Chemical Modification of Cellulose Nanofibers and its Impact on their Hydrophobicity and Dispersibility

Cellulose nanofibers (CNF) which isolated from wood and non woody plants have attractive advantages comparing with the synthetic fibers، some of the most relevant being the following: low density، renewable sources، biodegradability، availability، and high specific mechanical properties. Recently، the use of CNF in green materials، especially as reinforcement in different polymers has been increased greatly. However، the existence of the hydroxyl groups on the CNF surface leads to high hydrophilicity and limited dispersibility of CNF in non- polar polymers. In this study، the chemical modification has been used to enhance the hydrophobicity and dispersibility of CNF in non-aqueous mediums. Therefore، isolated CNF from Kenaf bast fibers was acetylated with acetic anhydride to obtain acetylated cellulose nanofibers (ACNF). The properties of both acetylated and non-acetylated nanofibers were studied. FTIR analysis was used to confirm the replacement of hydroxyl groups with acetyl groups. The degree of substitution was calculated by using titration method and it was found to be 0. 22. XRD analysis indicated crystalinty index of ACNF decreased compared to untreated CNF. The dynamic contact angle measurement showed that the hydrophilic surfaces of CNF become more hydrophobic due to the partial acetylation. In addition، TGA results clearly demonstrated an increase in thermal stability of acetylated nanofibers. The study of the dispersion illustrated that acetylated cellulose nanofibers formed stable، well-dispersed suspensions in both acetone and ethanol.