Reprocessing Postconsumer Polyurethane Foam Using Carbamate Exchange Catalysis and Twin-Screw Extrusion

Abstract

Cross-linked polyurethane (PU) is extensively used as thermoset foam; however, methods to directly reprocess PU foam waste derived from commercial sources into similar value materials have not been developed. We demonstrate that introducing dibutyltin dilaurate (DBTDL) into cross-linked PU foams and films enables their reprocessing at elevated temperatures via dynamic carbamate exchange reactions. Both model and commercial cross-linked PU foams were continuously reprocessed using twin-screw extrusion to remove gaseous filler and produce PU filaments or films with elastomeric or rigid thermoset mechanical properties. The properties of microcompounded model PU foam were in excellent agreement with PU film synthesized using the same monomers, indicating that this process occurs efficiently. These findings will enable the bulk reprocessing of commercial thermoset PU waste and inspire the further development of reprocessing methods for other thermosets and the compatibilization of chemically distinct cross-linked materials.

Selectively Depolymerizable Polyurethanes from Unsaturated Polyols Cleavable by Olefin Metathesis

“…Alternatively, the dynamic nature of the carbamate linkage has been exploited to enable reprocessing of PUs via catalysts familiar in PU polymerizations, namely tertiary amines, Lewis acids, and organotin compounds. [ 33–39 ] In a similar vein, polyhydroxyurethanes can be reprocessed through catalyst‐free exchange of hydroxyl and carbamate functionalities. [ 40–44 ] However, reprocessing of PUs and polyhydroxyurethanes also requires high temperature and/or extended reaction times.…”

Innovation in Additive Manufacturing Using Polymers: A Survey on the Technological and Material Developments

“…Covalent adaptive networks (CANs) are polymer networks that contain exchangeable covalent bonds [ 139 , 140 , 141 ]. A subcategory of CANs, known as vitrimers, is particularly attractive as reprocessable and recyclable materials for AM.…”

Imine-Based Reactive Mesogen and Its Corresponding Exchangeable Liquid Crystal Elastomer

“… 15 Here, possible catalyst degradation complicates the system, and the dissociative nature of the carbamate bonds indicates that the dissociated isocyanate group can be susceptible to water attack at high temperature. 16 − 18 Disulfide exchange is also a fast reaction that does not require any catalyst, and the system also benefits from the radical-assisted dissociative mechanism. 19 − 21 Nevertheless, in the past, we found that this type of xLCE suffers from oxidative side reaction at temperatures above 170 °C with sample tarring, which prevents the xLCE from multiple recycling.…”