A study on recyclable waterborne polyurethane process with a photo and thermal hybrid treatment system

Development of a novel recycling process of waterborne polyurethane (WBPU) with a poly(oxytetramethylene)glycol (PTMG) soft segment was performed using characteristics of nitroxyl radical (TEMPO) dormant bond. A TiO2/hindered amine light stabilizer (HALS) combination produced the dormant bond in a 24 h UV irradiated WBPU. The WBPU extraction rate was 66% with a water-ethanol solvent, and its bond was found to contain a PTMG sequence by Py-GC/MS measurement. The binary blend of extracted WBPU and PTMG was immiscible and converted to miscible one by thermal treatment at 120 °C for 0.5 h in nitrogen. The WBPU was partially graft-polymerized onto the PTMG by the treatment and worked as a compatibilizer. The change to miscibility showed that the blend was recyclable as PTMG material.