The swelling of different nitrile rubbers in gasoline-methanol-ethanol (GME) ternary fuel blend

The consumption of ethanol and methanol as a fuel or GME mixture is expected to increase in the future. It is known that the use of polymeric components in fuel delivery systems of vehicles has increased and can experience swelling after being exposed to oxygenate fuels like GME. The effect of the GME fuel to the compatibility of the polymeric components in vehicles such as NBR is an critical point to investigate. To asses the compatibility of the fuel with the NBR, we studied the changes in the weight and chemical properties of this elastomeric during the immersion test with the GME fuels. This article summaries the compatibility of two elastomers, used in fuel delivery systems (NBR26 and NBR41), with test fuel representing gasoline blended with up to 20% alcohol. The immersion test were performed by 21 days at temperatures of 55°C. The mass were measured and compared with the original condition. The change in weight during the sorption processes were calculated. The swelling of the NBR exposed to the different gasolines increased with the addition of alcohol (methanol:ethanol=3:1). The NBR samples exposed to the gasoline doped with alcohol showed a two-fold increase in swelling compared with the original gasoline (Gasoline A). The low nitrile content samples immersed in GME20 (20% of alcohol) showed the decrease weight gain after 2 days of immersion due to the polar character of the alcohol, which caused the extraction of a large quantity of the polymeric blend constituents. The aromatic and alcohol were more aggressive for NBR26 than NBR41.