Preparation and characterization of cellulose nanocrystals/cellulose acetate composites

Author(s)

Liliane Samara Ferreira Leite

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2015-04-23

Examining board members

Maria do Carmo Gonçalves; Alessandra de Almeida Lucas; Ana Rita Morales

• Advisor: Maria do Carmo Gonçalves

Abstract

In this work, cotton fiber cellulose nanocrystals (CNC) were obtained by acid hydrolysis using three different acids: sulfuric acid, hydrochloric acid and phosphoric acid. Scanning (SEM) and transmission (TEM) electron micrographs confirmed that the acid hydrolysis conditions used were efficient to isolate their nanocrystals. However, in all samples analyzed, it was possible to observe the presence of some partially hydrolyzed fibers. Polarized Light Microscopy (PLM) showed that the freeze-drying process led to the formation of small CNC agglomerates with micron dimensions. CNC surface functionalization was carried out with the purpose of reducing the hydrophilic character, by using acetic acid and hexanoyl chloride. Chemical modifications at the surface were confirmed by infrared spectroscopy and the hydrophilic character decrease was confirmed by PLM images of the functionalized CNC. Cellulose acetate composites, reinforced with CNC, were obtained by melt extrusion using two techniques for the introduction of reinforcing agent: direct mixing and masterbatch. The latter were carried out prevent CNC agglomeration formation due to the freeze-drying process. Mechanical tests showed that there was no significant increase in of the composites prepared by direct mixing mechanical properties. However, composites prepared from masterbatch showed a 5% and 14% increase in Young's modulus for 10 and 15 wt% CNC content, respectively. These results show the importance of the hydrolysis conditions on the nanoparticle synthesis, as well as the choice of an appropriate reinforcing agent load method so as to avoid agglomeration and increase load dispersion in the matrix (AU)

• FAPESP's process: 13/10046-8 - Preparation and characterization of cellulose Acetate/Cellulose Nanocrystal nanocomposites
• Grantee: Liliane Samara Ferreira Leite
• Support Opportunities: Scholarships in Brazil - Master