Release mechanisms for PA6 nanocomposites under weathering conditions simulating their outdoor uses

The increased use of polymer nanocomposites in different applications could lead to potential nanofiller release into different human and environmental compartments and consequently, increase the exposure of human and environmental species to nanomaterials. This study aims at determining how the inclusion of nanofillers with diverse chemical nature (SiO2, TiO2, ZnO, multiwalled carbon nanotubes and two nano-organoclays) in polyamide 6 composites influences the nanomaterial release during the use of these products. The different nanocomposites were exposed to accelerated ageing processes, simulating outdoor conditions, through irradiation with UV light under a combination of dry-wet cycles. Release monitoring consisted of nanocomposites characterisation, run-off waters collection and released materials quantification and characterisation. The study confirmed that the chemical surface nature of the nanofiller strongly impacts on polymer degradation, in some cases enhancing its protection and in others promoting polyamide hydrolysis and/or photo-degradation processes. Polymer degradation and nanomaterial-polymer compatibility are the main determinants for the release and consequent exposure to nanofillers.