Tratamento químico e caracterização da bucha vegetal (Luffa cylindrica) visando à preparação de espumas de poliuretano

Abstract

The use of natural fibers in the composition of polymeric materials has been studied since the beginning of this century due to the high demand for biodegradable raw materials, aiming to replace those that take centuries to decompose or are difficult to recycle. Luffa cylindrica, commonly used as a bath sponge, natural exfoliant, and promoted as an alternative to synthetic dishwashing sponges, contains lignocellulosic fibers composed of cellulose, hemicellulose, lignin, and amidocellulose. It features a fibrous lignin network, which, when cut and chemically treated with solvents that degrade hydrophobic compounds, exhibits a significant water absorption capacity compared to untreated samples and commercial foams, besides being a biodegradable material. With these attributes, this study aimed to chemically treat and characterize the Luffa cylindrica fiber to obtain rigid polyurethane foams. The natural luffa was structurally and morphologically characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. Next, the sample was chemically treated with a 5.0% NaOH solution and characterized using the same techniques mentioned previously. The chemical treatment altered its characteristics, particularly the removal of part of the lignin and hemicellulose, highlighting the crystalline region of the cellulose. After the evaluation stage, both the untreated and treated luffa were tested as part of a rigid polyurethane foam formulation, being added to the formulated polyol and reacted with diisocyanate to form an alternative polyurethane foam. The foams composed of 5.0% treated luffa showed the same visual appearance, characteristic polyurethane functional groups, and thermal degradation similar to the material without the fiber. In other words, it was possible to formulate foams with luffa in part of the composition, but an alkaline treatment was necessary. The development of this project aimed to contribute to the environment by promoting alternative foam compositions with fewer non-renewable resource-derived reagents.