Research Information System
Journal of the Faculty of Engineering and Architecture of Gazi University, vol.38, no.2, pp.1247-1261, 2023 (SCI-Expanded)
In this study, the possible product composition and distribution of the functional products obtained as a result of the depolymerization of waste PET were investigated using DSC technique. Thus, it was provided to obtain data for the optimization and standardization of the reaction conditions. First, waste PET flakes obtained from postconsumer water bottles were depolymerized at high pressure by simultaneous hydrolysis-glycolysis reactions. The reactions were carried out using a fixed amount of water, at different mole ratios of PET/diol, in the presence or absence of solvent, and at different temperatures. Raw depolymerization products were extracted with boiling water and separated into “water-soluble and crystallizable (WSCF)” and “water-insoluble (WIF)” fractions. Then, the yields% by weight (conversion ratios) of depolymerization reactions and, these fractions' ratios% by weight, functional group contents (acid value (AV), hydroxyl value (HV) analyses), theoretical number average molecular weights (Mn) were determined, and DSC analyzes were performed. The optimum conditions for most efficient fragmentation were observed in the depolymerization reaction that mole ratio of PET/diol was 1/5, in the presence of 2.5 moles of water, on the xylene medium and at 200oC. In these conditions, 99% conversion was achieved, and product distribution was observed as 81% WSCF and 19% WIF. In the WSCF product composition, PET's hydroxyl-terminated monomer (BHET) and in the WIF product composition, PET's carboxyl-terminated monomer were obtained at around~80% and ~80%, respectively. The Mn value of the final product composition is 234, the AV and HV values are 121 mg KOH/g and 358 mg KOH/g, respectively.