Tribological studies of α-lipoic acid esters as effective environmentally friendly multifunctional lubricant additives

摘要

Enzymatic synthesis of six esters of alpha-lipoic acid with different fatty alcohols and diols was carried out to produce novel compounds with lubricant additive properties. The synthetic route was mild and efficient with good yields. The synthesized compounds were characterized by IR, NMR, and mass spectral studies and screened for their thermal stability, antiwear (AW), extreme pressure (EP), and antioxidant (AO) properties. The tribo tests in a synthetic base fluid indicated that all the synthesized compounds act as antiwear and extreme pressure additives. All the prepared esters exhibited very good thermal stability and excellent antioxidant properties with better performance compared to commercial antioxidant BHT as determined by differential scanning calorimetry.