Synthesis and characterization of copolymers of poly(ethylene terephthalate) and cyclohexane dimethanol in a semibatch reactor (including the process model)

Abstract

Although poly(ethylene terephthalate) (PET) has excellent basic properties, this polymer tends to crystallize rapidly and has a rather high melting temperature, a low glass-transition temperature, and low impact on notched articles for some potential applications. Copolymerization is a reasonable method for improving the properties of PET. 1,4-cyclohexane dimethanol (CHDM) is one of the most important comonomers for PET. In this research, PET and PET copolymers containing 5-30% CHDM were prepared from comonomer mixtures by two-step melt polycondensation. The copolymers were synthesized in a homemade laboratory setup. The first synthesis step was conducted under pressure, and the second was performed in vacuo at a high temperature (230-290 C). The microstructure of the synthesized copolymers was studied with Fourier transform infrared and nuclear magnetic resonance. The comonomer content in the polymer chain was determined from the nuclear magnetic resonance spectrum. The presence of the comonomer in the copolymer chain was random. Differential scanning calorimetry was used to study the thermal properties of the copolymers to detect changes in the polymer properties. CHDM reduced the heat of fusion and melting and glass-transition temperatures of the PET copolymers. Process modeling was performed with mass balances of different functional groups and species. Equations of mass balances were integrated numerically. Numerical simulation and experimental results were in very good agreement. By modeling, the effects of the reaction temperature and feed molar ratio on the conversion and formation of diethylene glycol were studied.

Combined effect of isophthalic acid and polyethylene glycol in polyethylene terephthalate polymer on thermal, mechanical, and gas transport properties

“…Pure PET shows T g of 80.39°C and for IPA‐PEG copolymer series T g values are within 2°C difference up to 4% IPA‐PEG and above 4% IPA‐PEG T g starts decreasing rapidly. As reported elsewhere,15–30 the reduction of T g in PET is due to the kinking effect in the molecular structure, which arise due to the copolymer addition. The addition of comonomers in PET increases the T ch temperature and suggests that the crystallization takes place at higher temperature.…”

“…Since this building block of CHDM is much larger (six additional carbon atoms) than the ethylene glycol unit it replaces, it does not fit in with the neighboring chains the way an ethylene glycol unit would. This interferes with crystallization and lowers the polymer's melting temperature 24–26. Replacement of MEG with PEG in PET polymer is also reported in the literature, and this copolymer is extensively used in biomaterial applications 27–29.…”

Synthesis and properties of amorphous translucent c-PET

“…По сравнению с условиями выполнения экспериментов, описанных в работе [13], в которых мольное отношение смеси гликолей к ТФК составляло 1,3, в наших опытах исследованы условия синтеза при более высоком значении этого соотношения (от 2,2 до 2,4). Исходное значение избыточного давления в реакторе, создаваемого с помощью азота при температуре 200 °С, устанавливали на уровне (0,12 ± 0,01) МПа.…”

“…Исследование синтеза сополиэфира из ТФК и смеси ЭГ и ЦГДМ-1,4 в лабораторных условиях описано в работе [13]. ЭГ, ЦГДМ-1,4, ТФК и трёхокись сурьмы в качестве катализатора поликонденсации при мольном соотношении суммы гликолей к терефталевой кислоте равном 1, 3 Кроме технологических вариантов получения на основе ТФК полиэфиров и сополиэфиров с использованием различных алифатических мономеров и сомономеров, получивших широкое практическое применение и которые, по всей видимости, будут являться основными методами ещё длительное время, в научной литературе уделяется всё больше внимания способу получения полиэфиров и сополиэфиров путём раскрытия кольца циклических олигомеров [18][19][20].…”

“…На основе данных ДСК показано, что поли(этилен-со-циклогексилендиметилентерефталат), содержащий в первичной структуре 33 моль % ЦГДМ-1,4 не способен кристаллизоваться. По спектрам ЯМР на ядрах 13 С проведена оценка характера распределения звеньев ЦГДМ-1,4 в макромолекуле сополиэфира. Показано, что количество триад ЕТС и СТС в составе макромолекулы увеличивается с возрастанием доли связанного сомономера.…”