Influence of carbon black on decompression failure and hydrogen permeation properties of filled ethylene‐propylene–diene–methylene rubbers exposed to high‐pressure hydrogen gas

Abstract

Eight carbon black (CB)-filled ethylene-propylene-diene-methylene linkage (EPDM) rubbers were manufactured by varying the content and type of CB. Then, the relationship among crack damage caused by high-pressure hydrogen decompression, the hydrogen permeation properties, and the mechanical properties of the rubbers was investigated. The hydrogen gas permeability of the rubbers decreased with an increase in the CB content and depended little on primary particle size. In contrast, the hydrogen gas diffusivity and solubility depended on both the CB content and primary particle size, that is, the hydrogen gas diffusivity decreased with an increase in the CB content and a decrease in the primary particle size, and the hydrogen gas solubility increased with an increase in the CB content and a decrease in the primary particle size. As for the mechanical properties, the CB-filled rubbers were more strongly reinforced by an increase in the CB content and a decrease in the primary particle size. The crack damage by high-pressure hydrogen decompression became larger as the ratio of the hydrogen gas solubility to estimated internal pressure at crack initiation relating to the mechanical properties became larger. As a smaller CB particle increases the hydrogen gas solubility of EPDM rubbers, while at the same time it reinforces the rubbers, the crack damage in the CB-filled rubbers was not influenced by the primary particle size.

Polymers for hydrogen infrastructure and vehicle fuel systems :

“…Many of the small differences in transport properties from one study to another for the same material can likely be attributed to microstructural differences (including differences in additives and fillers). While the role of additives and microstructure on gas transport in elastomers has not been extensively studied, several recent studies by Yamabe et al have investigated the role of fillers in elastomers exposed to high-pressure hydrogen [52,[74][75][76][77].…”

“…In particular, a study on EPDM shows that changes of hydrogen transport properties due to filler materials are relatively small: the hydrogen diffusivity decreases and the hydrogen solubility increases by factors of up to 2 or 3 with filler (relative to a baseline with no filler) under conditions used in the tests [75]. These changes are attributed to adsorption of hydrogen by the filler material, especially carbon black, which is known to interact strongly with hydrogen [75].…”

Tensile Properties and Swelling Behavior of Sealing Rubber Materials Exposed to High-Pressure Hydrogen Gas

“…Such phase hardly exits at the interface between silica particle and matrix. Our previous studies mentioned that the carbon black absorbs hydrogen, whereas the silica does not (5), (8) . We inferred that the residual hydrogen content of CB was higher than that of NF or SC because a large quantity of hydrogen was dissolved in the bound rubber phase at the interface between the carbon black and the matrix, as shown in Fig.…”

“…Because it took about 30 minutes to commence the measurement of the hydrogen content, the residual hydrogen contents were measured 35 minutes after decompression and the results are shown in Fig. 3 considered to be barely soluble in the fillers (5), (8) , so the residual hydrogen content is expressed on the basis of the weight of the rubber matrix in Fig. 3.…”

“…Sulfur-vulcanized NBR was used as the base polymer. Carbon black (primary particle size: 28 nm (7) , N 2 surface area: 76 m 2 /g (8) ) and silica (primary particle size: 16 nm (9) , N 2 surface area: 211 m 2 /g (8) ) were added as fillers. Table 1 shows the material composition, density, and durometer hardness of the rubbers used in this study.…”