Synthesis and characterization of multifunctional polymer additives for lubricating oils based on 2-ethylhexyl acrylate and N-isopropylmethacrylamide

Abstract

The long-chain acrylate monomer, 2-ethylhexyl acrylate (EHA), was obtained by esterification of acrylic acid with 2-ethylhexanol, and the copolymer by free radical polymerization with N-isopropylmethacrylamide (PMA) in various proportions using azobisisobutyronitrile (AIBN) as the initiator in a benzene solvent. High conversion polymers were obtained: polyEHM, polyPMA, 3EHM/1PMA, 1EHM/1PMA and 1EHM/3PMA, which were named P1, P2, P3, P4 and P5, respectively. The chemical structure was confirmed by Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H-NMR). The percentage of nitrogen was used to determine the reactivity coefficient of EHA-co-PMA using the Kelin-Todosa method, rEHA = 1.14 and rPMA = 0.321. Based on the reactivity and solubility coefficients in the virgin SN 500 base oil, the performance of polymers, except P2, as additives to lubricating oils was assessed. Polymers with a high content of hydrophobic EHA monomer (P1 and P3) showed good performance as viscosity increasing and freezing point lowering agents, while P4 had the best anti-corrosion properties.