Title: Mechanistic Insights on the Chemical Recycling of Polyurethane Foam using Computational and Kinetic Modeling

 

Abstract: Polyurethane (PU) is the sixth most produced plastic globally, with 21 million metric tons produced in 2021. Its properties can be tuned by varying the structure and ratio of the polyol and isocyanate monomers used during synthesis, enabling broad use across industrial and consumer applications. As a highly crosslinked polymer with high chemical and thermal stability, conventional mechanical recycling of PU typically yields low-value products. As a result, about 80% of PU is landfilled or incinerated. Chemical recycling offers a more sustainable end-of-life pathway by recovering high-value starting materials that can be reused in PU production.

 

Using benzoic acid and its electronic analogues, I show that acid electrophilicity strongly influences urea acidolysis rates. I then quantify the conformational landscape of dicarboxylic acid conformations and show that acid structure and chain length govern urethane acidolysis primarily through entropic effects. In contrast, carboxyl group number affects the enthalpic barrier, as dicarboxylic acids access transition state stabilization through hydrogen bonding involving the second acid group. Finally, I present an initial study of PU glycolysis, showing how glycol polarity influences both intrinsic reactivity and apparent reactivity through mass transport effects.
 

Overall, this work establishes a mechanistic framework linking molecular-scale reactivity to macroscopic depolymerization behavior in PU acidolysis and glycolysis. These insights provide a foundational understanding necessary for the design of scalable PU chemical recycling processes.