Organically modified montmorillonite has been extensively used as nanofiller in studies of polymer layered silicate nanocomposites, promising materials for today's automotive industry because the nano-materials reduce the overall weight of vehicle. However, industrial applications have not followed suit primarily due to cost/performance issues. Supercritical carbon dioxide is promising as an aid in the production of a fully exfoliated polymer layered silicate nanocomposite but has not been fundamentally studied in this regard at present. As the first stage in studies of using supercritical carbon dioxide for aiding the production of thermoplastic elastomer nanocomposites, this thesis investigates the influence of this unique supercritical fluid on the microstructure and surface chemistry of five organically modified clays. Four alkyl-based quaternary ammonium surfactants with different number and length of chains attached and one aromatic quaternary ammonium surfactant were chosen to vary the degree of C02-philicity exhibited by the organoclay. In a high pressure batch vessel, the different organoclays were suspended in the supercritical solvent at temperatures of 50°C and 200°C and pressures of 7.6 MPa and 9.7 MPa for a fixed time and then removed after depressurization at 0.2 MPa/s or 4.8 MPa/s. The structures of these treated clays were characterized by XRD, TEM, DSC, TGA, FT -IR, and SEM, and their chemical properties were analyzed by various methods including atomic absorption spectroscopy, and contact angle measurement. The potential role of water to favor the interaction between scC02 and an organoclay was also investigated. Solute-solvent interactions plasticized the organic modifier while suspended in the supercritical fluid, which resulted in greater chain mobility and further cation exchange. The results indicate that surfactants exhibiting a paraffin-type conformation within the galleries of the clay were most likely to experience significant basal expansion, provided the tilt angle was not already close to being perpendicular to the silicate surface. For those organoclays demonstrating basal expansion, it was noted that the resulting particle size was increased due to enhanced porosity. Water proved useful in clay expansion in certain cases and primarily while operating conditions allowed the co-solvent to remain adsorbed to the clay surface. / Thesis / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/23278 |
| Date | 08 1900 |
| Creators | Liu, Jinling |
| Contributors | Thompson, Michael, Chemical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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