The Size Distribution of Cellulose Nanocrystals in the Variation of Acid-to-Microcellulose Crystals Ratio and Reaction Time Through Catalyzed Acid Hydrolysis

Abstract

Literature has shown that cellulose nanocrystals (CNCs) which are produced through hydrochloric (HCl) acid hydrolysis catalyzed by inorganic chlorides can enhance the mechanical properties of organic polymers further than CNCs by pure HCl acid hydrolysis. The results have shown that the level of reinforcement may be negatively correlated to the dissociation constant of the inorganic chlorides. However, titanium tetrachloride’s dissociation constant is 1.3, lower than that of ferric chloride, 2.2, which is the lowest dissociation constant among the four inorganic chlorides that have been studied. Therefore, for this study, titanium tetrachloride was investigated along with ferric chloride. The only two variables in this study are reaction time and acid-to-microcellulose crystals (MCCs) ratio. The results of laser diffraction spectroscopy (LDS) show that the resultant solutions exhibit binomial size distributions which contain both MCCs and CNCs. At acid-to-MCCs ratio of 40 for ferric chloride, any increase in reaction time above 1.5 hours did not result in size reduction. The Fourier transform infrared (FTIR) spectroscopy results of CNCs showed that the catalyzed hydrolysis did not change the molecular structure of MCCs. The color of CNCs varies with increasing reaction time, but, based on the FTIR and LDS results, the color is not an indication of CNCs’ size nor their chemical composition.