In this work, the thermal decomposition of copolymers based on polyethylene glycol fumarate with the acrylic acid using various ratios of initial monomers has been studied for the first time. The samples were studied in air and nitrogen. According to the thermograms analysis, it was found that the copolymer sample decomposition begins at higher temperatures for a copolymer with high content of polyester resin. The copolymer is vigorously oxidized by the oxygen when heated in air, and one can observe almost complete sample decomposition, whereas it decomposes with a residue of ~ 15% in an inert medium. The activation energies for copolymers with different compositions were estimated using the differential methods of Freeman-Carroll, Achar and Sharpe-Wentworth. The activation energy values found by the three methods demonstrated a good convergence. It was shown that, the activation energy values are higher (~ 200 kJ/mol in the inert medium, and ~ 95 kJ/mol in the oxygen atmosphere) for a copolymer with a lower composition of polyester resin, and the activation energy is ~180 and ~85 kJ/mol for a copolymer with a greater composition of p-EGF-AA. The copolymer is more thermostable in the nitrogen atmosphere according to the kinetic parameters. Additionally, there were determined the thermodynamic characteristics, such as the Gibbs energy (∆G) and the entropy (∆S). They also confirm the destruction process dependence on the components ratio in the synthesized copolymer.
The study of the kinetic parameters of copolymers based on polyethylene glycol fumarates, as well as the external and internal effects on them, is essential for production processes at various levels. This will solve a whole range of issues in the field of the shelf life of materials and storage conditions. All these point to the relevance of this research. The authors of the research attempt to test the most common thermogravimetric data processing methods and to improve them in terms of the quality of the predictive capabilities of the resulting regression equation. Both of them are important for the production of initial components and the manufacture of the final product from the studied materials. Therefore, the study and further use of the numerical data of the TG/DTA curves applies to both theoretical and practical branches of science. Thus, summarizing the experimental data on the thermal stability studies, we assume that p-EGF: AA copolymers with compositions of 21.03:78.97 and 68.96:31.04 wt.% have a relatively high degree of resistance to heating. It was found that the calculation by the FR method agreed well with the results of the KAS method. It should be noted that for the p-EGF: AA copolymer (21.03:78.97 wt.%) at heating rates of 5.0, 10.0, 20.0 °С∙min–1, the average activation energy data obtained for two methods increase in the following series:KAS E = 187.34 kJ /mol <FR E = 200.17 kJ/mol.
Thermal decomposition of the copolymer based on polyethylene glycol fumarate with acrylic acid (p-EGF:AA) at four different heating rates in a nitrogen atmosphere has been investigated by the dynamic thermogravimetry (TGA) method. The TGA curves show that the decomposition process occurs in several stages. The experimental data processed by the Kissinger–Akahira–Sunose and Friedman isoconversion methods made it possible to calculate the activation energy of the main decomposition stage. According to the calculations results, one can see that the values found by these methods do not strongly depend on the conversion. The Achar–Brindley–Sharp method has been applied to determine the compensation parameters. Then, using the compensation effect, the invariant kinetic parameters of the decomposition processes have been found. An experimental curve has been plotted to find the reaction model in comparison with theoretical ones.
Synthesis and characteristics of metal-polymer complexes of p-EGM/AA-Ni 0-Co 0 and p-PGM/AA-Ni 0-Co 0 Possibility of using the copolymers of poly-(ethylene)-propylene glycol maleate (p-EGM, p-PGM) with acrylic acid (АA) as a matrix for obtaining effective metal-polymer complexes of different application was shown. The compositions, structures and dimensions of particles of nickel and cobalt stabilized in polymeric matrix were determined using the methods of transmission electron microscopy and scanning microscopy, infrared spectroscopy, laser-emission spectroscopy, dispersive microscopy and thermogravimetric analysis. The average size of nanoparticles, which have spherical shape and equal distribution along cross-section of polymer, was 100-170 nm. Percentage content of nickel and cobalt in the complex was equal to 0.52 and 0.48, respectively, in the p-EGM/AA copolymer, 0.49 and 0.51 in the p-PGM/AA copolymer. The analysis of electromagnetic force-pictures of p-EGM/AA (14.8:85.2 mass.%) and p-PGM/AA (15.1:84.9 mass.%) copolymers' films showed a relatively equal distribution of the filler (Ni 0 , Co 0) along the cross-section of polymer. The average number of metal particles on 10 microns was 600-700 units for particles of Ni and 550-650 units for particles of Co. Thermal decomposition of metal-polymer complexes occurred in the temperature range of 200-500 ºС. The average weight loss on TG-curves was 80 %. Therefore, p-EGM/AA-Ni 0-Co 0 and p-PGM/AA-Ni 0-Co 0 metal-polymeric complexes obtained can be used as a template for the creation of catalytically effective composite materials.
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