Penetrated hydrogen content and volume inflation in unfilled NBR exposed to high-pressure hydrogen-What are the characteristics of unfilled-NBR dominating them?

A series of unfilled acrylonitrile butadiene rubber (NBR) composites, which consists of several types of NBR with acrylonitrile (AN) monomer unit ratio (ΧAN) and sulfur or dicumyl peroxide (DPO) as a vulcanizer, were exposed to 90 MPa hydrogen gas to measure the saturated hydrogen content: C.H(0) and the volume change ratio when the sample volume is the maximum: VMAX/V0. The aim of this paper is to reveal the dominant characteristics for C.H(0) and VMAX/V0 of unfilled NBR composites. Mechanical properties, ΧAN, the molecular weight of the number average molecular weight between the effective crosslinks (Mef), the molecular weight between the chemical crosslink (MC) and the fractional free volume (FFV) were employed to examine the relationship between the characteristics and C.H(0) and VMAX/V0 of the NBR composites. Judging from the results of the comparisons of C.H(0) and VMAX/V0 with ΧAN, Mef, MC and FFV, it is revealed that C.H(0) and VMAX/V0 were dominantly correlate with FFV and MC, respectively.