Investigation of Frictional Transfer Films of PTFE by Infrared Emission Spectroscopy and Phase-Locked Ellipsometry

Publisher Website
Google Scholar
Abstract
When a PTFE sheet was rubbed lightly and unidirectionally over a smooth surface of stainless steel an essentially monomolecular transfer film was formed. By special ellipsometric and emission infrared spectroscopic techniques it was possible to show that the film was 10–15 Å thick and birefringent. From the intensity differences of infrared bands obtained with a polarizer passing radiation polarized in mutually perpendicular planes, it was possible to deduce transfer film orientation with the direction of rubbing. After standing in air for several weeks the transfer film increased in thickness by as much as threefold. At the same time both the index of refraction and the absorption index decreased. Examination of the surfaces by optical and electron microscopies showed that the films had become porous and flaky. These observations were consistent with previous tribological measurements. The coefficients of friction and were decreased with the formation of the transfer film but increased again as the film developed breaks. The applicability of the ellipsometric and polarized infrared emission techniques to the identification of unimolecular tribological transfer film of polymers such as PTFE has been demonstrated.