Effects of PFPE Lubricant Properties on the Critical Clearance and Rate of the Lubricant Transfer from Disk Surface to Slider

Abstract

The transfer of perfluoropolyether (PFPE) lubricant from the disk surface to the slider as a function of head-disk clearance has been investigated experimentally. The effects of lubricant thickness, bonding ratio, molecular polarity, and main chain stiffness on the lubricant transfer rate and the critical clearance below which lubricant transfer gets much enhanced are clarified. The critical clearance can be effectively reduced by decreasing the lubricant thickness or increasing the number of polar hydroxyl end-groups per lubricant molecule. Increasing the film bonding ratio or using lubricants with stiffer backbone can significantly decrease the lubricant transfer rate especially below the critical clearance. The results are discussed in terms of the effective disjoining pressure and its slope with respect to the film thickness.