Date of Award
5-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Automotive Engineering
Committee Chair/Advisor
Srikanth Pilla
Committee Member
James Sternberg
Committee Member
Craig Clemons
Committee Member
Morteza Sabet
Committee Member
Hongseok Choi
Abstract
The commercial epoxies market in automobiles has been growing mainly in terms of usage as automotive coatings and lightweight composite structures manufacturing. Most of these commercial epoxies are bisphenol-based. Bisphenol-based epoxies are a class of high-performance polymer materials that, when cured, yield thermosets with high mechanical, thermal and chemical resistance properties. Roughly, North America produces around 123 billion pounds of these epoxies which are used in various industrial applications like coatings, composites, structural parts, automotive, electronics, construction etc. These epoxies are mainly manufactured from bisphenol-A (BPA) and epichlorohydrin (EPH). These raw materials are sourced from fossil fuel resources and are acutely toxic and carcinogenic. With emerging environmental concerns on climate and atmosphere, raw materials not sourced from fossil fuels are vital. In addition, the toxicity of these chemicals imposes an alarming threat to human health and other bio-ecosystems’ safety. Based on a survey during the life cycle of these plastics in various applications, roughly 1 million pounds of BPA is released into the environment. All these concerns impose the need for more eco-friendly and sustainable plastic materials.
The sustainability of epoxies would be enhanced by using a biobased material and preventing the usage of epichlorohydrin and bisphenol-A. Of available epichlorohydrin-free biobased epoxies, the existing methods employ allyl bromide which is still acutely toxic and carcinogenic. Some vegetable oil-based epoxies do employ green methods in their synthesis. However, these epoxies are from non-aromatic sources and have poor mechanical and thermal properties. In this work lignin from biomass is chosen as a suitable sustainable replacement for these toxic chemicals in manufacturing bio-based epoxies through a non-toxic route. The use of lignin has the advantage of targeting high-performance epoxy applications. Currently no route exists to make epoxies from lignin without using epichlorohydrin or allyl bromide in the process. So, the scope of the work was developing an epichlorohydrin-free way of making epoxies from Kraft lignin. Vanillic acid was used as a model compound to build and test the sustainable route using organic carbonates and peracids. Initial trials with model compound showed high conversion rates enabling a path forward for Kraft lignin. Future work will study how to increase epoxy equivalent weight and create materials with similar mechanical and thermal properties as commercial epoxies. Future work will also include using greener solvents for epoxidation to improve the overall sustainability of the epichlorohydrin-free protocol.
The other scope was to develop a one-step method to make sustainable epoxy precursors and recycle them. A one-step strategy was designed to extract and functionalize lignin directly from biomass. A new solvent was designed for this purpose and the reaction was carried out in the Parr reactor under controlled conditions. The obtained lignin’s chemistry was characterized using spectroscopic analysis. This work proves that lignin-based epoxy precursors could be synthesized through a sustainable non-toxic route in one step.
Recommended Citation
Ganesan, Kavya, "Green Chemistry Design Of Epoxies From Biomass For Circular Economy" (2024). All Dissertations. 3609.
https://tigerprints.clemson.edu/all_dissertations/3609