Long-Term Storage of Aged NBR in Kerosene in Consideration of Long Material Service Life

Abstract

Elastomeric parts with long service lifetimes and contact to fuels or oils are exposed to aging. Acrylonitrile-butadiene-rubber (NBR) with acrylonitrile contents of 18, 28, and 39 wt%, sulfur- and peroxide-cured, is the subject of this study. The impact of the accelerated aging, induced by storage of specimens at 120 $^{\circ }$C in air, on mechanical properties, the additive composition, and long-term sorption experiments in Jet A-1 kerosene for up to 423 days is investigated. Peroxide-cured NBR shows different tensile properties and sorption behavior compared to the sulfur cured analog. The investigated mechanical properties for varying acrylonitrile contents degrade similarly with increasing aging durations. The uptakes and uptake rates of Jet A-1 in sorption experiments correlated inversely with the acrylonitrile content. Aging-caused crosslinking leads to a reduction in equilibrium mass uptakes and the fuel uptake rate. In severely aged samples, soluble polymer fragments are extracted from the elastomer. With regard to the evaluation of long-term use of elastomer parts, it is challenging that for high acrylonitrile contents and aged samples, the static sorption equilibrium is not reached after 423 days.