Depletion of Antioxidants in Tensioned HDPE Geomembranes Exposed to Synthetic MSW Leachate

Geomembranes (GMs) used in the liner systems of waste containment facilities can be subjected to tensile strain due to various field conditions. Antioxidant depletion under such strain may compromise the long-term durability of the GMs. Laboratory-accelerated aging tests were conducted to evaluate the effect of tensile strains on the depletion of antioxidants from a high-density polyethylene (HDPE) GM. GM samples were immersed in synthetic municipal solid waste (MSW) leachate at temperatures of 22°C, 40°C, 65°C, 75°C, and 85°C to accelerate the antioxidant depletion. HDPE GM samples were prepared with three different tensile strains (i.e., 3%, 8%, and 12%) on both machine and cross-machine directions. Comparative tests were conducted with nontensioned GMs. The antioxidant depletion in GMs was measured using standard oxidative induction time (Std-OIT) test. The results indicated that antioxidant depletion rates were 1.28–1.47 times faster for 3% tensioned samples, 1.68–1.88 times faster for 8% tensioned samples, and 2.14–2.42 times faster for 12% tensioned samples compared to nontensioned samples. These findings illustrated that antioxidant depletion rates of the HDPE GM increased as the tensile strain became larger. In addition, the strain direction has an insignificant effect on antioxidant depletion. A temperature-strain-dependent model was developed to predict the antioxidant depletion of the HDPE GM at different temperatures and strain levels.