Keywords
Surface modification
Acetylation
Silylation
How to Cite
Abstract
In order to improve the interaction between cellulose nanocrystals (NCCs) and hydrophobic polymer matrices, the present work proposes to change the polarity of the nanocrystals by means of two surface treatments: acetylation and silylation. NCCs are the crystalline domains present in lignocellulosic fibers, extracted by acid or enzymatic hydrolysis. These nanoparticles have unique properties and great ecological advantage of use, which makes increasing interest in using these nanocrystals in the production of nanocomposites. Acetylation was carried out using a solution of acetic anhydride and acetic acid, catalyzed by sulfuric acid. The silylation was a greenhouse reaction with a solution of hexamethyldisilazane (HMDS). The success of the modifications was confirmed by infrared spectroscopy (FT-IR) and X-ray excited photoelectron spectroscopy (XPS). The thermogravimetric analysis (TGA) indicated that the silylated nanocrystals maintained the thermal stability in relation to the unmodified ones, but that the acetylated nanocrystals showed improvement in relation to the others. By contact angle, it was verified the polarity change of the modified nanocrystals, which were potentially hydrophobic. The images obtained by atomic force microscopy (AFM) showed that the silylated nanocrystals maintained the original morphology and showed good dispersion after being submitted to ultrasound. However, the morphology of the acetylated nanocrystals changed and they presented agglomerations, which may be related to the solvent used in the preparation of the sample. Therefore, the modified NCCs present application potential, but more studies are required as tests on polymers with hydrophobic characteristics.
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