THE INFLUENCE OF THE CHEMICAL STRUCTURE OF LIQUID-CRYSTALLINE COMPOUNDS ADDED TO PARAFFIN OIL ON TRIBOLOGICAL PROPERTIES OF LUBRICANT MIXTURES
Journal Title: Tribologia - Year 2009, Vol 227, Issue 5
Abstract
Liquid-crystalline compounds added to typical lubricants, such as mineral oils, improve their tribological properties [L. 13]. The aim of this work was to study the influence of the chemical structure of liquid-crystalline compounds added to paraffin oil on tribological properties of lubricant mixtures. A few homological series, differing in the structure of rigid core as well as of terminal groups (polar groups CN, NCS, F or non-polar alkyl chain), were used for investigations. They are able to form different liquid-crystalline phases (nematic and smectic) in a pure state. They were added to paraffin oil as doppants in the following quantity order: 0.5, 1 and 2 wt.%. The obtained lubricant mixtures were tested with the use of T-11 tribotester. The friction coefficient was established for applied load 20, 30, 40 and 50 N. The best improvement of tribological properties was obtained for compounds having strongly polar terminal groups: F and CN. The compounds having less polar group NCS, improve the tribological properties less, even thought they contain a sulphur atom, known as a good lubricant. Lubricant mixtures containing compounds, which can form a nematic phase in the pure state, have a lower friction coefficient than mixtures with smectic mesogenes.<br/><br/>
Authors and Affiliations
Barbara Ważyńska, Justyna Okowiak-Chinalska, Anna Małysa
Keywords
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