Malleable and thermally recyclable polyurethane foam†
Thermosetting polyurethane (PU) foams, which cannot be recycled economically and efficiently due to their permanently crosslinked structures, have caused significant environmental concerns after service. To improve the sustainable development of the PU foam industry, herein, we report malleable PU foams that contain a dynamic disulfide bond. The disulfide exchange reaction under heat enables the rearrangement of the network topology of the PU foam, imparting malleability and thermal processability. The disulfide containing PU foams (PUSFs) have similar appearance and physical properties to common PU foams and were prepared using conventional foaming technology without any modification. The PUSFs can be easily recycled into PU films through thermal compression molding. The recycled PU films show excellent and tunable mechanical properties depending on the compositions of the original malleable PU foams. Furthermore, the PU film recycled from PU foam with a well-designed composition can be further reprocessed several times without obvious loss in mechanical proprieties and change in chemical structures. This investigation provides a novel methodology to recycle and reuse PU foams and is expected to promote the sustainable development of the PU foam industry.