Changes of Dimension and Molecular Orientation with Annealing and Boiling of Strip-biaxially Stretched Poly(ethylene terephthalate) Film.

Abstract

Poly (ethylene terephthalate) sheets were prepared by T die extrusion. PET sheets were then stretched at a draw ratio 4.0 x 1.0 using a biaxial stretcher. The stretched films were annealed at various temperatures for 5 min. These annealed films were then boiled at 100°C for 1 h. The dimensional changes of non-annealed and annealed films were explored after boiling at 100°C. Crystallinity measurements were undertaken to relate the dimensional changes for strip-biaxially stretched non-annealed, annealed and boiled PET films. Wide angle X-ray pole figures of strip-biaxially stretched nonannealed, annealed and boiled films were taken to study the preferential orientation of diffracted planes.