Avaliação da despolimerização do poliestireno expandido por micro-ondas utilizando óxido de grafeno e carvão ativado

Abstract

Polymers are increasingly present in everyday life to replace other materials. Because they are cheap and have attractive mechanical properties, they were and still are produced on a large scale and, consequently, their large volumes in landfills present a challenge for their recycling. Thus, the objective of this study was to evaluate the depolymerization of expanded polystyrene (EPS) through the use of microwaves and, with the aid of two agents that have carbon in their constitution to assist in the depolymerization: graphene oxide (OG) and activated charcoal (CA). Different amounts of OG and CA (0.125, 0.250, 0.5 g) were used, always keeping the EPS sample mass constant of 1 g. The tests in the microwave were carried out in 3 cycles of 4 minutes each, with a total time of 12 minutes per batch. Inside the microwave, the sample was placed inside a round-bottomed balloon wrapped up with rock wool. To characterize the material obteined from the depolymerization, a mass balance was performed to evaluate the depolymerization yelds, the Fourier Transform Infrared Spectroscopy (FTIR) and a thermogravimetric analysis (TGA). For the sample containing 0.125 g of GC, it was observed the formation of a larger solid fraction, little gaseous fraction and no liquid fraction. The sample with 0.25 g of GC had the best volatile yield, with 22.58% of volatiles, and it was possible to observe both the fraction and liquid to gas. Tests with 0.5 g of OG were unsatisfactory as they cracked the balloon at the beginning of the experiment. The semples with CA did not show a great visual evidence of depolymerization, however, those with 0.125 g, those with 0.250 g and those with 0.5 g yielded gas fractions of 5.13; 9.16; and 3.06, respectively. The FTIR analysis for the samples containing OG showed new absorption bands when compared to a neutral EPS sample, while for the samples with CA it was not possible to observe. Some degradation peaks in the TGA of the OG-containing sample may be correlated with the formation of more volatile compounds after depolymerization. The sample with CA did not present significant peaks. This study suggests that heat transfer from the dark particle to the EPS sample is more effective with the use of OG, which may contribute to EPS depolymerization. [resumo fornecido pelo autor]