Cotton Nanofibers Obtained by Different Hydrolytic Acid Conditions

The thermal stability of cellulose nanofibers is related to their application and especially to polymer processing normally occurring at ca. 200 degrees C. In this work, nanofibers of commercial cotton were obtained by acid hydrolysis employing, different acids: sulfuric, hydrochloric and a mixture (1:1; sulfuric acid: hydrochloric acid). The morphology of the nanofibers were characterized by transmission microscopy (TEM), zeta potential, elemental analysis, crystallinity by X ray diffraction (XRD) and thermal stability (TGA) in air atmosphere by thermogravimetric analysis. The results indicated a very similar morphology and crystallinity among them. The main differences were lie in the aggregation state and thermal stability. The aggregation state of the suspensions decreases in the order HCl< H2SO4 due to the increase in surface charge as determined by zeta potential measurements. The hydrolysis with a mixture of HCl and H2SO4 resulted in cellulose nanofibers with higher thermal stability than those hydrolyzed with H2SO4. The hydrolysis employed with a mixture of sulphuric and hydrochloric acids also showed a better dispersion than those suspensions of nanofibers obtained by hydrolysis with only HCl.