Effect of environmental humidity on the friction/stiction and durability of lubricated magnetic thin-film disks

Drag and CSS (contact start and stop) tests were conducted to study the effects of the degree of chemical bonding of the lubricant and environmental humidity on the friction/stiction and durability of the head-disk interface. Disks with untreated, partially bonded and fully bonded films of a polar perfluoropolyether lubricant were tested at different levels of humidity. Static friction is low for unlubricated disks and disks with a fully bonded lubricant film as compared to disks with untreated and partially bonded lubricant films. Static friction gradually increases with an increase in the relative humidity and the effect of humidity at high humidity values is more pronounced in the case of disks with untreated and partially bonded lubricant films. At high humidities, durability is low for all lubricated disks but is high for unlubricated disks, as compared to that at low humidities. At low humidities, durability in drag tests is more sensitive to the degree of bonded fraction than that in the CSS tests. In general, partially bonded lubricant films are desirable for low friction/stiction and high durability and lubricated disks perform best at low to moderate humidities. Operation at high humidities must be avoided.