A new type of surface structuring accompanying the rolling of glassy poly(ethylene terephthalate)

Abstract

158 A popular type of inelastic deformation of glassy and crystalline polymers is rolling (1). At the same time, the mechanism of structural rearrangements accompanying the rolling of polymers has been stud� ied and understood much less than in the case of other, more frequently used types of inelastic deformation, such as uniaxial tension and uniaxial compression. Rolling underlies a popular technological method by which a polymer film is continuously pulled between two rollers rotating in opposite directions. Such a treatment leads to molecular orientation of polymers (2), and also to other significant structural rearrangements (3). By such a treatment, the mechan� ical and strength properties of polymer can be opti� mized. Importantly, most studies of the structural rear� rangements accompanying the rolling of polymers were performed on crystalline polymers with a two� phase structure. In this case, Xray powder diffraction analysis, electron microscopy, and other methods based on phase contrast can be efficiently used. For this reason, investigations of the structural rearrange� ments in the course of the rolling of amorphous poly� mers are much fewer. Nonetheless, there are quite a lot of studies of the effect of rolling on the deformation and strength properties of amorphous glassy polymers (4). These studies showed that rolling of polymers can be considered as a sort of modifying influence on a polymer that can be used for optimizing its mechani� cal properties. Previously (5-9), we described a procedure for visualizing and characterizing the structural rear� rangements accompanying polymer deformations of various types (uniaxial tension, uniaxial compression, rolling, etc.). This procedure is quite simple and con� sists in applying a thin (nanosized) metal coating to the polymer surface. The subsequent deformation (shrinkage) of the polymer leads to structuring of a special kind on the polymer surface. The structures forming thereat contain information on the structural rearrangements of the polymer substrate. In particular, this procedure was used for investi� gating the thermally stimulated shrinkage of amor� phous polycarbonate subjected to rolling in the glassy state (10). It was shown that the polycarbonate sub� jected to deformation of this kind, in contrast loadings of other types (tension and compression), demon� strates a complex pattern of surface structuring. It turned out that the rolled polymer contains quote extensive discrete zones in which the polymer is ori� ented in various directions. The detected structural features of the amorphous polymer deformed under the rolling conditions have not yet been adequately explained. In this work, we made a direct microscopic study of the structural rearrangements accompanying the roll� ing of another amorphous polymer, polyethylene