Chemical recycling of poly(ethylene terephthalate). Application to the synthesis of multiblock copolyesters

The chemical recycling of the poly(ethylene terephthalate), (PET), has been successfully carried out by glycoly- sis in the presence of bis (2-hydroxyethyl) terephthalate (BHET) resulting in the formation of hydroxytelechelic oligomers. These oligomers were then treated with carboxytelechelic poly(!-caprolactone) oligomers of —n = 2300 and —n = 730 g·mol -1 molecular weight, in the absence or presence of the titanium tetrabutyloxide (Ti(OBu)4) as a catalyst to get multiblock copolyesters. The chemical structure of the synthesized copolyesters was investigated by size exclusion chro- matography (SEC) and proton Nuclear Magnetic Resonance ( 1 H NMR) spectroscopy. Moreover the differential scanning calorimetry (DSC) was used to explore their thermal properties. The ester-ester interchange reaction was observed between the two oligopolyesters, was studied and discussed in detail.