Visualization of structural rearrangements responsible for temperature-induced shrinkage of amorphous polycarbonate after its deformation at different conditions

Abstract

Structural rearrangements during the temperature-induced shrinkage of amorphous polycarbonate after its tensile drawing below and above the glass transition temperature, rolling at room temperature, and solvent crazing have been studied with the use of the direct microscopic procedure. This evidence demonstrates that the character of structural rearrangements during the temperature-induced shrinkage of the oriented amorphous polymer is primarily controlled by the temperature and mode of deformation. In the case of the polymer sample stretched above the glass transition temperature, the subsequent temperature-induced shrinkage is shown to be homogeneous and proceeds via the simultaneous diffusion of polymer chains within the whole volume of the polymer sample. When polymer deformation is carried out at temperatures below the glass transition temperature, the subsequent temperature-induced shrinkage within the volume of the polymer sample is inhomogeneous and proceeds via the movement of rather large polymer blocks that are separated by the regions of inelastically deformed polymer (shear bands or crazes).

Effects of Molecular Weight Reduction on Brittle–Ductile Transition and Elastic Yielding Due to Noninvasive γ Irradiation on Polymer Glasses

“…To study the origin of stress arising from large ductile extension of polymer glasses, we investigated the nature of the elastic yielding phenomenon − by exposing four different precold-drawn polymer glasses to γ irradiation of different dosages. In each case, the γ irradiation at sufficient dosages causes the molecular weight to decrease considerably, as confirmed by GPC measurements.…”

“…In dealing with the challenge to explicitly demonstrate how the polymeric nature manifests itself in large deformation of common glassy polymers, elastic yielding is one of the most insightful phenomena. The elastic yielding behavior refers to the emergence of a significant retractive stress during annealing of a cold-drawn polymer glass above the storage temperature. − The behavior of elastic yielding is interesting in its own right because it affords us an opportunity to investigate whether the retractive stress is due (at least in part) to chain networking or not. Further study of the elastic yielding may also help us explore the origin of strain hardening in uniaxial extension of ductile polymer glasses.…”

Elastic Yielding in Cold Drawn Polymer Glasses Well below the Glass Transition Temperature

“…This dimensional change [28][29][30][31][32][33][34] at temperatures far below T g is actually rather revealing: it must be caused by the strained chain network. The slight degree of specimen shrinkage has been seen before [28][29][30][31][32][33][34][35]. However, the explanation for the emergence of a "retractive stress" during annealing of cold drawn polymers as volume change [30] is entirely inconsistent with the present data.…”

Plastic deformation of polyethylene terephthalate films during rolling

“…was described in [29][30][31][32]. This technique consists of applying a nanometer metallic coating to the surface of a polymer.…”