(154k) Kinetics of Polyurethane Foam Acidolysis with Carboxylic Acids

Polyurethane (PU) is the 6^th most produced polymer, with a global market size of $37.8 billion in 2020. Unlike polyolefins, polyurethanes contain reactive C-O and C-N bonds which permit facile chemical decomposition to monomeric units (polyol and isocyanate) for use in the synthesis of new PU materials. Reaction of PU materials with organic reagents such as glycols, acids, or amines has shown promise in recovering polyol products; however, each has drawbacks which have thus far prevented their widespread use. Acidolysis, the reaction of PU with organic carboxylic acids, offers polyol recovery under mild temperatures (< 200 °C) and atmospheric pressure, but its kinetics, mechanism, and scalability are not well understood. In this work, the kinetics of acidolysis of a flexible polyurethane foam with mono- and dicarboxylic acids are explored via real-time monitoring of gas (CO₂) emissions. Through a combination of kinetic measurements, analysis, and theoretical models, insights are provided into the role of acid structure on rate of acidolysis. The viability of this reaction in a real-world application is validated with kinetics of post-consumer polyurethane mattress waste. Our findings offer insights into the mechanism and kinetics of PU acidolysis and progress towards circularity of PU materials.