Swelling Of Elastomers Research Articles

An in-situ view cell system for investigating swelling behavior of elastomers upon high-pressure hydrogen exposure

The transition to hydrogen as a clean and efficient energy carrier is impeded by challenges in the compatibility of hydrogen with materials used within hydrogen infrastructure. Elastomers, crucial in sealing components, often exhibit premature failures in high-pressure hydrogen environments due to excessive swelling. This study employs an innovative in-situ view cell system to assess the swelling behavior of hydrogenated nitrile butadiene rubber (HNBR) under various hydrogen conditions. The system, designed to withstand pressures up to 96.5 MPa, incorporates Digital Image Correlation (DIC) for strain measurements and volume estimation. Results reveal non-linear volume increases during depressurization, challenging conventional assumptions. Furthermore, investigations into peak hydrogen pressures and pressure-holding scenarios during decompression highlight complex swelling trends. The introduction of a novel computer vision (CV) method enhances precision in volume estimation, overcoming DIC limitations. The study provides insights into mitigating elastomer swelling, crucial for developing robust materials to support future hydrogen-driven energy systems.

Chemomechanical equilibrium at the interface between a simple elastic solid and its liquid phase.

Applying diffusion coupled deformation theory, we investigate how the elastic properties of a solid body are modified when forced to keep its chemical potential aligned with that of its melt. The theory is implemented at the classical level of continuum mechanics, treating materials as simple continua defined by uniform constitutive relations. A phase boundary is a sharp dividing surface separating two continua in mechanical and chemical equilibrium. We closely follow the continuum theory of the swelling of elastomers (gels) but now applied to a simple two phase one-component system. The liquid is modeled by a local free energy density defining a chemical potential and hydrostatic pressure as usual. The model is extended to a solid by adding a non-linear shear elastic energy term with an effective modulus depending on density. Imposing chemomechanical equilibrium with the liquid reservoir reduces the bulk modulus of the solid to zero. The shear modulus remains finite. The stability of the hyper-compressible solid is investigated in a thought experiment. A mechanical load is applied to a rectangular bar under the constraintof fixed lateral dimensions. The linear elastic modulus for axial loading is evaluated and found to be larger than zero, implying that the bar, despite the zero bulk modulus, can support a weight placed on its upper surface. The weight is stabilized by the induced shear stress. The density dependence of the shear modulus is found to be a second order effect reducing the density of the stressed solid (chemostriction).

Characterisation of Elastomers as Food Contact Materials-Part 1: Quantification of Extractable Compounds, Swelling of Elastomers in Food Simulants and Release of Elements.

Elastomers are not a uniform class of materials but comprise a broad spectrum of chemically different polymers. Sealing gaskets, gloves, teats, conveyor belts and tubing are examples of elastomers being used as food contact materials (FCMs). Ten elastomer samples were evaluated with respect to the content of extractable compounds, migration of substances into ethanolic food simulants, swelling in food simulants and release of elements in different food simulants. The number of extractable substances <1000 Da was determined by comprehensive two-dimensional gas chromatography coupled with flame ionisation detection (GC × GC–FID) analysis of tetrahydrofuran (THF) extracts. The number of signals ranged from 61 (a thermoplastic elastomer (TPE)) to 690 (a natural rubber/styrene-butadiene-rubber blend (NR/SBR)). As for risk assessment, the decisive factor is which substances reach the food. The extent of substances that migrate into ethanolic food simulants was investigated. Elastomer FCMs can be the source of food contamination with heavy metals. Notably, contamination with lead was detected in some samples investigated in this study. It was shown that food simulants harbour the potential to morphologically alter or even disintegrate elastomeric materials. The results presented here highlight the importance to carefully choose the elastomer type for the intended use as FCMs as not every application may prove safe for consumers.

Anisotropic swelling of elastomers filled with aligned 2D materials

A comprehensive study has been undertaken on the dimensional swelling of graphene-reinforced elastomers in liquids. Anisotropic swelling was observed for samples reinforced with graphene nanoplatelets (GNPs), induced by the in-plane orientation of the GNPs. Upon the addition of the GNPs, the diameter swelling ratio of the nanocomposites was significantly reduced, whereas the thickness swelling ratio increased and was even greater than that of the unfilled elastomers. The swelling phenomenon has been analyzed in terms of a modification of the Flory–Rehner theory. The newly-derived equations proposed herein, can accurately predict the dependence of dimensional swelling (diameter and thickness) on volume swelling, independent of the type of elastomer and solvent. The anisotropic swelling of the samples was also studied in combination with the evaluation of the tensile properties of the filled elastomers. A novel theory that enables the assessment of volume swelling for GNP-reinforced elastomers, based on the filler geometry and volume fraction has been developed. It was found that the swelling of rubber nanocomposites induces a biaxial constraint from the graphene flakes.

Realising biaxial reinforcement via orientation-induced anisotropic swelling in graphene-based elastomers.

The biaxial mechanical properties constitute another remarkable advantage of graphene, but their evaluation has been overlooked in polymer nanocomposites. Herein, we provided an innovative and practical method to characterise biaxial reinforcement from graphene via swelling of elastomers, where graphene nanoplatelets (GNPs) were controlled to be oriented in-plane. The in-plane-aligned graphene imposed a biaxial constraining force to the elastomer during the swelling process that led to the anisotropic swelling behaviour of the bulk nanocomposites. This unconventional swelling behaviour was successfully modelled using statistical mechanics. Novel in situ Raman band shift measurements were also performed during the de-swelling process of the samples. The characteristic 2D band shift of the GNPs, imposed by stress transfer during the de-swelling procedure, was of the order of 0.1 cm-1 per % strain, enabling the calculation of the effective biaxial Young's modulus of the GNPs in the nanocomposites (∼2 GPa). The determination of the biaxial modulus of GNPs contributed to the evaluation of their Poisson's ratio (∼0.34), which is very important but highly impractical to be measured directly on a nanoscale-sized specimen.

O-Rings Material Deterioration due to Contact with Biodiesel Blends in a Dynamic Fuel Flow

O-rings are a primary component made from polymeric materials in most diesel engine systems. For oil-fuelled operations, O-rings tend to degrade after exposure to fuel in certain operating condition and periods. Degradation of O-rings can cause engine leakage. This study is intended to test the O-rings material which contacted with biodiesel in dynamic flow by considering the potential deterioration caused. The use of biodiesel may contribute to accelerating deterioration of O-rings. The boiler fuel system was duplicated in this test, where the biodiesel used was palm oil based. The O-rings tested are made of materials of Fluorocarbon elastomer (FKM), Nitrile Rubber (NR) and Silicone Rubber (SR). The effects on O-rings were observed on changes in mass, volume, and thickness. The material compatibility is indicated by elongation, swelling and chemical resistance of elastomers with various fuel flow rates. The fuel flow with high volumetric rate tends to damage the O-rings faster as effected on the immersion test. FKM-Viton performed as materials with the best physical and chemical resistance. Dynamic fuel flow in the engine system showed that SR is deteriorated faster than NBR and FKM. The resistance of O-ring material to fuel in the system is not linearly influenced by the amount of biodiesel in the fuel.

Исследование гидрофильности полиуретановой пленки методами фотоупругости и релаксометрии ЯМР

The method of optical polarimetry was used to study the hydrophilicity of polyurethane. It was shown that upon swelling of elastomers, the initial optical anisotropy increases, but the photoelasticity coefficient decreases. The change in optical anisotropy under deformation of polyurethane under conditions of prolonged action of constant force is investigated. The NMR relaxometry method with the inversion of integral conversion was used to study the effect of polyurethane swelling on the dynamics of elastomer macromolecules.

Diffusion-based swelling in elastomers under low- and high-salinity brine

Swelling elastomers are designed to swell when immersed into fluids like water, oil, or acid. The mechanism of swelling can be either diffusion or osmosis, initiating the imbibition of fluid inside the elastomer and progressively swelling it. Work presented here investigates diffusion as the swelling mechanism. Swelling experiments are conducted at two temperatures (room and 50°C) using water of different salinities (0.6% and 12%) as the swelling medium. Changes in volume, thickness, mass, and hardness are recorded. Measurements are taken before swelling and after 1, 2, 4, 7, 10, 16, 23, and 30 days of swelling. As expected, volume, thickness, and mass of the elastomer increase with increase in the number of swelling days, while hardness shows a decreasing trend. More variation is observed for all quantities in low-salinity brine as compared to high salinity, at both temperatures. However, density values are larger for high-salinity brine at both temperatures. Stokes–Einstein formula is used to determine the diffusion coefficients. Viscosity is measured using a Cannon–Fenske apparatus of size 50. Larger values of diffusion coefficient are found in low-salinity water at both temperatures, consistent with the higher amount of swelling and the faster swelling rate. These results and the diffusion-based approach will help in understanding the mechanics of swelling phenomenon. This work can aid in the development of new analytical and semi-analytical models that can predict seal pressure and other performance factors more accurately for applications in oil and gas wells.

Performance evaluation of swelling elastomer seals

Swell packers are now being widely used for increased recovery from difficult oil and gas reservoirs and for remediation of various well problems. It is important to know how the elastomer actually swells in a particular well, how much time is required to achieve sealing, and what sealing pressure is generated. No published work is available that numerically investigates elastomer seal performance based on actual material properties at various stages of swelling. Current work uses finite element simulation to investigate swelling elastomer seal behavior in downhole petroleum applications. Variations in sealing pressure are studied for seal length, seal thickness, compression ratio, water salinity, swelling time, and type of well completion. Month-long swelling experiments on samples of two actual elastomers provide input to the numerical model in terms of real material and deformation data. Contact pressure was found to increase with swelling, at a higher rate in the first few days, then more slowly. Higher sealing pressure was observed in the case of swelling in lower-salinity brine, larger length of the sealing element, higher compression ratio of the seal, and elastomer swelling against rock formation as compared to steel outer-casing. These results can help field engineers decide which swelling elastomer and what seal configuration to use under a given set of field parameters. The study can also be used by application designers and academic researchers as a starting point for swelling elastomer based seal design and analysis.

Effect of biaxial deformation on ulimate swelling of elastomers

Effect of biaxial deformation on ulimate swelling of elastomers

Droplet-train induced spatiotemporal swelling regimes in elastomers.

In this work, we perform a combined experimental and numerical analysis of elastomer swelling dynamics upon impingement of a train of solvent droplets. We use time scale analysis to identify spatiotemporal regimes resulting in distinct boundary conditions that occur based on relative values of the absorption timescale and the droplet train period. We recognize that when either timescale is significantly larger than the other, two cases of quasi-uniform swelling occur. In contrast, when the two timescales are comparable, a variety of temporary geometrical features due to localized swelling are observed. We show that the swelling feature and its temporal evolution depends upon geometric scaling of polymer thickness and width relative to the droplet size. Based on this scaling, we identify six cases of localized swelling and experimentally demonstrate the swelling features for two cases representing limits of thickness and width. A finite element model of local swelling is developed and validated with experimental results for these two cases. The model is subsequently used to explore the swelling behavior in the rest of the identified cases. We show that depending upon the lateral dimension of the sample, swelling can locally exhibit mushroom, mesa, and cap like shapes. These deformations are magnified during the droplet-train impact but dissipate during post-train polymer equilibration. Our results also show that while swelling shape is a function of lateral dimensions of the sample, the extent of swelling increases with the elastomer sample thickness.

On the CO2 sorption and swelling of elastomers by supercritical CO2 as studied by in situ high pressure FTIR microscopy

An FTIR (Fourier Transform InfraRed) microscope combined to a high pressure cell has been used to determine the CO2 uptake in several common elastomers. Both the CO2 sorption and the resulting swelling of the elastomers have been determined as function of pressure (P=5–15MPa) at constant temperature (T=50°C). A significant quantity of CO2 is sorbed in all studied elastomers, between 15 and 20% at T=50°C and P=15MPa for most elastomers and up to 30% for Ethylene Vinylacetate (EVM) in the same conditions. The resulting percentage of swelling of the majority of studied elastomers is significant (up to 30%), and varies quite proportionally with the CO2 mass uptake (linear variation with a slope equal to 1). The effect of temperature has been studied for Ethylene Propylene Diene (EPDM), between T=50°C and T=110°C (P=5–15MPa) and demonstrate that the swelling and CO2 sorption display only a weak variation in this temperature range.

Compressor Lubrication -the key to Performance

Today, Low Global Warming Potential Refrigerants are being evaluated, optimized and applied. Higher-pressure refrigerants, refrigerant blends, and new chemical families of refrigerants are candidates. Compressor designs and system components are being evaluated to deliver the desired capacity, efficiency and reliable performance for intended applications.Once the Refrigerant family is chosen based on Environmental and Heat transfer properties, System Chemistry between the Refrigerant and Lubricant families are scrutinized for optimum miscibility and solubility. These directly affect the Phase separation between the 2 liquid phases and reduction of viscosity. Over the entire Operating Envelope, the “oil return” and “viscosity reduction” problems are assessed. Compatibility aspects between chemicals (Refrigerants, Lubricants) and materials of construction (metallic, polymeric, elastomeric) are verified to avoid failures in use. System Components, compressor bearings, expansion devices and heat transfer coils are adversely affected due to contaminants circulating in systems. Rust, Copper plating, Formicary corrosion, elastomer swelling are example. Advances in Analytical Chemistry Techniques help the compressor and system manufacturers characterize the problems. Further, System Chemistry guides selection of lubricant additives.This presentation explains how lubricant selection is accomplished using Tribology and System Chemistry aspects.

Effects of Carbon Black and the Presence of Static Mechanical Strain on the Swelling of Elastomers in Solvent.

The effect of carbon black on the mechanical properties of elastomers is of great interest, because the filler is one of principal ingredients for the manufacturing of rubber products. While fillers can be used to enhance the properties of elastomers, including stress-free swelling resistance in solvent, it is widely known that the introduction of fillers yields significant inelastic responses of elastomers under cyclic mechanical loading, such as stress-softening, hysteresis and permanent set. When a filled elastomer is under mechanical deformation, the filler acts as a strain amplifier in the rubber matrix. Since the matrix local strain has a profound effect on the material’s ability to absorb solvent, the study of the effect of carbon black content on the swelling characteristics of elastomeric components exposed to solvent in the presence of mechanical deformation is a prerequisite for durability analysis. The aim of this study is to investigate the effect of carbon black content on the swelling of elastomers in solvent in the presence of static mechanical strains: simple extension and simple torsion. Three different types of elastomers are considered: unfilled, filled with 33 phr (parts per hundred) and 66 phr of carbon black. The peculiar role of carbon black on the swelling characteristics of elastomers in solvent in the presence of mechanical strain is explored.

Effect of carbon black content on the swelling of elastomers in solvent in the presence of static mechanical loading

The effect of carbon black on the mechanical properties of elastomers is of great interest because filler is one of the necessity items for manufacturing of rubber products. While fillers can be used to enhance the properties of elastomers, it is known that filler yields to significant inelastic responses such as stress-softening, hysteresis and permanent set. Moreover, under tensile loading, the filler acts as a strain amplifier in the rubber matrix resulting in a higher local strain state in the matrix as compared to the applied macroscopic strain. The study of the effect of carbon black content on the swelling characteristics of elastomeric components undergoing mechanical loading and simultaneously exposed to aggressive solvent is a prerequisite for durability analysis. The present study investigates the effect of carbon black content on the swelling of elastomers in solvent in the absence and in the presence of static tensile loadings.

Examination of zwitterionic polymers and gels subjected to mechanical constraints

The effect of mechanical constraints on the anti-polyelectrolyte behavior of zwitterionic polymers was studied systematically in this work via viscosity examination of uncross-linked polymer solutions, swelling of cross-linked polymer gels and swelling of elastomers compounded with these gels. Zwitterionic polymers, poly(sulfobetaine methacrylate) (polySBMA), poly(2-methacryloyloxyethyl phosphorylcholine) (polyMPC) and copolymers of polySBMA with a polyelectrolyte, poly(sodium methacrylate) (polyNaMA) were used in this study. Anti-polyelectrolyte effects were observed both in solution and as gels. However, when the zwitterionic gels were compounded with hydrogenated acrylonitrile butadiene rubber (HNBR), the anti-polyelectrolyte behavior of the native polymer was lost. This is attributed to mechanical constraints imposed by the elastomeric HNBR matrix that dominate Coulombic interactions. Without the manifestation of chain relaxation and extension afforded by the charge screening, the zwitterionic polymers serve as hydrophilic agents that facilitate water diffusion into rubber.

Development of a Novel Experimental Device to Investigate Swelling of Elastomers in Biodiesel Undergoing Multiaxial Large Deformation

The lifetime of an elastomeric product depends on the nature of mechanical loading and the environmental condition during the service. In this context, at least two important aspects contribute to the degradation of the elastomeric parts in service: diffusion of aggressive liquids leading to swelling and fluctuating multiaxial mechanical loading leading to fatigue failure. Moreover, the amount of swelling of elastomers in solvent is affected by the presence of mechanical loading. Hence, it is essential to understand the interactions between the two phenomena for durability analysis of the component. The present study investigates the swelling of elastomers due to diffusion of palm biodiesel in the presence of static multiaxial large deformation. For this purpose, new experimental device and specimen are developed. The device consists of a hollow diabolo elastomeric specimen attached to specially-designed circular metallic grips and plates such that immersion tests can be conducted while the specimens are simultaneously subjected to various mechanical loadings: simple tension, simple torsion and combined tension-torsion. Thus, diffusion of liquids takes place in the material which concurrently undergoes multiaxial large deformation. Two types of elastomers are investigated: Nitrile Rubber (NBR) and Polychloroprene Rubber (CR). The particular features of the device and specimen are discussed and perspectives for further improvement are drawn.

Diffusion of Palm Biodiesel in Elastomers Undergoing Multiaxial Large Deformations

Petroleum-based fuel is facing significant depletion issue due to its limited reserves and increasing demand from various industries. Thus, various considerations from economical, environmental and political concerns have motivated researchers to develop alternative energy sources such as biofuel to decrease dependence on petroleum-based fuel. However, the changes in the fuel composition of biofuel affect the material compatibility. In engineering applications where elastomeric components are exposed to hostile environment such as palm biodiesel medium, at least two aspects contribute to the degradation of the materials during the service: diffusion of the liquids leading to swelling and fluctuating multiaxial mechanical loading leading to fatigue failure. Therefore, it is of utmost importance to study the mechanical responses of elastomers under this coupled diffusion-mechanical loading in order to predict accurately their fatigue failure. The present work investigates the swelling of elastomers under simultaneous diffusion of palm biodiesel and multiaxial large deformations.

Physical Phenomena Facilitating the Penetration of Solutions of TiO2 Nanoparticles through Protective Gloves

Titanium dioxide nanoparticles (nTiO2) are found in numerous manufactured products such as sunscreens and paints. Nevertheless, some studies have expressed concern about their likely harmful effects on health. Application of the precautionary principle has led to the recommendation for the use of protective gloves by numerous Health & Safety agencies. However, recent work has shown that solutions of nTiO2 can penetrate the protective materials of gloves under conditions simulating occupational use. This study has been designed to identify some of the physical phenomena that may facilitate the penetration of nTiO2 through elastomer membranes subjected to mechanical deformations (such as those produced by flexing the hand). Nitrile rubber and latex gloves were brought into contact with two solutions of nTiO2. Mechanical deformations were applied to samples of protective gloves during their exposure to nanoparticles. Repetitive mechanical deformations affected both the physical and mechanical properties of protective materials. Moreover, the elastomers used in protective gloves were also shown to be sensitive to the action of the nTiO2 solutions. Elastomer swelling was observed, leading to a modification of the mechanical and chemical properties of the gloves.

Swelling of Elastomers in Solutions of TiO2 Nanoparticles

Elastomers used in protective gloves can be sensitive to the action of solvents used to disperse commercial solutions of nanoparticles. These effects may include the swelling of the polymer, leading to a modification of its mechanical and chemical properties. Modifications to the properties of the polymer will impact the protection provided by the protective gloves. The goal of this work was therefore to study the swelling of several elastomers when exposed to commercial solutions of nanoparticles. The study involved four elastomers and three commercial solutions of colloidal titanium dioxide (TiO2). Swelling was assessed by measurements of mass gain and length change. Tests were also performed with technical and ultrapure solvents corresponding to the liquid carriers. The solutions had a significant effect on the swelling of nitrile rubber, latex, and neoprene. A large mass gain was recorded for short immersion times, indicating a possible penetration of the nanoparticle liquid carrier into these elastomers. Length change measurements revealed a swelling anisotropy effect with nitrile rubber and latex in the solutions of colloidal TiO2. No effect was measured with butyl rubber. The results show that great care must be taken when selecting protective gloves for the handling of nanoparticle dispersions.