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

Paper Number: 123528

123528 - Experiments on Influence of Depressurization Rates and Test Temperatures on Polymers in High- and Low-Pressure Cycling Hydrogen Environments as Applicable to the Hydrogen Infrastructure 

Polymers are used in stringent environments as part of hydrogen transportation, production, storage, and dispensing operations of the hydrogen infrastructure. Demanding conditions with wide ranges in performance temperatures (-60°C to +140°C) and pressures (0.9 MPa to 87 MPa), under static and cycling conditions of hydrogen exposure, can cause permanent changes in polymer viscoelastic properties such as storage modulus and mechanical properties such as compression set, accompanied by internal damage in the form of microcracks and voids, all affecting their functions as seals, gaskets, and other parts in hydrogen components. Cycling environments, in particular, are constituted of pressurization and depressurization stages which directly control the transport of hydrogen through these soft materials in a series of rapid compression and decompression steps. For conditions where pressure changes are minimal, thermal environments can play an influential role based on polymer glass transition behaviors.

To address knowledge gaps for conditions described above, we evaluated the influence of varying rates of depressurization (1, 10, 20, 40 MPa/min and uncontrolled) on model elastomer compounds exposed to high pressure (17 MPa to 87 MPa) cycling at ambient temperature with the goal of understanding the impact of rapid decompression steps, conditions common to hydrogen fueling operations. Additionally, the influence of high (17 MPa to 87 MPa) and low pressure (10 MPa to 31 MPa) cycling at a given pressurization and depressurization rate was investigated for three different temperatures (+85°C, ambient, and -40°C) to separate thermal from pressure effects on elastomeric polymer seals. Model compounds of EPDM, FKM, HNBR, and NBR, along with select thermoplastics often used as back-up seals, were tested under these conditions followed by ex-situ characterization for changes in properties. Dynamic Mechanical Thermal Analysis (DMTA), compression set, nanoindentation, Raman spectroscopy, and X-ray tomography were used to compare critical polymer properties before and after cycling.

For decompression testing, failure modes observed under these conditions of testing can help with identifying the right material for sealing and gasket applications and use conditions. These studies involving model compounds of known composition will highlight the role played by fillers and other additives for these operational conditions, which can inform the design of hydrogen-resistant materials for the infrastructure. Ultimately, this work will impact and help form our technical basis for polymer lifetime prediction, as applicable to the hydrogen infrastructure.  

Presenting Author: Nalini C. Menon Sandia National Laboratories

Presenting Author Biography: Ms. Nalini Menon is a Principal member of Technical Staff at Sandia National Laboratories in Livermore, California. Prior to joining Sandia, she worked for 20 years as a polymer chemist/materials scientist and has extensive background in formulating adhesives, paint/coatings, encapsulants, and potting compounds for the automotive and aerospace industries. Her specialties include leading long-term materials-focused R&D projects with emphasis on characterization and evaluation of mechanical, thermal, and rheological properties of organic materials. Nalini leads the polymer compatibility in hydrogen effort at Sandia in support of the Fuel Cell Technologies Office, DOE’s overall goals of building a hydrogen infrastructure and economy here in the US. Her work, as part of a consortium including National Labs and industry partners (PNNL, SRNL, ORNL and Ford), has been recognized by the DOE with a “Team award 2018 DOE Award for exceptional contribution to FCTO/EERE (Fuel Cell Technology Office/Office of Energy Efficiency and Renewable Energy) goals”. As part of this effort, she has played a significant leadership role in the development of the Canadian Standards Association (CSA)’s CHMC2 standard for the compatibility of polymers in hydrogen environments, for use by the hydrogen community. She was an Invited speaker at the International Symposium of Hydrogen, Japan in the year 2018 where she presented on “Compatibility of polymeric materials in hydrogen service”.

Authors:

Nalini C. Menon Sandia National Laboratories
April Nissen Sandia National Laboratories
Keri Mcarthur Sandia National laboratories
James Mcnair Sandia National Laboratories
Bernice Mills Sandia National Laboratories
Kevin Simmons Pacific Northwest National Laboratory