Carboxymethyl Chitosan: Preparation and Use in Colloidal Ceramic Processing

The use of natural macromolecules from rejects of the fishing industry, such as chitosan and derivatives, may be advantageous in replacing synthetic polymers to stabilize ceramic suspensions. In this paper, a carboxymethylated chitosan (CMCh) was synthesized, characterized with FTIR, 1H NMR and SEC methods, and tested as stabilizing agent of alumina suspensions. Close to the point of zero charge (pzc) of the alumina suspensions (approximately pH 7), the incorporation of only 0.2 wt% of CMCh (DS, degree of substitution, 0.8) caused the suspension viscosity to decrease from ca. 40 × 103 Cps to approximately 16 × 103 Cps. This decrease in viscosity was accompanied by a decrease in particle size, as the incorporation of CMCh led to a narrower distribution of smaller particles. Furthermore, at the pzc of the aqueous alumina suspension, negative zeta potentials were measured when CMCh was added. Upon combining information from viscosity, particle size and zeta potential, it was possible to infer that CMCh induced the stabilization of alumina suspensions via steric and electrosteric effects. Because the latter can be tuned by changing parameters of the suspensions as well as of the CMCh derivatives, one may envisage further applications of alumina suspensions with tailored properties.