A Useful Equation for Estimating Surface Charge of Pulp Fibers (original) (raw)

The externally exposed charge of pulp fibers plays a significant role in the inter-fiber bond formation. It is also beneficial for the necessary good adsorption of the additives used for paper manufacturing. The quantification of the polyelectrolyte adsorption capacity of the fibers is a common method used to measure surface charge. A linear cationic polyelectrolyte with high charge density, the pDMDAAC (poly-DiMethylDiAllylAmmonium Chloride) with a molecular mass higher than 100,000 Daltons, is used under the assumption that it does not penetrate the micropores of the cell wall. In order to build the adsorption isotherm, pulp samples are added to solutions of different concentration of pDMDAAC and after equilibrium is reached, the concentration of polymer in the solution is determined by polyelectrolyte titration. We propose a simple equation that can be very useful to measure the surface charge since it allows analyzing the isotherms with a uniform criterion.