Hydrophobicity Enhancement of Cellulose-Based Material via Heterogeneous Surface Acetylation
Heterogeneous cotton fibre surface acetylation with acetic anhydride was performed in an oil bath at 130 °C with Na2CO3 as a catalyst to enhance the reaction activity. The effect of reaction time on fibre acetylation was characterised by the ester content of acetylated fibres, attenuated total reflectance-Fourier transform infrared spectrometry (ATR-FTIR), x-ray diffraction (XRD), static and dynamic contact angle measurements and field emission scanning electron microscopy (FESEM). The ester content increased with increasing reaction time, and the increase of ester content was not evident at a reaction time over 90 min. The emergence and intensity of the absorption peak characteristic of C=O and the reduction of the absorption peak of O-H clearly proved the occurrence of acetylation. The XRD data of the fibres exhibited the typical XRD pattern of cellulose I, and the diffracted intensity decreased after acetylation. Static and dynamic contact angle measurements demonstrated enhanced hydrophobicity and decreased surface energy with increasing reaction time. FESEM micrographs showed that the acetylation removed the wax layer of fibres and smoothed the fibre surfaces.