Resumo:
Nowadays, it is essential to add value to polymeric waste to promote sustainability.
The present study reports on the synthesis of silver nanoparticles (AgNPs) using silver
nitrate (AgNO3) as a metallic precursor and polyurethane (PU) waste from mechanical
recycling of refrigerators as a reducing agent. Samples were synthesized ranging from
10% to 60% Ag based on the weight of PU. Characterization of the PU waste was
performed using thermogravimetric analysis (TG), scanning electron microscopy
(SEM), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. In
addition to these techniques, the PU-AgNPs nanocomposites were also characterized
using energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and
ultraviolet-visible spectroscopy (UV-Vis), then their antimicrobial activity was analyzed
through the disk diffusion test. TG analysis revealed that the thermal decomposition of
the PU waste occurred by a complex mechanism and the polymer was constituted of
methylene diphenyl diisocyanate (MDI) and unidentified polyol. The incorporation of
AgNPs into the PU waste affected significantly its thermal stability, confirmed by
activation energy value, calculated by Arrhenius’ equation. Diffractograms confirmed
the presence of AgNPs in the PU waste, as well as contaminants. Utilizing Scherrer’s
equation, the average size of the AgNPs was 10,82 nm. SEM images exhibited a
morphology characterized by particles sprinkled with AgNPs and contaminants, which
were further confirmed by EDS analysis. The combined use of FTIR and Raman
techniques confirmed the AgNPs formation by decrease of intensity of characteristic
bands of PU. The disk diffusion test did not reveal antimicrobial activity in the
nanocomposites, which suggests the use of other technique to evaluate the
antimicrobial activity.
