Molecular dynamics simulation of H2 in amorphous polyethylene system: H2 diffusion in various PE matrices and bubbling during rapid depressurization

JW Zhao and XG Wang and QQ Yang and H Yin and B Zhao and SJ Zhang and CJ Wu, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, 47, 39572-39585 (2022).

DOI: 10.1016/j.ijhydene.2022.09.124

Polyethylene (PE) is a candidate liner material for Type IV storage devices. In this case, all -atom molecular dynamics simulations are employed to study the properties of Poly-ethylene with the presence of H2, including tensile properties, glass transition, diffusion in different PE and bubbling during rapid depressurization. The presence of H2 deteriorates the polyethylene matrix's tensile performance and decreases the glass transition temper-ature. The branch, side chain and small molecules promote the diffusion of H2 in the amorphous region by introducing more free volume below Tg. With a sufficient length, the length of polymer chain has minor effect on the diffusion of H2. Graphene, as a 2D rein-forcement, could decrease the diffusion of H2 but suffers from poor interfacial bonding. Finally, H2 bubble(s) formed from the over-saturated H2 molecule and were observed in both the exclusive and free volume and stabilised at low pressure during rapid depres- surization. According to the result obtained in this work, branchless HDPE is expected to give superior performance while the viscosity, which is important during processing, could be tailored by molecular weight. Processing technique leads to orientation is preferred, such as injection moulding.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

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