Effects of a very low pH solution on the properties of an HDPE geomembrane

The effects of a very low pH solution (pH = 0.5) on a high-density polyethylene (HDPE) geomembrane (GMB) are evaluated using accelerated ageing tests. The GMB specimens were incubated at 65°C, 75°C, and 85°C for up to 19 months. They were periodically removed from the immersion media and tested for retained chemical, mechanical and physical properties. The antioxidant depletion rates obtained from standard oxidative induction time (Std-OIT) tests were consistently lower than that obtained from high-pressure oxidative induction time (HP-OIT) tests at the three temperatures. This difference led to two substantially different estimates of antioxidant depletion time. The relationship between Std-OIT and HP-OIT was non-linear. It indicates the importance of using both methods to assess antioxidant depletion time of GMBs. Crystallinity, melt flow index (MFI) and tensile test results show that physical ageing has occurred, but no significant changes in physical properties due to oxidative degradation were observed after 19 months’ immersion.