Session: MF-02-03 Materials for Hydrogen Service-Polymers 2

Paper Number: 123520

123520 - In Situ and Ex Situ Studies on the Morphology Changes of Polymer Pipeline Materials for Use in Hydrogen and Hydrogen-Natural Gas Environments 

The US natural gas infrastructure is a national asset that could be used to deliver hydrogen and hydrogen blends of natural gas as a pathway to reduce carbon emissions. The distribution system comprises nearly 50 % plastic pipe composed of medium- and high-density polyethylene materials (MDPE and HDPE).  While these materials perform adequately for natural gas, research on their hydrogen compatibility is essential to understand if any immediate and long-term risks are associated with hydrogen addition. The Blended Gas CRADA, a HyBlend project, has established a comprehensive test method for evaluating MDPE and HDPE of various plastic resin compositions of pipeline material in pure hydrogen and 20% hydrogen/80% methane blends. Both in-situ and ex-situ measurements were performed to capture hydrogen-induced changes in the polyethylene material's crystalline, amorphous and their interphase regions.

We investigated two MDPE and two HDPE pipeline materials made from different polymer resin systems to evaluate the effects of hydrogen and blended hydrogen gases. The materials were characterized by their branching, branch spacing, molecular weights, and polydispersity. Various advanced characterization methods, including in situ NMR, high-pressure differential scanning calorimetry, ex situ X-ray diffraction, and ex situ Fourier transform infrared spectroscopy, were used to analyze the effects of changes in crystalline, amorphous, and interphase regions due to gas exposure. In situ (0.7 to 1.7 MPa) fracture tests using single-edge notched beams were conducted to evaluate the effects of two gases on fracture energy and morphology of the pipe materials. Creep tests with different stress levels were performed to evaluate the long-term slow crack growth behavior of the pipe materials due to two gases. Moreover, time-dependent post-decompression quasi-static tensile tests were conducted to explore the effects of gas exposure time on the mechanical behavior of the pipe materials.  

This work will highlight the time sensitivities during and after gas exposure. The correlation between gas-induced polyethylene morphology changes and the associated material performance will be addressed for the intended applications. These studies will show that polyethylene resin composition and material exposure are important factors when considering whether hydrogen or hydrogen blends affect pipeline materials positively or negatively.

Presenting Author: Kevin Simmons Pacific Northwest National Laboratory

Presenting Author Biography: Dr. Simmons has over 30 years experience in polymer and composite materials. He has been working on polymer materials compatibility in hydrogen atmosphere over the last 15 years. He is the co-lead for the H-Mat program and thrust lead for the Blended Gas Pipeline CRADA - HyBlend Project. Dr. Simmons has 20 patents, two R&D 100 Awards, and two FLC Awards for technology transfer.

Authors:

Kevin Simmons Pacific Northwest National Laboratory
Seunghyun Ko Pacific Northwest National Laboratory
Wenbin Kuang Pacific Northwest National Laboratory
Yao Qiao Pacific Northwest National Laboratory
Yongsoon Shin Pacific Northwest National Laboratory
Kee Sung Han Pacfic Northwest National Laboratory
Nalini Menon Sandia National Laboratory