Espumas de poliuretano com cinzas de casca de arroz : análise da utilização na sorção de óleo diesel e como retardante de chama

Abstract

The research consisted of producing an innovative material through the use of the incorporation of rice husk ash (RCA) in a polyurethane foam (PUF) polymeric matrix based on reagents of plant origin to verify the removal of diesel oil by sorption and in the flame propagation resistance. The calcined residue has a low specific surface area of 5.58 m2 /g obtained by adsorption of N2, 93.64% of silica evidenced by X-ray fluorescence, with a predominantly amorphous structure shown using X-ray diffraction, and recorded vibrations inherent to the siloxane functional groups observed by Fourier transform infrared spectroscopy. The PUF synthesized and used as a matrix to receive the incorporation of RHA residue showed a contact angle of 119.35°, with morphology evidenced by X ray microtomography showing pore diameters between 500-700 𝜇m, open porosity greater than 96%, an essential factor for the availability of active sites in composites. Three types of composites were synthesized with contents of 2%, 8%, and 20% of RHA incorporated into the PUF. The materials showed particles of residue rich in silica present in the polymer morphology evidenced in scanning electron microscopy, an increase in the average thickness of the walls of the PUF matrix without changes in the open porosity of the porous complex verified in the X-ray microtomography, improvement in the hydrophobicity of the PUF with a contact angle of 128.32°, in addition to an increase in thermal stability of up to 13% compared to the mass loss analyzed in thermogravimetry. As for the sorption in a single-phase diesel oil system, the composites with the highest levels of RHA incorporation (8% and 20%) significantly increased the hydrocarbon removal capacity to the PUF, obtaining gains of up to 43, 4% in sorption capacity, which removed 5348 mg.g−1 with the 8% RHA composite and 5518 mg.g−1 with the foam with 20% RHA. In biphasic systems of water and diesel oil varying the concentration from 10 to 150 g/L, there is a perspective that the contact angle of the composites has interfered with the sorption performances, being the composite with 2% the one that most absorbed the hydrocarbon. The sorption kinetics showed a high rate of contact times of less than 8 minutes. The pseudo-second-order non-linear models fit the observed sorption phenomenon satisfactorily with R2 of 0.90. The flame retardancy potential between one of the composites and the PUF was evaluated by establishing a better propagation resistance potential for the composite with an RHA content of 8%.