Date of Award
Doctor of Philosophy (PhD)
Andrew G Tennyson
Stephen E Creager
The consumption of traditional plastics continues to climb to meet increasing consumer needs, despite growing awareness that these petrochemical-derived materials are detrimental to the environment. Sustainability scientists are faced with the task of trying to replace some of these materials with sustainably sourced compounds, leading the industry away from fossil fuel-derived monomers. Fatty acid derivatives have proven to be versatile sources for monomers. As constituents of several high-volume and low value waste streams and, given their origins in plant and animal sources, fatty acid derivatives are an ideal starting material. The presence of alcohol, carboxylic acid and olefin functional groups also makes fatty acid derivatives quite versatile for use in a panoply of polymerization techniques. Reactions, such as the thiol-ene reaction and inverse vulcanization, in combination with fatty acid starting materials have been recently employed to produce sustainable plastic-type materials, and overview of which is highlighted in Chapter 1. Inverse vulcanization to prepare materials featuring elemental sulfur as the majority component will be the main route investigated in subsequent chapters. Chapter 2 focuses on the reaction of varying amounts of commercially available oleic acid, a monounsaturated fatty acid, with elemental sulfur. A key discovery in this work is that the addition of zinc oxide can suppress the evolution of dihydrogen sulfide, a toxic byproduct of the reaction. Characterization of the materials, thermal stability and recyclability are discussed. While the use of oleic acid in inverse vulcanization served as proof-of-concept, the ultimate goal is to use fatty acids found in low-value, high volume waste products from animal rendering and biodiesel refining. In Chapter 3, to begin to mimic waste products, polymers synthesized from the inverse vulcanization of elemental sulfur and a commercially available blend of fatty acids, containing saturated, mono-, di-, and poly-unsaturated fatty acids, were compared to those prepared with a pure diunsaturated fatty acid. Both classes of materials exhibited robust thermal and mechanical properties, providing an incremental step towards valorization of waste materials. Chapter 4 showcases efforts to increase the sustainability of the synthesis, while also addressing the environmentally deleterious production of Portland cement. Sulfur-based cement products are increasing in popularity as the cost of Portland cement-based materials soars. Couple that with the exceedingly high CO2 emissions from Portland cement production, and the need for cleaner alternatives is clear. Pozzolans, such as fly ash, silica fume, ground granulated blast furnace slag, and metakaolin, have been studied as alternative cementitious materials. When combined with oleic acid, a marked improvement on properties like acid resistance and thermal healing were noted for the pozzolan-sulfur-fatty acid cements when compared with ordinary Portland cement.
Smith, Ashlyn Dennis, "High Sulfur-Content Materials from Free Fatty Acids" (2020). All Dissertations. 2714.