Boundary Lubricant Film Properties versus Molecular Polarity of Perfluoropolyethers Containing a Pendant Chain

Abstract

The thin film properties of some novel branched perfluoropolyether (PFPE) boundary lubricants are investigated as a function of molecular polarity and end-group bonding to the underlying carbon film. The PFPE main chain, comprised of n-perfluoroethylene oxide monomer units, is stiffer than the Fomblin Z main chain that is a copolymer of perfluoro-methylene oxide and -ethylene oxide monomer units. Terraced flow and bonding kinetics show decreased lubricant mobility compared to PFPEs based on a Fomblin Z main chain. Lubricant pick-up is reduced for the tetraol adduct due to the larger Hamaker constant and increased intermolecular cohesion.

Keywords

• tribology
• perfluoropolyether
• disk lubricant
• surface energy
• bonding kinetics