Effect of Molecular Weight (MW) and End-Groups on the Thermal and Lewis-Acid Catalyzed Decomposition of Fomblin Z-Type Lubricants

The high-temperature stability of disk lubricants has attracted a lot of interest in recent years because smaller head-media spacing may cause head-media contact and thus a local temperature rise. At elevated temperatures, the lubricant may either evaporate or decompose, leading to the eventual failure of the head-media interface. The decomposition might result from heating and/or may be catalyzed by the presence of a Lewis acid site at the head-disk interface (HDI). In this paper, we study how the chemical structure, namely, molecular weight (MW) and end-groups (see Fig. 1), of disk lubricants will affect the thermal and Lewis-acid catalyzed decomposition of the lubricant.

Degradation of Perfluoropolyether Fluids With Metal Ions

Chemical degradation of lubricant fluids of perfluoropolyether (PFPE), such as Fomblin Z-DOL, Fomblin AM-2001, Fomblin Z-25, Demnum SP-3, and Demnum SA, with bivalent metal ions was examined. The respective reaction mechanisms involve an ether cleavage process which is caused by the coordination of metal ions with oxygen atoms in the main chains of the PFPE. Metal ions were evaluated for their ability to degrade the PFPE, and the results demonstrate that the ions ranking in terms of this ability is as follows: Cu2+ > Ni2+ > Co2+ > Fe2+ > Mn2+ > Mg2+. This trend can be explained by the ionization potentials of the metal atoms. For an identical metal ion, the Demnum lubricants showed a greater stability than the Fomblin lubricants.