Mechanical behavior of fluoroelastomer considering long term ageing

Stress-elongation behavior of a Viton A-401C based compound established for backup seals of 500 MW(e), Prototype Fast Breeder Reactor is depicted. Stress-softening effects are negligible during room temperature (RT) or 110 °C measurements on unaged samples at strain rates of 50 mm/min and 500 mm/min because of low filler content. Relaxation is observed during RT property determination at lower strain rate. Stiffening of behavior at 50 mm/min and 110 °C is attributed to Joule-Gough effect and absence of relaxation because of increased molecular chain mobility. The two zone stress-elongation behavior (determined by chemical cross-links up to ∼85% strain and by ionic interactions beyond) propounded in the article by combining air-aged specimen data (32 weeks at 140/170/200 °C) provides a behavior map of bisphenol cured, low filler, fluoroelastomers made of vinylidene fluoride and hexafluoropropylene. This could be extended to peroxide cured fluorocarbon rubbers for verifications and providing qualified compounds of better grades for critical nuclear elastomeric sealing applications.

► Tensile stress-strain of aged (32 weeks; 140/170/200 °C) Viton A-401C specimens at RT, 110 °C.
► Stress-softening negligible at 50/500 mm/min and RT/110 °C because of low black filler.
► RT relaxation at lower strain rate; 110 °C curve stiffening from Joule-Gough effect.
► Two zone stress-elongation behavior (cross-link, ionic domains) proposed.
► Extendable to peroxide cured fluoroelastomers with Iodine at mid and end of chains.