Silver effect on the biodegradation process of styrene-ethylene/ butylene-styrene based thermoplastic elastomers compounds upon weathering exposure

The incorporation of antibacterial additives in polymeric materials has become common to reduce the colonization of microorganisms in daily household items. This kind of product can be helpful to prevent diseases, but following the end of its useful lifetime, it might become an environmental problem, causing hazards also to the beneficial soil-borne microbes. This study aims to evaluate the effect of thermoplastic elastomers (TPEs) compounds loaded with silver ions (Ag+_bentonite, Ag+_phosphate) and nanoparticles (AgNp_silica) in the soil microbiota. Samples were exposed to weathering for 3, 6, 9 and 12 months, and monitored by carbon dioxide (CO2) production in the soil for 4 months. Standard sample exposed to weather by 6, 9 and 12 months showed higher CO2 production than samples unexposed or exposed for 3 months. By contrast, silver-loaded samples had higher CO2 production in samples pre-aged for 3 months, but the values decreased in samples pre-aged for 6, 9 and 12 months. Moreover, soil microbial counts were lower in samples that had lower CO2 production. Though the amount of silver in the soil has been lower than the limit of detection, after intense exposure to weather, the degradation of the polymer may have facilitated the release of silver from the TPE matrix, and on these terms, silver may have caused a harmful effect on soil fungi and bacterial population.