Conclusion
Four novel ricinoleate anion-based ionic liquids were synthesized by
metathesis of sodium ricinoleate with bromide salts and were evaluated
as green lubricant additives in two base oils EKE and DOS. The
synthesized additives exhibited excellent thermal stability and
tribological performance. At optimal IL concentration the fatty acid
constituted ILs greatly reduced the wear scar diameter and improved the
weld point of both base oils. The results obtained from tribological
tests confirmed that there is a significant effect of changing the
cation on their tribological performance. The ionic liquids BHI-RA and
TBA-RA exhibited better tribological performance compared to TPA-RA and
CTB-RA under boundary lubrication conditions. Elemental mapping and worn
surface morphology studies further confirmed the deposition of tribofilm
by ricinoleate constituted ionic liquid. This study illustrates that
fatty acid constituted ILs are excellent lubricating oil additives to
minimize or replace the use of environmentally hazardous ILs.