Date of Award


Publication Type


Degree Name



Civil and Environmental Engineering


Jerald Lalman



Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


This thesis is focused on evaluating and statistically modelling the depolymerization of polylactic acid (PLA) and polyhydroxybutyrate (PHB) to their constituent monomers, lactic acid (LA) and 3-hydroxybutyric acid (3-HBa), respectively, via hydrolysis in sodium hydroxide (NaOH) or hydrochloric acid (HCl). In order to compare the ability of NaOH and HCl to depolymerize PLA and PHB to their constituent monomers, a 3-factor 3-level Box-Behnken Design (BBD) was used to assess the impact of particle size, temperature, and reaction treatment time. The associated levels of the experimental factors evaluated in the BBD were as follows: particle size (0.225 mm, 0.45 mm, and 1.77 mm); temperature (22.5°C, 40°C, and 60°C); and reaction treatment time (3 days, 5 days, and 10 days). The BBD experiments were used to statistically model the hydrolytic depolymerization using Minitab (Version 21, Minitab Inc., State College, PA). The three factor BBD experiments were conducted under the following conditions: PLA in 10 M NaOH, PLA in 10 M HCl, PHB in 10 M NaOH, and PHB in 10 M HCl. The results of the BBD experiments revealed that PLA and PHB can be hydrolytically depolymerized to their respective constituent monomers in NaOH and HCl. Results of the four BBD experiments in this study produced four statistically significant response surface models at the 95% confidence level.

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