Structural Evolution of Tensile-Deformed High-Density Polyethylene during Annealing:  Scanning Synchrotron Small-Angle X-ray Scattering Study

• Published in: Macromolecules Vol. 40; no. 20; pp. 7263 - 7269
• Main Authors: Jiang, Zhiyong, Tang, Yujing, Men, Yongfeng, Enderle, Hans-Friedrich, Lilge, Dieter, Roth, Stephan V, Gehrke, Rainer, Rieger, Jens
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 02.10.2007
• Subjects: Applied sciences; Exact sciences and technology; Mechanical properties; Organic polymers; Physicochemistry of polymers; Properties and characterization; Structure processing relationship; Annealing; Deformation; Oriented polymer; Supramolecular structure; High density ethylene polymer; Temperature effect; Small angle X ray scattering; Experimental study; Mechanism; Elongation (mechanics)
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma0627572

The structural evolution of high-density polyethylene subjected to uniaxial tensile deformation was investigated as a function of strain and after annealing at different temperatures using a scanning synchrotron small-angle X-ray scattering (SAXS) technique. The results confirm that in the course of tensile deformation intralamellar block slips were activated at small deformations followed by a stress-induced fragmentation and recrystallization process yielding thinner lamellae with their normal parallel to the stretching direction. The original sheared lamellae underwent severe internal deformation so that they were even less stable than the newly developed thinner lamellae. Accordingly, annealing results in a melting of the original crystallites even at moderate strains where the stress-induced fragmentation and recrystallization just sets in and generates a distinctly different form of lamellar stacks aligned along the drawing direction. It was found that the lamellae newly formed during stretching at moderate strains remain stable at lower temperature. Only at a very high annealing temperature of 120 °C can they be melted, leading to an isotropic distribution of the lamellar structure.