Researcher(s)
- Ethan Speerli, Chemical Engineering, University of Delaware
Faculty Mentor(s)
- Dionisios Vlachos, Chemical & Biomolecular Engineering, University of Delaware
Abstract
The issue of plastic waste is one of the many great challenges of our time. As our consumption of and reliance on plastic has expanded exponentially, we become ever more threatened by the environmental impacts levied by discarded plastic products. In a world so dependent on plastic, it is critical that we focus on minimizing the amount of new plastic that must be manufactured via the traditional petroleum-based method. To this end, we must look to expand chemical recycling. At the center of this issue is polyethylene terephthalate (PET). PET is found in everything from water bottles to fabrics and has become one of the central pillars upon which our petroleum-based world has been built. Like other forms of consumer waste, waste PET can be reclaimed as part of a circular economy, where material is recycled to reduce the demand for new material and the waste produced by the system. Although chemical recycling has greater capability to produce pure products than mechanical recycling, it is also very energy intensive, the problem that our research looks to address. Polymers, like PET, are composed of small, repeating monomers. Traditional chemical recycling of PET entails breaking PET down to its monomer, BHET, or even smaller components. This project aims to evaluate the efficiency of shortening the process by halting depolymerization once molecules are formed between the monomer and polymer, resulting in long-chain oligomers for melt polycondensation repolymerization. Our goal is to prove that it is possible to produce commercially viable upcycled plastic in this way and to evaluate success using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to compare the thermal properties of our upcycled plastic to commercial PET. Based on this data, we found strong support that upcycling PET from oligomers sourced from PET waste is possible and that it can produce plastic that is similar to virgin PET better than upcycling from monomer. In the future, we plan to explore the copolymerization of BHET and PET oligomers with biomass-derived monomers, primarily BHEF, the monomer of PEF. We will also expand our testing of repolymerized oligomers and novel copolymers to include other characteristics that are important to commercial success, such as gas barrier properties.