Produção e caracterização de nanocompósitos expandidos de poliestireno, reforçados com nanofibras e nanowhiskers de celulose obtidas a partir de fibra de curauá

Abstract

The search for materials of natural origin, with less environmental impact and with the same properties of synthetic materials is increasingly focused on research in the field of engineering. One way to doing this is a development of nanocomposites reinforced with materials obtained from natural fibers, because that have on your biologic structure cellulose and the cellulose is present in greater quantity in the planet. Within the nanocomposites there is a class of expanded nanocomposites that combine good mechanical properties with reduced density and superior capacity of thermal and acoustic insulation when compared to conventional non-expanded nanocomposites. Expanded nanocomposites are materials that have at least three phases: a continuous (polymer matrix), the dispersed phase (reinforcing elements) and the presence of voids inside the structure, called cells. Polystyrene (PS) is a polymer widely used in the production of expanded materials. In this sense, the aim of the present study were firstly to obtain nanofibers (NFC) and nanowhiskers (NWC) of cellulose both extracted from curauá fibers (CF). The NFCs were obtained by the defibrillation process and the NWC from the oxidation method. These were characterized by their transmission electron microscopy (TEM), scanning electron microscopy with field emission (SEM), degree of polymerization (GP), their crystalline structure (XRD), and their thermal properties (TG) and the chemical structure by Fourier-transform infrared spectroscopy (FTIR). After that, the next step was the development of PS/NFC and PS/NWC nanocomposites in the following reinforcement concentrations: 0.25%, 0.50% and 1.00% (w/w). The influence of the incorporation of the reinforcements in the matrix by DMA was evaluated, where an increase in the storage and loss modulus was observed for all the nanocomposites, in relation to the PS without reinforcement. After the nanocomposites were expanded using carbon dioxide in the supercritical state as an expander and the expanded nanocomposites were evaluated by mechanical properties (compressive strength), in the final morphology of the expanded nanocomposite by SEM and by cell size distribution. In the expanded nanocomposites, the incorporation of the NFC promoted an increase in the compressive strength and a decrease in the cell size when compared to the samples reinforced with NWC and pure PS. In general, the incorporation of NWC in nanocomposites prior to expansion provided better results when purchased from NFC-reinforced ones. On the other hand, th incorporation of NFC in the expanded nanocomposites provided better results when compared to those reinforced with NWC. [resumo fornecido pelo autor]