ABSTRACT
Six copolymers, based on polyacrylates, were prepared and evaluated as viscosity index improvers. The synthesizing process begins by estrification of acrylic acid with different alkyl chain length alcohols (octyl, decyl, odecyl, tetradecyl, and hexadecyl alcohol), ranging from C8 to C16. The completion of the esterification process was confirmed by FIIR spectrometry. Linear copolymerization was carried out to produce six copolymeric viscosity index improvers. All copolymers were tested for solubility in the selected base oil (SAE 30). Acceptable solubility in the base oil has been recorded. Molecular weight of the prepared copolymers was determined by the technique of Gel Permeation Chromatography (GPC). Samples with different concentrations from each copolymer (0.5%, 1%, 1.5%, 2%, 2.5%, 3% by weight) were prepared and evaluated as viscosity index improvers. Also, a rheological test for oil samples, with and without additives, was carried out with different shear rates and at different temperatures, for characterization of the improved lubricant. It has been found that all of the prepared compounds are effective as viscosity index improvers, and their effectiveness becomes more pronounced by increasing either the molecular weight of copolymer (140,000 – 236,000) or the alkyl chain length (C8 – C12). Effectiveness could be increased by increasing the concentration of the additives in the base oil (6% - 46%). There are no reflection points through the tested range of concentrations. Finally, the executed rheological tests oil showed that the improved oils exhibits a Newtonian behavior, except a slight non-Newtonian behavior at the starting of shear application.