Obtenção e modificação de nanofibras celulósicas para produção de nanocompósito híbrido

Abstract

The main objective of this study was to obtain and deposit silica in cellulose nanofibrils by means of the sol-gel method using the silica tetraethyl orthosilicate - TEOS precursor at different concentrations, producing hybrid cellulose-silica aerogels. After obtaining cellulose nanofibrils by mechanical defibrillation from pretreated jute fibers, the chemical composition of the raw materials, related to the defibrillation degree had a positive influence over the mechanical properties of the produced films, consisting of different lignin and hemicelluloses residual concentrations (Article 1). When evaluating six concentrations of TEOS (0.00%, 0.25%, 0.50%, 1.00%, 2.00% and 3.00%) on the silica deposition in cellulose nanofibrils from mixed commercial and bleached pulp of hardwood and softwood, the presence of the silica precursor, even at lower concentrations (0.25%) influenced the cellulosic morphology, favoring the production of cellulose-silica hybrid nanocomposites. The increase in the concentrations of TEOS promoted the formation of hybrid aerogels more thermally stable. The reduced capacity for moisture adsorption of the hybrid aerogels was obtained mainly using the concentrations of 0.50% and 1.00%, presenting a porous and uncompressed structure (Article 2). Based on the results obtained for the six concentrations tested (Article 2), aerogels were produced from Eucalyptus cellulose nanofibrils, by testing four concentrations of TEOS (0.00%, 0:25%; to 0.50% and 1.00%), verifying that 0.25% of TEOS favored the formation of porous, homogeneous and smooth structured hybrid aerogels. The concentration of 0.50% TEOS influences the formation of porous and more thermally stable hybrid aerogels. The reduced adsorption capacity was observed for the concentration of 0.25% TEOS. Mechanically, all hybrid aerogels exhibited an elastic behavior, and are capable of partially recovering their original dimensions after subjected to compressive forces (Article 3).