Inhomogeneity in acrylonitrile butadiene rubber during hydrogen elimination investigated by small-angle X-ray scattering

Ohyama, Keiko; Fujiwara, Hirotada; Nishimura, Shin

doi:10.1016/j.ijhydene.2017.10.162

Cited by 23 publications

(6 citation statements)

References 19 publications

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“…EPDM and other rubbers are known to have inhomogeneities in their cross-link densities. 62,63 The varying behavior at different cross-link densities found here could therefore occur in the same material due to spatial inhomogeneities in crosslink density. Indeed, variations in cross-link density have been related to the origins of nanoscale failure in EPDM and NBR.…”

Section: ■ Results and Discussionmentioning

confidence: 77%

Subdiffusive High-Pressure Hydrogen Gas Dynamics in Elastomers

Frischknecht

Wilson

2022

Macromolecules

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Elastomeric rubber materials serve a vital role as sealing materials in the hydrogen storage and transport infrastructure. With applications including O-rings and hose liners, these components are exposed to pressurized hydrogen at a range of temperatures, cycling rates, and pressure extremes. High-pressure exposure and subsequent rapid decompression often lead to cavitation and stress-induced damage of the elastomer due to localization of the hydrogen gas. Here, we use all-atom classical molecular dynamics simulations to assess the impact of compositional variations on gas diffusion within the commonly used elastomer ethylene–propylene–diene monomer (EPDM). With the aim to build a predictive understanding of precursors to cavitation and to motivate material formulations that are less sensitive to hydrogen-induced failure, we perform systematic simulations of gas dynamics in EPDM as a function of temperature, gas concentration, and cross-link density. Our simulations reveal anomalous, subdiffusive hydrogen motion at pressure and intermediate times. We identify two groups of gas with different mobilities: one group exhibiting high mobility and one group exhibiting low mobility due to their motion being impeded by the polymer. With decreasing temperatures, the low-mobility group shows increased gas localization, the necessary precursor for cavitation damage in these materials. At lower temperatures, increasing cross-link density led to greater hydrogen gas mobility and a lower fraction of caged hydrogen, indicating that increasing cross-link density may reduce precursors to cavitation. Finally, we use a two-state kinetic model to determine the energetics associated with transitions between these two mobility states.

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Section: ■ Results and Discussionmentioning

confidence: 77%

Subdiffusive High-Pressure Hydrogen Gas Dynamics in Elastomers

Frischknecht

Wilson

2022

Macromolecules

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“…[50,53,96] Simmons et al [97] also conducted similar tests on NBR exposed up to 28 MPa hydrogen gas for 24 h at RT and detected the dissolved hydrogen within the matrix observing the peaks in the NMR spectrum. Further investigations of bubbling and initiation of cracks at RGD were conducted by identifying the change of submicron-scale morphological structures during the hydrogen elimination process by Ohyama et al [98] In this study, they used a SAXS, observing the submicron-scale voids in peroxide-vulcanized NBR composites during hydrogen elimination after exposure to 90 MPa of high-pressure hydrogen gas at 30 C for 24 h. Based on the SAXS and Debye-Bueche function, they managed to identify two phases in NBR with a clear interface, which originated from penetrated hydrogen; one phase corresponds to voids with hydrogen, which is identified as a low-density phase and the other phase is from rubber chain molecules, which are closely packed and identified as a high-density phase. [98] Ohyama et al [98] assumed the voids generated within the matrix had started from the precursors, which already existed in the matrix due to the inhomogeneity of vulcanized rubber.…”

Section: Observations On Bubble Formation and Fracture Initiationmentioning

confidence: 99%

“…When the external pressure is released then the dissolved gas is concentrated at the low-density phases and inflates until it generates submicron-sized voids, and it expands to bubbles and even up to fracture, depending on the environmental conditions. [98] Figure 5 shows this model of void and bubble formation at low strength sites and leading up to the blister formation. Moreover, the blisters in rubber composites as a result of high-pressure hydrogen decompression may also be initiated easily as sub-micrometer-sized bubbles in the vicinity of inherent defects as well as at irregular shaped filler agglomerates as illustrated in Figure 6.…”

Section: Observations On Bubble Formation and Fracture Initiationmentioning

confidence: 99%

A Review on Applicability, Limitations, and Improvements of Polymeric Materials in High-Pressure Hydrogen Gas Atmospheres

et al. 2021

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Typically, polymeric materials experience material degradation and damage over time in harsh environments. Improved understanding of the physical and chemical processes associated with possible damage modes intended in high-pressure hydrogen gas exposed atmospheres will help to select and develop materials well suited for applications fulfilling future energy demands in hydrogen as an energy carrier. In high-pressure hydrogen gas exposure conditions, damage from rapid gas decompression (RGD) and from aging in elastomeric as well as thermoplastic material components is unavoidable. This review discusses the applications of polymeric materials in a multi-material approach in the realization of the "Hydrogen economy". It covers the limitations of existing polymeric components, the current knowledge on polymeric material testing and characterization, and the latest developments. Some improvements are suggested in terms of material development and testing procedures to fill in the gaps in existing knowledge in the literature.

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“…The damages induced by rapid gas decompression (RGD) or explosive decompression (XDF) are common upon the sudden release of high‐pressure gas 14,15 . RGD in the NBR can lead to the formation of submicron‐scale voids or bubbles, and two phases with a clear interface between them 16 . The dissolved state of hydrogen in the NBR matrix can induce the expansion of the bubbles, leading to fractures 10,17–19 .…”

Section: Introductionmentioning

confidence: 99%

Study on the expansion of nitrile rubber in high‐pressure hydrogen gas atmospheres: Calculations and experiments

Lei,

Zheng,

Xue

2024

Polymer Engineering & Sci

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Hydrogen with small molecule size under high pressure can permeate most materials, being a challenge for rubber sealing materials used in hydrogen storage. The volume expansion of rubber materials due to high‐pressure hydrogen is an important indicator of their degradation and failure. Here, both microscopic calculations and experimental investigations of the nitrile rubber were conducted to evaluate the relation between the structure features and the expansion performance. Three factors, the acrylonitrile amount, the chain length, and the crosslinking degree, were considered to impact on the expansion of the nitrile rubber. Current study indicates that the increasing of acrylonitrile amount can result in the reduction of the volume expansion, owing to the preferential interactions between hydrogen and the butadiene group of nitrile rubber. Both of the chain length and the crosslinking degree are positively proportional to the chain elongation and then the volume of the nitrile rubber. Especially, the amount of acrylonitrile was found to be a key factor for evaluating the expansion of nitrile rubber under high‐pressure hydrogen. This study performs microscopic calculations and macroscopic experiments to investigate the expansion of nitrile rubber, which is expected to be used in designing the sealing rubber material for high‐pressure hydrogen storage applications.Highlights Acrylonitrile determines the expansion performance of NBR within high‐pressure hydrogen. Short chain and low crosslinking density suppressed the expansion of NBR. Evaluating the expansion of nitrile rubber exposed to high‐pressure hydrogen.

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Inhomogeneity in acrylonitrile butadiene rubber during hydrogen elimination investigated by small-angle X-ray scattering

Cited by 23 publications

References 19 publications

Subdiffusive High-Pressure Hydrogen Gas Dynamics in Elastomers

Subdiffusive High-Pressure Hydrogen Gas Dynamics in Elastomers

A Review on Applicability, Limitations, and Improvements of Polymeric Materials in High-Pressure Hydrogen Gas Atmospheres

Study on the expansion of nitrile rubber in high‐pressure hydrogen gas atmospheres: Calculations and experiments

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