Changes in the Chemical and Physical Properties of Untreated and Finished Polyamide 6.6 Fabrics Buried in Different Soil Matrices, from the Lab-Scale to a House Garden

This paper aims to analyze the biodegradation behavior of a common synthetic fiber, well-known for its environmental recalcitrance: polyamide 6.6. In particular, polyamide 6.6 fabrics finished with chitosan to impart antibacterial properties and the natural red dye carmine were studied. Fabrics of standard polyamide 6.6 served as references. Some specimens were buried in compost-enriched soil for 1, 2 and 3 months and kept in the laboratory; simultaneously, others were placed in an outdoor house garden to simulate landfill conditions. After each sample withdrawal, various characterization techniques were employed to assess the status of the fibers. The first evidence was that, in general, there were no weight changes or significant macroscopic damage within three months, except for white stains as an index of microorganism colonization, which was confirmed by microscopic analyses, where bacteria and fungi could be clearly seen. On the one hand, some effects were revealed during the burial in the house garden that impacted the fabrics’ surface characteristics in terms of interaction with soil derivatives (susceptibility to adsorption of water and soil-derived substances). On the other hand, the samples buried under laboratory conditions showed a weak antibacterial efficacy, leading to the hypothesis that more aggressive degradation may have occurred at the expense of chitosan. Still, three months of burial led to mild surface deterioration, opening possibilities for further research.