Tunable micro-structure of dissolving pulp-based cellulose nanofibrils with facile prehydrolysis process

Abstract

In this study, eucalyptus raw materials were pre-hydrolyzed and cellulose nanofibrils (CNFs) were prepared. The effect of prehydrolysis conditions on the micro-structure of dissolving pulp-based CNFs was studied, and the hydrogen bond change and crystal structure in CNFs were analyzed by FTIR peak fitting and X-ray diffractometer. The results showed that prehydrolysis would not change the crystal structure of CNFs, but could break up the intermolecular and intramolecular hydrogen bonds of CNFs. An increase in the prehydrolysis temperature would promote the breaking of the intramolecular hydrogen bonds in the amorphous region of CNFs, which leads to an increase in the crystallinity of CNFs. Long-time prehydrolysis treatments not only broke up the intermolecular hydrogen bonds in the amorphous region of CNFs, but also intramolecular hydrogen bonding in the crystalline region. Analyses of SEM and gas adsorption revealed that some nanopores became more and more large, and some small nanopores appeared on the surface of the CNFs with the increase of prehydrolysis intensity. The appearance of large or small nanopores on the surface of the CNFs were likely due to the breakage of hydrogen bonds in CNFs. The intermolecular and intramolecular hydrogen bonds of cellulose could be destroyed by changing prehydrolysis conditions, which resulted in appearance of a lot of nanopores on the surface of the CNFs. The DSC and TGA analyses revealed that the prehydrolysis has a little impact on the thermal stability of CNFs. This work can provide a tunable pathway of micro-structure of CNFs by controlling prehydrolysis process.