Compatibility of High-Density Polyethylene Piping and Associated Elastomers with the Renewable Fuels Ammonia and Dimethyl Ether

Ammonia (NH3) and dimethyl ether (DME) have been identified as sustainable hydrogen carrier fuels in a low-carbon-emission economy. Here, the compatibility of polymer materials within the natural gas distribution network is investigated, specifically high-density polyethylene (HDPE) plastic piping and two associated elastomer materials, poly(styrene-co-butadiene) (SBR) and poly(acrylonitrile-co-butadiene) (NBR). The compatibility between hydrogen carrier fuels and these piping systems is expressed in terms of polymer solubility, diffusivity, and importantly permeability. The sorption of methane, ammonia, and DME into HDPE and the two elastomers was linear with pressure, indicative of rubbery polymer behavior, and modeled through Henry's law. The highly condensable nature of ammonia and DME resulted in substantially higher solubility in all materials compared to methane, with both SBR and NBR having significantly higher solubility for both fuels compared to HDPE. Similarly, the permeability of ammonia and DME in HDPE and both elastomers was greater than that of methane, with NBR permeating both ammonia and DME orders of magnitude faster than HDPE, indicative that the elastomers will be a significant leak source. DME plasticized both HDPE and the elastomers, as evident by strong pressure-dependent and time-dependent permeability. As a result, a deterioration of up to 14 and 13% in the tensile stress and elongation at break, respectively, was observed in HDPE exposed to DME. We conclude that conventional HDPE pipeline material can successfully transport ammonia, with high leakage expected from the associated elastomers, but the HDPE pipeline transport of DME is not viable due to the fuel's strong interactions that alter the intrinsic properties of both HDPE and the elastomers.

Automated summary

This study investigates the compatibility of high-density polyethylene (HDPE) plastic piping and two elastomer materials, poly(styrene-co-butadiene) (SBR) and poly(acrylonitrile-co-butadiene) (NBR), with ammonia and dimethyl ether (DME) as hydrogen carrier fuels. The results show that the elastomers have higher solubility and permeability for both fuels compared to HDPE, and DME has a significant impact on the intrinsic properties of HDPE and the elastomers, leading to material deterioration. Therefore, while HDPE pipelines can transport ammonia, it is not feasible for DME transportation.