Abstract
Two acceleration incubation methods were used to evaluate the oxidative resistance of high-density polyethylene (HDPE) geogrids. In Series #1, forced air ovens at elevated temperatures of 55, 65 and 75 °C were utilized to assess two types of HDPE geogrids, GG-1 and GG-2. After 84 months of incubation, the tensile properties and molecular weight remained unchanged, while the amount of antioxidants, which was measured by the standard oxidation induction time (OIT), decreased as incubation time increased. The depletion mechanisms of antioxidants were found to be significantly different between the two geogrids. For geogrid GG-1, depending on the incubation temperature, the OIT versus incubation time curves can be divided into two or three linear regions: Regions I, II and III. In Region I, the OIT-retained values remained constant. Region II occurred within few months of incubation; it consisted of a steep slope indicating rapid depletion rate of antioxidants. Region III, which followed immediately after Region II, exhibited a gradual decrease of OIT. In contrast, geogrid GG-2 showed an exponential decrease of OIT with aging time. Under the temperature acceleration condition, the predicted lifetimes of antioxidants in GG-1 and GG-2 are 172 and 122 years, respectively, using the Arrhenius model at a constant site temperature of 20 °C. The second incubation method, Series #2, combined elevated temperature with high oxygen pressure. The acceleration of antioxidant depletion is governed by the oxygen partial pressure instead of total pressure in the incubation pressure cell. The antioxidant reaction rate increases exponentially with pressure. The lifetime of antioxidant is predicted to be 116 years for GG-1 at conditions of 20 °C and 1 atm.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call