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How does Carbon Dioxide Affect the Surface Zeta Potential?

The surface zeta potential is sensitive to the outermost surface chemistry of a material. Hydro-phobic polymer surfaces are prone to adsorption of carbon dioxide, which is dissolved in the aqueous measurement solution. This effect renders the material surface more acidic and affects its zeta potential. Nitrogen purge of the electrolyte solution prevents the dissolution of carbon dioxide from ambient air and thus allows for a highly reliable surface zeta potential analysis.

The stability of a solid surface or surface coating in an aqueous solution may be determined by the temporal change of the zeta potential at the solid-liquid inter-face. In general, a decrease in the negative zeta po-tential indicates an increasing surface hydrophilicity. For natural fibers this behavior is interpreted in terms of fiber swelling. After a fast initial decrease the zeta potential ap-proaches an equilibrium value. The experiment shows the same effect for a polypropylene foil. Bismarck et al. found a similar behaviour for polyamide and poly(ether ether ketone) and interpreted this phenom-enon in terms of swelling and the removal of surface-adsorbed soluble components. For rigid polymer films this behavior is more difficult to understand. This report demonstrates that the adsorption of carbon dioxide (CO2) dissolved in the aqueous solution is responsible for this phenomenon.

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