Abstract
Aim: To investigate whether the sample preparation process of poly(ethylene oxide) (PEO) affects kinetic analysis of the thermal degradation process. Kinetic analysis was performed to describe the course of a chemical reaction regardless of the reaction conditions and the reaction system complexity. One differential method, the Friedman method, and one integral Kissinger-Akahira-Sunose method (KAS), were applied in this work. Methods: The PEO sample was prepared in 4 different ways. Thermogravimetric analysis was performed to determine the thermal degradation of prepared samples. Infrared spectroscopic analysis was performed during the preparation of the PEO film obtained by casting from the solution. Results: Dynamic thermal decomposition of PEO, regardless of the method of preparation, takes place through a single decomposition stage, which is manifested by the appearance of one peak on derivative thermogravimetric (DTG) curve. During the preparation of the PEO film, the procedure was carried out at a temperature higher than its melting temperature (Tm=65°C). After the cooling, the obtained sample didn’t solidify and it had an intense odor of acetic acid, which was confirmed by infrared spectroscopic analysis. Samples III and IV were re-prepared at a temperature lower than the melting point of PEO, obtaining samples of satisfactory quality. Conclusion: In order to prepare poly(ethylene oxide) films by solution casting technique, drying should be carried out at temperatures below the melting point of PEO. If TG analysis of pure PEO powder is compared with the results of hot pressed samples and solution cast samples, it can be concluded that the preparation of the sample doesn’t affect the thermal stability of the PEO. The dependence of activation energy calculated by the differential Friedman and integral KAS method on conversion is constant for all samples in a broad conversion range, regardless of how the samples were prepared. The hot pressed samples and solution cast samples have lower activation energy than the commercial PEO powder.
Highlights
Poly(ethylene oxide) (PEO) is a relatively cheap, conductive, water-soluble and biodegradable polymer
The process of thermal decomposition of polymeric materials is investigated by dynamic thermogravimetric analysis
Experimental data collected by this method allow the implementation of kinetic analysis of thermally activated heterogeneous chemical reactions such as polymer degradation
Summary
Poly(ethylene oxide) (PEO) is a relatively cheap, conductive, water-soluble and biodegradable polymer. Mechanical properties and has a very wide application in various fields of industry It is used as a component of packaging materials, in the textile industry and coating industry, as a solid electrolyte in batteries, as a material for thermal energy storage and in the manufacture of dosage forms with controlled release of the active substance [1,2,3,4,5]. During their lifetime, polymers are constantly exposed to various loads and interactions with the environment. There are different methods for determining kinetic parameters, but is generally accepted today that for reliable determination of kinetic parameters, it is necessary to accurately determine the dependence of activation energy on conversion [8, 9]
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