Oberflächenanalytische Untersuchungen an nasschemisch, photochemisch und photothermisch modifizierten Titandioxid-Oberflächen
To find an approach for reusable offset printing plates hydrophobic and hydrophilic modified Titanium Dioxide surfaces (TiO2 surfaces) were studied with regard to macroscopic wetting properties and molecules relevant for wettability. The macroscopic wetting behaviour was studied by Contact Angle measurements and calculation of surface free energy Sigma. Surface end groups responsible for the wettability could be detected for hydrophilic and hydrophobic TiO2 surfaces by Infrared Spectroscopy (FTIR) and X-Ray Photoelectron Spectroscopy (XPS). Surface topography and the arrangement of molecules on different modified TiO2 surfaces were measured with an Atomic Force Microscope (AFM). In addition measurements with the Friction Force Mode (FFM) of the AFM led to nanoscopic values of the adhesion force for hydrophobic and hydrophilic TiO2 surfaces. Therefore hydrophobic AFM tips were used and measurements were carried out in water. The changes in adhesion forces on TiO2 surfaces which were two-dimensionally micro-structured in hydrophilic and hydrophobic areas could be imaged as well by FFM. On such structured surfaces the distribution of elements was determined by the two-dimensional mapping of X-Ray Photoelectrons (XP-Mapping). To carry ink in the offset printing process hydrophobic TiO2 surfaces were prepared by covering initially hydrophilic TiO2 surfaces with adsorbates (hydro-carbons) by storage in air or by dipping in 1 mM ethanolic solutions of octadecyl phosphonic acid (OPA) or semiperfluorinated octadecyl phosphonic acid (SF-OPA). The contact angles for such surfaces were in the range of 50-80° for TiO2 surfaces stored in air and in the range of 80-150° for TiO2 surfaces covered with OPA or SF-OPA. Hydrophilic TiO2 surfaces could be generated by wet chemistry (NH4OH:H2O2:H2O) as well as by selective irradiation with IR- or UV-Laser. Hydrophilic areas of an offset printing master represent the non-printing areas in the printing process.
info:eu-repo/classification/ddc/530, Titandioxid, Oberfläche, Modifizierung, Benetzung, Oberflächenanalyse, Offsetdruckplatte, Physik, TiO2-Oberflächen, Octadecylphosphonsäure, FTIR, AFM, XPS, Kontaktwinkel
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