Chemical degradation of an uncrosslinked pure fluororubber in an alkaline environment

S. Mitra, A. Ghanbari-Siahkali, P. Kingshott, Søren Hvilsted, K. Almdal

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The chemical degradation of an uncrosslinked pure fluoroelastomer (FKM; Viton A) in an alkaline environment (10% NaOH and 80 degreesC) was investigated. Scanning electron microscopy images showed that on a microscopic level, significant degradation substantially increased the surface roughness after prolonged exposure (e.g., 12 weeks). The molecular mechanisms of the chemical degradation processes at the surface were evaluated with X-ray photoelectron spectroscopy and attenuated total reflectance/Fourier transform infrared spectroscopy. The results revealed that the early degradation proceeded primarily via dehydrofluorination reactions, creating double bonds in the rubber backbone. This further accelerated the degradation after longer exposure times. Furthermore, the resulting double bonds underwent nucleophilic attack by an aqueous NaOH solution to form several oxygenated species. All these species ultimately recombined to form crosslinks, as evidenced by the increase in the gel fraction and surface hardness (Shore A). The pronounced effect of chemical degradation through a reduction in the thermal stability of the pure FKM rubber upon exposure was also evident from thermogravimetric analysis and differential thermogravimetry.
Original languageEnglish
JournalJournal of Polymer Science. Part A, Polymer Chemistry
Volume42
Issue number24
Pages (from-to)6216-6229
ISSN0887-624X
DOIs
Publication statusPublished - 15 Dec 2004

Keywords

  • attenuated total reflectance (ATR)
  • chemical degradation
  • differential thermogravimetry (DTG)
  • fluoroelastomer (FKM ; Viton A)
  • fluororubber
  • FT-IR
  • gel fraction
  • surface hardness (Shore A)
  • thermogravimetric analysis (TGA)
  • X-ray photoelectron spectroscopy (X-PS)
  • alkaline environment

Cite this