Mechanochemistry Recycling of Polyurethane Foam Through Transcarbamoylation Mediated by Free Alcohol

It is highly desirable to provide an effective methodology to recycle polyurethane foam (PUF) wastes into similar or even higher value products, which is expected to promote the sustainable development of the PUF industry. In this work, a mechanochemical pretreatment and hot pressing process via free alcohol mediated transcarbamoylation (associative exchange mechanism) is proposed to reprocess commercial PUF into high value-added polymers. The effects of the content of the catalyst (p-toluenesulfonic acid, PTSA) and the free alcohol (−OH) groups (glycerol, GLY) on the structure and properties of reprocessed commercial PUF were investigated. The results showed that the tensile strength increased from 11.8, 20.24, to 27.28 MPa and that the cross-linked density increased from 825.9, 1872.86, to 2469.33 mol/m3 for reprocessed PUF, PUF–5 wt % PTSA, and PUF–5 wt % PTSA–1 wt % GLY, respectively. The relaxation time of reprocessed PUF sheets was greatly shortened from 9935.75 s for the PUF sheets to 1832.95 s and 820.05 s for the PUF–5 wt % PTSA and PUF–5 wt % PTSA–1 wt % GLY sheets, respectively. Furthermore, PUF sheets could still maintain 92.3% of their tensile strength after three cycles of recycling. The possible reason could be that the catalyst PTSA and the free alcohol GLY could accelerate the dynamic carbamate exchange, resulting in faster stress–relaxation and realizing the multiple reprocessability of PUF. This simple method shows great potential for value-added recycling of commercial PUFs and improves the sustainability of the PUFs industry effectively.