Bio-based additives for sustainable polymer and rubber applications: design, synthesis, and functional performance

The ongoing environmental crisis, exacerbated by human activities, has led to resource depletion and severe pollution of air, soil, and water. Among the contributors, plastic pollution stands out due to its long-term persistence and escalating production. Addressing this issue requires sustainable alternatives to petroleum-based plastics and additives. This PhD research develops and optimizes bio-based plasticizers and additives to reduce the environmental footprint of polymer and rubber industries without compromising performance or scalability. A core focus of this work is the synthesis of Glycerol Trilevulinate (GT), a bio-based plasticizer derived from renewable feedstocks like glycerol and levulinic acid. GT was designed to enhance the mechanical properties, thermal stability, and processability of polymers such as polylactic acid (PLA) and polyhydroxybutyrate (PHB), which, despite their bio-based origins, face mechanical and processing limitations. Using techniques like solvent casting and molten processing, GT demonstrated significant improvements in flexibility, crystallinity, and thermal behavior, enabling suitability for industrial applications like extrusion, injection molding, and 3D printing. Comparative studies with conventional plasticizers such as DINCH and ATBC highlighted GT's superior biodegradability, migration resistance, and stability, along with its low toxicity profile, underscoring its potential for sustainable polymer systems. Beyond bioplastics, this thesis explores GT in natural rubber (NR) and epoxidized natural rubber (ENR), enhancing their flexibility, crosslinking behavior, and recyclability. GT combined with hexamethylene diamine (HMDA) enabled the development of a bio-based, reversible crosslinking system for ENR, aligning with circular economy principles. Additionally, the synthesis and application of Triphenyl Acetic Glyceroate (TPAG) for food packaging materials were investigated, offering solutions to improve PLA's mechanical and barrier properties. This research demonstrates the potential of bio-based additives to reduce reliance on fossil-based resources, minimize plastic waste, and foster sustainable materials for diverse industrial applications.