Papers by Author: Volker Ribitsch

Abstract: The determination of electrokinetic properties such as the zeta-potential of polymer samples with classical methods is laborious and time-consuming. For this reasons, a reliable, fast, and easy to use measurement system based on streaming potential measurement was developed. In this novel measurement system, streaming potential is created by an oscillating flow of a small amount of electrolyte solution through the sample media. In addition, this setup allows direct titration and therefore time-resolved monitoring of changes in zeta-potential in a seconds timescale. With this instrument, the concentration- as well as the time-dependent adsorption behaviour of various non-ionic, anionic and cationic surfactants on a novel, regenerated cellulosic polymer was investigated. This new cellulose-based, fibrous textile polymer is permanently cationised, not only at the surface but throughout the whole fibre. The results show that even very low concentrations of surfactant, due to its charge and chemical composition, highly influence the surface charge of the polymer in a large range. Furthermore, the results for this new textile material are compared with other textile fibres, e. g. wool.

Abstract: Dispersions of colloidal particles of polycyclic aromatic hydrocarbons were obtained by nanosecond laser ablation. Aqueous suspensions of micron-sized crystals were irradiated with the second harmonic output of a Nd:YAG laser and converted into colloidal particles. Ionic and nonionic surfactants were used in the ablation process to stabilise the particles. Dispersions with good long term stability were obtained. A strong dependence of particle formation rate on laser fluence was found and the particle formation process is discussed on the basis of UV-Vis spectra and microscopic examination of the crystals.

Abstract: Zeta potential (ZP) of poly-tetrafluoroethylen (PTFE) and polyamide 6 (PA 6) foils was measured using the streaming potential method. All measurements were carried out in a flat cell where PTFE foils are usually used in electrokinetic measurements as a part of the measuring device, to form the channel and to achieve a proper distance between the foils surface of measured samples. The primary interest of the present work was to investigate the influence of pretreatment of PTFE foils on their electrokinetic properties in order to find out to what extent such pretreatment may affect measuring results of other samples and to develop a procedure of PTFE foils preparation with purpose to achieve the same initial conditions for all measurements.