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Compatibility of Elastomers with Oxymethylene Ethers and Blends with Diesel Fuel
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
Oxymethylene ethers (OMEs) have shown promise as candidates for diesel fuel blendstocks due to their low sooting tendency, high cetane number, and diesel-comparable boiling point range. However, there is a lack of literature regarding compatibility of OMEs with common automotive elastomers, which would be a prerequisite to their adoption into the marketplace. To address this need, an exposure study and complementary solubility analysis were undertaken. A commercially available blend of OMEs with polymerization degree ranging from 3 to 6 was blended with diesel certification fuel at 0, 33, 67, at 100% by volume. Elastomer coupons were exposed to the various blends for a period of 4 weeks and evaluated for volume swell. The elastomer materials included multiple fluoroelastomers (Viton and fluorosilicone) and acrylonitrile butadiene rubbers (NBR), as well as neoprene, polyurethane, epichlorohydrin (ECO), PVC-nitrile blend (OZO), ethylene propylene diene monomer (EPDM), styrene-butadiene rubber (SBR), and silicone. The exposure results indicated overall poor compatibility for OME, with every elastomer except for fluorosilicone exhibiting greater than 30% volume swell at the 33% blend level. The general trend across the elastomers was either a consistent increase in volume swell with OME concentration, or maximum in volume swell at an intermediate blend fraction. One notable exception is EPDM, which is not generally compatible with diesel fuel and which exhibited a reduction in volume swell with increasing OME concentration. The same elastomers and OME/diesel blends were evaluated using Hansen solubility analysis, which predicted similar trends to the exposure study. From these results, we conclude that adoption of OME as a diesel fuel blendstock will require either the development of specialized elastomers, or that the blend fraction be kept to a low level to maintain compatibility with existing elastomers.