Abiotic and biotic degradation of oxo-biodegradable foamed polystyrene

An alternative for improving the degradability of polyolefins and polystyrene is the addition of pro-oxidant substances to their formulations. The materials obtained are then called oxo-biodegradable. This work aimed to assess the biotic and abiotic degradation of atactic polystyrene (PS), utilising as test material foamed PS plates used in the manufacture of trays, formulated with Co- and Mn-based pro-oxidant additives. The plates were exposed to artificial weathering (ultraviolet radiation and heat) and were periodically analysed for changes in structural properties. The oxidised surface residues detached from the samples were incubated in a stabilised compost of urban waste (58 °C) or in an aqueous mineral medium (25 °C), the latter being inoculated with urban waste compost and also with a microbial consortium. It was found that the molar masses of the eroded materials from the pro-oxidant activated samples were significantly lower than the initial sample molar masses, with simultaneous incorporation of oxygen into the chains during the accelerated weathering. These samples underwent biodegradation and gave mineralisation values of 2-5% over 2-3 months of incubation in compost and perlite or in mineral aqueous medium. Biodegradation of the residues from the samples not containing pro-oxidant additives was also observed, but at levels which were lower than those obtained for oxo-biodegradable samples.