Fracture properties of HDPE exposed to chlorinated water

High density polyethylene (HDPE) is often used in applications that include both structural loads and oxidative environmental conditions. In this study, the effect of an oxidative environment on HDPE mechanical performance is evaluated. Thin 75 micron HDPE samples are exposed to 5ppm chlorinated water at 70 °C for up to 1250 hours. Changes in polymer morphology as a function of exposure time are evaluated and compared with fracture and tensile test data. FTIR data show an increase in the carbonyl group after 250 hours of exposure, while GPC data show a 20-50% loss in molecular weight after 500 hours exposure. The decrease in molecular weight is associated with shortening of the higher molecular weight chains. Essential work of fracture data and strain at break show significant loss in ductility for exposed samples. This set of data demonstrates the correlation between morphology changes and embrittlement in unimodal HDPE.