Chemical degradation of an uncrosslinked pure fluororubber in an alkaline environment

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Title: Chemical degradation of an uncrosslinked pure fluororubber in an alkaline environment
Author(s): Mitra, Susanta; Ghanbari-Siahkali, Afshin; Kingshott, Peter; Hvilsted, Soren; Almdal, Kristoffer
Abstract: The chemical degradation of an uncrosslinked pure fluoroelastomer (FKM; Viton A) in an alkaline environment (10% NaOH and 80C) 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.
Publication type: Journal article
Source: Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 42, no. 24 (Dec 2004), pp. 6216-6229
Publication year: 2004
FOR Code(s): 0303 Macromolecular and Materials Chemistry; 0912 Materials Engineering
Keyword(s): Alkaline environment; Attenuated total reflectance; Attenuated total reflection; Chemical degradation; Degradation; Differential thermogravimetry; Differential theromogravimetry; Fluorine containing polymers; Fluoroelastomers; Fluororubber; Fourier transform infrared spectroscopy; FT-IR; Gel fraction; Gels; Hardness; Light reflection; Scanning electron microscopy; Surface hardness (Shore A); Surface roughness; Synthetic rubber; Thermodynamic stability; Thermogravimetric analysis; X ray photoelectron spectroscopy
Publisher: John Wiley & Sons
ISSN: 0887-624X
Publisher URL: http://dx.doi.org/10.1002/pola.20473
Peer reviewed