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Characterizing and modeling the mechanical behavior of an anion exchange membrane for carbon capture applications

Sara Sarbaz, Zhi Xin Liu, Heidi Feigenbaum, Samaneh Bayati, Winston Wang, Jennifer Wade, Husain Mithaiwala, Matthew D. Green

TL;DR

This paper addresses the mechanical performance of the moisture-swing AEM FAA-3 for carbon capture, measuring hygroscopic swelling, thermal expansion, and time-dependent deformation under varied humidity and temperature. It develops a predictive parallel-network model combining a Neo-Hookean elastic framework with Bergström-Boyce viscoplasticity, calibrated and validated against DMA, tensile, and cyclic loading data, and extended to environmental dependence through empirical RH and temperature relationships. The findings show humidity as the dominant factor softening stiffness and promoting relaxation and plastic deformation, with positive excess volume of mixing indicating non-ideal water–polymer interactions, and establish NMAD errors below 10% for calibrated conditions. The model provides a path toward integrated chemo-mechanical simulations for MS-DAC systems, informing material selection, fiber design, and operating strategies to enhance durability and efficiency.

Abstract

A new direct air capture (DAC) technology uses a moisture swing (MS) process with anion exchange membranes, potentially offering a more energy-efficient way to remove CO2 from the air. In this MS process, the membrane absorbs CO2 as it dries and releases it when water is added. Understanding the mechanical behavior of these membranes is essential for improving the design and efficiency of DAC systems and prolonging sorbent lifetime. This study tested one anion exchange membrane, Fumasep FAA-3, under mechanical loading and various temperature and humidity conditions to measure its swelling, stiffness, strength, plastic deformation, and stress relaxation. Experimental results were used to identify a mechanical model for FAA-3 that can be used to predict the material's nonlinear viscous behavior under various loads and environments.

Characterizing and modeling the mechanical behavior of an anion exchange membrane for carbon capture applications

TL;DR

This paper addresses the mechanical performance of the moisture-swing AEM FAA-3 for carbon capture, measuring hygroscopic swelling, thermal expansion, and time-dependent deformation under varied humidity and temperature. It develops a predictive parallel-network model combining a Neo-Hookean elastic framework with Bergström-Boyce viscoplasticity, calibrated and validated against DMA, tensile, and cyclic loading data, and extended to environmental dependence through empirical RH and temperature relationships. The findings show humidity as the dominant factor softening stiffness and promoting relaxation and plastic deformation, with positive excess volume of mixing indicating non-ideal water–polymer interactions, and establish NMAD errors below 10% for calibrated conditions. The model provides a path toward integrated chemo-mechanical simulations for MS-DAC systems, informing material selection, fiber design, and operating strategies to enhance durability and efficiency.

Abstract

A new direct air capture (DAC) technology uses a moisture swing (MS) process with anion exchange membranes, potentially offering a more energy-efficient way to remove CO2 from the air. In this MS process, the membrane absorbs CO2 as it dries and releases it when water is added. Understanding the mechanical behavior of these membranes is essential for improving the design and efficiency of DAC systems and prolonging sorbent lifetime. This study tested one anion exchange membrane, Fumasep FAA-3, under mechanical loading and various temperature and humidity conditions to measure its swelling, stiffness, strength, plastic deformation, and stress relaxation. Experimental results were used to identify a mechanical model for FAA-3 that can be used to predict the material's nonlinear viscous behavior under various loads and environments.

Paper Structure

This paper contains 35 sections, 22 equations, 21 figures, 6 tables.

Table of Contents

  1. Introduction
  2. Materials and Methods
  3. Materials
  4. Dynamic Mechanical Analysis Tests
  5. Hygroscopic Swelling
  6. Water Uptake and Water Content
  7. Thermal Expansion
  8. Ultimate Tensile Test
  9. Rate Variance
  10. Humidity Variance
  11. Load-Hold-Unload Test
  12. Humidity Variance
  13. Temperature Variance
  14. Cyclic Loading Test
  15. Experimental Results
  16. ...and 20 more sections

Figures (21)

  • Figure 1: Schematic of the Carbon Capture setup using FAA-3 hollow fibers.
  • Figure 2: Schematic diagram of the ASTM D-1708, dog-bone sample geometry in millimeters adapted from ASTM.
  • Figure 3: Experimental set-up for the swell test in a humidity chamber.
  • Figure 4: Setup for testing thermal expansion in submerged conditions using an external hotplate to control temperature, (a) picture and (b) schematic.
  • Figure 5: Experimental set-up for the humidity varied ultimate tensile tests in a sealed chamber around the ELECTROPULS E3000 Instron with salt solutions to control humidity, (a) picture and (b) schematic.
  • ...and 16 more figures