(227a) Application of Supercritical Carbon Dioxide to Polymer Recovery from Multilayer Plastic Packaging: Experimental Thermodynamic Phase Behaviors

Multilayer plastic packaging possesses barrier properties to extend the storage stability of packaged content and is essential to our daily lives. However, millions of tonnes of polymeric material waste are generated and disposed of annually during manufacturing and/or after use, provoking the importance of packaging polymer reclamation and reuse. In order to address the growing packaging waste burden across the globe, developing novel strategies to reclaim valuable polymers without degrading material properties is critical. Supercritical carbon dioxide (scCO₂) utilized technology is one of the novel recovery processes for both post-industrial and post-consumer multilayer food packaging wastes. Unfortunately, there is still a lack of understanding of the systematic phase behavior of scCO₂ solvent interchangeable with commercial packaging polymer materials. Specifically, a solvent system with a mixture of scCO₂ and co-solvents should be developed to separate poly(ethylene co-vinyl alcohol)/polyamide from polyolefin-based multilayer plastic packaging. In this presentation, I will share the experimental thermodynamic phase behaviors of the solvent mixtures (scCO₂ + co-solvent) with food packaging polymer components. Our experimental design and results can be researched to optimize conditions for the polymer separation and recovery. Co-solvents are selected using Hansen solubility parameter calculations for efficient separation of poly(ethylene co-vinyl alcohol)/polyamides from polyolefins in scCO₂. By implementing a high-pressure variable-volume reactor system coupled with a scCO₂ injection system, the phase behavior of the solvent mixtures and demixing point of the targeted virgin polymers under the solvent mixtures are examined with various temperature and pressure conditions. The results will provide a fundamental understanding of the conditions (including temperature, pressure, and co-solvent composition) that lead to the separation and reclamation of the target polymer under scCO₂. Our proposed mechanism will provide a novel pathway to recover high-value polymer materials.