One-pot Preparation of Flame-retardant Waterborne Polyurethane by Glycolysis of PET with Ionic Liquids

Recycling waste polyethylene terephthalate (PET) to prepare high-value chemicals can achieve resource recycling and reduce environmental pollution, which has important scientific significance. In this work, waterborne polyurethane (WPU) was prepared in one-pot method using non-metallic ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ( [Emim] [OAc]) as catalyst in the PET degradation. There is no need to separate the products and IL catalyst, avoiding product loss and metal residue. Meanwhile, the flame-retardant choline dihydrogen phosphate (N 1112OH DHP) was added, combining with the [Emim] [OAc], the WPU with good flame retardancy was obtained by using flame retardant with the phosphorus-nitrogen synergistic effect. The testing results indicated that the number average molecular weight (M n ) of WPU was as high as 23703 g/mol under the optimal conditions, the total heat release (THR) of WPU was reduced by 44.86%, the limiting oxygen index (LOI) was increased to 31.5%. Besides, the UL-94 testing of the WPU has reached V-0 level. In the end, the flame retardancy mechanism was studied through analyzing the perspectives of condensed phase and gas phase of of WPU. Thus, the WPU with good flame retardancy can be prepared in one-pot method by glycolysis of PET with ILs, which has certain guiding significance for the recycling and utilization of PET.