Abstract
This paper concerns thermomechanical analysis (TMA) on poly (ethylene terephthalate) (PET) films, in relation with their application to floppy disk base. When environmental conditions of data retrieval from a floppy disk are different from those of data recording, off-track of the head on the floppy disk occurs, and the extent of off-track can be estimated by using the TMA data. Both the linear thermal and linear hygroscopic expansion coefficients of PET films depend on the direction of their manufacture. The anisotropy (i. e., direction dependence) of those coefficients usually get higher as the position of the measurement gets closer to the widthwise edge of PET film manufacturing process. The extent of off-track increases with increase of the anisotropy.
