Surface studies of oil-seal degradation

• Published in: Applied surface science 1995-11, Vol.90 (3), p.357-371
• Main Authors: Smith, G.C., Park, D., Titchener, K.J., Davies, R.E., West, R.H.
• Format: Article
• Language: English
• Subjects: Application fields; Applied sciences; Exact sciences and technology; Polymer industry, paints, wood; Technology of polymers
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/0169-4332(95)00165-4

Fluoroelastomers are frequently used as engine oil-seal materials. Under certain test conditions specific fluoroelastomers may show degradation of mechanical properties. A range of fluoroelastomers of different chemical composition have been aged in simple oil/additive blends and in oil formulations equivalent to commercial blends. These were then examined using XPS, SEM/EPMA and XRD to elucidate the physical and chemical changes associated with degradation. The interaction is shown to proceed through amine catalysed post-curing of the constituent polymers. These reactions promote defluorination, embrittlement and cracking of elastomers with a consequent decline in tensile properties as fracture failure mechanisms dominate performance. Degradation of these materials was found, even in the most extreme case, to be limited to the near-surface region of the samples, to a depth of less than approximately 50 μm. Degradation was reduced in elastomers with a higher fluorine level, higher terpolymer content, and a greater extent of cross-linking.