Plastic deformation of polyethylene terephthalate films during rolling

Amorphous polyethylene terephthalate was oriented via rolling on a laboratory mill under room conditions. The influence of rolling on the polymer structure was investigated. The plastic deformation of the polymer was inhomogeneous at the initial stages of rolling. The deformation was localized in a system of almost perpendicular shear bands forming a zigzag. In polarized light, the zigzag area of plastic flow looked like a regular system of parallel optical bands and possessing approximately identical thicknesses. The distance between the shear bands was approximately equal to double the thickness of the film. The development of the zigzag after compression was attributed to the true effect of strain softening of the polymer. While moving to the opposite surface, the perpendicular band emerged in the existing band after the release of shear bands on the film surface.