The mean Hansen solubility parameters of the fatty acid methyl
esters are shown in Table 1, which are the average values obtained
by the van Krevelen and Stefanis-Panyiotou methods [19]. The solubility
parameters of NBR are dd = 17.2, dp = 8.6, dh = 4.3, according
to Guo et al.’s work [20]. According to Table 1, the polarity (dp) and
hydrogen bonding forces (dh) decrease with the carbon chain
length for saturated methyl esters, while the dispersion forces
(dd) are almost the same. Meanwhile, the dispersion (dd), polarity
(dp) and hydrogen bonding forces (dh) of unsaturated ester
(C18:1) are relatively higher than its counterpart (C18:0).
The difference between the solubility parameter of a solvent
and NBR could then be determined using the Dd factor [19].