Extreme Pressure Performance
The extreme pressure (EP) behaviour of the synthesized ILs was analyzed
in two base oils and the results were shown in Fig. 8. It can be seen
that the weld point of two base oils improved with addition of
synthesized ILs. The base oils EKE and DOS exhibited weld points 160 and
120 kg respectively, further the addition of ILs showed significant
enhancement in weld points due to the development of effective tribofilm
on the rubbing surface. Fig. 8 compares the weld points of base oils
with different IL concentration from 0.25 wt% to 1.5 wt%. While
increasing the concentration from 0.25 to 1.25 wt% increase in weld
point of the base oil was observed and further increasing the
concentration to 1.5 wt% resulted in decrease of weld point, thus 1.25
wt% is taken as the optimized additive concentration. At this
particular concentration all the synthesized additives were greatly
effective in improving the weld point of the two base oils. The IL’s
BHI-RA, TBA-RA, TPA-RA and CTB-RA enhanced the weld point by 43, 31, 25
and 25% respectively in base oil EKE. Exclusively, BHI-RA exhibited
superior extreme pressure performance in both base oils. Yang et al.
reported that the nitrogen containing heterocyclic compounds are capable
to develop strong tribofilms under extreme pressure conditions (Yang et
al., 2013). The weld points obtained with all the synthesized ILs were
compared with commercially available additive dibenzyl disulfide (DBDS)
and the results indicate that the synthesized ILs exhibited either
comparable or better EP performance to DBDS.