MECHANICAL EVALUATION OF CASTOR OIL BASED POLYURETHANE BIOCOMPOSITES REINFORCED BY EUCALYPTUS WOOD RESIDUE

Abstract

Wood has been used as a structural material for a long time. It can be understood as a natural composite material with polymer matrix reinforced by natural lignocellulosic fibers. In Brazil, the Eucalyptus species has been widely used due to its rapid growth and great adaptability, making this variety one of the most cultivated. During wood processing, even using modern techniques, about 30% of the material is not used, which causes a large amount of waste and which is normally burnt. Thus, the objective of this work was to investigate mechanical properties of biocomposites with castor oil-based polyurethane matrix reinforced with Eucalyptus obtained as a residue from the wood industry. Composites were produced from 10 up to 40 vol% of residues obtained in three different processing stages. The biocomposites were subjected to flexural, tensile, and charpy and izod impact tests. The results showed that for both flexural and tensile strength, low volumetric fractions of the residues cause a drop in performance mostly associated with the appearance of bubbles in the matrix. As the volumetric fraction of the residue increases, there was a tendency for an increase in the performance of the composites. Regarding the impact tests, the biocomposites show almost no significant difference from the pure resin, with a tendency of lower impact resistances. Moreover, it became clear that both the volume fraction and the geometry of the reinforcement influences the biocomposites mechanical behavior. Indeed, the longer the residue the greater was its tensile and flexural performance.