Efficient Purification of the Glycolysis Monomer of Polyester Enabled by Its Unique Phase Transition Property

To overcome the difficulties of purification and decolorization of bis(2-hydroxyethyl) terephthalate (BHET) that is associated with the recycling of wasted polyester (PET) textiles, this work studies the unique phase transition behavior of crystalline BHET in hope to find new and efficient purification strategies of the glycolysis product monomer of PET. With sublimation in vacuum, pure and decolorized BHET can be obtained with yield of up to 86.4%, purity of up to 99.7% and whiteness (L* value) of up to 99.8, respectively. Repolymerization of the obtained purified BHET afforded recycled PET, which possessed similar properties with respective to the PET derived from petroleum-based BHET, including molecular weight, the distribution of molecular weight and whiteness, respectively. The effectiveness of this recycling strategy of wasted polyester textile was also verified by evaluating a series of PET samples, including PET textile blends and the real wasted polyester textiles that were picked from waste bins. This purification strategy of BHET requires less purification steps, affords high purity of the product, obviates the uses of toxic chemicals, avoids the high propensity of BHET powders to polycondensation under the commonly purification conditions and will provide a new strategy for high-quality recycling of waste polyester textiles. [GRAPHICAL ABSTRACT]