Nanoscale Functional Additives Application in the Low Temperature Greases

Abstract

Due to the fact that the application of AW and EP additives in low-temperature greases may lead to worse high-temperature and anti-corrosion characteristics as well as additional burden on the environment due to the content of aggressive components, in this paper, the possibility of replacing these additives with NFA, which do not have these disadvantages, was investigated. The analysis of nanosized particles being used as functional additives in greases was carried out. The morphology of the following nanoparticles was studied: montmorillonite K 10, silica, calcium car-bonate and borate, halloysite, and molybdenum disulfide incorporated in halloysite tubes. The effect of nanostructured components on the physicochemical characteristics and anti-wear and anti-scuffing properties of complex lithium, polyurea, and polymer greases were studied. Maximal improvement of anti-wear and anti-scuffing characteristics of cLi-greases was reached when using silica and calcium borate. Maximal improvement of anti-scuffing properties of PU-lubricant was reached when using calcium carbonate and the two-component NFA based on halloysite, for anti-wear properties when adding silicon dioxide and halloysite. When the concentrations of silicon dioxide and calcium carbonate was increased from 1 to 3 wt.%, there was a decrease in yield stress of the structural frame of the PU-lubricant and its colloidal stability was worse. The increase of the concentration of calcium carbonate and borate nanoparticles in the studied range led to a significant improvement of the anti-wear and anti-scuffing characteristics of the PU grease, respectively. The greases properties’ dependence from the nanostructured functional additives’ introduction method and their concentration were investigated. Nanoparticles were added into the test lubricants before and after the thermo-mechanical dispersion stage. The addition of silicon dioxide and calcium carbonate NFA after the heat treatment stage led to worsening of the characteristics of the plastic material, and the increase of their concentration from 1 to 3 wt.% formed a harder structure of Li-grease. On the contrary, the addition of calcium borate NFA is recommended after the thermomechanical dispersion. The choice of nanoparticles and the method of their addition to the lubricants of various types was carried out according to the results of the previous stage of the research. Along with the analysis of the physicochemical characteristics and anti-wear and anti-scuffing properties of the lubricants, the structure of the dispersion phase of nanomodified lubricants were studied.