Browsing by Author "Liprini, Marehette Suzanne"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Developing marker technologies to probe complex polymers and products
    (Stellenbosch : Stellenbosch University, 2022-11) Liprini, Marehette Suzanne; Van Reenen, Albert; Lutz, Marietjie; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: Fluorescent imaging has proven to be a valuable tool across a wide variety of applications. It can help with detecting, locating and observing the interactions between different molecules. This study used fluorescence to evaluate interactions, provide detection and trace different components within complex polymer systems. Cellulose nanowhiskers (CNW) were isolated and characterized, then labelled using fluorescent labelling with fluorescein 5(6)-isothiocyante (FITC) and rhodamine B (RhB). The attachment of the fluorescent dyes was easily observed with fluorescence microscopy. Fluorescently labelled cellulose nanowhiskers (CNW) were incorporated into different crystalline fractions of two different types of polypropylene impact copolymers (CMR 648 and CMR 348). This part of the study focused on the visually assessing the interactions between the different crystalline fractions within polypropylene impact copolymers. The different fractions of the copolymers were first evaluated in the form of solvent-cast films. The solvent-cast films showed strong associations between the 30 oC fraction and the 60 oC fraction, as well as between the 60 oC fraction and the 80 oC fraction. The fluorescent images showed no strong association between the 30 oC fraction and the 80 oC fraction in the absence of the 60 oC fraction. The fraction interactions were also evaluated after mechanical agitation in the melt, followed by injection moulding. The injection-moulded samples showed the same interactions visually as observed with the solvent-cast films. The visual assessment after extracting the labelled 30 oC fraction and 60 oC fraction also showed that the labelled CNW did not migrate out of the fractions into which they were incorporated. The next section of this study focused on the detection of fluorescently labelled markers within paint samples. CNW labelled with fluorescent dyes were incorporated into two types of paint. The paint films were evaluated with confocal fluorescence microscopy and the different paint samples could be identified. The fluorescent markers could still be detected within the paint films even after accelerated weather testing by implementing confocal fluorescence microscopy (CFM), lambda scanning, and unmixing. The last part of the study focused on the release of ethyl formate from different polymer films of polylactic acid (PLA) and polyethylene glycol (PEG). The intrinsic fluorescence associated with the ethyl formate precursor, PLA and PEG was used to track the release of the ethyl formate after exposure to humidity and humidity with citric acid. The release could easily be tracked visually with CFM.