Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 145098

145098 - Exchangeable Dynamic Bonds Facilitated Self-Healing Behavior in Epoxy Vitrimer: A Molecular Dynamic Study 

Epoxy resins have become deeply ingrained in modern society, finding applications in various domains ranging from transportation to household items, biomedical devices, and industrial machinery. However, their insoluble and infusible nature leads to significant waste accumulation after their initial use. Vitrimer technology presents promising prospects for fostering sustainability by creating recyclable and reprocessable thermosets. Epoxy vitrimers, feature reversible covalent crosslinks with dynamic bonds. These materials combine the desirable mechanical properties of thermosets with the reprocessability of thermoplastics, offering a pathway towards a more sustainable future. Furthermore, the interchangeable network grants vitrimers remarkable functionalities in reprocessing, self-healing, welding, reshaping, and recycling. Consequently, vitrimers offer promising alternatives to traditional thermosets across various applications, such as aerospace materials, electronic devices, everyday consumer products, and beyond.

In this study, we conducted a series of molecular dynamics simulations focusing on analyzing the self-healing performance of epoxy vitrimers. We use the Diglycidyl ether of bisphenol A (DGEBA) as epoxy resin and aminophenyl disulfide (AFD) as a hardener/crosslinker for epoxy resins. DGEBA is a liquid epoxy resin widely used for its excellent chemical and mechanical properties, making it one of the most prevalent thermoset polymers. The inclusion of AFD as a hardener enables the formulation of epoxy vitrimers endowed with reprocessing, repairing, and recycling attributes.The design of vitrimer composites with high glass transition temperature (Tg) and robust mechanical strength is a desire. We first performed MD simulations to determine the Tg. Our simulation results agree well with the experiment-measured value. The effects of nanofillers, such as carbon fiber and graphene oxide, on Tg are studied and validated with relevant experiments. The strain rate effect on mechanical response is also examined, and our simulation results reveal that the stiffness and strength of vitrimer are highly strain rate dependent. Furthermore, this study underscores the remarkable capability of the epoxy vitrimer to restore its original shape after unloading, which demonstrates its potential as a self-healing material. The self-repair MD simulations are carried out, and the results prove the ability of epoxy vitrimer to repair the crack and hole under heat treatment due to the dynamic exchangeable covalent bonds within its network structure. Finally, the presence of exchangeable crosslink networks introduces remarkable attributes of stress relaxation and shape memory. The dynamic crosslinks facilitate stress relaxation by adjusting their configuration under sustained strain, thereby improving the longevity of the material. Additionally, these reconfigurable crosslinks endow the material with a shape memory effect, enabling it to revert to its pre-deformation shape upon exposure to a trigger like heat. In our MD simulations, a self-healing criterion is defined to determine whether the self-healing is successful or not.

In conclusion, this study offers a detailed molecular-level understanding of the self-healing performance of epoxy vitrimers. The unique characteristic of a vitrimer to dynamically reform its covalent bonds during thermal cycling enables it to exhibit enhanced performance compared to conventional thermosets, including the ability to self-heal damage. The findings pave the way for optimizing the design and synthesis of self-healing materials, with potential applications in areas such as coatings, adhesives, and composite materials. The research also underscores the power of molecular dynamics simulations as a tool for studying complex material behaviors and guiding experimental work in material science

Presenting Author: Amin Kuhzadmohammadi Baylor University

Presenting Author Biography: Amin Kuhzadmohammadi is a dedicated and passionate researcher, currently pursuing his PhD at Baylor University. He holds a master’s degree in Mechanical Engineering from the prestigious University of Tehran in Iran. His master's thesis focused on the investigation of the mechanical properties of crumpled graphene, utilizing molecular dynamics for his research.
Currently, Amin is engrossed in his work on green vitrimer, demonstrating his commitment to sustainable and innovative research. His academic journey reflects his deep interest in Mechanical Engineering and his dedication to contributing to the field through rigorous research. Amin's work is characterized by his meticulous approach to research and his ability to apply complex concepts to real-world problems.

Authors:

Amin Kuhzadmohammadi Baylor University
Ning Zhang Baylor University