Optimizing Acetic Anhydride Amount for Improved Properties of Acetylated Cellulose Nanofibers from Sisal Fibers Using a High-Speed Blender.

Acetylated cellulose nanofibers (ACNFs) have shown a great potential for strengthening non-polar polymer matrices and better dispersion which can improve composite properties. However, insufficient acetylation may cause inadequate nanofibrillation ACNF during the fibrillation process. The objective of this work was to evaluate the effect of different amounts of acetic anhydride (0, 45, 55, and 65 mL) on the degree of substitution (DS), morphology, crystalline structure, and thermal properties of ACNF obtained from sisal fiber produced using a high-speed blender. The attenuated total reflectance-Fourier transform infrared spectroscopy revealed the success of the acetylation process by the presence of the carbonyl signal around 1724 cm. Furthermore, the DS of ACNF was increased with the acetic anhydride amounts. X-ray diffraction analysis revealed that the crystalline structure of ACNF and non-ACNFs were cellulose I, and the crystallinity index of CNF was increased after acetylation treatment. Thermogravimetric analysis showed that the thermal stability of CNF was improved considerably after the acetylation process. The water contact angle of ACNF was higher than that of CNF, indicating that the structural property of CNF altered from hydrophilic to more hydrophobic after acetylation. In addition, the thermal resistance of CNF was improved significantly after acetylation treatment. The optimum amount of acetic anhydride was achieved in 55 mL of acetic anhydride (ACNF-55) which produced ACNF with a DS value of 0.5, a crystallinity index of 77%, a diameter of 87.48 nm, a maximum degradation temperature of 351 °C, and a contact angle of 37.7°. Overall, it was concluded that the obtained ACNF had great potential as reinforcement materials for nanocomposites based on non-polar polymeric matrices.