Thermoanalytical investigations on lithium stearate, lithium 12-hydroxystearate and related greases

Abstract

TG and DSC techniques proved useful in the study of the thermal properties of lithium stearate, lithium 12-hydroxystearate and related greases. Under an inert atmosphere, the stearates decompose into the oxalate prior to the formation of the carbonate. For the related greases, oil degradation-volatilization shows a discontinuity under ambient conditions, because of oxidation and carboxylic acid formation. The atmosphere "and the concentration of the soap affect the chemical kinetics of thermal decomposition of the stearates and the greases.The use of thermoanalytical methods in the study and the characterization of petroleum products is receiving increasing interest, as they furnish quick data on the stability of these products that are important for application purposes and for design and operation requirements [1,2].Lubricating greases which are petroleum-derived products are defined as a solid to semi-fluid dispersion of a thickening agent in a liquid lubricant [3]. The majority of thickeners are metal soaps of long-chain fatty acids. The predominant acid radicals in the metal soaps are stearate and 12-hydroxystearate. The preference for the use of these types of thickeners is due to the fact that greases containing such soaps have exceptional properties [3]. The liquid lubricants which contribute 80 to 95% of the composition are mostly solvent-refined mineral oils.Various thermoanalytical techniques are employed to study lubricating greases. These include differential thermal analysis and thermogravimetry [4,5]. The thermal stability of greases is usually governed by the metal soap content and the type of soap used [5].In the present work, differential scanning calorimetry and TG techniques are used to study the thermal properties of lithium stearate (LS) and lithium Limited, Chichester A kaddmiai Kiadr, Budapest

Effect of surface modification and exfoliation of molybdenum disulfide for application in batteries and supercapacitors

“…Lithium oxalate was under inert atmosphere because the two liquids couldn't be separated. The acid decomposes to carbonate at 550 0 C. A slight drop in initial degradation temperature of the composites shall be attributed to the early decomposition of intercalated and absorbed lithium stearate molecules [25].…”

Characterization of Lithium Stearate: Processing Aid for Filled Elastomers

“…According to the literature, lithium stearate first decomposes to lithium oxalate and then to carbonate at 550 °C. 9 Regardless, there are not many differences between the TGA thermograms and decomposition profiles for the three lots of lithium stearates. Figure 6.…”

“…[9][10][11][12][13][14][15] Solid state crystalline transition from orthorhombic to hexagonal packing transition is reportedly expected to occur from 102 °C to 104 °C. From 193 °C to 194 °C, a transition from crystalline to rotational or crystalline state occurs.…”

“…The DSC profiles of these metal stearates are very dependent on the atmosphere under which it is heated. 9 Under an inert atmosphere such as under nitrogen, helium, or argon, all three transitions are endothermic. However, if the sample is heating in air or oxygen, the two higher temperature transitions (at approximately 193 °C and 225 °C) become exothermic.…”