Theses and Dissertations

Advisor

Kundu, Santanu

Committee Member

Toghiani, Hossein

Committee Member

Pearson, Larry E.

Committee Member

Kim, Yunsang

Date of Degree

5-10-2024

Original embargo terms

Immediate Worldwide Access

Document Type

Dissertation - Open Access

Major

Chemical Engineering

Degree Name

Doctor of Philosophy (Ph.D)

College

James Worth Bagley College of Engineering

Department

Dave C. Swalm School of Chemical Engineering

Abstract

Synthetic plastics are intrinsic to modern human existence. Unfortunately, many challenges exist related to the accumulation of plastic waste, including greenhouse gas emissions, contamination of natural environments, and entrance into the food chain through microplastics. Therefore, new polymers are being developed that both compete with the capabilities and costs of petroleum-based plastics and have assured biodegradability. Through decades of research, plant oils have emerged as one of the leading options for alternative starting materials because of their feasibility for use in polymerization reactions, wide availability, renewability, and cost-effectiveness. In this work, cottonseed oil (CSO) and soybean oil (SBO) are successfully utilized to synthesize polymers with a range of promising properties. A nanocomposite was produced by incorporating cellulose nanocrystals (CNCs) into an epoxidized CSO (ECSO) polymer matrix. A significant improvement in properties such as tensile stiffness and strength, without any substantial decrease in extensibility or thermal integrity has been observed. This demonstrated that CNCs can be used to tune the CSO- based polymer properties. Enzymes are excellent alternatives to traditional catalysts as they eliminate the necessity of elevated reaction temperatures and pressures. Epoxidized SBO (ESBO) was polymerized using immobilized candida antarctica lipase B (Novozyme N435). The resulting polymer was inhomogeneous, with soluble waxy and insoluble solid components. Analyses of the soluble component indicated the formation of a multi-branched polymer, showing that a greener system may be used to produce ESBO-based polymers. It is necessary to test the biodegradability of biobased polymers to confirm their validity as alternatives to traditional plastics. Degradation of the CNC-incorporated CSO-based network polymer was characterized by submersing specimens into various aqueous media, including artificial seawater and saltwater, to simulate realistic end-of-use scenarios. Decomposition occurred due to hydrolysis of the many ester linkages within the polymer structure. The presence of CNCs appeared to enhance the rate of degradation. Overall, the hydrolytic susceptibility of the CSO-based network polymer was observed as enhanced by incorporating CNCs. In summary, this work demonstrates the viability of using plant oils and CNCs to produce biodegradable polymers with a range of properties, thus aiding in the effort to replace traditional plastics.

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