Indian Journal of Science and Technology

Abstract

Obiectives: In this article I have been looking at the determination of the solubility parameter by two methods for an additive hydrogenated poly (isoprene-co-styrene) used in lubricating oils. To determine the solubility parameter, it is necessary to know the intrinsic viscosities of the polymer hydrogenated poly (isoprene-co-styrene) in as many solvents with different solubility parameters. Methods: The viscosities of the dilute solutions copolymer hydrogenated poly (isoprene-co-styrene) were determined using Oa and I viscosimeters of the Ubbelodhe Schott capillary-type Viscosimeter set with the 0.04887 and 0.00976 constants at 25°C±0,1°C. From the values obtained for intrinsic viscosities it is concluded that the best solvent for this copolymer is cyclohexane, followed by trichlorethylene, carbon tetrachloride and SAE 10 W oil, and benzene is the weakest. Huggins constants, calculated from the intrinsic viscosity values obtained by extrapolating the reduced viscosities to the zero concentration of the copolymer, have values less than 0.4 for all four solvents. Findings: The value of the overall solubility parameter is comparable to the previous copolymer, which reflects its lack of polarity, and those due to polar interactions and hydrogen bonds are also very small: 1.2 (MPa)1/2 for those obtained by the Hansen method and between 1.4 and 2.4 (MPa)1/2 if the improved one is used. Analyzing the values determined by the two methods it is found that for the partial solubility parameters differences between 0.2 and 1.2 (MPa)1/2 are obtained, due to the intrinsic viscosity intake and the method of determination used. The difference between the global solubility parameters determined by the two methods is 0.4 (MPa)1/2. A larger difference also occurs in the sphere of solubility sphere: the obtained with the improved method is almost 30% lower, which means that fewer solvents are found in the sphere of solubility. The improved method applied to the studied copolymer used as an additive for lubricating oils is much more precise than the Hansen method. The solvents used are mostly included within the scope of the action sphere in the improved method. Application: Determination of the partial and global solubility parameters hydrogenated poly (isoprene-co-styrene) was done, first, using the Hansen method, then by an improved method. The improved method for determining the solubility parameter is much more precise than the Hansen method.  

Keywords: Additives, Copolymer, Lubricating Oil, Solubility Parameter