Adhesion and Friction Behavior of Magnetic Disks With Ultrathin Perfluoropolyether Lubricant Films Having Different End-Groups Measured Using Pin-on-Disk Test

In this paper, the adhesion and friction forces between a glass pin and disk surfaces coated by lubricants with different numbers of hydroxyl endgroups (Z-03, Z-dol, Z-tetraol, and Z-TMD) were measured using a pin-on-disk microtribotester. The adhesion force decreased in the order of Z-dol, Z-TMD, Z-tetraol, and Z-03. The friction force at the applied load force of 0 mN decreased in the order of Z-TMD, Z-tetraol, Z-dol, and Z-03. These trends could not be obviously explained by the number of hydroxyl endgroups. Next, we investigated the relationship between the adhesion energy and the total surface energy. The adhesion force was roughly proportional to the surface energy, and the friction force was proportional to the friction factor defined by the friction coefficients of the carbon overcoat and the lubricant film, the lubricant film coverage, and the total surface energy. Based on the results, we suggested a friction model of the contact between the pin and disk surfaces.