Direct conversion of waste polyesters to low molecular weight polyols for polyurethane production

•Waste PET was directly converted to low-molecular-weight liquid polyols through one-step glycolysis process using EDTA as a deactivator to prevent catalytic re-polymerization.•The effect of ethylenediaminetetraacetic acid (EDTA) on the blocking of transesterification catalysts (zinc acetate) was cl...

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Bibliographic Details
Published inPolymer degradation and stability Vol. 205; p. 110147
Main Authors Ngo, Dieu Minh, Lee, Kyunghan, Ho, Linh Nguyet Thi, Lee, Jinseok, Jung, Hyun Min
Format Journal Article
LanguageEnglish
Published Elsevier Ltd 01.11.2022
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Summary:•Waste PET was directly converted to low-molecular-weight liquid polyols through one-step glycolysis process using EDTA as a deactivator to prevent catalytic re-polymerization.•The effect of ethylenediaminetetraacetic acid (EDTA) on the blocking of transesterification catalysts (zinc acetate) was clarified.•Rigid polyurethane with good thermal stability and mechanical properties was synthesized from the obtained liquid polyols. An effective process for synthesizing liquid dihydroxyl group-ended oligomers directly from waste polyethylene terephthalate (PET) using a metal chelating agent, ethylenediaminetetraacetic acid (EDTA), is described in this study. The deactivation of transesterification catalyst was confirmed by a model process that involves the reaction of bis(2-hydroxyethyl) terephthalate with diethylene glycol under different catalytic conditions. The depolymerization of PET was performed with an excess amount of diethylene glycol and Zn2+ catalysts to form intermediates. The chelating agent was then introduced as a catalytic defunctionalizer, after which the residual glycols were distilled and recovered under reduced pressure. The obtained polyols were characterized by 1H and 13C nuclear magnetic resonance, gel permeation chromatography, and viscometry. Utilizing EDTA showed high efficiency in blocking catalysts during high-temperature distillation, resulting in maximum trimer chain-length sized and low-viscosity liquid polyols. Subsequently, thermoplastic polyurethanes (TPUs) were prepared using synthesized polyols as the soft segment, with 4,4’-methylene-bis(phenyl isocyanate) and 1,4-butanediol as the isocyanate and chain extender, respectively. The final TPUs were characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis, and mechanical testing.
ISSN:0141-3910
1873-2321
DOI:10.1016/j.polymdegradstab.2022.110147