(499d) Facilitating Circularity and Recycling of Post-Consumer-Use Polyurethane Foam

Polyurethane (PU) is the 6^th most used polymer in the world and is predominantly used as foams (mattresses, furniture, shoes, construction) and dispersions (barrier coatings, sealants). However, PU has a low recycling rate (<6%) owing to its thermoset nature. Nearly 1.2 million tons of post-consumer-use PU waste is generated annually in the US, 46% of which comprises flexible foam. The chemical composition is adapted to suit different applications (e.g., multilayer mattresses, furniture, shoes) leading to significant variability in the waste stream. An absence of comprehensive and field-employable strategies to classify flexible post-consumer-use PU foam based on chemical composition limits its thorough recycling and appropriate disposal. To address this, a simple and inexpensive test (ball-rebound) has been proposed to classify post-consumer-use foams.

Notably, the demand for flexible foam is predominantly in the form of mattresses (40%), and each mattress consists of multiple PU foam layers (e.g., memory foam, support foam), with varying chemical compositions (extent of cross-linking, the extent of foaming, etc.). The absence of classification strategies at mattress recycling facilities hinders the circularity of post-consumer-use PU foam mattresses. By characterizing over 100 foam samples from 60 post-consumer-use mattresses of different ages and from global manufacturers, it was established that the ball-rebound resilience test is directly correlated with the chemical composition and mechanical properties of PU foam. This facile classification technique will inform industrial chemical recycling strategies tailored to post-consumer-use PU foams.

Existing chemical recycling strategies (e.g., glycolysis, hydrolysis) are employed exclusively on post-industrial foams yield polyols with high functionality, a branched backbone, and an undesirable color. The lack of control over the chemical properties of these recycled polyols limits their complete utilization, and they are used only as a partial replacement (30–40 wt%) of virgin feedstock, thus preventing complete circularity. In this work, a simple one-pot strategy has been developed and optimized to utilize recycled polyols for the fabrication of high-strength organic/inorganic composites. These lightweight recycled composites possess flexural strengths (2–13 MPa) greater than or comparable to ordinary Portland cement (OPC; 4–12MPa), while being significantly lighter (0.7–1.4 g/cm³) than OPC (1.5–3.3 g/cm³). Through this dual approach of classification of post-consumer-use PU foam at source, and appropriate utilization of recycling products, this work aims to facilitate PU foam circularity.