Influência de tratamentos superficiais em partículas lignocelulósicas da casca do café para aplicação em biocompósitos de poliuretano vegetal

Abstract

Vegetable fibers have been extensively investigated and applied in polymeric biocomposites, mainly with the objective of improving their mechanical and thermal properties. However, when applied as reinforcement, these materials of a hydrophilic nature present problems of adhesion to polymeric matrices which, in turn, are more hydrophobic. In the present work, the effectiveness of three surface treatments applied to coffee husk residues was evaluated in order to improve the performance of castor oil-based polyurethane biocomposites, namely: i-chemical treatments with sodium hydroxide solutions , ii- hydrothermal under high temperature and pressure and iiibiological with solid state fermentation by the fungus Phanerochaete chrysosporium. In the results of chemical characterization, FTIR and SEM were observed the reduction of amorphous compounds for all methods and conditions tested, with emphasis on the treatments HYDRO 30 and NaOH 5 that presented anchorage points for the loads on their surfaces. The best mechanical performance was verified for biocomposites prepared with 20% of particles treated by the HYDRO 30 treatment. With gains of 65% in tensile strength compared to biocomposites prepared with the same percentage of fresh coffee husk, and 20% in value of the Elasticity Module in relation to polyurethane. In SEM analysis it was observed that these better particles adhered to the matrix. Furthermore, these biocomposites were the ones with the lowest water absorption content, 0.75%. Thus, the results obtained in this work indicate that the hydrothermal treatment presents itself as an ecological alternative to improve the particle/matrix interaction.