Evaluation of the use of rice husk cellulose fiber, acetylated rice starch and crude glycerol in foam formulation

This study aimed to evaluate the use of rice hull cellulose fiber, acetylated rice starch, and crude glycerol in foam formulations. These compounds were considered because they constitute residues from the rice industry, which is the most consumed cereal worldwide, and the biodiesel industry, which is a renewable alternative fuel for diesel. The novelty of this study lies in recognizing the potential of these raw materials (acetylated rice starch, rice husk cellulose, and crude glycerol) for foam production. Starch with a low degree of acetylation was obtained using an eco-friendly method with a few chemical reagents. Granulated rice was used to extract the starch, which was subsequently modified by acetylation. Crude glycerol was obtained without purification as a by-product of transesterification of soybean oil. Rice husk cellulose was obtained after delignification using non-aggressive chemical reagents. These materials were mixed in different proportions, incorporating acetylated starch (AcS) with two degrees of substitution, 0.2 and 0.4. Four formulations, along with fixed additives, such as water, magnesium stearate, and guar gum, were obtained by a thermopressing process at 160 °C. The foams were characterized using water contact angle measurements, morphology (SEM), chemical structure (FTIR) analyses, hardness, and solubility. The SEM images revealed mostly closed cells for all the four formulations. Microstructural analysis revealed chemical modifications and interactions between the formulation components. Hardness values were obtained in the range of 20–40 Shore A, with solubility in water between 18% and 27%, thickness of 2.449 ± 0.076 mm, and density of 0.268 ± 0.021 g/cm³. The AcS2-b sample demonstrated superior characteristics, showing higher hydrophobicity, a small change in contact angle over time, hardness of 30 Shore A, and solubility of 24%. The results showed that foams with adequate hydrophobicity and structural characteristics can be obtained using these raw materials.