Thermal degradation kinetic of poly(acrylamide-co-sodium acrylate) hydrogel applying isoconversional methods

Hydrogel of poly(acrylamide-co-sodium acrylate) may be used to remove water from liquid fuels. Synthesis, characterization, and thermal degradation kinetic are reported in this article. The hydrogel was obtained by free radical polymerization, using the acrylamide and sodium acrylate monomers. The conversion of C=C double bond of the monomers and identification of the functional groups in the structure of the polymer were confirmed by Fourier transform infrared spectroscopy. The swelling capacity in distilled water was 105.68 (g water g −1 dry hydrogel). Kinetic parameters were determined by Korsmeyer–Peppas equation, with a diffusional exponent of 0.6098 and a kinetic constant of 3.7652. TG and DSC experiments were carried out to verify the thermal stability and phase transitions, respectively. Hydrogels showed high thermal stability, with degradation at 463.15–843.15 K. The glass transition temperature was approximately 383.15 K. The thermal degradation kinetics revealed that the activation energy was approximately 500,000 J mol −1 . The experimental values obtained using the Vyazovkin method were compared with the models proposed by Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose. The Kissinger method exhibited the best performance describing the activation energy values for the studied conversion range.