Date of Award
Spring 5-2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Materials Science
First Advisor
Dr. Ram K. Gupta
Second Advisor
Dr. Serif Uran
Third Advisor
Dr. Timothy Dawsey
Keywords
Vitrimer, Bio-base, Mechanical Strength, Thermal Strength
Abstract
Epoxy thermosetting polymers are among the most versatile materials utilized across aerospace, automotive, construction, and electronic industries due to their exceptional mechanical strength, chemical inertness, and superior thermal stability. However, the majority of commercial epoxy resins are derived from non-renewable petroleum-based feedstocks such as bisphenol-A diglycidyl ether (DGEBA), which leads to inherent environmental challenges including non-biodegradability and the inability to be recycled or repaired after curing. These drawbacks arise primarily from the permanent covalent crosslinked architecture formed during the curing process, which prevents molecular mobility and reprocessability. To address these limitations, dynamic covalent chemistry (DCC) has emerged as a promising strategy, enabling the design of Covalent Adaptable Networks (CANs) or vitrimers — a novel class of polymers that combine the mechanical robustness of thermosets with the recyclability of thermoplastics. In such systems, dynamic covalent bonds can reversibly exchange under external stimuli such as heat, pH, or catalyst presence, allowing reprocessing, self-healing, and reshaping without loss of network integrity. In the present research, a fully bio-based epoxy vitrimer network was successfully developed by integrating vanillin-derived imine cross-linkers (VAN_HDA, VAN_BDA and VAN_EDA) with epoxidized hemp seed oil (EHSO) via oxirane ring opening reaction strategy. Initially, hemp seed oil underwent an epoxidation reaction using a peracid-mediated pathway to yield EHSO, which was confirmed through FT-IR and ¹H NMR analyses, demonstrating the formation of epoxy functionalities. The epoxy oxygen content (%EOC) was calculated as 7.53 g/100 g, accompanied by a substantial decrease in the iodine value from 148.76 g I2/100 g (HSO) to 23.85 g I₂/100 g (EHSO), verifying the conversion of double bonds into epoxide groups.
The synthesized Schiff-base (imine) crosslinkers, namely VAN_HDA, VAN_BDA, and VAN_EDA, were prepared via condensation of vanillin with respective aliphatic diamines, 1,2-Ethanediamine, 1,4-Butanediamine and 1,4-Hexane-diamine ), followed by comprehensive structural validation using FT-IR and ¹H NMR spectroscopy. These imine crosslinkers were then incorporated into the epoxy matrix through thermal curing of EHSO in the presence of 2-ethyl-4-methylimidazole (EMI, 1 wt. %) as a curing accelerator. The resulting vitrimer networks exhibited highly crosslinked yet dynamic architectures due to reversible imine exchange reactions. Thermal transition behavior investigated via Differential Scanning Calorimetry (DSC) revealed glass transition temperatures (Tg) corresponding to each crosslinker type, indicating the influence of diamine chain length on network flexibility. Thermogravimetric Analysis (TGA) further confirmed excellent thermal stability beyond 300 °C, while Mechanical testing demonstrated that the presence of dynamic imine bonds not only enhanced the tensile and flexural strength but also imparted reprocessability and self-healing efficiency, which are rarely achievable in conventional epoxy systems. Overall, this study establishes a sustainable, and mechanically robust epoxy vitrimer platform that effectively bridges the gap between performance and environmental responsibility. The developed vanillin–EHSO vitrimer network represents a significant step towards next-generation green thermosets capable of multiple life cycles, with potential applications in coatings, adhesives, and high-performance composites.
Recommended Citation
Patel, Varshikkumar R., "EXPLORING DYNAMIC IMINE BONDS IN HEMP-SEED OIL BASED REPROCESSABLE AND MECHANICALLY ROBUST EPOXY VITRIMER" (2026). Electronic Theses & Dissertations. 841.
https://digitalcommons.pittstate.edu/etd/841
