Stage ''C'' Lifetime Prediction of HDPE Geomembrane Using Acceleration Tests with Elevated Temperature

A major issue in the use of all geomembranes including high-density polyethylene (HDPE) is to estimate the material's lifetime to resist degradation. For polyolefins, this includes three stages: antioxidant depletion (Stage "A"), induction time to oxidation onset (Stage "B"), and the time to reach half-life of relevant engineering properties (Stage "C"). Utilizing temperature alone to accelerate oxidation degradation requires a very long incubation time. The focus of this study is to apply high pressure in addition to elevated temperature. With this pressure-temperature incubation method, the incubation time to reach Stage "C" is expected to be shortened significantly. This research-in-progress effort includes two types of HDPE geomembranes: unstabilized, and stabilized with an antioxidant package. All samples were incubated at temperatures of 45, 55, and 65°C, and pressures of 1.3, 2.8, 3.5 and 6.3 MPa (pure oxygen). For comparison purposes, the unstabilized geomembrane was also incubated in regular oven-aging (ASTM D5721), and in landfill simulating incubation devices. Both of the latter two incubations applied temperature alone as the acceleration factor. The temperatures were maintained at 55, 65, 75, and 85°C. All three types of incubation are currently ongoing.