Composites from the Reaction of Elemental Sulfur with Post-Consumer Plastic/Packaging Materials and Food Waste

Plastic waste is a growing epidemic. While advancements have been made in the chemical recycling of plastics, most waste plastics are deposited in the environment or landfills where they leech into their surroundings, creating a threat to ecological health. The reaction of these waste materials with elemental sulfur, an underutilized byproduct of the fossil fuel refining industry, to create high-sulfur content materials is a promising route to address the chemical recycling of plastics and proposes alternative building materials to environmentally unfriendly mineral-based materials. Single-use plastics such as food and beverage packaging account for a significant amount of plastic waste. The recycling of these materials is complicated by their multilayer compositions and contaminants such as foodstuffs. The development of new routes to effectively address the plastic waste problem is crucial in developing a green and sustainable economy. The manufacture of legacy building materials such as ordinary Portland cement (OPC) and C62 building brick, a standard construction brick, are responsible for a large amount of carbon emissions. Finding competitive structural materials with a lower environmental impact is a key component to addressing climate change by reducing greenhouse gas emissions. The work presented in this dissertation focuses on recycling post-consumer plastic waste and multi-layer food packaging to produce high sulfur content materials with attractive mechanical and thermal properties. Chapter One reviews recent innovation in the recycling or upcycling of the most widely produced consumer plastics. The studies discussed in this chapter cover new methods or modifications of existing methods which achieve the best yields and recovery ii of product. Finding innovative methods for the recycling of different types of plastic waste is a necessity in creating a quintessential green economy. Chapter Two reports a method for recycling post-consumer poly(ethylene terephthalate) (PET) by functionalizing it with alkenes provided by plant oils and its reaction with elemental sulfur to create high sulfur content materials having properties competitive with commercial mineral-based building materials. Chapter Three reports thiocracking as a one-pot method for recycling bisphenol-A polycarbonate to a highly crosslinked polymer with properties competitive with traditional building materials. The mechanical, thermal, and morphological properties, and proposed microstructures are discussed. Chapters Four describes a thiocracking method for recycling multi-layer postconsumer food packaging with foodstuff remnants to high-strength composites with mechanical properties far exceeding those required of OPC. A detailed analysis of this material’s morphological, mechanical and thermal properties is discussed. Chapter Five reports a method for recycling post-consumer fast food restaurant waste with elemental sulfur. The various components of the fast-food meal waste material were recycled to high-strength materials in a one-pot method. The thermal, mechanical, and thermal properties of these composites are discussed.