THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provision of the regulations for the degree

DOCTOR OF PHILOSOPHY

On Thursday December 12, 2019

11:00 AM

in MRDC 3403

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Luc Le

“Development of a High-Performance Reversible Crosslink Epoxy Composite by Using Diels Alder Chemistry”

Committee Members:

Prof. Karl Jacob, Advisor, MSE/ME

Prof. Kyriaki Kalaitzidou, Co-advisor, ME/MSE

Prof. Paul Russo, MSE/CHEM

Prof. Youjiang Wang, MSE

Prof. Anselm Griffin, MSE

Abstract:

With a combination of  high mechanical strength, thermal stability, and chemical resistance, thermoset polymer meets the standard specifications of multiple industries in both commercial/industrial and residential applications. For example, thermoset polymer is extensively used in a wide variety of industries such as manufacturing of electrical components for electronic materials and packaging, producing a small scale of durable goods for households and sports to a large scale of heavy-duty construction equipment, and fabricating interior frames and structures materials for aerospace and automotive industry, etc. One of the workhorses in thermoset polymer is epoxy-based resin. Epoxy is one of the most representative of thermoset polymer because of its characteristics of high heat resistance, good chemical and corrosion resistance, high tensile strength, high modulus, high adhesion, low percent shrinkage in cure,  and excellent adhesion to various substrates, etc. However, the only pitfall of thermoset is the non- recyclable at the end of their usage because of the irreversible and permanent chemically cross-linked nature. Therefore, most of the thermoset-based products end up in landfills or are incinerated after their functional use. Owing to the serious concern regarding the environment and the finite natural resources, new recycling technologies for thermosetting resins are urgently needed. The solution of this problem is to create a dynamic covalent adaptable network (CAN) via reversible chemical reaction to replace the permeant crosslink nature of traditional thermoset.

The focus of this research has been to develop strategies for repairing of damage and recycling of their end uses in the epoxy polymer composites through the use of the Diels-Alder reaction of a furan and maleimide, which forms an adduct at 60-90 oC, but reverts to the reactants at increased temperatures of 120-150 oC. Particularly, the goal is to selectively apply the Diels-Alder reaction to bio-based epoxy polymer composites in such a way that damage can be healed through adduct formation across a crack and the recycle process can be performed at the end usage while maintaining the thermal stability and mechanical properties that make composites desirable in many applications.

The efficacy of the CAN polymer and its mechanical properties strongly depend on the architecture of the prepolymer furan grafting epoxy and structure of the maleimide crosslinker. In order to engineer a robust remendable/recyclable polymer system with focus on restoration of mechanical property, the first objective is to able to synthesize and control the furan grafting density and molecular weight of furan-grafting epoxy.  The second objective is to understand the thermodynamic and kinetic of thermal reversible crosslink between the furan and maleimide in the polymer network. This knowledge allows for understanding the process parameters of curing procedure as well as developing the remendable/recyclable methods. The third objective is to investigate the effects of prepolymer and crosslinker’s architecture on its overall mechanical properties and recyclable efficiency. The result of this study will sort out the best combination of prepolymer and its crosslinker to have a high performance remendable/recyclable polymer system. Finally, the last objective is to determine if modified cellulose filler with dienophile characteristic enhances the mechanical strength and remendable/recyclable of previous optimized polymer system.