Date of Award
12-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Materials Science and Engineering
Committee Chair/Advisor
Dr. Igor Luzinov
Committee Member
Dr. Marek Urban
Committee Member
Dr. Thompson Mefford
Committee Member
Dr. Olga Kuksenok
Committee Member
Dr. Viktor Balema
Abstract
Polyolefins (POs) are inexpensive engineering materials with excellent physical and mechanical properties, accounting for nearly 60% of all thermoplastics. However, large-scale recycling remains limited, with only ~15% undergoing mechanical recovery. This dissertation addresses this challenge by fragmenting and functionalizing polypropylene (PP) chains to generate macromonomers and employing them, along with industrial reactive PP macromonomers, to synthesize, depolymerize, and repolymerize chemically recyclable polypropylene-based polyolefins (CR-POs). These CR-POs incorporate ester linkages that form covalent adaptable networks (CANs), maintaining a gel fraction of ~70% while remaining melt-reprocessable via extrusion and compression molding.
First, the fragmentation of PP is investigated by microwave irradiation. Microwave heating effectively localizes fragmentation without significant thermal oxidation, and silicon carbide is identified as an efficient microwave absorber that promotes PP chain scission. Next, solution-grafting efficiencies of maleic anhydride onto PP are established, enabling controlled preparation of maleinated PP macromonomers for CAN fabrication. A simple methodology is developed to introduce ester links into PP using an epoxy-based cross-linker and ZnCl2 catalyst, producing CR-POs with excellent processability and mechanical properties suitable for engineering applications.
Efficient chemical depolymerization of CR-POs into high-quality recyclates is achieved using zinc(II) acetate. In addition, the properties of CR-POs are tailored by using different cross-linkers—1,4-butanediol diglycidyl ether, bisphenol A diglycidyl ether, and poly(ethylene-co-glycidyl methacrylate), enabling systematic control over thermal stability, glass transition temperature, mechanical moduli, strength, and strain.
Overall, this work presents new strategies for creating chemically recyclable PP-based materials and demonstrates their potential as reprocessable, high-performance polyolefins for a circular, low-waste polymer economy.
Recommended Citation
Tiiara, Andrii, "Synthesis and Characterization of Chemically Recyclable Polyopropylene-Based Covalent Adaptable Networks" (2025). All Dissertations. 4109.
https://open.clemson.edu/all_dissertations/4109
Author ORCID Identifier
0009-0000-8486-1753