Embalagens sustentáveis à base de amido de milho, resíduos de rocha e fibra de café

Abstract

Native starch is not suitable for direct plastic applications due to its high water vapor permeability and brittle mechanical properties. To overcome these limitations, starch is plasticized by adding agents such as water or glycerol under controlled heat and shear conditions, promoting the disruption of starch granules and the formation of a gelatinized network. This process improves the flexibility and reduces the brittleness of the material. However, thermoplastic starch (TPS) films still exhibit inferior performance compared to petroleum-derived materials. Starch-based biocomposites, incorporating natural fibers or mineral fillers, have emerged as promising biodegradable alternatives, offering enhanced mechanical and thermal properties. Coffee husks, rich in cellulose and lignin, are an excellent source of bioactive compounds and can serve as reinforcing agents in biocomposites. Additionally, by-products such as ornamental stone sawing waste from the stone industry show potential for sustainable applications. This study investigated the development of TPS-based biocomposites reinforced with coffee husks (CH), potassium feldspar (PF), and Bahia Beige marble (BB), focusing on their chemical, mechanical, and morphological properties, offering an innovative approach to sustainable biocomposite development. The results confirmed that the chemical composition of the reinforcements influences the composites' performance, with calcium carbonate predominant in Bahia Beige marble, high silicon and potassium content in feldspar, and high carbon content in coffee husks. FTIR analysis showed that the reinforcements were incorporated without compromising the chemical structure of TPS. SEM micrographs indicated good dispersion of the reinforcements, although formulations with higher filler content showed decohesion. Mechanical tests revealed that the addition of CH and mineral fillers reduced TPS ductility but increased its stiffness and tensile strength, with the 70/20/5/5 composite showing the best results. Impact resistance was also improved by the addition of CH. Thus, the combination of these reinforcements enables the development of more rigid and resistant biodegradable composites, adjustable for different applications.