BIAXIAL DEFORMATION BEHAVIOR OF PET DEPENDENT ON TEMPERATURE AND STRAIN RATE

Abstract

Due to its material properties, PET is a very interesting and challenging material for thermoforming applications. During the thermoforming process it may be subjected to high deformations at elevated temperatures. Plug assisted deformation of PET was executed with a servo-hydraulic testing machine utilizing a special clamping device. The effect of strain induced crystallization for bi-axial deformation was investigated at different temperatures and strain rates. The influence on morphology and crystallization was investigated by x-ray diffraction and scattering as well as DSC measurements. The process of crystallization was investigated for different processing parameters. Although still transparent, the stretched PET has changed to a semi-crystalline material with distinct WAXD patterns known from uni-axial deformation.