Date of Award
Doctor of Philosophy (PhD)
Rhett C. Smith
Green gas emission has been a pervasive and persistent subject of debate for a prolonged period. The soaring number of industries and vehicle fuel emissions presage a concomitant rise in global CO2 emissions. Global cement production is responsible for 8% of the total CO2 release, yet, the production continues due to the surging demand. Hence, there is an ongoing quest to find alternatives for cement and building materials produced with zero to lower CO2 emissions. The work presented in this dissertation focuses on finding recyclable, zero CO2 gas-producing high sulfur biocomposites materials, which can compete with the mechanical properties of commercial building materials like Portland cement.
Chapter one describes the biopolymer substitution for commercially derived polymers. There is an emerging interest in substituting sustainable biopolymers fully or partially to the most commonly used commercial polymers. Lignin being the most abundant aromatic biopolymer, the tendency to use it as an alternative to commercial polymers is high-pitched. Technical issues associated with lignin incorporation and the impact of mechanical properties are specially discussed.
Chapter two elaborates the preparation of sulfur crosslinked lignin composites through inverse vulcanization. The accomplishment of High Sulfur Materials (HSMs) with a biopolymeric agent to secure a stabilized network of sulfur is discussed. The mechanical, thermal properties, and mechanical integrity in recyclability are also examined.
The work delivered in chapter three is about a new substrate development to access high sulfur materials as opposed to the traditional olefinic units in inverse vulcanization. The Radical induced Aryl halide Sulfur Polymerization (RASP) expands the substrate scope for high sulfur polymers. Two unmodified wastes – chlorolignin and sulfur were used as the most effective substrates to assess this concept. The materials’ thermal/mechanical properties and mechanical integrity over water absorption and harsh acidic conditions analogs to commercial building materials are discussed.
The RASP can be employed with small molecules containing halide atoms. Chapter four presents the work performed with the small molecules to fabricate high sulfur polymers. A HSM was prepared by copolymerizing 81wt.% of elemental sulfur with a xylenol derivative to result in a composite wherein the sulfur is distributed between crosslinking chains and trapped free sulfur, which is not covalently bound. The mechanical properties of the same were compared to previous RASP polymers and the commercial building materials.
Chapter five focuses on developing an easy route to make high sulfur polymers by employing organic molecules that generate radicals or radical reactive species via thermal degradation. Here, guaiacol ̶ a vast abundant lignin biopolymer precursor, and sulfur were directly reacted to form a stabilized matrix to retain polymeric sulfur. The microstructures analysis was done using NMR and GC-MS studies to identify possible mechanistic pathways.
Karunarathna, Menisha S., "Sustainable Composites from Agricultural and Petroleum Waste" (2022). All Dissertations. 3052.
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