Non-isothermal decomposition kinetics of commercial polyacrylamide hydrogel using TGA and DSC techniques

The thermal decomposition method was employed to analysis the non-isothermal kinetics of commercial polyacrylamide hydrogel. Malek model-based methods and Vyazovkin model-free advanced converter methods were used to analyze the non-isothermal kinetics of hydrogel decomposition using DSC and TGA data. Thermal decomposition takes place in two stages. FTIR diagrams showed that ammonia gas and CO2 were likely released during the first and second stages of decomposition, respectively. By breaking the main chain in the second stage, the polymer loses a significant amount of weight. The Sestak-Berggren model describes the reaction process. The activation energies for the first and second stages were calculated to be (40±3 kJ/mol) and (59±3 kJ/mol), respectively. Finally, a commercial polyacrylamide hydrogel decomposition explicit rate equation was derived. The increase in surface porosity with the progress of the degradation process can be evidence of autocatalysis effects.