Obtaining phthalate substituted post-consumer polyethylene terephthalate and its isothermal crystallization

Abstract

Objects. Due to the polymer waste accumulation, the search for new directions for their utilization is urgent. Chemical recycling methods are of considerable interest, which allow one to obtain the original monomers or change the compositions of the copolymers. From the point of view of building a circular economy, a promising material is polyethylene terephthalate (PET), on the basis of which amorphous copolyesters can be obtained. The study aimed to analyze the simultaneous glycolysis and interchain exchange reactions of PET in the presence of the oligoethylene phthalate modifier with hydroxyl end groups and the study of isothermal crystallization of poly(ethylene phthalate-co-terephthalates) with different phthalate contents obtained in this way.Methods. Oligoethylene phthalate is synthesized by polycondensation. Poly(ethylene phthalateco-terephthalates) were obtained by the interaction of post-consumer PET with oligoethylene phthalate. The composition of the oligomer and copolymers was confirmed using Fourier-transform infrared spectroscopy, thermal characteristics and crystallization half-times were determined by differential scanning calorimetry.Results. In this work, the use of the post-consumer PET chemical recycling process, aimed at obtaining copolyesters under the influence of small modifier amounts was proposed. The process consisted in carrying out the combined interchain exchange and degradation with a complex oligoester different from PET. Poly(ethylene phthalate-co-terephthalate) copolymers were obtained via reaction of post-consumer poly(ethylene terephthalate) flakes and synthesized oligoethylene phthalate resin in the melt phase in the absence of catalyst. The effect of phthalate concentration in polymer on the isothermal crystallization of phthalate substituted poly(ethylene terephthalate) was estimated.Conclusions. The hypothesis about the possibility of using an oligoester modifier to obtain the PET-based copolymer at the high rate and without reducing the molecular weight to values characteristic of a monomer or oligomer has been confirmed. The process can be used to obtain random copolyesters based on post-consumer PET. The phthalate unit concentration increase is followed by decrease in the glass transition temperature, temperature and heat of fusion, and increase in crystallization half-times. Phthalate has a better ability to retard PET crystallization than 2-methyl-1,3-propanediol or furandicarboxylic acid, but is inferior to some of the other modifiers known.

Three/Four-Dimensional Printed PLA Nano/Microstructures: Crystallization Principles and Practical Applications

“…To rapidly compare the crystallization rates of polymer materials, it is convenient to report the crystallization half-time ( t 1/2 ) defined as the time required to attain half of the final crystallinity ( X t = 0.5) [ 51 ]. The half-time is typically reported as a function of temperature, enabling the determination of the optimal temperature window.…”

Synthesis of L-Lactide from Lactic Acid and Production of PLA Pellets: Full-Cycle Laboratory-Scale Technology

“…It is worth noting that PLA is singled out among biopolymers because its main valuable qualities are considered to be environmental friendliness, biocompatibility and recyclability; it is non-toxic, as are its degradation products [ 5 , 6 ]. Biodegradability is one of the key advantages of PLA, distinguishing it from other polymers, the disposal of which requires mechanical (physical) [ 7 ] or chemical recycling [ 8 , 9 ] or incineration.…”

“…To synthesize pure L-lactide, it is required to use L-lactic acid and sustain the reaction conditions that minimize the production of meso-lactide. Namely, it is the necessary to maintain the temperature and pressure regime and use catalysts that allow the necessary stereospecificity to be achieved [ 8 , 9 ]. Currently, a two-step method consisting of lactic acid oligomerization followed by depolymerization to form lactide is commonly used.…”

Modeling of Poly(Ethylene Terephthalate) Homogeneous Glycolysis Kinetics

“…Glycolysis is classified depending on the phase composition of the reaction mixture as heterogeneous [ 36 , 37 , 38 ] and homogeneous [ 3 , 6 , 23 , 24 , 39 , 40 ]. In heterogeneous PET glycolysis, the system contains two phases at the beginning of the process, namely liquid glycol and particles of polyethylene terephthalate distributed in it.…”

“…In heterogeneous PET glycolysis, the system contains two phases at the beginning of the process, namely liquid glycol and particles of polyethylene terephthalate distributed in it. Homogeneous glycolysis can be carried out in solution [ 23 , 24 ] or in a melt at a temperature above the pour point of PET [ 3 , 6 , 39 , 40 ].…”