Synthesis of carboxymethylcelluloses with different degrees of substitution and their performance as renewable stabilizing agents for aqueous ceramic suspensions

Low average molar mass cellulose has been submitted to carboxymethylation reactions to yield carboxymethylcellulose (CMC) materials with different degrees of substitution (DS) that have been investigated as alternative renewable stabilizing agents for aqueous alumina suspensions to usual synthetic polyelectrolyte additives. The CMC materials were characterized by infrared, X-ray diffractiOn and H-1 nuclear magnetic resonance (NMR) spectroscopies, as well as by size exclusion chromatography (SEC), thermogravimetry (TG) and differential scanning calorimetry (DSC). All CMC materials reported (DS of 0.7, 1.3 and 1.8 as estimated by H-1 NMR) proved to be good additives to stabilize aqueous alumina suspensions with high solid concentrations (60%, w/w). Addition of low amounts of CMC (from 0.10% to 0.20%, w/w) produced suspensions with small and uniformly distributed particle sizes, thereby yielding colloids with lower viscosity, negative zeta potential values and longer sedimentation times. The present work demonstrates the viability of substituting synthetic fossil-based polyelectrolytes in traditional industrial activities with renewable cellulosic biomass-based ones.