Solubility and volume swell of fuel system elastomers with ketone blends of E10 gasoline and blendstock for oxygenate blending (BOB)

Abstract

The compatibility of key infrastructure elastomers with five ketone molecules was assessed via solubility studies and volume swell measurements. The elastomer materials included two fluorocarbons, six acrylonitrile butadiene rubbers (NBRs), and one each of fluorosilicone, neoprene, polyurethane, styrene butadiene rubber (SBR), and silicone. The ketone molecules included acetone, 2-butanone, 2-pentanone, 2-nonanone, and cyclopentanone. The ketones were added to gasoline containing 10% ethanol (E10) and a blendstock for oxygenate blending (BOB) in levels ranging from 0% to 30% by volume. The elastomers were exposed for 4 weeks in each test fluid. The solubility was modeled using Hansen solubility parameters and the volume change was determined for each material and test fuel. In general, the volume swell increased with ketone content and corresponded well to the predicted solubilities. In most cases, the highest level of swelling occurred with added cyclopentanone and acetone, while 2-nonanone produced the lowest levels of volume expansion. The chain length of the straight ketones was found to affect the volume swell behavior as volume expansion decreased with increasing chain length. This behavior is attributed to the reduction in polarity and hydrogen bonding with chain length. Neoprene, SBR, and silicone exhibited poor compatibility with the ketone molecules at all blend levels. Fluorocarbon and fluorosilicone also showed poor compatibility but may be suitable for use as static seals in very low blend levels with 2-nonanone. The results were more mixed for polyurethane and the NBRs. In general, better compatibility (low volume swell) was observed for mixtures containing BOB than for E10. This is due to the lower polarity and hydrogen bonding of the BOB.