MICROTRIBOLOGY OF PET POLYMERIC FILMS

Atomic force microscopy (AFM) and friction force microscopy (FFM) are used to conduct microtribological studies of thin polyethylene terepht halate (PET) films which ale commonly used in many industrial applicat ions including as a magnetic tape substrate. In the PET films, microsc ale friction values are found to be smaller than macrofriction values. Local variation in microscale friction is found to correspond to the local slope which suggests that a ratchet mechanism is responsible for this variation. There is also a directionality effect in the local va riation of microfriction. Microwear tests are also reported. The polym eric material tears in microwear tests. Ceramic particles added to the PET films as an anti-slip agent, affect the microfriction values, scr atch depth and wear depth. For the polymeric material, scratch depth a nd wear depth increase approximately linearly with an increase in the normal load and test duration. Nanoindentation behavior and nanohardne ss values of the films vary from one location to another because of ce ramic particles being present on ol below the film surface. AFM is fou nd to be a useful technique for microtribological and nanomechanical p roperty measurements of these thin films.