Assessment of the Water Sorption Properties of Several Microcrystalline Celluloses

This paper compares the water sorption behavior of commercial microcrystalline celluloses with those of cellulose II materials using several nonlinear models. Aqueous dispersions of cellulose II were spray-dried employing an inlet drying air temperature of 195 °C; atomizing air pressure of 1.0 kg-f/cm; drying air flow-rate of 0.44 m/min; feed flow-rate of 2.0 mL/min and nozzle diameter of 0.7 mm. Cellulose II samples were also spheronized in a Fuji Paudal spheronizer for 10 min at 1000 rpm. Products were analyzed for water sorption on a VTI symmetrical gravimetric analyzer in triplicates. The Guggenheim-Anderson-de Boer (GAB), Hailwood-Horrobin (HH), Generalized D’Arcy and Watt (GDW) and Young and Nelson (YN) models were employed for the data analysis. Most of the sorption isotherms exhibited a type II sigmoid shape. Celphere203, presented a type III isotherm and showed the highest monolayer capacity (m0 of 0.15 g water/g cellulose) and the lowest monolayer energy constant (C=1.0) given by the GAB model. The GDW model indicated that the monolayer capacity (m0) and the fraction of sorption sites available for multilayer sorption (w) were the highest for Celphere203 (1.0 g/g cellulose and 1.0, respectively). The HH model indicated that Celphere203 had the highest sorption capacity (W of 3.0 g/g sorption site). The YN model showed that this material had the largest water uptake by absorption into the core of the particles. Celphere203 and SPCII were the most hydrophilic materials. Neither polymorphic form, nor silicification, was responsible for the difference in the hydrophilic properties of cellulose.