College - Author 1
College of Engineering
Department - Author 1
Materials Engineering Department
Degree Name - Author 1
BS in Materials Engineering
College - Author 2
College of Engineering
Department - Author 2
Materials Engineering Department
Degree - Author 2
BS in Materials Engineering
Date
6-2026
Primary Advisor
Trevor Harding, College of Engineering, Materials Engineering Department
Additional Advisors
Shanju Zhang, College of Science and Mathematics, Chemistry and Biochemistry Department
Abstract/Summary
Plastic waste accumulation and continued reliance on fossil fuel-based polymer feedstocks remain major challenges in the plastics industry. While mechanical recycling is widely used, repeated thermal processing, contamination, and polymer degradation reduce recycled plastic quality. Chemical recycling offers an alternative by depolymerizing plastics into reusable monomers that can produce materials with properties closer to virgin plastics.
This study investigated the glycolysis of post-consumer poly(ethylene terephthalate) (PET) using ethylene glycol to produce bis(2-hydroxyethyl) terephthalate (BHET). Zinc oxide (ZnO) nanoparticles were synthesized by solution precipitation and used with 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) as a co-catalyst system. PET glycolysis was performed using 2.00 g PET, 20.0 g ethylene glycol, 5 mol% [Bmim]Cl, and 2 to 10 wt% ZnO at 165 °C for 2 h under reflux.
X-ray diffraction confirmed predominantly crystalline ZnO, while electron microscopy and light scattering showed nanoscale particles with some agglomeration. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy confirmed BHET formation through characteristic hydroxyl, ester, aromatic, and methylene signals. Average BHET yield varied with ZnO nanoparticle loading, but limited trials and product recovery variability prevented statistically significant conclusions about the effect of catalyst loading. Overall, the results demonstrated successful PET depolymerization and supported the feasibility of ZnO nanoparticle and [Bmim]Cl co-catalyzed PET glycolysis.
URL: https://digitalcommons.calpoly.edu/matesp/287