23rd International Colloquium Tribology - January 2022 125 Less Could Be More - Formulating High-Performance Greases Mehdi Fath-Najafi Nynas AB, SE-418 78 Gothenburg/ Sweden Corresponding author: Mehdi Fathi-Najafi - mefa@nynas.com George Diloyan Corresponding author: Mehdi Fathi-Najafi - mefa@nynas.com Nanotech Industrial Solutions Inc., Avenel 07001, NJ, USA Jinxia Li Nynas AB, SE-149 82 Nynäshamn/ Sweden 1. Abstract Proper lubrication is one of the core parts for equipment protection and life. To meet industry demands, grease manufacturers continuously improve the performance of the lubricating greases. The vital parameters such as extreme pressure, shock, wear, friction, shear, temperature, and presence of water are affecting the performance of the grease and subsequently the life of the tools and the productivity. Thus, formulators of the lubricating greases have to consider all the above parameters when designing a high-performance grease. Obviously use of various additives are “must” in most of the high-performance greases, but then both higher cost and some difficulties to predicate the behaviors of the product in a “real life” condition. For example, it is well known that some of the additives may interfere with each other or/ and result to chemical interaction with the metal surface which in some cases are undesirable. The aim of this work was to investigate the possibilities of developing a high-performance grease with two main features; 1) chemically neutral character such as solid lubricants and 2) as few components as possible which may also result to a reasonable cost for the formulators. 2. Introduction Industries widely use solid particles to enhance its tribological properties such as extreme pressure (EP), wear and friction. Micron size and platelet/ lamellar structure particles of WS 2 , MoS 2 , PTFE and Graphite have been known as a lubricious solid and widely used in various industrial applications. Tribological properties such as antifriction, Anti-Wear (AW) and extreme Pressure (EP) properties in greases play a very important role in industrial applications such as mining, automotive, steel production etc. The aim of this work was to demonstrate the possibility of formulating a high-performance grease with fewer components by using different solid lubricants instead for traditional anti-wear and extreme-pressure additives. 3. The Solid Lubricants IF-WS2 nanoparticles are spherical particles that were invented in 1992 by Reshef Tenne in the Weizmann Institute of Science. In this paper a paste dispersion of IF-WS 2 nanoparticles has been tested in various type of greases. Then, wear, friction, and extreme-pressure characteristic along with other physical properties have been evaluated and benchmarked against MoS 2 . Previous studies have demonstrated that IF-WS 2 nanoparticles provide excellent shock absorbing properties along with anti-wear, anti-spalling and pitting, friction reducing, and extreme pressure properties due its morphology and size, [2]. 4. Experimental work & Results The thickener type that was selected for this study was lithium complex and the base fluids were naphtenics, and the blends of naphthenics with paraffinic Gr I, II and polyalfaolefine respectively. More details of the selected naphthenic oils could be found on the website of Nynas, [3]. In total six different greases were prepared with different base oils. Table 1 shows properties of the base oils used in this study. The thickener consisted of lithium hydroxide, 12-hydroxy stearic acid and azelaic acid. Notable that the manufacturing conditions were kept constant for all six greases. IF-WS 2 and 2H-MoS 2 were mixed in the LiX base greases using FlakTec Speed Mixer IF-WS 2 and MoS 2 solids were tested at 0.25% and 1.00% respectively in each grease sample. 126 23rd International Colloquium Tribology - January 2022 Less Could Be More - Formulating High-Performance Greases Table 1: Typical characteristics of the base oils used in the preparation of the greases. Remarks Base Oil Visc. @40 °C, (mm 2 / s) Visc @100 °C, (mm 2 / s) Pour Point, (°C) Oil 1 Napht A 700 29.0 -15 Oil 2 Napht B 600 21.8 -12 Oil 3 Napht B + Paraf (Gr II) 194 14.9 -30 Oil 4 Napht B + PAO 198 14.8 -30 Oil 5 Napht B + Paraf (Gr I) 200 14.3 -27 Oil 6 Napht C + PAO 75 8.7 -42 In total six grease formulations were evaluated in this study in which the base oils described in Table 1 were used. Results in Figure 1 below demonstrates that the Lithium complex grease with IF-WS 2 particles even at low percentages increase the performance in extreme pressure and wear. Figure 1: EP properties comparison of tested samples according to ASTM D2596 MoS 2 particles showed some friction reducing properties however no improvements in EP properties and in some cases increased wear. It is worth to note that Grease #2, that contained naphthenic oil, showed significantly high EP properties and overall excellent tribological properties. 5. Summary The aim of this work was to investigate possible platforms to produce high performance grease with minimized components. Both to have high tribological and physico-chemical properties yet at lower cost. Within the frame of this study, six lithium complex greases were produced based on various naphthenic base oils as well as blends of naphthenic oils and paraffinic group I, II and polyalfaolefine respectively. Although, the use of naphthenic base oil has reduced the thickener content, but a direct correlation between the viscosity of these naphthenic base oils and the thickener content, the degree of oil separation and the mobility of the greases at -20 °C were also been found. The work benched marked two solids - MoS 2 and IF- WS 2 . The outcome demonstrated if one percent of IF- WS 2 is used in Lithium complex grease significantly higher load carrying capability (620kgf weld point) and up to fifty percent reduction in wear will be obtained. The unique spherical shape of IF-WS 2 and sub-micron size, could be responsible for the significantly better performance to the final lubricant formulation when compared with MoS 2 . Reference [1] H. Zhang, S. B. Lu, J. Zheng, J. Du, S. C. Wen, D.Y. Tang, and K.P. Loh, Optics Express, 22 (6), (2014), 7249 [2] P.U. Aldana, F. Dassenoy, B. Vachera, T. Le Mognea, B. Thiebautb, A. Bouffet, Tribology Transactions, 59 (1), (2016), 178 [3] www.nynas.com/ en/ product-areas/ base-oils