Chemical degradation of fluoroelastomer in an alkaline environment

S. Mitra, A. Ghanbari-Siahkali, P. Kingshott, K. Almdal, H.K. Rehmeier, A.G. Christensen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    We have investigated the time-dependent chemical degradation of a fluoroelastomer, FKM (Viton((R)) A), in an alkaline environment (10% NaOH, 80 degreesC). Optical microscopy and SEM analysis reveal that degradation starts with surface roughness right from the earliest stage of exposure (e.g., 1 week) and finally results in cracks on the surface after prolonged exposure. Initially the extent of degradation is mainly confined to the surface regions (a few nanometers) but with longer exposure (e.g., 12 weeks) it extends to below the subsurface region of the fluoroelastomer. The extent of this surface degradation is found to be strong enough to affect the bulk mechanical properties. The molecular mechanisms of the surface chemical degradation were determined using surface analysis (XPS and ATR-FTIR) where the initial degradation was found to proceed via dehydrofluorination. This leads to double bond formation on the rubber backbone which accelerates the degradation even further with longer exposure. Furthermore, the cross-link sites of the exposed rubber samples are also found to be vulnerable to hydrolytic attack under the studied chemical environment as evidenced by the decrease in cross-link density and gel fraction (%). (C) 2003 Elsevier Ltd. All rights reserved.
    Original languageEnglish
    JournalPolymer Degradation and Stability
    Volume83
    Issue number2
    Pages (from-to)195-206
    ISSN0141-3910
    DOIs
    Publication statusPublished - Feb 2004

    Keywords

    • chemical degradation
    • FKM (Viton A )
    • fluoroelastomer
    • XPS and ATR-FTIR
    • mechanical properties

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