4. Results and discussion
Fig. 1 shows a comparison of the changes in mass of NBR samples
immersed in different fuels at room temperature for 168 h.
According to the figure, compared with diesel fuel, biodiesel results
in a larger increase in mass of the NBR samples. Among the three
kinds of biodiesel, it is obvious that SME causes larger increase in
mass of the NBR samples compared with WCOME and PME. With
the increase of carbon chain length, it is possible to observe a smaller
increase in mass of the NBR samples. Moreover, the swelling
(increase in mass or volume) of the NBR samples is higher in the
unsaturated fatty acid esters as compared to that in the saturated