It can be observed that the surface of a NBR sample immersed in
biodiesel shows more pits and fewer cracks as compared to that
immersed in diesel fuel, attributed to the attack and penetration
by the solvent, which started to create ampoules [24].
Subsequently the formation and propagation of cracks could assist
biodiesel in removing base material from the NBR’s surface, which
could explain the degradation of mechanical properties of NBR.
Moreover, after immersed in biodiesel, new functional groups
could be generated at the C@C bond as a consequence of reaction
between biodiesel and the methylene (ACH2) or vinyl (@CH) group
of NBR, which takes place at the unsaturated point of acrylonitrile
part [25]. This structural change reaction may take place at more
active site in NBR molecules, resulting in the degradation of
mechanical properties of NBR.