Impedance spectroscopy for in situ and real-time observations of the effects of hydrogen on nitrile butadiene rubber polymer under high pressure

Jae Kap Jung,Kyu-Tae Kim,Un Bong Baek,Ki Soo Chung,Chang Hoon Lee,Sang Koo Jeon

doi:10.1038/s41598-019-49692-y

Abstract

Nondestructive impedance spectroscopy (IS) was developed and demonstrated to detect the effects of hydrogen on nitrile butadiene rubber exposed to hydrogen gas (H2) at high pressures up to 10 MPa. IS was applied to obtain an in situ and real-time quantification of H2 penetration into and its desorption out of rubber under high pressure. The diffusion coefficients of H2 were also obtained from the time evolution of the capacitance, which were compared with those obtained by thermal desorption gas analysis. The in situ measurements of the capacitance and the dissipation factor under various pressures during cyclic stepwise pressurization and decompression demonstrated the diffusion behaviour of H2, the phase of the rubber under high pressure, the transport properties of H2 gas, and the physicochemical interaction between H2 and the rubber. These phenomena were supported by a COMSOL simulation based on the electric current conservation equation and scanning electron microscopy (SEM) observations.

Highlights

Hydrogen gas (H2) is expected to be a future clean-energy source to mitigate global warming and the exhaustion of fossil fuels
Many kinds of rubber polymers are used as sealants in H2 environments: polytetrafluoroethylene (PTFE) is used as a sealant in mechanical compressors, and nitrile butadiene rubber (NBR), ethylene propylene diene monomer (EPDM), and fluoroelastomer (FKM) rubbers are used as sealants and gaskets in valves and pipelines[9]
For d < 1 mm, the C-simul deviated from the capacitances (C-analytic) calculated using an ideal parallel-plate model, CNBR = ε0 · R2/d, because of the limits of the geometric precision in the mesh modelling

Summary

Results and Discussion

A dielectric constant (~3) smaller than the value in a normal rubber polymer suggests that the decrease in the dielectric constant may occur because, due to the solvent, H2 causes the formation of a rigid plastic phase or a glass phase This finding suggests that the penetration of high-pressure H2 with a low molecular mass in the process of pressurization, which generally induces www.nature.com/scientificreports plasticization for many polymers[13,14,15], resulted in a reduction in the dielectric constant and capacitance of the polymers, whereas the increase in Cnor during decompression (Fig. 6) was caused by deplasticization after the release of pressure. H2 effect on NBR are consistent with that already proposed by IS in views of greater permeation capability, stronger effects on physically and chemically in H2 more than Ar

Conclusions

Author Contributions

Additional Information