Investigation of the conditions for the formation of oligoether polyols ia glycolysis of waste PET

The aim of this work is to optimize the synthesis conditions for polyether polyols based on recycled polyethylene terephthalate and glycerol. The effect of glycerol concentration, temperature, and duration of the alcoholysis process in the presence of a catalyst (zinc acetate) on the physical and chemical properties of the final product was studied.The concentration of glycerol was varied from 0.4 to 4.0 mol of glycerol per 1 mol of the elementary unit of secondary PET, providing partial or complete alcoholysis, respectively. Increasing the glycerol concentration to a threshold value leads to the formation of fusible oligomers, while a higher concentration results in a liquid final product. As the concentration of glycerol increases, there is a decrease in molecular weight, ether, and acid numbers, as well as an increase in hydroxyl group concentration, indicating a deeper chemical degradation of secondary PET.The glycerolysis temperature was increased from 180°C to 250°C, and the reaction time was increased from 6 to 30 hours. The product characteristics change non-linearly with increasing temperature: molecular weight, ether number and dynamic viscosity decrease, while the content of hydroxyl groups and acid number increase. The degree of change in all product characteristics becomes less sensitive to temperature increases.It was found that during the first six hours, alcoholysis at 220°C leads to a decrease in the molecular weight of secondary PET, and then polycondensation occurs with the formation of aromatic polyester polyols, leading to an increase in the molecular weight, acid number and dynamic viscosity of the products. The structure of alcoholism products has been studied by IR, PMR, and NMR13C spectroscopy. It has been shown that due to the replacement of residual ethylene glycol with glycerol in the macrochain, glycerol residues are present in its composition.

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