Avaliação da utilização do bagaço de malte cervejeiro como carga em espuma de poliuretano

Abstract

Agro-industrial waste, such as that from food processing, is abundant and harmful to the ecosystem if improperly disposed of due to its high organic matter content. The brewing industry in the European Union, for example, generates about 3.4 million tons of waste annually, 85% of which is brewers' spent grain (BSG). In Brazil, BSG amounted to 2.8 million tons in 2018. Recently, there has been growing interest in using lignocellulosic materials, such as BSG, in polymer composites due to their low cost, light weight, strength, biodegradability, and non-polluting properties. Specifically, incorporating BSG into polyurethane (PU) foams is attractive due to the advantageous properties of PU, including good adhesion, affordability, and rapid polymerization. This study evaluates the use of BSG as filler in PU foams by characterizing BSG, synthesizing PU foams with different amounts of BSG, and analyzing their properties, such as apparent density, water absorption, thermal decomposition, and chemical composition. The characterization of BSG included the determination of moisture, proteins, extractives, crude fibers, and ash. The PU foams were examined using FTIR, SEM, TGA, and DSC to evaluate their structure, morphology, and thermal properties, as well as the apparent density and water absorption of the samples. BSG showed a high concentration of crude fibers, exceeding 75%, and thermal stability up to about 200°C, indicating its viability as a structural reinforcement in polymer composites. FTIR analysis revealed that adding BSG to PU foams did not significantly alter the material's chemical structure. SEM indicated that this addition reduced the cell size of the PU foams and increased the number of broken cells. An increase in apparent density and water absorption proportional to the amount of BSG incorporated into the foam was also observed. Thermal studies using TGA and DSC showed that the inclusion of BSG did not significantly change the thermal stability or behavior of the PU foams with increasing temperature.