Paper Number
RS2
Session
Real-World Rheology & Sustainability
Title
Rheology-driven melt phase separation of PE/PET blends, a new approach to recycling. Part 2: SC CO2-assisted separation of depolymerized PET
Presentation Date and Time
October 14, 2024 (Monday) 10:10
Track / Room
Track 7 / Room 502
Authors
- Vecchi, Steven (Case Western Reserve University, Macro)
- Lu, Max (Case Western Reserve University, Macro)
- Hampton, Lauren (Case Western Reserve University, Macro)
- Ghassemi, Hossein (Case Western Reserve University, Macro)
- Schiraldi, David (Case Western Reserve University, Macro)
- Maia, Joao (Case Western Reserve University, Macromolecular Science and Engineering)
Author and Affiliation Lines
Steven Vecchi, Max Lu, Lauren Hampton, Hossein Ghassemi, David Schiraldi and Joao Maia
Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 44106
Speaker / Presenter
Vecchi, Steven
Keywords
experimental methods; data-driven rheology; polymer blends; polymer melts; polymers; real-world rheology; sustainability; techniques
Text of Abstract
Multilayer, multicomponent films are widely used for their excellent barrier properties, which makes them the construction of choice in flexible packaging. More than 40 million tons of all plastic being produced annually are composed of multilayer polymer systems. This creates an enormous challenge as recycling of these multilayer systems is not technically feasible at large scales. In fact, the component plastics often have differing recycling pathways which prevents these films from being recycled. This work is the second part of a more general project aimed at developing a novel chemical-mechanical approach that leads to achieving in-process melt separation of polyethylene/polyethylene terephthalate (PE/PET) blends in twin-screw extrusion for posterior individual recycling. Herein, we use various levels up to 8% w/w of ethylene glycol (EG) to depolymerize PET at 260 °C and demonstrate that significant chain depolymerization occurs with a reduction of PET molecular weight (MW) greater than 95%, as confirmed by rheology and intrinsic viscosity testing. The corresponding decrease in PET Mw allowed for the PET to be depolymerized to a level that was extractable with the aid of SC CO2. The purity of the separated PET wax and PE were confirmed with TGA, FTIR, and dissolving/filtrating away one phase. The resulting PET wax separated from the PET/LLDPE film was further depolymerized into monomeric form with the aid of zinc acetate. This work further studies the effect EG%, time, temperature, screw design, feed rate, and screw speed have on the depolymerization in a twin-screw extruder. Four different reagents MEG, DEG, TEG and BHET (Bis(hydroxyethyl)terephthalate) were used to look at the depolymerization efficiency, with EG being the more efficient depolymerization reagent. Rheology was used as the bases of determining the effectiveness of all these factors by comparing viscoelastic properties and relations to Mw.