Temperature effects on ageing properties and diffusivity of a HDPE GM in landfill.

High-density polyethylene (HDPE) geomembranes (GMs) play a crucial role in preventing the leakage and migration of pollutants. GM service life and ageing properties are the main concerns for the choice of materials. However, it is not clear how the mechanical properties and anti-fouling performance of geomembranes change with ageing time. To solve this problem, a HDPE GM was selected for testing under exposed air condition. The tests included oxidation induction time (OIT), melt flow index (MFI), tensile properties and diffusivity under four temperature conditions for 1½ years. The test results showed that the GM has higher OIT degradation rates. Stage I - depletion of antioxidants occurred at only 10 years for the GM, which was approximately 1/4 that of the GM-GSE. The GM engineering properties index showed the same changes as those of the GM-GSE. However, MI rapidly decreased with the incubation time. The molecular weight degradation of the GM was approximately 57% and far greater than that of GM-GSE after 15 months, but the tensile properties of the two GMs showed little change. The diffusion coefficient Di of GM increases gradually with the increase of temperature in methane and trichloromethane. Under the same conditions, the diffusion coefficient Di of the GM in methane is significantly higher than that in trichloromethane, indicating that the GM has better barrier to trichloromethane.