Flame Retardancy of Polymer Nanocomposites based on Layered Aluminum Phosphate and Computational Study of Intercalation of Amines into α-Zirconium Phosphate and Adsorption of a Model Organic Pollutant
Date of Award
Master of Science (MS)
Jeanne M. Hossenlopp
James R. Gardinier
Layered metal materials, such as layered metal hydroxides, hydroxy double salts, and layered metal phosphates can be used for applications such as fire retardancy, ion exchangers, or removal of pollutants. Optimization of materials for these applications requires an understanding of their physical and chemical properties.
Part A: Flame retardancy of polymer nanocomposites based on taranakite
Taranakite with tunable interlayer spacing has been prepared and modified by sodium dodecyl sulfate (AL-SDS). The layered materials are used as the additive to study the fire retardancy of polymers, including polystyrene (PS), polypropylene (PP), and polyvinyl alcohol (PVA). The dispersion of taranakite was characterized by X-ray diffraction. The thermal stability of taranakite and polymer composites was assessed by thermogravimetric analysis, and the results obtained suggest that the presence of taranakite improved the thermal stability of the polymer composites. The onset degradation temperature and mid-point temperature increased with increasing loading of taranakite in PS, PP and PVA. An understanding of the degradation mechanism of the polymer/taranakite composites allows us to explore the potential role of this layered material in enhancing polymer fire retardancy. The fire retardancy properties of the polymer composites were evaluated by cone calorimeter (PS, PP) or by use of a micro cone calorimeter (PVA). Polymer composites containing taranakite have been shown to exhibit lower peak heat released rate (PHRR) compared with the virgin polymers, especially for PVA. The source of the reduction in peak heat release rate for non-polar polymers, such as PS and PP, is hypothesized to be due to the formation of char that slows down the burning process and the formation of ester groups during decomposition of the polymers. For a polar polymer, such as PVA, hydrogen bonding of the phosphate ion and polymer molecule at the first degradation step is likely to contribute to the improved thermal stability.
Part B: Computational study of intercalation of amines into a-Zirconium phosphate and adsorption of a model organic pollutant
a-Zirconium Phosphate (a-ZrP) is an example of a layered material that can be used as an ion exchanger. The intercalation of amines into the interlayer of a-ZrP, and the adsorption of chlorophenol by the modified a-ZrP, was investigated. The intercalated a-ZrP can be used to remove the organic pollutants from aqueous solution. Density functional theory using the B3LYP functional with a 6-311G* basis set was used to explain the previous experimental results.
Previous experimental work in our laboratory has focused on the adsorption of 4-chlorophenol by ZrP-DHDA, XRD and FTIR data suggest that chlorophenol and DHDA were co-intercalated in the d-space of a-ZrP. Density functional theory calculations were carried out in this work using phosphoric acid as simple model systems. Based on the computational results reported here, the driving force for the adsorption was found to be hydrogen bonding between the phosphate and chlorophenol.