January 1, 2019.
This study is dedicated to determining the effect pressurized hydrogen gas has on polymer seals and liners used in the hydrogen infrastructure. The polymers tested in this study are nitrile butadiene rubber (NBR) and ethylene propylene diene monomer (EPDM). Each polymer was made with four formulations consisting of: filler and plasticizer, no filler and plasticizer, filler and no plasticizer, and no filler and no plasticizer. All samples also included ZnO particles which does not count as filler. X-ray computed tomography was used to take non-destructive interior 3D images of the samples. Samples were tested before and after exposure to hydrogen; the samples were exposed to 15,000 psi for 7 days at room temperature. The data was supplied in computer generated still images and videos which showed voids and ZnO particles, while some showed cracks and agglomerations of fumed silica. The data was then analyzed using an image segmenting software called Avizo. The total volume occupied by voids and cracks were compared between all polymers and all formulations. The void size distribution was compared between two samples. It was determined that EPDM with filler and plasticizer showed the lowest volume occupied by voids compared to all other formulations. The lowest volume represented by NBR was when it consisted of plasticizer and no filler. Key steps for this study include: creating size distributions for all samples, determining where voids are most likely to form, and determining the fraction of voids that form around ZnO particles. This research advances scientists‚Äô ability to generate a database so users can select the polymer to use for any function as well as developing better manufacturing processes of materials. The ultimate goal of this research is to develop a fundamental understanding of the effect filler and plasticizers have in how polymers are affected by high pressure hydrogen.
Sandia National Laboratory/California (SNL)
The 2018 STEM Teacher and Researcher Program and this project have been made possible through support from Chevron (www.chevron.com), the National Marine Sanctuary Foundation (www.marinesanctuary.org), the National Science Foundation through the Robert Noyce Program under Grant #1836335 and 1340110, the California State University Office of the Chancellor, and California Polytechnic State University in partnership with Sandia National Laboratory. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funders.