Evaluation of exhumed HDPE geomembranes used as a liner in Brazilian shrimp farming ponds

Abstract

The present work evaluated three high-density polyethylene (HDPE) geomembranes exhumed from two shrimp farming ponds in the northeast of Brazil with nominal thicknesses of 0.8 mm. The CAM sample was exhumed from the bottom liner, and the CAM1 sample was exhumed from the slope liner, both after 8.25 years of field exposure in the same pond. The third sample, called CAM2, was exhumed from another shrimp farming pond after 3.0 years of service. It can be observed that the environmental exposure changed the CAM1 sample's behavior compared to the CAM sample. Changes in viscosity, stress cracking, and polymer unprotection by the antioxidants demonstrated that the environmental exposure in the field changed the initial conditions of the CAM1 sample. The CAM2 sample presented a high-density value, brittle tensile behavior, and a different thermal behavior from the other samples, as observed by the thermogravimetry (TG). Moreover, the CAM2 sample showed an event in dynamic mechanical analysis (DMA) presenting a significant decrease in stiffness. The first heating of differential scanning calorimetry (DSC) analysis showed an event before the melting points for all samples analyzed. Finally, the application of CAM1 and CAM2 samples as a liner can cause a system failure.