Effect of different degradation types on properties of plastic waste obtained from espresso coffee capsules

Abstract

In terms of large use of plastic products, a necessity exists to minimize effects of the waste produced on environment by recycling, reuse and application in new products. In Brazil, the espresso coffee capsules are an emerging plastic waste, representing 0.9% of the coffee consumed in 2017. Therefore, Nescafé Dolce Gusto espresso coffee capsules were chosen in order to understand the polypropylene stabilization and degradation initiators with the purpose of recycling by applying in a composite material, as home composting product. In this context, the plastic capsule wastes were exposed to chemical, thermal, accelerated weathering (ultraviolet radiation + humidity) and natural weathering in order to analyze the influence of exposure and possibilities of a real application in a composting environment. Masses of the samples were monitored before and during the weathering conditions. Thermal (TGA and DSC) and chemical (FTIR) analysis were carried out before and after exposure. No changes in thermal stability were observed, however, samples conditioned in acid solution presented thermal degradation event beginning at 131 °C. In addition, all samples presented a similar behavior of melting and crystallization points, which did not change with exposure. FTIR analysis showed a disappearance of C[dbnd]C and C[dbnd]O bonds on samples exposed to natural weathering and basic solution conditioning. It also showed formation of chromophores groups on samples exposed to accelerated weathering. The visual analysis showed huge differences in samples exposed to accelerated weathering and acid solution, which were the most damaged. On the other hand, samples exposed to natural weathering, thermal and basic conditioning did not presented significantly changes supported by the TGA and FTIR results.