Evaluation of waste polyethylene terephthalate in polyol and polyurethane production

This study aims to eliminate the environmental damage and pollution caused by large quantities of waste Polyethylene terephthalate (PET) bottles, and to reuse depolymerized products which are by-products of recycled PET used as raw materials in the production of polyurethane film. In this study, the appropriate glycol type and the appropriate amount of glycol to be used in the depolymerization reaction were investigated. In addition, the comparisons betweena different catalyst and catalyst zinc acetate which is the most commonly used as catalyst in glycolysis processwas made. With this study, the glycolysis process was improved and as a result, an increase in the amount of polyol was obtained. With the increasing amount of polyol, the properties of the polyurethane resin was also improved. In this study, the proper amount of glycol was investigated. A mixture of adequate amount of waste PET and adequate amount of glycol which was determined by the molar ratio of the repeated step of PET, and 5% of total mass of zinc acetate were charged to a reactor which was fitted with stirrer, reflux condenser, and temperature controller. The same process was repeated with the addition of zinc sulfate catalyst. The temperature was increased to 210 °C for the destruction of solid particles in the reactor. Then, the hydroxyl numbers of the obtained polyols were determined according to the phthalic anhydride/pyridine method. Anionic polyurethane dispersion was made by acetone process. A homogeneous mixture was obtained by mixing the proper amount of polyol which was obtained from glycolysis of PET, hydrophilic monomer, and N-dimethylformamide used as a solvent in the reactor at 70 °C. Uniform distribution of hydrophilic monomer in the polyurethane was ensured. Isofuran diisocyanate and catalyst dibutyltin dilaurate were added to the homogenized mixture. In order to prevent the increase in viscosity and to obtain a homogeneous mixture, acetone was added, Phase transformation was achieved by cooling the mixture and adding water in a controlled manner. Characterization was performed using appropriate tests.