Obtenção de nanocristais de celulose e sua modificação utilizando utilizando 3-isopropenil-α-α'-dimetilbenzil isocianato (tmi)

Abstract

The work was divided into theoretical and experimental parts. Among the materials of biological origin, wood is undoubtedly the best known and most used. In its macromolecular composition is mainly cellulose, lignin and hemicelluloses. These polymers form the cell wall of wood and are responsible for most of its physical, mechanical and defined properties. Cellulose is the main component chemically defined as a complex carbohydrate, polysaccharide, insoluble in water and formed by large chains of glucose molecules. It is possible to obtain cellulose nanocrystals from cellulose, and the interest in isolating them is due to their low density, being a renewable, biodegradable resource, having a reactive surface, high surface area for contact with matrices based on nanocomposites, others. However, some disadvantages such as moisture absorption, incompatibility with many polymeric matrices and limited processing processing ingredients can be bypassed. However, a surface can be functionalized through composites of components, the development of composite materials or high performance nanocomposites. In this work, cellulose nanocrystals were extracted from Kraft cellulose pulp by acid hydrolysis using 9.17 M sulfuric acid and then modified using the reagent 3-isopropenyl-α, α’-dimethylbenzyl isocyanate (TMI). The chemical modification of cellulose nanocrystals was evaluated by Fourier Transform Infrared Spectroscopy, morphologically by High Angle X-Ray Diffraction and Atomic Force Microscopy. The FTIR data expanded that a cellulosic structure was maintained and there was a displacement of the carbonyl peak present in the TMI isocyanate group around 1690 cm-1 to 1715 cm-1 referring to the carbonyl present in the utera group formed in the NCCmod sample, proving the effectiveness of the chemical reaction between cellulose and TMI. The XRD analysis showed that a crystal structure was preserved with a modification, with maintenance of the cellulose I pattern. From the AFM images, the presence of acicular-shaped nanoparticles was verified, confirming that the NCC extraction was successful and that they underwent altered changes in dimensions after chemical modification with TMI. Thus, NCCmod can also be used as reinforcement agents in nanocomposites. We can conclude that the modification method adopted was efficient in effecting the insertion of the TMI on the surface of the NCC without any degradation or drastic alteration in its original structure.