Electrokinetic properties of processed cellulose fibers

Natural cellulose fibers (cotton) comprise several noncellulose compounds (hemicellulose, wax and pectin substances) and cationic impurities which cause problems during different adsorption processes such as dying, or final fiber finishing and coating. Therefore the chemical purification (NaOH boiling, enzymatic purification, demineralization, extraction or oxidative bleaching) is the most important step in cellulose textile finishing. Alternative ways to describe the success of different processes in fiber purification which result in distinct surface charge and hydrophilicity are the determination of electrokinetic properties and the water uptake of textile fibers. The zeta-potential (ζ) was determined by streaming potential measurement as a function of the pH. From the ζ–pH functions the adsorption potential for all ionic species Φ_i (i.e. (, in the case of potassium chloride solutions), the charge densities σ^k and the pK values are calculated according to the Börner and Jacobasch model.

The degradation and removal of hydrophobic noncellulose compounds which cover the primary hydroxyl and carboxyl groups of the cellulose polymer is clearly shown by an increase of the negative ζ of the plateau, which is in good agreement with the electrokinetic parameters of cotton samples determined by the Börner and Jacobasch model. The electrokinetic parameters determined by the Börner and Jacobasch model can be used to describe the adsorption/dissociation ability of textile fibers. The progress of the fiber processing (cleaning) is reflected by the surface charge as well as the hydrophilicity of the fiber.