Analysis of Thermal Ageing Effect (Hold Time - Crystallinity Rate - Mechanical Property) on High Density Polyethylene (HDPE)

Abstract

This work is devoted to the experimental study of thermal ageing effect on the large deformation stress–strain behaviour of PE100, tensions tests are conducted on this material samples submitted to a temperature of 90°C during different hold times. It is found that thermal ageing causes an increase of all properties measured, including crystallinity, melting temperature, Young Modulus, yield stress and stress at break. We show, by different investigation techniques like X-rays diffraction, Transform Infrared Spectroscopy (FTIR), that increase of mechanical properties is not due to a chemical change but is due to an increase of the crystallinity rate commonly designated by the post-crystallization phenomena. DSC and DMA experiments show secondary crystallization, homogenization of primary crystals and decrease of the amorphous phase mobility.