Seal Resistance Research Articles

Investigating the Effect of Nano-Crystalline Cellulose in Nitrile Butadiene Rubber Matrix for Improved Thermo-Mechanical Properties

The escalating demand for sustainable rubber products has spurred research into alternative reinforcing fillers, driven by concerns regarding the detrimental effects of using conventional fillers like carbon black and silica. In this investigation, nano-crystalline cellulose (NCC), derived from micro crystalline cellulose (MCC), sourced from sugarcane bagasse via acid hydrolysis, serves as a bio-filler to reinforce Nitrile Butadiene Rubber (NBR) matrices. NBR-NCC nano-composites were prepared using a two-roll mill, varying NCC from 1–5 parts per hundred rubber matrices, followed by hot press curing. NCC and NBR-NCC nano-composites were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), curing characteristics, thermo-mechanical testing, thermal aging and motor oil resistance. Chemical interactions between the NCC and NBR matrix were verified with FTIR. The SEM images of the NCC showed a combination of rod-like and spherical morphologies and a homogenous dispersion of NCC in NBR-NCC nano-composites with some agglomeration, notably at higher percentages of NCC. It is shown that the cure time decreases with increasing NCC loading which mimics a shorter industrial production cycle. The results also showed an increase in tensile strength, hardness, oil resistance and a rise in degradation temperature when compared to NBR at approximately 34%, 36%, 38% and 32 °C, respectively, at 3 phr NCC loading. Furthermore, NBR-NCC nano-composites showed a lower decrease in mechanical properties after aging when compared to NBR. The findings of this research suggest that the NBR-NCC nano-composites may find applications in high oil resistance seals and rubber gloves where higher thermal stability is strictly required.

Fire resistance of linear joint seals depending on the joint width and the type of mineral wool used

Fire resistance of linear joint seals depending on the joint width and the type of mineral wool used

Effects of aggregate shape on the macrotexture and performance of chip seal: a laboratory study

Chip seal is an efficient maintenance strategy for bituminous pavements, with aggregate shape significantly impacting its embedment and performance, but there is limited quantification of its effects. Using the Aggregate Image Measurement System II (AIMS-II) for shape classification, this study investigated the influence of aggregate shape on chip seal's macrotexture and performance through a series of tests, including 3D laser scanning test, aggregate coverage test, skid resistance test, and sweep test, employing response surface methodology (RSM) for quantification. Results indicated that an abundance of flat aggregates deteriorates surface quality by increasing roughness and altering texture spacing, recommending their proportion be kept under 10%. Conversely, elongated aggregates enhance performance by enriching texture depth and sharpening surface peaks. Spearman rank correlation analysis identified the arithmetic mean peak curvature (Spc ) and the root mean square height (Sq ) as reliable measures for evaluating skid resistance and aggregate retention of chip seals, respectively.

Estimation of persistent sodium-current density in rat hippocampal mossy fibre boutons: Correction of space-clamp errors.

We used whole-cell patch clamp to estimate the stationary voltage dependence of persistent sodium-current density (iNaP) in rat hippocampal mossy fibre boutons. Cox's method for correcting space-clamp errors was extended to the case of an isopotential compartment with attached neurites. The method was applied to voltage-ramp experiments, in which iNaP is assumed to gate instantaneously. The raw estimates of iNaP led to predicted clamp currents that were at variance with observation, hence an algorithm was devised to improve these estimates. Optionally, the method also allows an estimate of the membrane specific capacitance, although values of the axial resistivity and seal resistance must be provided. Assuming that membrane specific capacitance and axial resistivity were constant, we conclude that seal resistance continued to fall after adding TTX to the bath. This might have been attributable to a further deterioration of the seal after baseline rather than an unlikely effect of TTX. There was an increase in the membrane specific resistance in TTX. The reason for this is unknown, but it meant that iNaP could not be determined by simple subtraction. Attempts to account for iNaP with a Hodgkin-Huxley model of the transient sodium conductance met with mixed results. One thing to emerge was the importance of voltage shifts. Also, a large variability in previously reported values of transient sodium conductance in mossy fibre boutons made comparisons with our results difficult. Various other possible sources of error are discussed. Simulations suggest a role for iNaP in modulating the axonal attenuation of EPSPs. KEY POINTS: We used whole-cell patch clamp to estimate the stationary voltage dependence of persistent sodium-current density (iNaP) in rat hippocampal mossy fibre boutons, using a KCl-based internal (pipette) solution and correcting for the liquid junction potential (2mV). Space-clamp errors and deterioration of the patch-clamp seal during the experiment were corrected for by compartmental modelling. Attempts to account for iNaP in terms of the transient sodium conductance met with mixed results. One possibility is that the transient sodium conductance is higher in mossy fibre boutons than in the axon shaft. The analysis illustrates the need to account for various voltage shifts (Donnan potentials, liquid junction potentials and, possibly, other voltage shifts). Simulations suggest a role for iNaP in modulating the axonal attenuation of excitatory postsynaptic potentials, hence analog signalling by dentate granule cells.

Minimisation of Friction Resistance of Elastomeric Lip Seals on Rotating Shafts

This article presents the results of a study of oil lip seals with a modified outer lip layer texture. In the first step, the interaction of flat rubber samples with different surface layer textures with the steel surface was recognised. Measurements of the friction coefficient of flat samples with different surface layer textures were carried out. The next step was an experimental study of rotating shaft lip seals in standard and prototype versions. The contact width of the sealing lip before and after durability tests was examined, and the clamping force of the lip on the shaft before and after durability tests was measured. The final step was to create a FEM model of the interaction of the sealing ring lip with the shaft to determine the lip seal pressure and width. These calculations, in cooperation with the previously determined friction coefficient and porosity of the lip seal, allowed the calculation of the friction torque. The solution proposed in this article was intended to be simple and viable for industrial applications. Satisfactory results were achieved with prototype rings in terms of reduced resistance to movement, tightness, and durability.

Alternatives to Fluoropolymers for Motion-Based Energy Harvesting: Perspectives on Piezoelectricity, Triboelectricity, Ferroelectrets, and Flexoelectricity.

Fluoropolymers, including polytetrafluoroethylene (PTFE, Teflon), polyvinylidene difluoride (PVDF), and fluorine kautschuk materials (FKMs, Viton) are critical polymers for applications ranging from non-stick coatings, corrosion resistant seals, semiconductor manufacturing, membranes, and energy harvesting technologies. However, the synthesis of these fluoropolymers requires the use of per- and polyfluorinated alkyl substances (PFAS) known colloquially as "forever chemicals," and as such there is a pressing need to develop alternative technologies that can serve the end-use of fluoropolymers without the environmental cost of using PFAS. Further, fluoropolymers themselves fall under the PFAS umbrella. Here, alternative mechanical-to-electrical energy harvesting polymers are reviewed and benchmarked against the leading fluoropolymer energy harvesters. These alternative technologies include nonfluoropolymer piezoelectric polymers, triboelectric nanogenerators (TENGs), ferroelectric elastomers, and flexoelectric polymers. A vision towards sustainable, non-fluoropolymer-based energy harvesting is provided.

Electrophysiology of fluoride channels in the yeasts Saccharomyces cerevisiae and Candida albicans.

Tight regulation of molecules moving through the cell membrane is particularly important for free-living microorganisms because of their small cell volumes and frequent changes in the chemical composition of the extracellular environment. This is true for nutrients, but even more so for toxic molecules. Traditionally, the transport of these diverse molecules in microorganisms has been studied on cell populations rather than on single cells, mainly because of technical difficulties. The goal of this chapter is to make available a detailed method to prepare yeast spheroplasts to study the movement of fluoride ions across the plasma membrane of single cells by the patch-clamp technique. In this procedure, three steps are critical to achieve high resistance (GΩ) seals between the membrane and the glass electrode: (1) appropriate removal of the cell wall by enzymatic treatment; (2) balance between the osmotic strength of sealing solutions and cell membrane turgor; and (3) meticulous morphological inspection of spheroplasts suitable for gigaseal formation. We show now that this method, originally developed for Saccharomyces cerevisiae, can also be applied to Candida albicans, an opportunistic human pathogen.

Numerical study on the dynamic response of coal mine seals under methane explosion loads

Seals play an important role in regulating air flow and preventing disasters in coal mines, so it is essential to ensure their effectiveness. However, the generation of large amounts of explosive methane and the enclosed space in mines lead to impact strength that far exceeds the explosion pressure in open space, causing damage to seals. Therefore, it is necessary to study the dynamic response of seals under explosion loads. In this paper, the blast resistance of seals constructed of concrete material is analyzed by LS-DYNA under four explosion overpressure history curves, which correspond to normal overpressure, moderately high overpressure, high overpressure, and worst-case scenarios of coal mine gas explosion. The stresses and displacement distribution of the seal are obtained, as well as the damage pattern under the impact action. In addition, the effects of interlayer material, reinforcement, arch structure seal, constraint conditions and seal thickness on the blast resistance performance are analyzed. The results show that adding constraints and thickening the seal are the most convenient measures to strengthen seals. The optimal formula is selected by comparing five thickness calculation formulas with the results of this paper.

Adaptive Super-Twisting Sliding Mode Control of Underwater Mechanical Leg with Extended State Observer

Underwater manipulation is one of the most significant functions of the deep-sea crawling and swimming robot (DCSR), which relies on the high-accuracy control of the body posture. As the actuator of body posture control, the position control performance of the underwater mechanical leg (UWML) thus determines the performance of the underwater manipulation. An adaptive super-twisting sliding mode control method based on the extended state observer (ASTSMC-ESO) is proposed to enhance the position control performance of the UWML by taking into account the system’s inherent nonlinear dynamics, uncertainties, and the external disturbances from hydrodynamics, dynamic seal resistance, and compensation oil viscous resistance. This newly designed controller incorporates sliding mode (SMC) feedback control with feedforward compensation of the system uncertainties estimated by the ESO, and the external disturbances of the hydrodynamics by fitting the parameters, the dynamic seal resistance, and the compensation oil viscous resistance to the tested results. Additionally, an adaptive super-twisting algorithm (AST) with integral action is introduced to eliminate the SMC’s chattering phenomenon and reduce the system’s steady-state error. The stability of the proposed controller is proved via the Lyapunov method, and the effectiveness is verified via simulation and comparative experimental studies with SMC and the adaptive fuzzy sliding mode control method (AFSMC).

Leak current, even with gigaohm seals, can cause misinterpretation of stem cell-derived cardiomyocyte action potential recordings.

Human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have become an essential tool to study arrhythmia mechanisms. Much of the foundational work on these cells, as well as the computational models built from the resultant data, has overlooked the contribution of seal-leak current on the immature and heterogeneous phenotype that has come to define these cells. The aim of this study is to understand the effect of seal-leak current on recordings of action potential (AP) morphology. Action potentials were recorded in human iPSC-CMs using patch clamp and simulated using previously published mathematical models. Our in silico and in vitro studies demonstrate how seal-leak current depolarizes APs, substantially affecting their morphology, even with seal resistances (Rseal) above 1 GΩ. We show that compensation of this leak current is difficult due to challenges with obtaining accurate measures of Rseal during an experiment. Using simulation, we show that Rseal measures (i) change during an experiment, invalidating the use of pre-rupture values, and (ii) are polluted by the presence of transmembrane currents at every voltage. Finally, we posit that the background sodium current in baseline iPSC-CM models imitates the effects of seal-leak current and is increased to a level that masks the effects of seal-leak current on iPSC-CMs. Based on these findings, we make recommendations to improve iPSC-CM AP data acquisition, interpretation, and model-building. Taking these recommendations into account will improve our understanding of iPSC-CM physiology and the descriptive ability of models built from such data.

Impedance spectroscopy of the cell/nanovolcano interface enables optimization for electrophysiology

Volcano-shaped microelectrodes have demonstrated superior performance in measuring attenuated intracellular action potentials from cardiomyocyte cultures. However, their application to neuronal cultures has not yet yielded reliable intracellular access. This common pitfall supports a growing consensus in the field that nanostructures need to be pitched to the cell of interest to enable intracellular access. Accordingly, we present a new methodology that enables us to resolve the cell/probe interface noninvasively through impedance spectroscopy. This method measures changes in the seal resistance of single cells in a scalable manner to predict the quality of electrophysiological recordings. In particular, the impact of chemical functionalization and variation of the probe’s geometry can be quantitatively measured. We demonstrate this approach on human embryonic kidney cells and primary rodent neurons. Through systematic optimization, the seal resistance can be increased by as much as 20-fold with chemical functionalization, while different probe geometries demonstrated a lower impact. The method presented is therefore well suited to the study of cell coupling to probes designed for electrophysiology, and it is poised to contribute to elucidate the nature and mechanism of plasma membrane disruption by micro/nanostructures.

Numerical and experimental study of convergent integral embedded magnetic fluid seal

To enhance the pressure resistance of small clearance magnetic fluid seals, a new convergent integral embedded magnetic fluid seal (CIEMFS) structure was proposed. The magnetic field distributions in the radial sealing clearance and axial sealing clearance were studied, and the theoretical pressure resistance capability values were obtained. The effects of magnetic fluid injection volumes, pole tooth (PT) heights and sealing clearance on the pressure resistance capability of the CIEMFS were experimentally investigated and compared with that of the ordinary magnetic fluid seal (OMFS). The results showed that the experimental pressure resistance capability of the CIEMFS was in good agreement with the theoretical pressure resistance, and both of them were better than the OMFS. The pressure resistance capability of the CIEMFS is not only affected by the radial sealing clearance but also limited by the axial seal clearance. The height of the pole tooth and the magnetic fluid (MF) injection volume will also have an impact on the pressure resistance capability, the higher the pole tooth, the higher the pressure resistance capability of the magnetic fluid sealing (MFS) structure. As the magnetic fluid injection volume increases, the pressure resistance capability of the CIEMFS increases and then plateaus.

Numerical and experimental study of divergent magnetic fluid seals with stepped pole pieces

It is crucial that the pressure resistance of ordinary magnetic fluid seals is under small clearance conditions. Therefore, a new structure for magnetic fluid seals, i. e. a dispersion type with stepped pole pieces, is proposed in this paper to further improve the pressure resistance under such operating conditions. For the divergent magnetic fluid seal with stepped pole piece, the magnetic field distribution in the clearance can be calculated, as well as the theoretical pressure resistance of the new seal structure. In this paper, it is calculated the magnetic field distribution and theoretical pressure resistance utilizing the magnetic field finite element method based on the theory of divergent magnetic fluid seals, investigated the influence of the amount of injected magnetic fluid, the number of steps, the height of the steps and the sealing gap on the pressure resistance of the new sealing structure of stepped magnetic fluid seals, as well as compared and analyzed with that of ordinary magnetic fluid seals and normal magnetic fluid seals. The results show that the pressure resistance of the normal magnetic fluid seal is significantly worse than that suggested by the split magnetic fluid seal. The pressure resistance of the stepped magnetic fluid seal increases as the number of steps increases, while the pressure resistance of the proposed structure decreases and then increases as the height of the steps increases; and the pressure resistance of the proposed structure increases and then decreases as the radial clearance increases, while the pressure resistance of the proposed structure decreases as the axial clearance increases.

There is no F in APC: Using physiological fluoride-free solutions for high throughput automated patch clamp experiments.

Fluoride has been used in the internal recording solution for manual and automated patch clamp experiments for decades because it helps to improve the seal resistance and promotes longer lasting recordings. In manual patch clamp, fluoride has been used to record voltage-gated Na (NaV) channels where seal resistance and access resistance are critical for good voltage control. In automated patch clamp, suction is applied from underneath the patch clamp chip to attract a cell to the hole and obtain a good seal. Since the patch clamp aperture cannot be moved to improve the seal like the patch clamp pipette in manual patch clamp, automated patch clamp manufacturers use internal fluoride to improve the success rate for obtaining GΩ seals. However, internal fluoride can affect voltage-dependence of activation and inactivation, as well as affecting internal second messenger systems and therefore, it is desirable to have the option to perform experiments using physiological, fluoride-free internal solution. We have developed an approach for high throughput fluoride-free recordings on a 384-well based automated patch clamp system with success rates >40% for GΩ seals. We demonstrate this method using hERG expressed in HEK cells, as well as NaV1.5, NaV1.7, and KCa3.1 expressed in CHO cells. We describe the advantages and disadvantages of using fluoride and provide examples of where fluoride can be used, where caution should be exerted and where fluoride-free solutions provide an advantage over fluoride-containing solutions.

Investigating Peripheral Regional Anesthesia Using Induced Pluripotent Stem Cell Technology: Exploring Novel Terrain.

Investigating Peripheral Regional Anesthesia Using Induced Pluripotent Stem Cell Technology: Exploring Novel Terrain.

Influence of magnetic fluid evaporation on pressure resistance of magnetic fluid seal

Magnetic fluid seals have the advantages of zero leakage, long life, simple structure and high reliability, and have become one of the most widely used applications of magnetic fluids. In this paper, the effect of magnetic fluid evaporation on the pressure resistance of magnetic fluid seals is studied. In terms of theory, through theoretical calculation and simulation analysis, a calculation method for the pressure resistance of magnetic fluid seals is established. In terms of experiments, firstly, five groups of control groups were set up to conduct evaporation experiments under the same conditions, and magnetic fluids with different evaporation rates were obtained; Secondly, the performance of magnetic fluids with different evaporation rates was tested, and the flow curves, viscosity-temperature curves, and magnetic-viscosity curves of magnetic fluids were obtained respectively, and the effect of evaporation on the performance of magnetic fluids was analyzed; Finally, magnetic fluid sealing experiments with different evaporation rates were carried out. It is found that evaporation increases the pressure resistance of static seal to a certain extent, which is of great significance.

High-Temperature Behavior of Silicone Sealants

Since the early 2000s, an increasing number of globally reported fires in tall buildings, which have spread quickly, have been attributed to the façade. These dramatic events have raised concerns regarding the fire risk posed by materials used in façades and inside the building. Improved performance in both reaction to fire and fire resistance is a necessary requirement for construction materials. Silicone is used in many locations of the façade and buildings, such as sealing of linear joints or firestopping of penetrants in fire-rated walls and floors. Standardized testing enables the evaluation of the fire resistance of such linear and penetration seals in terms of integrity (avoiding the passage of hot smoke and flames) and insulation (limiting the rise of temperature on the non-exposed side). Silicone can also be used to assemble glass-to-metal frames in bonding applications such as smoke barriers. In these applications, retention of bonding and the mechanical properties of the silicone are a cause for concern when exposed to smoke and high temperature. This paper reviews the high-temperature behavior of a selected range of silicones used for sealing and bonding in construction.

Rear boot swing door closing effort: Calculations, objective and subjective evaluations in an LCV model

The prediction model for the energy contributors is studied to define the effect of door components. The model is validated by experimental measurements on produced vehicles. The correlation of the control results and the evaluation methods among the representative customers, appraisers and senior experts are performed and compared by objective energy measurements. The subjective evaluation aims to clarify real customer expectations in door closing process and carry it to new product development phase. This will also improve the competency of appraisers in final assembly approval zones. The energy contributors for boot swing door is numerically calculated and validated by experimental measurements in easy and hard-closing doors. Subjective evaluations in 45 vehicles with different closing energies were performed by three different groups as representative customers, appraisers, and senior experts. The results were evaluated by statistical tools. The major energy contributors were found as air binding, seal resistance and check strap both in the calculations and in the experiments. The results demonstrated good correlation between numerical model and objective measurements. Besides, the subjective evaluations showed parallel trends with objective energy measurements. The variation in customer evaluations is more than appraisers and experts. Customers are severer in the evaluations of hard-closing doors and more sensitive in 10° door closing angle. This is a unique study for rear boot swing door closing effort in an LCV model. The study contains both definitions of factors, components that contributes in door closing energy and subjective evaluations to correlate the closing behaviors of representative customers, appraisers, and senior experts. The output of the study would be used to improve the vehicle control plan (VCP) and design standards in new model development phase.

A nonlinear and time-dependent leak current in the presence of calcium fluoride patch-clamp seal enhancer.

Automated patch-clamp platforms are widely used and vital tools in both academia and industry to enable high-throughput studies such as drug screening. A leak current to ground occurs whenever the seal between a pipette and cell (or internal solution and cell in high-throughput machines) is not perfectly insulated from the bath (extracellular) solution. Over 1 GΩ seal resistance between pipette and bath solutions is commonly used as a quality standard for manual patch work. With automated platforms it can be difficult to obtain such a high seal resistance between the intra- and extra-cellular solutions. One suggested method to alleviate this problem is using an F - containing internal solution together with a Ca 2+ containing external solution - so that a CaF 2 crystal forms when the two solutions meet which 'plugs the holes' to enhance the seal resistance. However, we observed an unexpected nonlinear-in-voltage and time-dependent current using these solutions on an automated patch-clamp platform. We performed manual patch-clamp experiments with the automated patch-clamp solutions, but no biological cell, and observed the same nonlinear time-dependent leak current. The current could be completely removed by washing out F - ions to leave a conventional leak current that was linear and not time-dependent. We therefore conclude fluoride ions interacting with the CaF 2 crystal are the origin of the nonlinear time-dependent leak current. The consequences of such a nonlinear and time-dependent leak current polluting measurements should be considered carefully if it cannot be isolated and subtracted.

Time-lapse submicrometer particle motion reveals residual strain evolution and damaging stress relaxation in clinical resin composites sealing human root canals

Polymer based composites are widely used for treatment, for example as biofilm resistant seals of root canal fillings. Such clinical use, however, fails more frequently than other dental composite restorations, due to stress-related misfits. The reason for this is that the biomaterials used are inserted as viscous masses that may bond to the substrate, yet shrinkage stresses arising during setting of the cross-linking polymer, work against durable adhesion. Here we combine phase contrast enhanced time-lapse radiography (radioscopy), digital image correlation (DIC) and submicrometer resolution phase-contrast enhanced microtomography (PCE-CT), to reveal the spatial and temporal dynamics of composite polymerization and strain evolution. Radioscopy of cavities located in the upper part of human root canals demonstrates how the composite post-gelation “densification” is dominated by viscous flow with quantifiable motion of both particles and entrapped voids. Thereafter, these composites enter a “stress-relaxation” stage and exhibit several structural adaptations, induced by residual shrinkage stresses. Consequently critical alterations to the final biomaterial geometry emerge: (i) entrapped bubbles expand; (ii) microscopic root filling pull-out occurs; (iii) the cavity walls deform inwards, and (iv) occasionally delamination ensues, propagating out from the root canal filling along buried restoration-substrate interfaces. Our findings shed new light on the interactions between confined spaces and biomedical composites that cross-link in situ, highlighting the crucial role of geometry in channeling residual stresses. They further provide new insights into the emergence of structural flaws, calling attention to the need to find new treatment options. Statement of significanceThis work quantifies recurring spatial and temporal material redistribution in composites used clinically to fill internal spaces in teeth. This knowledge is important for both promoting biomaterial resistance against potentially pathologic biofilms and for improving structural capacity to endure years of mechanical function. Our study demonstrates the significant role of geometry and the need for improved control over stress raisers to develop better treatment protocols and new space filling materials. The use of high-brilliance X-rays for time-lapse imaging at submicrometer resolution provides dynamic information about the damaging effects of stress relaxation due to polymerization shrinkage.