Date of Award
12-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
Committee Chair/Advisor
Prof. Rhett C. Smith
Committee Member
Prof. Andrew G. Tennyson
Committee Member
Prof. Byoungmoo Kim
Committee Member
Prof. Leah Casabianca
Abstract
The growing environmental impact associated with conventional plastics and construction materials has intensified the global demand for sustainable alternatives. Sulfur-based composites are one of the promising alternatives to overcome these challenges. This dissertation focuses on the development of sulfur-based composites using agricultural waste lignin and industrial waste elemental sulfur to create high performance, environmentally friendly materials that support circular economy goals and offer viable replacements for traditional cement and petrochemical systems.
Chapter one reviews the most recent advancements in multi-component flame-retardant systems that utilize bio-derived phenols, polysaccharide derivatives, and green phosphorus sources. Lignin, tannins, alginate, cellulose, starch, chitosan, and phytic acid have been discussed as promising natural additives to enhance flame retardancy, thermal stability, and smoke suppression in polymers. Further, key challenges and future directions for incorporation of green additives into conventional polymers are discussed.
Chapter two explores recent innovations in lignin modification techniques and their integration into diverse polymer matrices including polyurethanes, epoxy resins, phenol-formaldehyde resins, and elastomers. The property enhancement of the lignin-derived polymers, due to lignin’s structural diversity and reactive functionalities is discussed in detail. Furthermore, the chapter highlights lignin’s applications in developing green materials used in construction, packaging, textiles, and wastewater treatment, discussing its role in circular materials economy and bio-based industry transformation.
Chapter three investigates the reactivity between different lignin model compounds and elemental sulfur, under various sulfur ratios and thermal conditions. This chapter mainly focuses on the lignin derivatives with olefin functionalities which can undergo inverse vulcanization at 180 °C and S–Caryl bond formation at 230 °C. Using the 1H NMR and GC-MS studies, we have investigated that compounds undergo S–Calkyl, S–Callylic/benzylic, S–Caryl bond formation, isomerization, intramolecular cyclization, C–C s-bond scission, C–O s-bond scission and desulfurization at different temperatures. This fundamental understanding of biomass and sulfur interactions opens new possibilities for designing sulfur-based functional materials from renewable feedstocks.
The valorization of lignin and sulfur into high sulfur-content materials (HSMs) is presented in chapter four. Lignin-derived guaiacol and syringol were reacted with elemental sulfur to yield GS80 and SS80 composites, respectively. Structural characterization confirmed the formation of diverse sulfur–carbon linkages. Thermo-morphological and mechanical property analysis showed that SS80 exhibits higher thermal stability and superior mechanical properties compared to GS80 and C62 construction bricks. These findings demonstrate the feasibility of lignin–sulfur composites as sustainable substitutes for conventional construction and structural materials.
Chapter five introduces a novel sequential crosslinking strategy combining radical-initiated sulfur polymerization (RASP), inverse vulcanization, and sulfenyl chloride bond formation reactivity. The synthesis of DAClS51 terpolymer from 2,4-dichloro-3,5-dimethylphenol (DDP), sulfur and O,O′-diallylbisphenol A (ABPA) illustrates efficient utilization of toxic byproducts like S2Cl2. The findings from the thermo-morphological and mechanical property analyses highlight the potential of integrating diverse sulfur–carbon bonding pathways and waste valorization into the design of sustainable polymers for a wide range of applications.
Recommended Citation
Kapuge Dona, Danushi Nawoda Lakrandi, "Development of Sulfur-Based Composites From Agricultural and Industrial Waste for Sustainable Materials" (2025). All Dissertations. 4182.
https://open.clemson.edu/all_dissertations/4182
Author ORCID Identifier
0009-0009-3829-0561