A new method for the recycling of a polyester tire cord under the action of oligoethylene terephthalates, bis(2-hydroxyethyl) terephthalate and ethylene glycol has been proposed. The method involves simultaneous homogeneous glycolysis of polyethylene terephthalate and devulcanization of crumb rubber. Polyester cord and glycolysates were characterized by FTIR spectroscopy and gel permeation chromatography (GPC). The devulcanization process was investigated by swelling-based methods. The rate of the proposed method of homogeneous glycolysis in a melt phase was proved to be higher than one of the heterogeneous glycolysis. The assumption of a more efficient devulcanization in the presence of a softener was also confirmed. The degree of devulcanization 46.07%, the apparent degree of swelling 167.4%, and the apparent swelling rate constant 0.0902 min−1 were achieved. The results indicate that the proposed method made it possible to carry out the glycolysis of the polyester cord of the tire more deeply than the known heterogeneous glycolysis with various agents, but further research is needed for industrial implementation.
Post-consumer poly(ethylene terephthalate) (PET) waste disposal is an important task of modern industry, and the development of new PET-based value added products and methods for their production is one of the ways to solve it. Membranes for various purposes, in this regard are such products. The aim of the review, on the one hand, is to systematize the known methods of processing PET and copolyesters, highlighting their advantages and disadvantages and, on the other hand, to show what valuable membrane products could be obtained, and in what areas of the economy they can be used. Among the various approaches to the processing of PET waste, we single out chemical methods as having the greatest promise. They are divided into two large categories: (1) aimed at obtaining polyethylene terephthalate, similar in properties to the primary one, and (2) aimed at obtaining copolyesters. It is shown that among the former, glycolysis has the greatest potential, and among the latter, destruction followed by copolycondensation and interchain exchange with other polyesters, have the greatest prospects. Next, the key technologies for obtaining membranes, based on polyethylene terephthalate and copolyesters are considered: (1) ion track technology, (2) electrospinning, and (3) non-solvent induced phase separation. The methods for the additional modification of membranes to impart hydrophobicity, hydrophilicity, selective transmission of various substances, and other properties are also given. In each case, examples of the use are considered, including gas purification, water filtration, medical and food industry use, analytical and others. Promising directions for further research are highlighted, both in obtaining recycled PET-based materials, and in post-processing and modification methods.
A method for producing nanocomposites of unsaturated polyester resins (UPR) based on recycled polyethylene terephthalate (PET) as a matrix has been proposed. The upcycling method involves three successive stages: (1) oligoesters synthesis, (2) simultaneous glycolysis and interchain exchange of oligoesters with PET, (3) interaction of the obtained resins with glycol and maleic anhydride. UPRs were characterized by FTIR spectroscopy and gel permeation chromatography. The mechanical properties of nanocomposites obtained on the basis of these resins and titanium dioxide have been investigated. It has been shown that 1,2-propylene glycol units, despite their lower reactivity, significantly improve the properties of UPR. The most promising nanocomposite sample exhibited tensile strength 112.62 MPa, elongation at break 157.94%, and Young’s modulus 29.95 MPa. These results indicate that the proposed method made it possible to obtain nanocomposites with high mechanical properties based on recycled PET thus allowing one to create a valuable product from waste.
В работе исследован гликолиз вторичного полиэтилентерефталата при одновременном растворении и разложении смесью бис(2-гидроксиэтил) терефталата и его олигомеров. Показана высокая эффективность процесса. Для агента гликолиза, содержащего 75% масс. бис(2-гидроксиэтил) терефталата и 25% масс. димера и олигомеров, оптимальным является мольное отношение звеньев агента гликолиза к звеньям полиэтилентерефталата 5:1. Процесс может быть взят за основу производительной и экономически выгодной технологии химической деструкции вторичного полиэтилентерефталата. Предложена формула расчета конверсии по бис(2-гидроксиэтил) терефталату с учётом присутствия в нём олигомеров.Ключевые слова: полиэтилентерефталат, ПЭТ, ПЭТФ, гликолиз, утилизация отходов, сложные олигоэфиры, реакционноспособные олигомерыIn this work, glycolysis of post-consumer polyethylene terephthalate with simultaneous dissolution and decomposition with a mixture of bis(2-hydroxyethyl) terephthalate and its oligomers is studied. High effi ciency of this process was shown. For the glycolysis agent containing 75 wt% bis(2-hydroxyethyl) terephthalate and 25 wt% dimer and oligomers, the optimal molar ratio of the glycolysis agent units to the polyethylene terephthalate units is 5:1. On the basis of the process, a productive and cost-eff ective technology can be developed for the chemical destruction of post-consumer polyethylene terephthalate. A formula for calculating the bis(2-hydroxyethyl) terephthalate conversion taking into account the presence of oligomers in it is proposed.
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