The compatibility of high‐density polyethylene piping and elastomers with the future fuel methanol

Methanol is an attractive hydrogen carrier that can assist the transition away from natural gas (NG) as a source of fuel. In this study, the compatibility of methanol with the existing plastic NG distribution network is investigated, focusing on high-density polyethylene (HDPE) piping and associated elastomers. Poly(styrene-co-butadiene) (SBR), poly(acrylonitrile-co-butadiene) (NBR), and polytetrafluoroethylene were investigated, as they are the base polymers for many elastomer materials. Commercial elastomers that are used in the NG distribution network were also studied, to determine the impact of methanol on polymer additives. The methanol solubility and diffusion in HDPE and associated elastomers, as well as changes to the mechanical properties, were determined to evaluate the compatibility of methanol with these materials. Methanol had a considerably higher diffusion coefficient than methane in HDPE, leading to a permeability that was two orders of magnitude greater. The flexibility of HDPE piping reduced upon exposure to methanol, as demonstrated by a reduction in tensile strain. In contrast, the sorption of methanol into the SBR and NBR was orders of magnitude greater than HDPE, due to their rubbery structure. The additives in commercial elastomers were extensively leached during methanol immersion, leading to significantly compromised mechanical properties. Hence, existing HDPE pipelines are compatible for the transport of methanol, but elastomer materials will be localized points of methanol loss and failure.