Defending my Thesis
Author: Angelina Sagardui | Major: Chemical Engineering | Semester: Fall 2022
I have been synthesizing and characterizing aerogels from cellulose-starch mixtures for advanced packaging applications with the help of my mentor, Dr. Ali Ubeyitogullari of the Food Science and Biological & Agricultural Engineering departments, over the course of the Fall 2022 grant term. One of my interests with chemical engineering was the food and beverage industry, so I took Dr. Ali’s “Principles of Food Processing” during the Fall 2021 semester as a technical elective. I was very interested when hearing him discuss his research in supercritical carbon dioxide extraction and drying, so I reached out for him to be my thesis advisor.
Through my research, I sought to address glaring sustainability problems – i.e. depleting oil reserves and waste from food and non-biodegradable materials – by synthesizing a material from a couple of natural polymers, specifically microcrystalline cellulose (MCC) and corn starch, which have many attractive qualities not present in petroleum-based polymers – such as renewability, biodegradability, and being able to be recovered from food waste and agricultural by-products. The material was prepared through a green, safe, non-toxic process – specifically supercritical carbon dioxide (SC-CO2) drying. The resulting material is an aerogel – a noteworthy porous material in which gas replaces the liquid component while retaining its shape. Aerogels have been gaining interest from researchers due to having high porosity, large surface area, low thermal conductivity, and the lowest density of all recognized solids.
The specific objectives of this research were to (i) form nanoporous cellulose-starch aerogels using SC-CO2 drying, (ii) investigate the effect of cellulose-starch weight ratio on aerogel properties, and (iii) characterize the aerogels for their density, porosity, surface area, pore size, pore volume, texture, microstructure, crystallinity, surface chemistry, and thermal stability. Five weight ratios of samples were generated: pure MCC, 2:1 MCC-starch, 1:1 MCC-starch, 1:2 MCC-starch, and pure starch. Overall, the 1:2 MCC-starch aerogel had the lowest density and highest porosity. Conversely, the pure MCC aerogel demonstrated the highest mechanical strength, highest thermal stability, and highest specific surface area. These results indicate that these generated aerogels are promising insulators and advanced packaging materials, potentially serving as a sustainable alternative to Styrofoam.
However, I encountered several challenges throughout my research. I did some preliminary trials in the previous spring term, and it took several weeks to find an aerogel composition that worked. The most difficult part was managing my time to generate enough samples for the many characterization experiments. It would take a long time (1 to 3 weeks depending on the size) to make my samples with the setup and methodology that was followed, as there are many steps in the aerogel formation process that needed to be followed closely. It was also a struggle to find a thermal conductivity instrument that was sensitive to very low values and would not require a very large sample size. Despite the setbacks, all the time and hard work spent paid off, and it was very fulfilling to see the final product of my thesis.
None of this work would have been possible without the immense help and guidance of my mentor Dr. Ali Ubeyitogullari and his postdoc Dr. Safoura Ahmadzadeh, as well as the U of A Food Engineering for Health Research Group. Dr. Ali was very helpful in helping me come up with specific research objectives and the types of characterization experiments to perform. He also provided very beneficial suggestions and critiques on my manuscript and defense presentation. Dr. Safoura kindly provided invaluable guidance in the lab itself, such as helping me refine the aerogel methodology, teaching me how to operate the SC-CO2 extractor, and helping with the numerous characterization experiments since she was very experienced with the majority of the tests. This research was also very collaborative across the U of A, since a lot of the instruments had to be used from different departments. Dr. David Huitink and Dr. Ange Iradukunda from Mechanical Engineering and Dr. Jingyi Chen from the Chemistry department kindly helped with the thermal conductivity and thermal stability testing respectively.
Although I was not able to attend a research conference, I was able to successfully defend my thesis in November. I would also like to thank Dr. Heather Walker, Dr. Jamie Hestekin, and Dr. Griffiths Atungulu for supporting my Thesis Defense Presentation. While my thesis has come to a close, I have gained invaluable experience and lessons that I will take with me as I start my professional career in February working as Process Improvement Engineer at Eastman Chemical Company. Even though I have decided to pursue industry rather than research post-graduation, this research experience has taught me more about sustainable materials and various lab techniques as well as strengthened many soft skills (i.e. time and project management, communication, and cross-collaboration). I am very grateful to the Honors College for providing such a wonderful opportunity.