Caracterização de compósito de matriz de poliuretano à base de óleo de mamona e resíduo de caroço de açaí

Abstract

The growing environmental concern and the search for sustainable materials are driving research into composites with natural reinforcements. The use of natural fibers and particulates in polymeric matrices is a consolidated area in materials engineering due to promising results in mechanical performance. In this context, the large quantity of acai waste without proper disposal, combined with a castor oil-based polyurethane (COPU) polymeric matrix, represents a viable and sustainable option for the development of new materials. Therefore, the main objective of this work was to investigate the influence of particle size and volumetric fraction of acai (Euterpe oleracea) particulates on the properties of castor oil polyurethane (COPU) composites, aiming at the development of sustainable materials. The methodology involved the characterization of the particulates by optical microscopy, SEM/EDS, pycnometry, XRD, TGA/DTG, and FTIR, and the composites by mechanical tests (tensile, compression, flexural, Izod impact, Shore D hardness), water absorption, and flammability. The main results showed that the incorporation of acai particulates significantly altered the matrix properties. The 60G1 formulation (60% fine particulates) stood out for optimizing tensile strength (16.51 ± 1.62 MPa, 8% higher than the pure matrix) and compression (37.94 ± 2.17 MPa, a 544% gain), in addition to presenting the greatest reduction in burning rate (10.37 ± 1.86 mm/s, a 60% decrease) and suppression of dripping. Formulations 50G2 and 60G2 (intermediate particulates) exhibited the best performance in flexural strength (21.45 ± 1.75 MPa for 60G2). Shore D hardness increased with the addition of particulates, with 60G3 (coarse particulates) showing the highest value (64.9 ± 2.71). Water absorption increased due to the hygroscopic nature of the particulates but remained within acceptable limits for certain applications. Microstructural analysis by SEM revealed the presence of voids and interfacial failure, which negatively impacted mechanical properties, especially impact toughness. The application of these composites is promising in indoor environments, such as cladding panels. It is concluded that COPU/acai composites show great potential as engineering materials, with the 60G1 formulation offering the best balance of properties. To optimize performance, future studies should focus on reducing the void fraction and improving interfacial adhesion.