Amide polymers based on N‐phenyl‐p‐phenylenediamine with α‐olefins‐co‐maleic anhydride as multifunctional additives for lubricant application

Abstract The high temperature and harsh oxidizing conditions in engine sump results in sludge and varnish deposits in the engine, due to which wear debris and corrosion developed in the internal parts of the engine. This is also responsible for the increased oil viscosity. To address these problems, four polymeric multifunctional amides of N‐phenyl‐p‐phenylenediamine were synthesized from copolymer intermediates poly(α‐olefins‐co‐maleic anhydride) having C‐12, C‐14, C‐16, and C‐18 chain length. This article describes the systematic study of poly(α‐olefin‐co‐maleic anhydride)amides chemistry as multifunctional lubricant additives. Molecular elucidation was carried out by Fourier transform infrared and nuclear magnetic resonance while molecular weight and thermal stability were measured by gel permeation chromatography and thermogravimetric analysis. Standard methods were used to analyze the viscosity‐temperature relationship along with detergent‐dispersant, anti‐oxidant, and anti‐corrosion activities in reference base oil at varying concentration levels. All the prepared polymer compounds effectively addressed the concern problems, but poly(octadecene‐co‐maleic anhydride)amide of N‐phenyl‐p‐phenylenediamine showed better performance over the other additives due to the increased solubility. The pour point depressed from the base value −15 to −30°C while viscosity index (VI) increased to 197 from 178 with longer chain additive at 5000 ppm concentration. Dispersancy was found to be increased by 145%, while as far detergency was concerned, sludge deposition was reduced to 20.1 mg from 87.5 mg base value of reference base oil at 5000 ppm. 2,2‐diphenyl‐1‐picrylhydrazyl assay was used to determine the anti‐oxidant activity and at 1000 ppm, long alkylated polymer shows the excellent result by increasing the inhibition efficiency by 95.58% while the same additive impart the best results at 5000 ppm by reducing the corrosion and penetration rate by 75.80% and 75.43% respectively. Rheology also studied to examine the shear and temperature effect on the dynamic viscosity of the reference oil.