Viscoelastic properties of nafion at elevated temperature and humidity

M. Barclay Satterfield, Jay B. Benziger

Research output: Contribution to journalArticle

100 Scopus citations

Abstract

Tensile stress-strain and stress relaxation properties of 1100 equivalent weight Nafion have been measured from 23 to 120°C at 0-100% relative humidity. At room temperature, the elastic modulus of Nafion decreases with water activity. At 90°C, the elastic modulus goes through a maximum at a water activity of ∼ 0.3. At temperatures ≥90°C, hydrated membranes are stiffer than dry membranes. Stressrelaxation was found to have two very different rates depending on strain, temperature, and water content. At high temperature, low water activity, and small strain, the stress relaxation displays a maximum relaxation time with stress approaching zero after 10 3-104 s. Water absorption slows down stress-relaxation rates. At high water activity, the maximum stress relaxation time was ≥105 s at all temperatures. No maximum relaxation time was seen at T ≤ 50°C. Increasing the applied strain also resulted in no observed upper limit to the stress relaxation time. The results suggest that temperature, absorbed water, and imposed strain alter the microstructure of Nafion inducing ordering transitions; ordered microstructure increases the elastic modulus and results in a stress relaxation time of >105 s. Loss of microphase order reduces the elastic modulus and results in a maximum stress relaxation time of 103-104 s.

Original languageEnglish (US)
Pages (from-to)11-24
Number of pages14
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume47
Issue number1
DOIs
StatePublished - Jan 1 2009

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Materials Chemistry

Keywords

  • Elastic modulus
  • Microphase separation
  • Nafion
  • Stress
  • Stress relaxation
  • Structure-property relations
  • Thermal properties
  • Transitions
  • Viscoelastic properties

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