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The oxidation of five different high density polyethylene (HDPE) geomembranes was produced in a forced air oven at a temperature of 115°C. The antioxidant packages of three of the geomembranes contained hindered phenols and phosphites types of antioxidants. The antioxidant packages of the other two geomembranes consisted of either thiosynergists or hindered amines together with hindered phenols and phosphites. The consumption of antioxidants after given time periods of oven incubation was monitored by two oxidative induction time (OIT) tests: standard OIT and high pressure OIT together with tensile tests. The results indicated that both OIT tests can effectively track the consumption of hindered phenol and phosphite types of antioxidants. However, for thiosynergists and hindered amines, the high pressure OIT is the appropriate test. The study clearly demonstrated that mechanical properties do not decrease until all (or most) of the OIT value has been depleted. Thus, the reduction of OIT values is the precursor of material degradation.
oxidative induction time (OIT), differential scanning calorimetry, polyethylene, geomembrane, oxidation
Assistant Professor, Civil and Architectural Engineering, Drexel University, Philadelphia, PA
Graduate Student, Civil and Architectural Engineering, Drexel University, Philadelphia, PA