Joint Research Team Led by Professor Park Je-young of the Department of Chemical & Biomolecular Engineering Develops Low-Temperature Upcycling Technology to Convert Waste PET into High-Performance Engineering Plastic PBT
A research team led by Professor Park Je-young of the Department of Chemical & Biomolecular Engineering at the university, in collaboration with a research team led by Professor Oh Dong-yeop of Korea University and researchers from Hyundai Motor and Kia, has developed a low-temperature chemical upcycling technology that converts waste PET into polybutylene terephthalate (PBT), a high-performance engineering plastic.
To transition to a carbon-neutral chemical industry, it is crucial to develop technologies that convert not only C1-based chemical feedstocks, such as methanol, but also the polymeric carbon resources accumulated in post-consumer plastics into high-value-added chemical materials. In particular, PET is a representative polyester-based plastic widely used in everyday life, including beverage bottles, textiles, and packaging materials. However, a significant portion of post-consumer PET is not recycled into high-quality materials, and existing recycling processes have limitations such as degraded physical properties, high energy consumption, and complex separation and purification processes. Meanwhile, PBT is a high-value-added engineering plastic used in the automotive and electronics sectors, but it is primarily produced using petroleum-based raw materials, highlighting the growing need for sustainable alternative production pathways.
The joint research team proposed a molecular-level upcycling strategy that transforms waste PET into high-performance PBT, rather than simply converting it back into low-value recycled plastic. In this study, the team effectively induced the depolymerization of PET at a low temperature of 150 °C by using a deep eutectic solvent (DES) catalyst, specifically choline chloride/zinc acetate, in combination with a co-solvent, anisole. The DES catalyst simultaneously increased the nucleophilicity of the reactants and the reactivity of the PET ester bonds, while anisole interacted with the aromatic structure of the PET chains to promote internal polymer swelling, enabling high depolymerization efficiency even under low-temperature conditions.
As a result, under optimal conditions, a PET conversion rate of 95% and a monomer yield of bis(4-hydroxybutyl) terephthalate (BHBT) of 84% were achieved after only a 4-hour reaction. The recovered BHBT was converted into recycled PBT (r-PBT) through repolymerization, and the resulting r-PBT exhibited thermal properties and mechanical strength comparable to those of commercial PBT. In particular, it demonstrated a tensile strength of 64 MPa and an elongation at break of 290%, achieving excellent physical properties that make it suitable for use as an engineering plastic despite being derived from waste PET.
The team also verified the environmental sustainability of this technology through a life cycle assessment (LCA). The comparison was made against an existing methanol-based PBT recycling process that uses methanol, which is a representative C1 chemical feedstock. The analysis revealed that this technology can reduce the Global Warming Potential (GWP) by 19% and the Non-Renewable Energy Use (NREU) by 4% compared to the conventional process. This demonstrates that the technology can convert the carbon resources accumulated in waste PET into high-value-added PBT while simultaneously reducing the environmental impact compared to existing C1-based recycling pathways.
This study is significant in that it goes beyond simply converting waste PET back into conventional recycled PET material, instead transforming it into high-performance PBT suitable for use in automotive and electronic materials. Furthermore, by achieving both high yields and excellent physical properties under low-temperature conditions without using toxic halogenated solvents, the study presents a new upcycling platform for realizing a sustainable circular economy for plastics.
Researcher Shin Mi-ra, the first author, stated, “This study presents a low-temperature chemical upcycling strategy capable of converting waste PET into high-performance engineering plastics.” She added, “By comparing our method with methanol-based chemical processes, we confirmed the importance of designing low-carbon catalytic processes, which we expect will contribute to the future development of technologies for adding high value to carbon resources.”
Conducted with support from the Ministry of Science and ICT’s C1 Gas Refinery Value-Up Project and Hyundai Motor and Kia, this study was published in Chemical Engineering Journal, a leading international academic journal in the field of chemical engineering. The findings have drawn attention as a notable achievement, recognizing the significance of this new chemical upcycling strategy that converts waste PET into high-value-added engineering plastic PBT under low-temperature conditions.
▶ Paper Title: ‘Synergistic low-temperature upcycling of post-consumer PET into engineering-grade PBT: Dual-activation by deep eutectic solvents and anisole-induced swelling’
▶Paper Link: https://doi.org/10.1016/j.cej.2026.177960
▶Lab Website: https://sites.google.com/view/jyp-plastic-research/
To transition to a carbon-neutral chemical industry, it is crucial to develop technologies that convert not only C1-based chemical feedstocks, such as methanol, but also the polymeric carbon resources accumulated in post-consumer plastics into high-value-added chemical materials. In particular, PET is a representative polyester-based plastic widely used in everyday life, including beverage bottles, textiles, and packaging materials. However, a significant portion of post-consumer PET is not recycled into high-quality materials, and existing recycling processes have limitations such as degraded physical properties, high energy consumption, and complex separation and purification processes. Meanwhile, PBT is a high-value-added engineering plastic used in the automotive and electronics sectors, but it is primarily produced using petroleum-based raw materials, highlighting the growing need for sustainable alternative production pathways.
The joint research team proposed a molecular-level upcycling strategy that transforms waste PET into high-performance PBT, rather than simply converting it back into low-value recycled plastic. In this study, the team effectively induced the depolymerization of PET at a low temperature of 150 °C by using a deep eutectic solvent (DES) catalyst, specifically choline chloride/zinc acetate, in combination with a co-solvent, anisole. The DES catalyst simultaneously increased the nucleophilicity of the reactants and the reactivity of the PET ester bonds, while anisole interacted with the aromatic structure of the PET chains to promote internal polymer swelling, enabling high depolymerization efficiency even under low-temperature conditions.
As a result, under optimal conditions, a PET conversion rate of 95% and a monomer yield of bis(4-hydroxybutyl) terephthalate (BHBT) of 84% were achieved after only a 4-hour reaction. The recovered BHBT was converted into recycled PBT (r-PBT) through repolymerization, and the resulting r-PBT exhibited thermal properties and mechanical strength comparable to those of commercial PBT. In particular, it demonstrated a tensile strength of 64 MPa and an elongation at break of 290%, achieving excellent physical properties that make it suitable for use as an engineering plastic despite being derived from waste PET.
The team also verified the environmental sustainability of this technology through a life cycle assessment (LCA). The comparison was made against an existing methanol-based PBT recycling process that uses methanol, which is a representative C1 chemical feedstock. The analysis revealed that this technology can reduce the Global Warming Potential (GWP) by 19% and the Non-Renewable Energy Use (NREU) by 4% compared to the conventional process. This demonstrates that the technology can convert the carbon resources accumulated in waste PET into high-value-added PBT while simultaneously reducing the environmental impact compared to existing C1-based recycling pathways.
This study is significant in that it goes beyond simply converting waste PET back into conventional recycled PET material, instead transforming it into high-performance PBT suitable for use in automotive and electronic materials. Furthermore, by achieving both high yields and excellent physical properties under low-temperature conditions without using toxic halogenated solvents, the study presents a new upcycling platform for realizing a sustainable circular economy for plastics.
Researcher Shin Mi-ra, the first author, stated, “This study presents a low-temperature chemical upcycling strategy capable of converting waste PET into high-performance engineering plastics.” She added, “By comparing our method with methanol-based chemical processes, we confirmed the importance of designing low-carbon catalytic processes, which we expect will contribute to the future development of technologies for adding high value to carbon resources.”
Conducted with support from the Ministry of Science and ICT’s C1 Gas Refinery Value-Up Project and Hyundai Motor and Kia, this study was published in Chemical Engineering Journal, a leading international academic journal in the field of chemical engineering. The findings have drawn attention as a notable achievement, recognizing the significance of this new chemical upcycling strategy that converts waste PET into high-value-added engineering plastic PBT under low-temperature conditions.
▶ Paper Title: ‘Synergistic low-temperature upcycling of post-consumer PET into engineering-grade PBT: Dual-activation by deep eutectic solvents and anisole-induced swelling’
▶Paper Link: https://doi.org/10.1016/j.cej.2026.177960
▶Lab Website: https://sites.google.com/view/jyp-plastic-research/