Preliminary Assessment of Antioxidant Depletion from a Polypropylene Coating on a Geosynthetic Clay Liner

ABSTRACT: Multicomponent geosynthetic clay liners (MGCLs) often have a polypropylene coating about 200 g/m2 applied to a standard geosynthetic clay liner (GCL) to reduce the hydraulic conductivity and minimize premature hydration of the GCL. These MGCLs may be used in applications with design lives of 100 years or more. However, the service life of the coating is unknown. This paper described testing that is being conducted to evaluate the depletion of the antioxidants used to protect the polymer from thermal oxidative degradation. Samples of the impregnated coated geotextile (GTX) are immersed into a simulated municipal solid waste leachate aged at 65oC, 75oC and 85oC. Based on the data available at the time of writing, the early depletion takes places rapidly within few days of oven-aging at these temperatures and the rate of antioxidant degradation at 75oC and 85oC temperatures appears to be similar but 2.5 times that of 65oC. There is need for more data to provide the Arrhenius relationship that will allow for the prediction of the time to antioxidant depletion at temperatures relevant to a particular landfill application, hence the critical stage in the service life of the coating component of a MGCL.