The swelling behavior of vulcanized acrylonitrile-butadiene rubber (NBR) having different nitrile content, styrenebutadiene rubber (SBR) and fluorine rubber (FKM) were examined in ethanol blended gasoline. For NBRs, the swelling rate of extra and medium high nitrile NBR is highest in the gasoline containing 25 vo1% ethanol (E25). In the gasoline containing less than 50 vol% ethanol, extra high CN NBR showed higher resistance to the solvent than the other whereas no such clear difference was observed in the gasoline containing 85 or more vol% of ethanol (E85).
For SBR, the swelling rate is highest in gasoline without ethanol (E0) and decreased with the content of ethanol.
FKM showed almost no swelling in the mixture with wide range of ethanol content.
Although the ethanol-blended gasoline can be considered as a mixture of aliphatic and aromatic hydrocarbon and polar ethanol, aromatic hydrocarbon was selectively absorbed in NBR and SBR. This can be explained using the Hansen solubility parameter.