Date of Award
8-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
Committee Chair/Advisor
Andrew G. Tennyson
Committee Member
Rhett C. Smith
Committee Member
Shanna L. Estes
Committee Member
Byoungmoo Kim
Abstract
This dissertation investigates the development of sulfur-based composites from elemental sulfur and diverse waste-derived feedstocks, including agricultural residues, food waste, brown grease, poultry byproducts, and lignocellulosic fillers. By combining abundant industrial sulfur with renewable and underutilized organic waste streams, this work aims to transform low-value materials into high-performance composites that may serve as sustainable alternatives to cement-based construction materials. Emphasis is placed on understanding how feedstock composition, chemical modification, filler selection, and reinforcement strategies affect mechanical strength, thermal behavior, water resistance, processability, and recyclability. Collectively, this dissertation demonstrates the potential of waste-derived high sulfur-content materials as environmentally friendly alternatives to conventional cementitious and petroleum-based systems while supporting broader circular economy objectives. Chapter One reviews recent advances in the use of nutshell-derived lignocellulosic waste as sustainable fillers and reinforcements in polymer composites and biocomposites. The chapter emphasizes how filler type, particle size, loading, processing conditions, and surface modification influence mechanical, thermal, tribological, moisture-resistance, and biodegradation behavior across different polymer matrices. It also discusses key challenges, including filler dispersion, interfacial adhesion, moisture uptake, scalability, and long-term durability, while highlighting the potential of nutshell waste as a low-cost, eco-friendly alternative to conventional reinforcements. iv Chapter two investigates the upcycling of mixed-material waste using elemental sulfur to prepare high sulfur-content materials (HSMs). The chapter focuses on combining petroleum-refining sulfur waste with food-derived waste streams, including peanut hulls, peanut oil, and post-consumer French fries, through inverse vulcanization. It evaluates how the composition of these waste-derived feedstocks influences the chemical, thermal, morphological, mechanical, and environmental properties of the resulting materials. The chapter highlights that these HSMs are remeltable, mechanically robust, and capable of achieving compressive strengths comparable to or superior to those of ordinary Portland cement, while also demonstrating favorable green chemistry metrics, including high atom economy, a low E-factor, and a low global warming potential. Chapter three investigates the upcycling of brown grease, a high-free fatty acid waste from the food industry, into high sulfur content materials through esterification followed by inverse vulcanization. The chapter focuses on modifying brown grease with methyl or allyl groups to improve its miscibility with molten sulfur and avoid the need for transition metals or food-grade compatibilizers. It evaluates how these chemical modifications affect crosslinking, homogeneity, sulfur incorporation, thermal behavior, and mechanical performance. The chapter highlights that the resulting materials are remeltable, thermally stable, and mechanically promising, with some compressive strengths exceeding the minimum requirement for residential foundation-grade cement. It also emphasizes improved upcycled mass efficiency compared to earlier brown grease-based sulfur composites. v Chapter four investigates the use of low loadings of liquid polybutadiene to reinforce brown grease-derived HSMs. The chapter focuses on two sulfur-rich matrices, SunBG90 and aBG90, and evaluates how adding 0.5–2 wt. % polybutadiene affects stiffness, flexural behavior, thermal stability, and reprocessability. The results show that polybutadiene significantly increases storage modulus, especially in aBG90, while flexural properties respond in a more complex, non-linear way depending on matrix compatibility and additive loading. Overall, the chapter highlights polybutadiene reinforcement as an effective strategy to improve the mechanical performance of bio-derived sulfur polymers while maintaining thermal robustness and remeltability. Chapter five investigates post-modification strategies to tune the properties of RWS90, a high sulfur-content material prepared from mixed post-consumer fast-food waste. The chapter focuses on modifying RWS90 with low loadings of polybutadiene and multifunctional thiols to evaluate how these additives affect network structure, thermal behavior, stiffness, flexibility, and mechanical performance. Polybutadiene incorporation maintained thermal stability and remeltability but did not produce systematic improvements in flexural strength or modulus. In contrast, thiol modifiers produced functionality-dependent effects: dithiols formed more flexible materials with lower stiffness, trithiols improved stiffness at low loadings, and tetrathiols produced more rigid but brittle materials. Overall, the chapter demonstrates that multifunctional thiols are more effective than polybutadiene for tuning the stiffness of RWS90 and highlights crosslinker functionality as an important factor controlling the mechanical response of sulfur-rich polymer networks. vi Chapter six explores the reinforcement of a chicken fat/sunflower oil-based HSMs, GFS90, using poultry-industry and lignocellulosic waste additives. The chapter evaluates eggshell powder, feather meal, peanut hulls, sawdust, and eggshell/feather meal blends as fillers and compares their effects on density, water uptake, thermal properties, and compressive strength. The results show that most composites exhibit negligible water absorption and compressive strengths above the ordinary Portland cement benchmark, with the peanut hull-reinforced material giving the strongest performance. Overall, the chapter highlights the potential of agricultural and poultry-derived waste additives to produce water-resistant, mechanically robust sulfur composites for sustainable construction applications.
Recommended Citation
Guerra de Souza Guinati, Barbara, "Upcycling Mixed-Material Waste Into Reinforced Sulfur-Based Polymer Composites" (2026). All Dissertations. 4361.
https://open.clemson.edu/all_dissertations/4361
Author ORCID Identifier
https://orcid.org/0000-0001-7415-5687