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Temperature Influence on the Process of the Gelation of the Engine Oil

Krzysztof Biernat
Published: 29 July 2020
Progress in Petrochemical Science , Volume 3, pp 1-6; doi:10.31031/pps.2020.03.000565

Abstract: Krzysztof Biernat1* and Monika Ziółkowska2 1Department for Fuels and Bioeconomy, Poland 2Department of Petroleum Engineering, Poland *Corresponding author: Krzysztof Biernat, Department for Fuels and Bioeconomy, Poland Submission: July 02, 2020;Published: July 29, 2020 DOI: 10.31031/PPS.2020.03.000565 ISSN 2637-8035Volume3 Issue3 The article discusses the process of gelation of engine oils and its influence on exploitative properties. The results of research on the propensity of engine oils for gelation at low and high temperatures are presented. The influence of various factors such as: base oil, vegetable oil, FAME and soot on the gelling process was determined. It was found that the cause of gelation of oils, depending on the operating conditions, oil components, may be several factors independent of each other. These factors are discussed in the article. Keywords: Gel; Gelling process; Engine oil; Oil components; Vegetable oil; Fame; Soot In the 1990s, the problem of forming a gelatinous (gel) oil structure in the operation of vehicles powered by diesel oil appeared in Poland. However, the problem of gelation of motor oils was already noticed in Europe in the 1980s. At that time, it was assumed that this could be related to the introduction of a new category of engine oils, including the CD class according to API. The quality class CD introduced then a new generation of additives improving detergents and dispersants. In addition, the process of limiting sulfur content in diesel oil started, which was initially thought to have adversely affected the performance of engine oil. In Poland, the phenomenon of gelation was observed mainly in the late autumn and early spring periods, i.e. during periods in which large temperature fluctuations could occur. In winter or summer, when the temperature jumps were not large, this problem did not occur. In addition, the problem of gelation included engine oils of various quality and viscosity grades of known domestic and foreign producers. A characteristic feature of gelation is the rapid increase in kinematic viscosity at both 40°C and 100°C, the other parameters do not change much in relation to fresh oil. The problem of gelation is a very unfavorable phenomenon for the engine. Gelled oil completely loses its operational functions, i.e. it does not provide lubrication, does not dissipate heat, does not neutralize acidic products originating, among others from incomplete burning of fuel, etc. which leads to engine seizure. Based on the collected literature on the operational problems of motor oils, including the phenomenon of gelation, several factors can be distinguished that can cause the formation of a gelatinous oil structure. The most important of them are: But in addition to the factor that triggers the gelling process, temperature also plays a key role. Under the same atmospheric conditions, during the operation of vehicles, some oils show a greater tendency to form a gel while others are less and undoubtedly related to the temperature, not only of the engine itself, but also of the ambient temperature. A gel is a colloidal system that consists of at least two components. Each of the components forms a separate continuous phase extending over the entire volume of the mixture. The gelling agent forms a rigid, branched, porous network spreading in the liquid constituting the second component of the gel, causing it to immobilize [1]. The gel structure consists of network nodes, loops, and free ends of chains. The diagram of the gel structure is shown in Figure 1 [2,3]. The division of gels is related to the type of interactions responsible for creating a rigid network, and thus with the type of gelling agent. There are chemical gels in which in the process of gel formation gelling agent molecules create covalent bonds between them, and physical gels in which the molecules of the gelling agent are bound by much weaker intermolecular interactions, mainly hydrogen bonds and electrostatic, dipoledipole interactions, van der Waals, as well as hydrophobic. The physical gels are thermally reversible, because the change of external parameters such as temperature and pressure lead to the disintegration of the gel network. In contrast, chemical gels are formed in the polycondensation, polymerization and copolymerization of multifunctional monomers or because of introducing a cross-linking agent into the polymer. The chemical (covalent) bonds formed in this way create nodes of the network [4]. The best-known methods for obtaining gels are shown in Figure 2 [4,5]. Figure 1: Gel structure scheme. Figure 2: Chemical and physical methods of obtaining gels. Multigrade engine oils have been introduced to reduce the viscosity of the oil at low temperatures to facilitate engine starting. With the easier start-up of the engine at low temperatures, there was a problem with the oil pumpability. This problem turned out to be much more serious because the lack of pumpability of the oil could lead to engine damage. In bench tests, it was found that at low temperatures we have two types of problems related to pumpability: Research on oil-air binding led to the development of a method for testing the tendency of oil to gel using a Brookfield scanning viscometer. The STB method as an international standard ASTM D 5133 allowed the study of the tendency of oil to form a gel. The method consists in heating the tested sample to 90 °C, and then slowly cooling it, while continuously measuring the viscosity [7]. Based on this method, you can designate: The literature data show that the highest gelation and consequent air retention were found at temperatures much higher than those associated with limited flow, for the same class of SAE motor oils. Modern multi-grade motor oils require a maximum gelation index value of 12. This is the value at which the resulting gels in the engine oil do not endanger the engine's operation. The value of the gelation...
Keywords: temperature / structure / Heat / Grade / oil / Gelling Process / Operation of Vehicles / leads to engine

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