Compatibility of Biologically Derivable Alcohols, Alkanes, Esters, Ketones, and an Ether as Diesel Blendstocks with Fuel System Elastomers

Abstract

The compatibility of 11 bioderivable diesel blendstocks with 17 elastomer materials common to fuel storage, dispensing, and delivery systems was evaluated though volume and hardness measurements. The blendstocks included two alcohols (1-octanol and 1-nonanol), two acid esters (methyl decanoate and hexyl hexanoate), tri(propylene glycol) methyl ether (TPM), butylcyclohexane, two ketones (2-nonanone and 2-pentanone), biodiesel, and renewable diesel. Each blendstock was blended with diesel in concentrations of 0, 10, 20, and 30 wt %. The elastomers included two fluorocarbons, six acrylonitrile butadiene rubbers (NBRs), and one each of fluorosilicone, neoprene, polyurethane, styrene butadiene rubber (SBR), hydrogenated acrylonitrile butadiene rubber (HNBR), a blend of NBR and PVC (OZO), epichlorohydrin/ethylene oxide (ECO), ethylene propylene diene monomer (EPDM), and silicone. Specimens of each elastomer material were immersed in the test fuels for a period of 4 weeks and measured for volume and hardness. Afterward, they were dried at 60 °C for 20 h and remeasured. The results showed that the alkanes, esters, and alcohols were suitable with many of the elastomers. For some materials, such as neoprene, these blendstocks improved the compatibility compared to neat diesel. In contrast, the ketones and TPM produced unsuitable volume expansion (>30%) and softening in many of the elastomers including the high-performance fluoroelastomers. Analysis of the results showed that the swelling behavior is predominantly due to polarity of the elastomer and test fuels.

The compatibility performance of fuel system elastomers with two dioxolane molecules as blends with diesel

“…These elastomers have shown similar behavior in other nonpolar blendstocks blended with diesel. 24 The primary difference is a slight reduction in volume swell with blend level was reported for many nonpolar blendstocks. In this study, it was noted that the polyurethane specimens exposed to a 10% blend of the D2 structure did exhibit a pronounced swell.…”

“…These results closely match those found when these same NBR grades were exposed to other nonpolar blendstocks blended with diesel. 24 The most notable impacts were with NBR3, where the dioxolanes only increased the volume by around 2% over the neat diesel and NBR6 which expanded 3% higher with D2 at the 30% blend level. As with the other elastomer materials evaluated in this study, the dioxolane structure had little impact on the swell performance.…”

“…The elastomer materials in this study were selected based on their applicability in fueling systems and relevance to other studies investigating elastomer-fuel compatibility. 15,17,[22][23][24][25][26] A total 17 materials were evaluated. They are listed in Table 2 along with their applications.…”

“…Other studies have also shown that increasing the polarity of a fuel (solvent), by adding a polar blendstock, will reduce the swelling in many elastomers (as the polarity is increased). 3,[23][24][25][26] Because the volume expansion of EPDM, silicone and SBR greatly exceeds the 30% allowable guidance for most seal applications, these materials would not be suitable for use with diesel fuel. The CR specimens were also predominantly affected by the diesel as the volume expansion hovered close to the 30% guideline regardless of whether the dioxolanes were added or not.…”

“…These studies have shown that ketones, and some alcohols and ethers, can produce unacceptable swelling levels in many key elastomer materials. 15,17,[22][23][24][25][26] Fluorcarbons, neoprene, and nitrile rubbers have been shown to be especially susceptible to excessive swelling due to the polar nature of these elastomers aligning with the polarity of the blendstock.…”