Influence of metal ions on the oxidation resistance of polypropylene geotextiles

Like other polymeric materials, geotextiles may degrade through oxidation, potentially affecting their performance and lifespan. In certain applications (e.g. mining sites or waste containment systems), geotextiles are used in contaminated or aggressive environments, with possible exposure to metals or metal ions. This work examines how metal ion solutions (cobalt, copper, iron, manganese, nickel and zinc nitrates) influence the oxidation resistance of two polypropylene geotextiles. For this, the materials were exposed in isolation (individual exposures) and in sequence (consecutive exposures) to metal ion solutions (immersion at ≈20°C for 100 days) and oxidation (oven-ageing at 100°C for 28 and 56 days). The effect of the degradation tests was evaluated by tracking changes in the tensile performance of the geotextiles. The results showed that the geotextiles had a relatively high resistance to metal ion solutions and oxidation (individual exposures). Conversely, the consecutive exposures led to very marked changes in tensile behaviour (in most cases, reductions in tensile strength higher than 85%). The oxidation process was highly accelerated by prior exposure of the geotextiles to metal ion solutions, which contaminated them. The catalytic action of metal ions in the oxidation process was identified as the most likely cause of the accelerated degradation.