Visualization of temperature-induced structural rearrangements in oriented amorphous polymers

Visualization of structural rearrangements during annealing of solvent-crazed isotactic polypropylene

“…This process is accompanied by an increase of the linear dimensions of the sample in the direction perpendicular to the direction of tensile drawing, and this conclusion is proved by the orienta tion of the cracks growing in the coating. This pattern has an obvious similarity with the surface relief pat terns observed for the affine shrinkage of amorphous polymers after their tensile drawing at temperatures above glass transition temperature [18]. The proposed visualization procedure does not allow us to reveal the structural details of the delocalized solvent crazing since, in this case, typical pore dimensions are too small.…”

“…How ever, progress in this direction is limited by the absence of any direct experimental methods for studying the evolution of structural rearrangements in the course of deformation. In recent years, a new microscopic pro cedure has been proposed [1][2][3][4]; the use of this proce dure makes it possible to gain direct information on the above structural rearrangements and offers new knowledge concerning the deformation mechanism of amorphous polymers at temperatures below [5] and the above glass transition temperature [6]. In particu lar, annealing of PET samples oriented above the glass transition temperature was accompanied by both shrinkage and elongation along the direction of pre liminary tensile drawing, the so called phenomenon of spontaneous self elongation [6,7].…”

“…In recent years, a new microscopic pro cedure has been proposed [1][2][3][4]; the use of this proce dure makes it possible to gain direct information on the above structural rearrangements and offers new knowledge concerning the deformation mechanism of amorphous polymers at temperatures below [5] and the above glass transition temperature [6]. In particu lar, annealing of PET samples oriented above the glass transition temperature was accompanied by both shrinkage and elongation along the direction of pre liminary tensile drawing, the so called phenomenon of spontaneous self elongation [6,7]. In this case, after annealing, the resultant length of the sample is smaller as compared with its initial length, but the use of the above microscopic procedure allows a direct and vivid visualization of the spontaneous self elongation of PET under the above conditions [1][2][3][4].…”

Structural aspects of deformation of amorphous polymers

“…In a recent publication, 105 new, fairly important fea tures of the thermally stimulated shrinkage of amorphous polymers subjected to inelastic deformation under uniaxial compression have been identified using the above de scribed procedure. It was shown that the deformation of a glassy polymer can be conventionally divided into two phases.…”

“…Direct microscopic data indicate that the highly dis perse material of crazes is responsible for the unusual thermomechanical behavior of the crazed polymer. 87 The dependences of the relative variation of the linear dimen sions of crazes and the gaps between them on the anneal ing temperature obtained in direct microscopic examina tion are presented in Fig. 11.…”