Mechanical Behaviour of Polyurethane from Castor oil Reinforced Sugarcane Straw Cellulose Composites

Abstract

Ecological concerns have resulted in a renewed interest in natural, renewable resources-based and compostable materials. For this reason, material components such as natural fibres and biodegradable polymers can be considered as interesting alternatives for the development of new biodegradable composites.The aim of this work was the obtainment of castor oil polyurethane reinforced with cellulose fibres from sugarcane straw. For the obtainment of cellulose, sugarcane straw was pretreated by steam explosion, followed by a delignification with NaOH 1.5% (wt/v). For the production of the polyurethane, the mass ratio between polyol (castor oil) and diisocyanate was 1.5:1.0. Reinforcement of the matrix was done changing the concentration of cellulose fibres (5,10,15,20% wt/wt). Chemical characterization of the materials obtained during the process was carried out. SEM micrographs of the fibres and fractured surfaces of flexural tests were done. SEM images of the fibres corroborate the results of chemical analysis, which showed a large solubility of components, making the fibres more exposed. The incorporation of cellulose fibres in the matrix showed that the composites stiffness increased, the Young's modulus also increased when compared to the pure matrix. SEM analysis of the fractured surfaces showed a poor dispersion of fibres in the matrix, and high interaction fiber-matrix.