Thermal oxidation stability of lubricating greases – can a rapid small-scale method replace the classical method?

The article presents the results of tests of the oxidation resistance of 26 samples of selected lubricating greases available on the market. Various types of lubricant samples (according to the type of thickener), produced with oils of different chemical nature and viscosity, were tested. The basic parameters of the greases were determined: the worked penetration and the dropping point. Two different test methods were used to determine the thermal oxidation stability: the classical oxidation method according to PN-C-04143 and the rapid small-scale test method according to ASTM D 8206. The method of determining the correlation between these methods was presented. A correlation was found between the two methods of testing the resistance to oxidation, which can be roughly described using the exponential dependence. For the quick method, better compliance with the classical method was obtained at 140°C than at 160°C, which is confirmed by the determination coefficients determined by the ranking method. Based on the results of the quick method, using the determined exponential dependency, the results of the classical method can be estimated. However, the determined correlation between the PN-C-04143 and ASTM D 8206 methods is insufficient to use these methods interchangeably.

Investigation of tribological characteristics of lubricant grease based on Solidoil and urea resin thickener

The results of laboratory investigation of the tribological characteristics of a new grease based on Solidol, a polyurea thickener providing an increase in the dropping point to 118 °C, and a complex of additives are presented. It has been established that the proposed lubricant is efficient in a wider temperature range, provides higher antiwear properties for tribocoupling parts and considerably reduces friction losses during boundary lubrication in comparison with the original grease Solidol. The developed composition of the lubricant grease is supposed to be used when operating road construction machines in the tropical conditions of Vietnam.

Epoxidation of Palm Olein as Base Oil for Calcium Complex Bio Grease

The development of palm oil bio grease aimed to substitute grease made from petroleum with a material that is more environmentally friendly. The enhancement of bio grease characteristics can be performed by chemical synthesis. This research aimed to obtain best mole ratio of palm olein and H2O2 in the epoxidation process, and to analyze the physical characteristics of the bio grease products. This process used acetic acid and H2O2 with mole ratio variations of olein and H2O2 of 1: 3, 1: 6, and 1: 9. The mole ratio was selected based on the analysis of iodine and oxiran numbers, which was then processed into bio grease with the addition of calcium stearate and calcium acetate. Epoxidized olein with a mole ratio of olein and H2O2 of 1: 9 was selected because it achieved the highest average oxiran number (0.99), the lowest iodine number (33.09), and it was based on ANOVA and LSD tests. The higher the oxiran number, the more epoxide compounds produced. Low iodine number indicated low unsaturation in fatty acids. The peroxy acid used in the epoxidation process reacted with unsaturated compounds, so that the lower iodine number in the epoxidized olein produced more epoxide compounds. Bio grease had a light cream color, density of 0.96 g/cm3, viscosity of 31,280 mPa.s, unworked penetration of 438 (0.1 mm), worked penetration of 443 (0.1 mm), dropping point < 26°C, corrosion resistance of 2c and NLGI number 00.

Synthesis of Layered Octadecyltrimethylammonium-Templated Aluminosilicate and its Use as a Thickening Agentfor Lubricating Grease

We describe herein the use of octadecyltrimethylammonium-templated aluminosilicate (designated as LS) as a thickener to induce gelation. LS samples with different aluminum/silicon molar ratios (Al/Si = 0, 0.05, 0.10, 0.15, 0.20) were synthesized hydrothermally and characterized by X-ray diffraction analysis, 27Al MAS NMR spectra, elemental analysis, and scanning electron microscopy. The aluminum/silicon molar ratio was shown to be an important factor affecting the rheological properties of LS gels. With increasing Al/Si molar ratio, the viscoelasticity and structural strength of LS gel were enhanced, the dropping point increased, and the amount of oil separation decreased. LS(0.20) gel exhibited superior relative elastic character. The strength of the LS(0.20) gel was also enhanced with increasing LS(0.20) content. In SRV tests, LS(0.20) gel with different contents showed good performance in terms of load-bearing ability and anti-wear property, indicating that LS was strongly adhered on the friction surface, and thereby promoted lubrication. Owing to simple preparation, the promising rheological and tribological properties, LS gel hold great potential application in lubricating grease.

DEVELOPMENT OF THE METHOD AND OPTIMIZATION OF THE COMPOSITION AND MODES OF OBTAINING THE BIODEGRADABLE GREASE WITH THE LITHIUM-CALCIUM THICKENER

It is noted that the development of biodegradable lubricants is an integral part of the development of a modern “green” economy. The distinctive features of the proposed method are described for producing a biodegradable grease on a mixed lithium-calcium thickener, providing for the introduction of alkaline initial components of the dispersed phase (lithium hydroxide monohydrate and calcium hydroxide) into the reaction mass not in the form of their aqueous solutions, but in a powdery state, and the exception of prolonged exposure to water and high temperature on a component of a dispersion medium of plant origin (rapeseed oil) in the process of lubricant synthesis. Along with this, it was proposed to use a highly refined oil of group III according to the API (American Petroleum Institute) standard as a mineral component of the dispersion medium. This provides, in aggregate, the higher stability of the rheological and tribological characteristics of the grease (for at least 12 months) at a given level of biodegradability. The experimental-statistical mathematical model of the process of obtaining the biodegradable lithium-calcium grease is developed, which makes it possible to determine the parameters of the component composition (the content of the mixed lithium-calcium thickener in the grease and the content of lithium stearate in the mixed thickener) and the synthesis modes (the heat treatment temperature of the reaction mass) to achieve the given level of the main characteristics of the finished grease (penetration, dropping point) while ensuring its biodegradability of at least 80 %.