Rubber Seals Research Articles

Thermal oxidative aging behavior and lifetime prediction of fluoroether rubber

Fluoroether rubber's performance offers extensive application potential in harsh conditions. This article investigates the thermal-oxidative aging behavior and life prediction of fluoroether rubber using methods such as Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analyzer (TGA), Differential Scanning Calorimeter (DSC) and Compression Set. Results indicate that with prolonged aging, fluoroether rubber exhibits decreased heat resistance, damaged TAIC crosslink structures, and weakened characteristic peak intensities of main chains and side groups, leading to changes in rubber structure. Throughout the aging process, hardness, physical crosslink density, glass transition temperature, and compressive stress gradually increase, while mechanical properties decline. Using compression set as an indicator, service life at various temperatures was predicted, providing theoretical guidance for improving the reliability of fluoroether rubber seals and expanding their engineering applications.

The Change of Sealing Property in the Aging Process of NBR Sealing Equipment Based on Finite Element Analysis

Sealing rings are the core components of flange sealing structures and play a crucial role in the storage and operation of gas generators. The aging and deformation of seals affect the safe operation of the device. This paper aims to investigate the effect of rubber aging on the sealing performance of the components, which is realized by nonlinear finite element analysis. Firstly, an accelerated degradation test method was used to obtain the compression permanent deformation and stress–strain curve of rubber during the aging process. A two-dimensional finite element model of the sealing structure was constructed and the Yeoh model was utilized to describe the mechanical response of rubber. During the simulation, the contact area was modified based on the compression permanent deformation, and the Yeoh model was updated based on the stress–strain curve changes obtained by the test. The impact of key parameters such as material property changes, rubber physical section deformation, and fluid pressure on sealing performance during the seal ring aging process was systematically studied. The numerical results indicate that due to the aging deformation of rubber seals, there is a significant decrease in contact stress and contact width, as well as a shift in maximum equivalent stress area. Taking into account these findings, this study proposes a new design concept for sealing structures. This provides a relatively simple research method for studying flange sealing structure performance.

Sealing rubber ring design based on machine learning algorithm combined progressive optimization method

In this study, a progressive optimization method combining machine learning and optimization method is proposed and applied to seal structure design. The method is divided into two stages to select the optimal design gradually. So as to find the best design scheme meeting the design requirements. For optimal design, numerical calculation method is commonly used, but hard to evaluate the optimal solution. In this work, a series of numerical model considering the effect of super elastic material about O-ring study the waterproof performance behavior of a rubber seal. K nearest neighbors (KNN) of machine learning algorithms applied to the simulation data to predict the appropriate bolt pretension classification. Furthermore, use TOPSIS method to optimize the groove depth of 30 N bolt pretension classification. By using the TOPSIS method to consider the stress of the rubber component, optimization analysis is conducted to find the optimal design. Results show that the dual optimization method can quickly predict the best design scheme. Through the experiment, a prototype test under the condition of IPX7 verify the method. The design scheme selected by this method meets the waterproof grade requirements. There are no water stains on the surface of the O-ring and inside the motor. This paper provides a fast optimization design method for the design of sealing structure.

Hydrogen permeation behavior and mechanisms in nitrile butadiene rubber composites for hydrogen sealing

As the most widely used sealing component in hydrogen systems, rubber seals are affected by hydrogen over long-term service. Hydrogen molecules can dissolve into rubber materials and diffuse through the material. Studies have shown that adding fillers can enhance rubber's performance, improve its compatibility with hydrogen, and reduce the damage caused by hydrogen diffusion. Therefore, this study integrates experimental hydrogen permeation research with finite element modeling for nitrile butadiene rubber (NBR). The aim is to investigate the influence of filler properties on the microstructure, hydrogen permeation behavior, and hydrogen concentration distribution within NBR. Ultimately, the study elucidates the mechanisms governing hydrogen distribution evolution and permeation in NBR under hydrogen environments. The results indicate that the crosslink density of NBR filled with carbon black (NBR-CB) and silica (NBR-SC) is directly proportional to the filler content. NBR with higher filler content exhibits a lower hydrogen permeation coefficient and superior hydrogen barrier properties. In contrast to silica fillers, carbon black fillers demonstrate strong adsorption and a more pronounced barrier effect against hydrogen molecules, thereby enhancing the hydrogen barrier efficiency. The increase in carbon black's hydrogen solubility (from 2.2 × 10-4 to 16.9 × 10-4 cc(STP)·cm-3(polymer)·cmHg-1) effectively reduces the hydrogen permeation coefficient. In contrast, the rise in carbon black's hydrogen diffusion coefficient (from 0.1 × 10-6 to 4.1 × 10-6 cm2·s-1) exacerbates the overall hydrogen permeation coefficient of NBR-CB, thereby intensifying the hydrogen permeation process.

Computational and experimental substantiation of the operability of seals of localizing safety system elements of power units with VVER

The relevance of this work is determined by the need to predict the operation of sealing assemblies for elements of localizing safety systems (LSSs) of power units with VVER, which include (penetrations, hatches, locks, doors and other elements of hermetic fencing (GF) in operational modes. Operational modes are understood as modes of normal operation, modes of violation of normal operation, as well as emergency situations. During the manufacture and operation of LSS elements, the problem arises of uneven protrusion of a double-row rubber seal from the grooves in the web of the LSS element, which leads to the need to clarify the integral compression force of the seal as a whole for this element. The problem is caused by the imperfection of the manufacturing technology of large canvases for LSS elements (doors, hatches, locks: the perimeter of the seals can reach 10-20 m, the diameter of the canvas 2-6 m) and the need to withstand stringent technological requirements for flatness, parallelism and marginal deviations in linear and angular dimensions. The manufacture of overall structures is complicated by the presence of welded joints, heat treatment, and the complexity of metalworking. Compression force of the PNAE rubber gasket-7-002-86 it is not regulated, therefore, for the reliable design of gasket compression mechanisms, the magnitude of this force was determined. Based on the obtained results of tests of rubber seals for tightness and cyclic loading [7], an assessment of the tightness of the applied rubber seals is performed, calculations of deformations of rubber seals are performed using the FEM software package. Recommendations have been developed to increase the reliability of seal assemblies for elements of localizing safety systems (LSSs) of VVER power units in operational modes and to select the compression value to determine the necessary force to ensure tightness at the beginning of operation and after 5000 opening-closing cycles.

Thermal degradation and thermo-oxidative aging behavior of vinylidene fluoride-containing fluoroether rubber

Vinylidene fluoride-containing fluoroether rubber has better low temperature performance, expansion resistance and heat resistance. After curing by peroxide, it can be applied to a variety of fuel mixtures and is expected to be widely used in aerospace as a sealing material or other fields. In this work, the thermal degradation and thermo-oxidative aging behavior of Vinylidene fluoride-containing fluoroether rubber cured by 2,5-dimethyl-2,5-di-(tert‑butylperoxy) hexane/Triallyl isocyanurate (DBPH/TAIC) were investigated. For comparison, raw rubber without any crosslinking has been taken. The results indicated that the thermal degradation of vinylidene fluoride-containing fluoride rubber started with the degradation of TAIC in addition to the removal of HF on the backbone and the breakage of the side chain of ether monomers. During thermo-oxidative aging, the main chain formed C = C structure under the mechanism of dehydrofluorination. Meanwhile, the molecular chain broke under the action of thermal oxygen and was accompanied by the formation of carbonyl groups. The destruction of the polymer cross-linked structure occured at the TAIC cross-linking point and mainly occurred in the early stage of aging. However, the crosslinking was not completely disrupted, as the crosslinking density increased with aging time. The destruction and recombination of the crosslinked structure occurred simultaneously during the whole aging process and were dominated by recombination. Over-crosslinking after aging reduced the tensile properties of composites. This work contributes to a better comprehending of the stability of fluoroether rubber seals in a thermal-oxygen environment.

An Experiment on the Dwell Time Effect of Rubber Seal O-Rings: Friction Force in Intermittent Reciprocating Motion

The adhesive force between two contact surfaces often leads to an increase in the friction force of the rubber seal O-ring after a certain dwell time, forming dwell time effects and affecting the reliability of sealing. The dwell time effect may result in substantial instability with respect to the frictional behavior of rubber O-rings, which needs to be carefully taken into account in the design of rubber seals. Therefore, in this paper, the dwell time effect of the friction force was studied experimentally for intermittent reciprocating rubber seal O-rings coupled with stainless steel 316L and a sealing air medium. The friction force of three kinds of rubber materials, including fluorine rubber (FPM), silicone rubber (SI), and nitrile rubber (NBR), was measured under different dwell times, compression ratios, and seal pressure. The results showed that there was a rolling frictional force, and the second peak value of the frictional force caused by the O-ring’s rolling under shear action and after the maximum static frictional force was observed at the starting stage of reciprocating motion. For FPM O-rings, the rolling friction force was much greater than the maximum static frictional force at about four times the value of the compression ratio at 9% and seal pressure at 0; moreover, the force was much greater at greater compression ratios. The dwell time effect was significant in the friction forces of rubber O-rings. The friction force increases with an increase in dwell time. The increase in maximum static friction force exceeded 50% after 5 dwell days. The increase in seal pressure led to the disappearance of the rolling friction feature and the rapid increase in friction during the starting stage. Under gas seal pressure conditions, the dwell time effect still led to a significant increase in friction force. The obtained results might provide guidance for the material selection of sealing designs.

From Formulation to Application: Effects of Plasticizer on the Printability of Fluoro Elastomer Compounds and Additive Manufacturing of Specialized Seals.

This work investigated material extrusion additive manufacturing (MatEx AM) of specialized fluoroelastomer (FKM) compounds for applications in rubber seals and gaskets. The influence of a commercially available perfluoropolyether (PFPE) plasticizer on the printability of a control FKM rubber compound was studied using a custom-designed ram material extruder, Additive Ram Material Extruder (ARME), for printing fully compounded thermoset elastomers. The plasticizer's effectiveness was assessed based on its ability to address challenges such as high compound viscosity and post-print shrinkage, as well as its impact on interlayer adhesion. The addition of the PFPE plasticizer significantly reduced the FKM compound's viscosity (by 70%) and post-print shrinkage (by 65%). While the addition of the plasticizer decreased the tensile strength of the control compound, specimens printed with the plasticized FKM retained 34% of the tensile strength of compression-molded samples, compared to only 23% for the unplasticized compound. Finally, the feasibility of seals and gaskets manufacturing using both conventional and unconventional additive manufacturing (AM) approaches was explored. A hybrid method combining AM and soft tooling for compression molding emerged as the optimal method for seal and gasket fabrication.

Simulation on metal-rubber contact behavior based on a reconstructed 3D topography of rough surfaces

A contact model with refined surface topography is important to the frictional wear study of rubber seal. But the traditional modeling method relies on the measurement of surface characteristics of rubber material, which increases the cost due to high-precision instruments and complex data processing. In the paper, a new modeling method on reconstructing the 3D surface topography is proposed. The coordinate cloud of the surface is generated based on the random distribution of asperity height, which is established according to the initiate parameters of the surface roughness. The metal-rubber assembly model with 3D topography of rough surfaces are built. The simulation on metal-rubber contact behavior is conducted in ANSYS. The result shows a power-exponent relation is between the real contact area and the external pressure, and three contact states of no contact, adhesion and slippage are defined to describe the dynamic distribution of real contact area. The authors proved the reliability of the topography reconstruction method by an indentation experiment on rubber material. The area ratio reflects not only the change rule of contact area under an increasing pressure, but also the difference of contact behavior of the contact pairs under different surface roughness.

Organizing and Conducting Bench Tests of Junctions between Reinforced Rubber Seals and Shafts

Organizing and Conducting Bench Tests of Junctions between Reinforced Rubber Seals and Shafts

Friction Performance of Rubber Sealing Disc Inside Pipe Robots for the Production of High-Paraffin Oil

The in-pipe robot is the most commonly used technique in offshore pipelines. The use of rubber sealing discs is important for in-pipe robots to ensure that the robots are moved by fluid pressures inside offshore pipelines. This paper focuses on the measuring and modeling of the wax–oil gel-breaking process at the soft frictional area between sealing discs and the pipe wall. In this study, a detailed characterization of the gel-scraping process and in situ probing portable microscopy are performed. Two contributions are made in this study. First, a direct observation of wax–oil deposition breaking is employed to detect the minute changes at the in-pipe robot. Second, we find that a simple function is possible to describe the relationship between the wax contents and dewaxing efficiency, in which the debris material removal ratio (DRR) is discussed. Thus, the gel deposition-breaking phenomena are quite different under the influence of rubber sealing discs. This result is further confirmed by the real contact ratio measurements. It is important to research the sealing disc further and apply it more in the petroleum industry, especially in in-pipe robots for deepwater pipeline systems.

Understanding Cu Sintering and Its Role on Corrosion Behaviour for High-Temperature Microelectronic Application

There has been a significant rise in interest from academic and industry communities on copper nano and micro-particles-based sinter pastes for harsh environment die attach. However, sintering these particles is a complex process which is affected by many parameters, such as (i) particles size, shape, and distribution, (ii) sintering temperature, pressure, environment, and (iii) organic compounds used for the paste formulation. In literature, various research groups demonstrated that sintered copper layer can achieve good electrical conductivity and high strength. In our previous research [1, 2], we explained that microscale etched flakes are also capable of shear strength >30Mpa while sintering with 10 MPa bonding pressure at 275°C for just 1 minute with negligible paste cost (in comparison to silver paste). However, very limited knowledge exists on literature about corrosion behaviour in sintered copper interconnects. This, from experience in the industry with silver sintering has proven to be critical to applications. For examples in high power LED headlamp applications, minor exposure to residual Sulphur emerging from vulcanized rubber seals has been observed to cause corrosion in silver sintered interconnects. Therefore, corrosion and its impact on performance and reliability must be considered, especially for safety critical applications. For this reason, we have studied the relationship between copper sintered samples and corresponding corrosion behaviours and compared again to pure copper (conventionally produced). The corrosion resistance of the samples in salt water was assessed via various electrochemical analysis techniques and correlated with sintered microstructure. Sample produced better corrosion resistance when fabricated with higher density (less porosity). However, in case of the microscale copper flakes-based interconnects, a pitting behaviour was observed. The sintered copper paste samples showed to be nobler than commercial copper. In addition, copper oxide and its role in accelerating/preventing oxidation is also studied.

Experimental and numerical evaluation of a rubber seal in a vacuum suction pad for an automatic mooring system

The utilization of automatic mooring systems is under extensive interest with the growing technological demands for autonomous ships and smart ports. A vacuum suction pad with a rubber seal, which endures external loads to the moored ship, such as mooring forces, is a critical element in an automatic mooring system. To develop a high-performance automatic mooring system, a vacuum suction pad and a rubber seal need to be thoroughly designed, manufactured, and evaluated. This work demonstrates a protocol for evaluating the performance of a vacuum suction pad through both simulation and experimental testing. Uniaxial tensile testing was conducted to understand the mechanical behavior of a rubber seal. Stabilized stress-strain curves were utilized to find an optimal strain energy density function model and to extract material parameters for 3D finite element method (FEM) simulations. The FEM simulations were conducted to calculate strain distributions, contact status and the maximum load capacity, and along with the FEM simulation results, experimental evaluations of the vacuum suction pad were designed and conducted against static and cyclic loads. Based on the simulation and experimental results, we can conclude that the vacuum suction pad can maintain the stable suction at least up to 25 kN suitable for the use in automatic mooring systems.

ВЛИЯНИЕ ГИДРОЛИЗАТА КОЛЛАГЕНА НА КИНЕТИКУ ВУЛКАНИЗАЦИИ И ПЛОТНОСТЬ СШИВАНИЯ РЕЗИН НА ОСНОВЕ БУТАДИЕН-НИТРИЛЬНОГО КАУЧУКА БНКС-18

The effect of collagen hydrolysate (CH) obtained from the swim bladder of northern fish species on the set of operational properties of elastomers based on BNKS-18 nitrile butadiene rubber with acrylonitrile content of 18 wt.% was studied. The vulcanization kinetics of elastomeric blends were determined on a D-RPA 3000 rotorlessrheometer (MonTech, Germany). Tensile strength and elastic properties of vulcanizates were determined on an Autograph AGS-JSTD testing machine (Shimadzu, Japan). Frost resistance was evaluated by the value of frost resistance coefficient according to elastic rebound after compression at -20, -30, -40, -50 °C. The density of the vulcanization network of the studied elastomers was determined according to the Flory-Rener equation by the method of equilibrium swelling of vulcanizates in chloroform. The analysis of vulcanization kinetics showed that the introduction of collagen hydrolysate obtained by us into the composition of BNKS-18 based elastomer increased the minimum torque. That is, the viscosity of the studied elastomers increased before the start of the main vulcanization process. As demonstrated in this study, CH significantly affects the crosslinking density of elastomer. Introduction of CH in the composition of elastomers leads to the formation of a sufficiently dense and strong vulcanization network. This is apparently associated with the fact that CH fragments interact with the ingredients of the vulcanizing system and the rubber macromolecules, participating in the structuring of the material. It was found that the introduction of CH increased modulus at 100% elongation and tensile strength, while elongation at break decreased. The maximum value of tensile strength corresponds to the introduction of 3phr of CH and amounts to 16.9 MPa, which is 37% higher in comparison with control elastomers without CH. It was shown that the increase of crosslink density of vulcanization network of the obtained elastomers was accompanied by increase of frost resistance coefficient at -30 and -40 °C. The field of application of the developed materials is manufacturing of rubber seals, cuffs, oil seals, gaskets designed for the Far North and the Arctic equipment.

ИЗМЕНЕНИЕ ТЕХНИЧЕСКОГО СОСТОЯНИЯ ДВИГАТЕЛЕЙ ЛЕГКОВЫХ АВТОМОБИЛЕЙ В УСЛОВИЯХ ЭКСПЛУАТАЦИИ

This study presents the results of collecting and analyzing statistics on the wear of pistons of budget-class passenger car engines during active operation. The devices and methods of collecting experimental data on the wear of the cylinder-piston group of engines are described. The main ones were: measuring piston wear in four projections with a micrometer MK-100 GOST 6507-90 with a measurement error of ± 0.005 mm and measuring the compression properties of engines with a compressor, the latter showed low accuracy of displaying the technical condition according to the results of the study. The purpose of the study was to verify the effectiveness of common methods of diagnosing internal combustion engines, as well as to identify the dependence of wear on the frequency of oil change, the design features of the engine lubrication system (the presence of oil nozzles cooling pistons). As a result of the study, the inefficiency of the diagnostic method by measuring compression with various devices was revealed, since when the cylinder-piston group wears out with simultaneous wear of the rubber seals of the valves, the oil acts as an additional seal in the engine cylinder and "masks" the actual compression index of the internal combustion engine. In addition, the results of the study confirmed the effectiveness of the presence in the design of the lubrication system of piston cooling oil injectors designed to supply oil when a certain pressure in the lubrication system is reached to a more loaded cylinder wall and piston bottom – based on the revealed fact, it becomes possible to make recommendations on the refinement of the engine design during major repairs at automobile enterprises, service stations by introducing oil injectors into the engine block, which will lead to an increase in the life of the cylinder-piston group and longer trouble-free operation of the engines.

Effect of Hydrothermal Aging on the Tribological Performance of Nitrile Butadiene Rubber Seals.

High temperature and humidity affect the tribological performance of nitrile butadiene rubber (NBR) seals, which affects the precise positioning of cylinder systems. Therefore, it is crucial to study the effect of hydrothermal aging on the tribological performance of the NBR seals. In this study, the changes in the tribological performance of the NBR seals under hydrothermal aging conditions were investigated. The results show that the volatilization of additives and the increase in crosslink density of the NBR seals occurs in the hydrothermal aging environment, leading to the deterioration of their surface quality, elastic deformability, and tribological performance. The formation of surface micropores due to additive volatilization is the main factor in the degradation of tribological performance.

Investigation of co-gasification characteristics of coal with wood biomass and rubber seals in a fixed bed gasifier

The thermochemical processing of waste in gasification to hydrogen-rich gas is considered to be a novel, promising technological option, complementing the currently employed hydrogen production methods and an effective and environment friendly way of waste utilization. The paper discusses the results of the experimental study on this novel technological option of co-gasification of coal with automotive rubber seals or wood chips in a fixed bed reactor with the application of oxygen and steam mixture as a gasification agent. The experiments were performed with the use of waste to coal blending ratio of 10:90, 15:85 and 20:80 (%w/w), and at the temperature range of 700–900 °C. The contents of carbon monoxide, carbon dioxide, hydrogen and methane in the gaseous product reported in the study were in the range of 35–36 %vol., 31–33 %vol., 29–31 %vol., and 0.10–0.16 %vol., respectively. The maximum values of the lower heating value and the total gas volume were reported for fuel blends of 10%w/w waste content at 900 °C. Hydrogen and carbon monoxide production increased with process temperature, and declined with waste fraction in a fuel blend. Gasification of fuel blends composed of coal and rubber resulted in higher hydrogen production than the gasification of coal-biomass fuel blends, which may be attributed principally to the higher fixed carbon content and higher alkali index of rubber when compared to the respective values of wood chips.

3D stack-up assembly tolerance analysis for sealing optimization of PEMFCs

As elastic rubber seals are in contact with rigid metal bipolar plates (BPPs), multi-layer stack seals are critical to PEMFC safety. The precision of rigid-flexible seals is significantly affected by assembly errors. To reveal the transformation mechanism from BPPs manufacturing tolerances to PEMFC sealing, this study adopted semi-analytical modeling and numerical simulation. A deviation transfer model with three parameters (deviation size |r→|, deviation direction φr, rotation angle θr) was constructed on the basis of manufacturing tolerances to evaluate BPPs deviation. Numerical simulations were further conducted to obtain rubber-metal contact status. The effect of varying deviations on leakage was also investigated. It is found that: 1) φr causes various sealing behaviors in various sealing zones; 2) θr slightly affects leakage rates; 3) |r→| is crucial for optimizing the BPPs tolerance. The proposed method investigates the effect of 3D stack-up assembly errors on sealing performance and provides a theoretical foundation for the tolerance design and optimization of PEMFCs.

Synergistic Effects of Multiple Environmental Factors on Degradation of Silicone Rubber Seals under Marine Atmosphere.

In this research, the degradation behavior and failure mechanism of silicone rubber seal rings under the synergistic effects of multiple factors in the marine atmosphere are fully investigated. Firstly, four aging factors of air, temperature, compressive stress, and chemical medium were determined by analyzing the service environment profile of silicone rubber seal under a marine atmosphere environment. Secondly, to better simulate the actual service environment of silicone rubber and shorten the test period, an artificially accelerated aging test was designed and carried out in the laboratory. In this paper, temperature is utilized as the accelerating stress. According to the results of the pre-test, the accelerating stress level is finally determined to be 110-150 ∘C. In addition, the compression set applied is consistent with the constant compression permanent deformation value of 28% of the silicone rubber in the actual service process. Finally, through the macroscopic physical properties and microstructure analysis of the samples before and after aging, the corresponding test results are given, and the failure mechanism is analyzed and discussed in detail. Through the above test results and discussion, it can be concluded that the aging process of multi-factor coupling on the lower silicone rubber seal ring is uneven, and its aging process is not a simple superposition of multiple environmental factors. More importantly, the above test data and results are of great significance for evaluating the service life of silicone rubber seals, which can be utilized in the future to improve the reliability and durability of related equipment in the marine environment.

ACS says plastic-eating bacteria turn waste into useful starting materials, and rubber seals can leak additives into drinking water

Mountains of used plastic bottles get thrown away every day, but microbes could potentially tackle this problem. On November 1, 2023, ACS reports that researchers in ACS Central Science report that they've developed a plastic-eating E. coli that can efficiently turn polyethylene terephthalate (PET) waste into adipic acid, which is used to make nylon materials, drugs and fragrances.