The Effect of Solvents on the Perfluoropolyether Lubricants Used on Rigid Magnetic Recording Media

The adsorption characteristics and tribological properties of the perfluoropolyether (PFPE) lubricants Zdol and Z-Tetraol on amorphous nitrogenated CNx carbon are investigated as a function of solvent used to apply the lubricants. The solvents used in these studies include perfluorohexane, CF3CHFCHFCF2CF3 and C4F9OCH3. Deposition studies indicate that the applied thickness of PFPE films is strongly solvent-dependent that can be related to differences in the solubility parameters between the various lubricants and solvents. The results of ab initio computations on the molecular electronic structure of the solvent molecules show that their solvent power is correlated to their polarity and in particular to the acidity of the protons on the CF3CHFCHFCF2CF3 and C4F9OCH3 molecules. Tribological reliability, as measured by contact start-stop testing, slider-disk clearance, lubricant pickup by the slider, lubricant smearing on the disk surface, etc., is independent of solvent and is limited to the physical properties of the adsorbed lubricant film. The kinetics of lubricant mobility are charateristic of confined liquids that are independent of solvent as shown by lubricant flow profiles, bonding kinetics, and contact angle goniometry.