THERMAL STABILITY OF CELLULOSE NANOCRYSTALS FROM CURAUA FIBER ISOLATED BY ACID HYDROLYSIS

摘要

Cellulose nanocrystals were directly extracted from curaua fibers by acid hydrolysis using two different acids (H2SO4 and HCl) and a mixture of the two. The morphology of curaua nanocrystals was investigated by atomic force microscopy (AFM) and the effect of the acids on the thermal stability of the cellulose nanocrystals was evaluated by thermogravimetry (TG). Vyazovkin's method was used to determine the apparent activation energy (E-a) of the nanocrystals, which were of similar shape and had a rod-like aspect. The nanocrystals extracted with HCl (NC-HCl) and with the mixture of acids presented higher thermal stability than the nanofiber extracted with H2SO4 (NC-H2SO4). No directly proportional correlationwas found between thermal stability and apparent activation energy ((E)a). The average E-a value obtained for NC-H2SO4 was similar to that for NC-H2SO4/HCl, indicating that the presence of sulfate groups influences the degradation behavior, resulting in nanocellulose structures with lower thermal stability, but degradation occurs at higher E-a values.