms of the dimension and life time of the wetting ridge that forms around any liquid droplet over a slippery surface due to the balance of surface tension forces around the contact line. Our experiments reveal that the adhesive effect of the substrate patterns become more significant with progressive reduction in hE, which in turn limits the maximum height attained by the wetting ridge and thus favours rapid evaporation of the droplet, despite the surface retaining slippery Wenzel wetting state under water. We also show some interesting intermediate evolution stages such as multiple overlapping wetting ridges under certain specific conditions, due to a competition between spreading of the oil layer and restriction in its flow imposed by the substrate patterns. Finally, we show that the effect of viscosity of the slip enhancing oil layer also exemplifies as hE progressively reduces.

Time fractional calculus for liquid-path dynamic modelling of an isolator with a rubber element and high-viscosity silicone oil at low frequency

Time fractional calculus for liquid-path dynamic modelling of an isolator with a rubber element and high-viscosity silicone oil at low frequency

Synergistic Lubrication for Textured Surfaces Using Polar and Nonpolar Lubricants

Abstract The synergistic effect of surface texturing and lubricants with various viscosity and polarity properties is an attractive and unexplored topic. In this study, surface texturing characterized by circular dimples has been manufactured on steel surfaces in advance, which can improve the lubrication of frictional units compared with the bare disc under different lubricants. Then, three lubricants, low-viscosity and nonpolar white oil, high viscosity and nonpolar silicone oil, and highly viscous and polar castor oil, were used to evaluate the interaction between surface texture and the lubricating oil. The contact angles of each lubricant on the textured and bare surface were measured to investigate the lubricant intermolecular force and wettability. The oil film thickness simulation and tribological experiments were conducted. The tribological results indicate that lubricants with varied characteristics work differently due to their different properties on textured surfaces. Castor oil exhibits the best tribological properties of the three oils used to supply the textured surfaces, which may attribute to its ability to generate strong boundary adsorption films as well as a thickened interfacial layer, and it could reduce the intensity of asperity interaction.

Effect of Lubricant Viscosity on Wetting Behaviors and Durability of Anti-icing Slippery Liquid-Infused Porous Surfaces

Icing accretion posed a safety hazard to power lines. Slippery liquid-infused porous surfaces (SLIPSs) are widely used in anti-icing applications. High-viscosity silicone oil has been reported to improve the durability of SLIPS. However, high viscosity can cause problems such as slow self-healing and weak mobility of water droplets on the surface. Herein, the effect of lubricant viscosity on the wetting behavior and durability of anti-icing SLIPS was investigated. The droplet shedding test was conducted to study the durability of SLIPS. The results show that low-viscosity silicone oil can make the prepared SLIPS have good lubricity and low ice adhesion strength, while high-viscosity silicone oil can improve the durability of SLIPS. Under the condition that SA does not exceed 5° and ice adhesion strength does not exceed 10 kPa, 200 cSt silicone oil can make SLIPS simultaneously exhibit excellent slipperiness and durability.

THE NOVEL USE OF HIGH-FLOW POLYIMIDE CANNULAS TO IMPROVE SILICONE OIL INJECTABILITY IN VITREORETINAL SURGERY.

The injection of high-viscosity silicone oil lengthens injection time. New polyimide cannulas offer a greater inner diameter than conventional metal cannulas at the same gauge. We compared the injection time for polyimide and metal cannulas at 23 G for a variety of silicone oils including a 12,500-mPas prototype oil. In this laboratory study, injection time was measured three times per cannula and per oil. Warming the oil before injection to up to 42°C was also evaluated. Finally, the feasibility of polyimide cannulas was tested in vitrectomized porcine eyes. The 23-G polyimide cannula mostly decreased injection times. The time to inject 5 mL of Siluron Xtra and Siluron 5000 decreased by 6:02 (76.9%) minutes (483 vs. 121 seconds) and 12:01 (74.7%) minutes (973 vs. 252 seconds), respectively. Although the 23-G metal cannula failed to inject 12,500 mPas oil, 5 mL was injected in 10:21 minutes using the polyimide cannula. Prewarming Siluron 5000 to 42°C lowered the injection time by 9.0% and by 12.1% when using the metal or polyimide cannula, respectively. Polyimide cannulas allow a clinically relevant decrease in injection time. They may not only shorten surgery time but could also ease the use of next-generation ultra-high-viscosity silicone oils. Prewarming silicone oil leads to decreased injection times.

Calibration Dependencies and Accuracy Assessment of a Silicone Rubber 3D Printer

Silicone rubbers are relatively new in additive manufacturing, with only a few commercial printing services and reports on custom-built printers available. Publications and standards on calibration and accuracy assessment are especially lacking. In this study, the printhead calibration process of a custom-built silicone printer is explained, and a set of test objects is proposed and evaluated. The printer in use is based on an open-source filament printer, capable of multi-material printing with silicone rubbers and thermoplastic polymers. Three different high-viscosity single-component liquid silicone rubbers and one polylactic acid thermoplastic filament were used as printing materials. First, the calibration process of the silicone printhead was conducted, and the dependency of the dosing accuracy on silicone viscosity, nozzle diameter and extrusion speed was evaluated. Second, various test specimens were proposed and printed to characterize the accuracy and geometric limitations of this printer. These test parts contained features such as thin walls, slender towers, small holes and slots, unsupported overhangs and bridges. It was concluded that silicone viscosity strongly affects geometric inaccuracies. Design recommendations were deducted from the results, advising for wall thicknesses above 1 mm, slenderness ratios below 2, bridging lengths below 2 mm and unsupported overhang angles below 30°.

Physicochemical Properties of Explanted Silicone Oil After Use as an Intraocular Tamponade.

PurposeWe studied the effects of exposure to biological media within the eye, such as contamination with lipophilic and amphiphilic substances, on the physicochemical parameters of silicone oil used as an intraocular tamponade.MethodsWe removed silicone oil with visible emulsification from 15 patients and measured each sample for shear viscosity and surface tension. We induced in vitro emulsification with balanced salt solution. Using the zeta-potential, we evaluated the emulsion droplet's electrochemical stability. We repeated all experiments in a control group of unused oil. Electrochemical stability and viscosity were additionally measured in oils with high-molecular-weight components.ResultsWe recovered silicone oils implanted between 30 and 506 days (mean, 196 days). Viscosity did not differ between explanted and control groups. Surface tension and zeta potential remained unchanged (P = 0.61 and P = 0.84, respectively). All oils showed a significant correlation of viscosity with temperature (P < 0.01 for all). Oils with added high-molecular-weight components showed a lower emulsion stability.ConclusionsProlonged contact to hydrophilic biological media does not alter high-viscosity silicone oil's physicochemical parameters. During typical durations of intraocular use, lipophilic and amphiphilic molecules had no deleterious effect. The addition of high-molecular-weight components might decrease the silicone oil's electrochemical emulsion stability, possibly easing the confluence of emulsion droplets.Translational RelevanceAlthough the physicochemical parameters of silicone oils are not altered after clinically relevant durations within the eye, emulsion stability significantly differs between oil types.

Therapeutic Effect of High Viscosity Silicone Oil for Treatment of Refractory Macular Hole: A Case Report

Therapeutic Effect of High Viscosity Silicone Oil for Treatment of Refractory Macular Hole: A Case Report

Design of a Four-Bar Latch Mechanism and a Shear-Based Rotary Viscous Damper for Single-Axis Prosthetic Knees

Abstract With over 30 million people worldwide requiring assistive devices, there is a great need for low-cost and high-performance prosthetic technologies that can enable kinematics close to able-bodied gait. Low-income users of prosthetic knees in the developing world repeatedly report the need for n inconspicuous gait to mitigate the severe socioeconomic discrimination associated with disability. However, passive prosthetic knees designed for these users have primarily focused on stability and affordability, often at the cost of the high biomechanical performance that is required to replicate able-bodied kinematics. In this study, we present the design and preliminary testing of two distinct mechanism modules that are novel for passive prosthetic knee applications: the stability module and the damping module. These mechanisms are designed to enable users of single-axis, passive prosthetic knees to walk with close to able-bodied kinematics on level-ground, specifically during the transition from the stance phase to the swing phase of the gait cycle. The stability module was implemented with a latch mounted on a virtual axis of a four-bar linkage, which can be engaged during early stance for stability and disengaged during late stance to initiate knee flexion. The damping module was implemented with a concentric stack of stationary and rotating pairs of plates that shear thin films of high-viscosity silicone oil. The goal of the resulting first-order damping torque was to achieve smooth flexion of the prosthetic knee within the able-bodied gait range (64 ± 6 deg). For preliminary user-centric validation, a prototype prosthetic knee with the stability module and two different dampers (with varying damping coefficients) was tested on a single subject with above-knee amputation in India. The stability module enabled smooth transition from stance to swing with timely initiation of knee flexion. The dampers also performed satisfactorily, as the increase in the damping coefficient was found to decrease the peak knee flexion angle during swing. The applications of the mechanisms presented in this article could significantly improve the kinematic performance of low-cost, passive prosthetic knees.

Vapor Deposition of Silicon-Containing Microstructured Polymer Films onto Silicone Oil Substrates.

In this study, a silicon-containing cross-linked polymer, poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane-co-ethylene glycol diacrylate) (p(V4D4-co-EGDA)), was deposited onto high-viscosity silicone oil using initiated chemical vapor deposition (iCVD). The ratio of the feed flow rate of V4D4 to EGDA was systematically studied, and the chemical composition and morphology of the top and bottom surfaces of the films were analyzed. The films were microstructured, and the porosity and thickness of the films increased with increasing V4D4 content. The top of the film was composed of densely packed and loosely packed microstructured regions. X-ray photoelectron spectroscopy on the top and bottom surfaces of the films showed a heterogeneous chemical composition along the thickness of the film, with higher silicon content on the top surface compared to that on the bottom surface. To the best of our knowledge, this is the first study of iCVD deposition of a silicon-containing polymer film onto silicone oil. The results of this study can be used for the synthesis of polymer precursor films for the fabrication, via pyrolysis, of silicon-based inorganic membranes for use in hydrogen production using silicone oil to prevent infiltration of monomer into the underneath membrane support structure during vapor deposition.

Axisymmetric bare freestanding films of highly viscous liquids: Preparation and real-time investigation of capillary leveling

Hypothesis: Thin liquid films are important in many scientific fields. In particular, films with both the surface layers exposed to a different fluid phase, known as freestanding films, are relevant in the ambit of foams and emulsions. Hence, there is a great interest in developing novel techniques allowing to form large and stable freestanding liquid films and to follow their dynamics.Experiments: We develop a novel opto-mechanical tool allowing to perform and study the preparation and the capillary leveling flow of axisymmetric bare freestanding liquid films. The tool is composed by a customized motorized iris diaphragm and by an innovative joint imaging setup combining digital holography and white light color interferometry that enables real-time measurement of film thickness over a large field of view. The dynamics of films made of a model Newtonian fluid, i.e., high-viscosity silicone oil, is studied. Direct numerical simulations and a hydrodynamic model based on the lubrication theory are used to support the experimental results.Findings: Iris opening induces the formation of large circular freestanding films with a stepped profile. Once iris opening is stopped, the films undergo a capillary leveling flow tending to flatten their profile. The leveling flow follows the theoretical scaling given by Ilton et al. [1]. We prove through numerical simulations that an equi-biaxial extensional flow occurs at the film center. Furthermore, we observe the formation and dynamics of dimples in bare freestanding films for the first time.

Mesoporous Metal-Organic Framework MIL-101 at High Pressure.

The chromium terephthalate MIL-101 is a mesoporous metal-organic framework (MOF) with unprecedented adsorption capacities due to the presence of giant pores. The application of an external pressure can effectively modify the open structure of MOFs and its interaction with guest molecules. In this work, we study MIL-101 under pressure by synchrotron X-ray diffraction and infrared (IR) spectroscopy with several pressure transmitting media (PTM). Our experimental results clearly show that when a solid medium as NaCl is employed, an irreversible amorphization of the empty structure occurs at about 0.4 GPa. Using a fluid PTM, as Nujol or high-viscosity silicone oil, results in a slight lattice expansion and a strong modification of the peak frequency and shape of the MOF hydroxyl vibration below 0.1 GPa. Moreover, the framework stability is enhanced under pressure with the amorphization onset shifted to about 7 GPa. This coherent set of results points out the insertion of the fluid inside the MIL-101 pores. Above 7 GPa, concomitantly to the nucleation of the amorphous phase, we observe a peculiar medium-dependent lattice expansion. The behavior of the OH stretching vibrations under pressure is profoundly affected by the presence of the guest fluid, showing that OH bonds are sensitive vibrational probes of the host-guest interactions. The present study demonstrates that even a polydimethylsiloxane silicone oil, although highly viscous, can be effectively inserted into the MIL-101 pores at a pressure below 0.2 GPa. High pressure can thus promote the incorporation of large polymers in mesoporous MOFs.

Effect of the structure of hydrogen-containing silicone oil on the properties of silicone rubber

A series of methyl-terminated and hydrogen-terminated hydrogen-containing silicone oil with different hydrogen content and chain length were synthesized by ring-opening polymerization design. Silicone rubber was prepared with hydrogen-containing silicone oil and vinyl-terminated silicone oil with a viscosity of 8033 mPa s. The silicone rubber was reinforced with vinyl MQ resin with a viscosity of 6223 mPa s and a vinyl content of 0.9%. Then the structure, thermal stability, viscosity of the synthesized hydrogenated silicone oil were characterized and the crosslinking density, mechanical properties, aging properties of the silicone rubber were analyzed. It was found that the mechanical properties of hydrogen-containing silicone oil with hydrogen content of 0.50% and chain length of 50% were the best. The parameters of silicone rubber were obtained as follows: viscosity 35.6 Pa s, tensile strength 5.05 MPa, elongation at break 339.01%, tear strength 7.23 kN/m, hardness 44°, compressive modulus 7.43 MPa. This provides an efficient method for designing high strength and low viscosity silicone rubber materials.

Measurement and modelling for harmonic dynamic characteristics of a liquid-filled isolator with a rubber element and high-viscosity silicone oil at low frequency

Key dynamic characteristics of a novel liquid-filled isolator with an annular orifice are investigated at low frequency by using experimental and analytical methods, both within the context of a simplified suspended cab model. The isolator is proposed to be characterized by a coupled parallel combination of a rubber path and a liquid path, through which motions or forces are transmitted to a resonant receiver, commonly an earthmoving machinery cab. To appropriately examine isolator dynamic properties, experimental results are compared with those of the corresponding rubber isolator while dynamic excitations under frequency-sweep and fixed-frequency are applied, respectively. It is observed that the liquid-filled isolator provides more desired dynamic performance for resonance mitigation and vibration isolation. It is suggested that an amplitude-dependent, softening nonlinearity presented in the dynamic stiffness should mainly result from the viscoelastic behavior of the silicone oil and also relate closely to the coupling properties. Also, small jerks in the acceleration response involved with asymmetric damping characteristics are present by a shock excitation, while almost no asymmetric characteristics are revealed under harmonic excitations although the isolator internal construction is asymmetric. Two models are developed by using Navier-Stokes equations, incorporating fluid rheological behavior and compressibility. Simulated and measured force-displacement loops are compared to indicate the models’ validity. Accordingly, a lumped model (Model 3) consisting of cubic elastic force and fractional-power damping force terms is proposed, yielding a better prediction. The studies in this paper suggest key design parameters and form an essential first step for design optimization.

Study of the Characteristics of EDM by Using Silicone Oils as Dielectric

A layer of silicon carbide (SiC) will be deposited on the working surface if the kerosene dielectric with silicon powders is applied for the electrical discharge machining (EDM). This SiC layer can enhance the hardness of the machining surface. However, silicon powders are easily reunited and deposited in the bottom of the dielectric, reducing SiC layer to merge on the working surface after EDM. Therefore, the kerosene with silicon powders was replaced by silicone oil as the dielectric to improve the reuniting and the depositing issues of the silicon powders in EDM, since silicone oils contain the liquid silicon elements and not silicon powders. Moreover, silicone oils are the uniformly viscous fluid and not easy to cycle in the small working gap of EDM, thus worth investigating the EDM phenomena of the silicone oils with different viscosities in this study. The results showed that debris by EDM were easily accumulates on the working surfaces of the electrode and the machined material when high viscosity silicone oils were utilized as the dielectrics, and the material removal rate of these dielectrics were small than the kerosene did. However, using the low viscosity silicone oil (100 mPa-S) as dielectric in EDM could transfer higher SiC elements to the steel surface, and the capibility of material removal rate is the best way.

One-step processing of highly viscous multiple Pickering emulsions

HypothesisSolid-stabilized Pickering emulsions have attracted a lot of attention recently due to their surfactant-free character, and exceptional stability. At the moment, how the viscosities of the liquid phases impact the processing of Pickering emulsions remain to be clearly understood – it is however an important parameter to consider when developing chemical engineering processes employing these multiphase liquids. Our first assumption was that the amount of emulsified dispersed phase would drastically decrease as viscosity increases. Experiments and findingsIn this work, we demonstrate that double water-in-oil-in-water (W/O/W) Pickering emulsions are obtained in a single processing step when using very high viscosity silicone oils (≥10,000 cSt) and a single type of sub-μm silica particles modified with two grafted silanes and sodium alginate. The formation of water sub-inclusions proceeds via a phase-inversion mechanism. These sub-inclusions are subsequently stabilized and retained in the oil phase due to its viscosity, limiting sub-inclusions mobility, and the presence of adsorbed particles forming dense layers at oil-water interfaces, acting as barriers. The process we present is simple, requires a minimum number of components, and allows the preparation of multiple emulsions which could then be used to efficiently protect and/or transport a variety of sensitive encapsulated compounds.