Strain softening of rolled polyethylene terephthalate films under transverse tension

Abstract

The plastic flow of glassy polyethylene terephthalate films under tension perpendicular to the preliminary rolling axis was studied. An unexpectedly strong strain softening was detected, which consisted in a decrease in the yield stress under transverse tension. The upper yield point at a degree of rolling of Λ = 1.7 was lower by a factor of 1.8 than that of the unrolled material. Recovery of the polymer under room conditions led to a gradual restoration of the properties of the unrolled polymer.