Factors Affecting Solvent Retention due to Gel Formation during Dissolution-Based Plastic Recycling
Hedam Kim1, Ali Altamimi2, Whitney S Loo1
1Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States.
ACS Sustainable Chemistry & Engineering
|May 22, 2026
Summary
Minimizing residual solvent in plastic recycling is key. This study identifies solvent vapor pressure and polymer molecular weight as crucial factors for efficient polymer gel processing in solvent-targeted recovery and precipitation (STRAP).
Area of Science:
- Polymer Science
- Materials Chemistry
- Sustainable Engineering
Background:
- Dissolution-based plastic recycling, like solvent-targeted recovery and precipitation (STRAP), selectively recovers polymers from mixed waste.
- A significant challenge in STRAP is the efficient removal of residual solvent from polymer gels.
- Understanding factors influencing solvent retention is crucial for optimizing this recycling process.
Purpose of the Study:
- To investigate the key factors affecting residual solvent content in polymer gels during dissolution-based plastic recycling.
- To develop a predictive model for solvent retention based on various influencing variables.
- To identify the most significant parameters for selecting optimal polymer-solvent systems in STRAP.
Main Methods:
- Experimental measurements were conducted to assess the impact of precipitation method, cooling rate, and filtration time on solvent retention.
- Six variables (solvent vapor pressure, polymer molecular weight, polymer-to-solvent mass ratio, predicted solubility, Hansen solubility parameter, Flory-Huggins interaction parameter) were investigated.
- A support vector regression model was developed to predict solvent retention and determine feature contributions for six common polymers and nine solvents.
Main Results:
- Precipitation method, cooling rate, and extended filtration time showed no significant effect on solvent retention.
- Solvent vapor pressure was identified as the most influential factor affecting residual solvent.
- Polymer molecular weight was the second most significant factor, while the Flory-Huggins interaction parameter had a lesser influence.
Conclusions:
- Solvent vapor pressure and polymer molecular weight are critical parameters for minimizing residual solvent in dissolution-based plastic recycling.
- The developed predictive framework aids in selecting polymer-solvent systems to reduce solvent retention.
- This research provides a foundation for enhancing the efficiency and sustainability of STRAP processes.
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