Heterogeneous modification of softwoods cellulose nanofibers with oleic acid: Effect of reaction time and oleic acid concentration

Heterogeneous esterification of softwood cellulose nanofibers (CNF) was performed by oleic acid. The effects of reaction time and oleic acid content on the extent of esterification and fiber properties were evaluated. The success of the modification reaction was confirmed by Fourier transform infrared (FTIR) spectroscopy. It was observed that the amount of oleic acid had a significant effect on the degree of substitution (DS value). The X-ray diffraction analyses showed the broadening of the diffraction peaks with increasing of the DS values of cellulose esters. Surface modification changed thermal stability of CNF by decreasing degradation temperature from 290.8 A degrees C for unmodified cellulose to 195.4 A degrees C for highly esterified sample. These properties were strongly affected by the DS values in the investigated range. The color properties of modified CNFs were weakened by increasing reaction time and oleic acid content.