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  • Surface and sorption properties of modified polyamide 6 : thesis submitted to the Natural Science Faculty of the Karl-Franzens University in Graz in partial fulfilmemt of the requirement for the degree Doctor in Natural Science
    Tušek, Lidija
    The structural and surface properties of PA 6, which is one of the most widely used semicrystalline engineering thermoplastic and one of the most important synthetic textile fibres were studied in ... this work. The structural modifications were applied to three different forms of PA 6 resulting from the use of various processing methods: (1) a thin film, spin-coated on a silicon wafer, (2) a freestanding film, i.e. foil and (3) two monofilaments. Annealing in a vacuum at 195°C causing recrystallization and shrinking, and treatment in a 4% phenol solution causing reorganisation due to swelling and breaking of hydrogen bonds modified the structures of the used PA 6 materials. The achieved results were evaluated regarding changes of surface and sorption properties. The modifications were characterised using AFM (topographic images, dimensions of characteristic features, roughness), contact angle (wettability), streaming potential measurements (surface chargeas a function of pH and dye concentration) and VIS spectrophotometric monitoring of anionic dye sorption (accessibility for dyes). The AFM images disclosed isolated spherulites on the surface of the thin film. The morphology of much thicker foils can be interpreted as a system of overdeveloped spherulites and both monofilaments showed a typical fibrillar structure. The annealing caused enlargement of the film's spherulites, resulted in higher and bigger structural features on the surface of the foil and induced the joining of the smallest filaments' fibrils and fibril bundles into wider fibril bundles. The contact angles and negative zeta potentials at pH of 9 increased, indicating more hydrophobic surfaces. The annealed materials are also the least accessible samples of all, with the lowest and the slowest rate of dye sorption. The phenol treatment loosened the structures of all PA 6 materials resulting in fuzzy structures based on destroyed spherulites or fibrils. These materials have superior wettability and accessibility for small ions and dyes. The sorption of dyes is the quickest and quantitatively the highest. The PA 6 foil was also treated with low-pressure NH3 plasma that modifies the chemical structure of the surfaces giving rise to N-functionalities and thus more cationic character to the surface. The introduced functionalities were observed by streaming potential measurements (surface charge), XPS analysis (nature of introduced functionalities), AFM (surface topography), and contact angle measurements (assessment of treatment effect). The results showed that the introduction ofN-containing groups increases with longer treatment times only to a certain extent where the negative effect of surface destruction prevails over the positive effect of the introduction of functional groups. The treatment causes a shift of the isoelectric point toward pH of 6.3 as compared to 4.0 found for the untreated foil. If the treatment time is longer than 1 min the isoelectric point is shifted to lower pH, the number of amino groups on the surface is reduced and the contact angle is increased.
    Vrsta gradiva - disertacija
    Založništvo in izdelava - Graz : [L. Tušek], Februar 2003
    Jezik - angleški
    COBISS.SI-ID - 7772950

Knjižnica Signatura – lokacija, inventarna št. ... Status izvoda
Knjižnica tehniških fakultet, Maribor pisarna A-003 (FERI) DD TUŠEK L. SURFACE prosto - za čitalnico
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