Abstract

Background: The glycolytic depolymerization of recycled polyethylene terephthalate (rPET) presents a promising route for producing polyols suitable for sustainable polyurethane (PU) applications. This study focuses on using polyethylene glycol 400 (PEG400) as a depolymerizing agent at a molar ratio of 1:2 (rPET:PEG400), with zinc acetate dihydrate (ZnOAc·2H₂O) as a catalyst. Methods: Depolymerisation was conducted with varying ZnOAc·2H₂O concentrations (0.00 – 0.50 wt%), and the resulting polyols were characterised through visual inspection, Fourier-transform infrared (FTIR) spectroscopy, size exclusion chromatography (SEC), and rheological analysis. Significant Findings: Without a catalyst, depolymerization was incomplete, leaving 29.24 % solid residue. Adding ZnOAc·2H₂O fully dissolved the rPET, with FTIR confirming hydroxyl groups that indicate successful polyol formation. The polyols had number-average molecular weights (M<inf>n</inf>) from 820 to 970 g/mol. Rheological tests showed shear-thinning at low shear rates, shifting to Newtonian flow above 0.10 s⁻¹. The optimal catalyst concentration of 0.20 wt% produced polyols with a TOF of 22.52 h⁻¹, OH value of 137.17 mg KOH/g, and functionality (f<inf>n</inf>) of 3.50, offering desirable clarity and properties for polyurethane