Physicochemical Properties and Performance Characteristics of Urea Greases Based on Group I Mineral Base Oils
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icochemical Properties and Performance Characteristics of Urea Greases Based on Group I Mineral Base Oils A. S. Lyadova, *, Yu. M. Yarmusha, and V. A. Ivlevb aTopchiev
Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, 119991 Russia bPeoples’ Friendship University of Russia, Moscow, 117198 Russia *e-mail: [email protected] Received April 29, 2020; revised May 8, 2020; accepted May 12, 2020
Abstract—A comprehensive study of urea greases obtained on the basis of Group I distillate oils, which have a viscosity in the range from 24.4 to 342.0 mm2/s at 40°C, has been carried out. The results obtained have made it possible to reveal the dependence of various physicochemical parameters of greases (dropping point, ultimate strength, colloidal stability, wear rate) on the viscosity of the base oil and the structure of diurea used as a thickener. The revealed relations allow prediction of the properties of greases at the stage of selecting the initial components. Keywords: greases, organic thickener, Group I base oils, performance characteristics of greases DOI: 10.1134/S0965544120090170
INTRODUCTION A number of requirements are imposed on modern greases, among which the main one is the ability to reduce the coefficient of friction, which in turn leads to a decrease in the rate of wear of rubbing surfaces [1]. Lubricating greases are colloidal systems in which the base oil is the dispersion medium and the thickener is the dispersed phase [2]. At the same time, both of these components influence the physicochemical and performance properties of lubricants. In the last decade, greases with thickeners based on di-, oligo-, and polyureas have become widespread in the world, since they are capable of operating at high loads, over a wide range of temperatures and speeds, and in contact with aggressive media and, in addition, are resistant to radiation. Moreover, the share of polyurea lubricants in the total world production volume is constantly increasing [3]. All groups of base oils are used for the production of greases. Despite the fact that Group I oils have a number of disadvantages (low viscosity index, low oxidative stability, high volatility, high sulfur content), they are widely used in the production of greases, since they have the lowest cost among all oils and possess high chemical affinity for all thickeners and additives that are introduced into lubricant formulations in order to improve their performance characteristics [4]. In addition, there are a large number of different brands of Group I base oils, the viscosity of which varies over a very wide range [5], thereby making it possible to create lubricant compositions for various friction units. It should be noted that there have been no
systematic studies until now to establish the relationship between the composition and structure of urea greases and their main performance characteristics and physicochemical and tribological properties. The purpose of this work was to reveal the relations of the structural features of diureas acting as a
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