Aproveitamento da madeira de seringueira e resíduos de mineração para produtos de maior valor agregado

Abstract

The rubber tree is widely used to obtain latex for the production of natural rubber, consolidating it as the main economic product of Brazilian rubber plantations. However, the wood resulting from this process still has low added value and is normally used in energy production. Seeking to develop new products and processes for the packaging industry and civil construction, the objective of the study was to produce and evaluate the characteristics of fibers and cellulosic micro/nanofibrils (CMF/CNF) from rubber trees for the production of films and fiber-cement composites. The fibers went through a chemical process, which consists of treating the particles with 5% NaOH (m/m) for 3 h at a temperature of 80°C. In the production of CMF/CNF, the fibers went through cycles in the grinder, and, at the end of the process, the suspension produced was diluted to a concentration of 1% (m/m). The films were prepared in 10 repetitions using the casting method. The films were characterized regarding chemical composition, microstructure, crystallinity, stability, physical, optical, mechanical and barrier properties and quality index. For the production of fiber cement, a controlled mineralization process was carried out with 9% aluminum sulfate (Al2(SO4)3) and 2.5% citric acid (C6H8O7) in the fibers. The fiber cements were produced with CPV-ARI Portland cement, quartzite waste and 5% fibrous reinforcement from the extrusion process. The physical, mechanical, thermal and microstructural properties of fiber cements were evaluated after 28 days of curing. The quality index (QI) of Hevea brasiliensis CMF/CNF was 51 ± 4.7, presenting potential for application in the packaging industry or even for high added value applications. The results obtained with alkaline pretreatment for Hevea brasiliensis wood are promising and competitive with other studies focused on Eucalyptus Kraft pulps for the same purpose. Cementitious composites with 5% fibers exhibited better mechanical performances. The results showed that it is possible to improve the microstructure and physical-mechanical performance of composites using small amounts of CMF/CNF (0.5%). The quartzite had a positive effect on the properties, in addition to providing thermal comfort (~0.11 W/mK). Therefore, the materials showed promise for the production of extruded fiber cement composites.