Graduate Studies
First Advisor
Lucia Fernandez-Ballester
Second Advisor
Antonella Esposito
Date of this Version
4-2024
Document Type
Article
Citation
A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science
Major: Mechanical Engineering and Applied Mechanics
Under the supervision of Professor Lucia Fernandez-Ballester
Lincoln, Nebraska, April 2024
Abstract
Poly(lactic acid), or PLA, is an increasingly utilized bio-sourced polymer with increasing value as a semi-crystalline material with good processing capabilities, making it a versatile material used in many applications. The main drawback of PLA is its slow crystallization kinetics, which has been improved with a variety of processing techniques and the use of additives or nucleating agents. This study uses a method called Self-Nucleation (SN) to increase the nucleation and crystallinity of the polymer by heating it to a temperature below melting, causing most of the polymer crystals to relax into the melt. Some crystal fragments or melt memory remain in the melt which can then serve as nuclei upon further crystallization during conditions that favor this transition.
This technique dramatically enhances nucleation density and overall crystallinity in the material and has potential as a simple, cost-effective method to increase nucleation in PLA. In this study, samples of various molecular weights and various D-isomer content in the PLA copolymer chain are studied using this technique to determine the range of the SN domain (Domain II) for each sample, and how this domain and the efficacy of the SN method changes with these variables. A non-isothermal protocol was utilized to minimize thermal degradation when kept at high temperatures and to show that SN can reasonably be utilized as a crystallization tool in a manufacturing environment where long isothermal treatments are impractical.
Advisor: Lucia Fernandez-Ballester
Comments
Copyright 2024, Shantell Wilson. Used by permission