Al2O3/chitosan nanocomposite: Preparation, characterization and kinetic study of its thermal degradation

Highlights: • The NH₂, −OH and −CO of chitosan and Al₂O₃ are investigated in 10%Al₂O₃. • Thermal degradation of 10%Al₂O₃ is similar to that of chitosan. • The thermal degradation mechanism of 10%Al₂O₃ is found that of the random session. • The estimated T and k of degradation of 10%Al₂O₃ are 565 K and 0.172 min⁻¹. - Abstract: The 10%Al₂O₃/Chitosan nanocomposite (10%Al₂O₃/CS) was prepared and characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Brunauer, Emmett and Teller method (BET). These techniques showed the formation of 10%Al₂O₃/CS by the interaction between functional groups of CS such as NH₂, OH and CO and Al₂O₃. The non-isothermal degradation process of 10%Al₂O₃/CS under an air atmosphere was investigated by Simultaneous ThermoGravimetric and Differential Thermal Analysis (TGA/DTA) and Differential Scanning Calorimetry (DSC) at different heating rates (β = 5, 10, 15 and 20 K/min). The kinetic parameters of thermal degradation were calculated using Kissinger-Akahira-Sunose (KAS) and Kissinger (KIS) methods, and it was found that the average values of activation energies were E_a = (110 ± 5) kJ/mol from Kissinger method, but the KIS method give three conversion domains in which E_a exhibits practically constant values, namely (0.15 – 0.30), (0.35 – 0.50) and (0.60 – 0.68) with average values of (131 ± 3) kJ/mol, (190 ± 10) kJ/mol and (71 ± 7) kJ/mol, respectively. At last, the value of range (0.15 – 0.30) was used to match the experimental and simulated Y(α) and Z(α) master plots. Indeed, it was found that the modified Sestak-Berggren $f\left(\alpha \right)=c{(1-\alpha )}^n{\alpha }^m$ does not correctly describe the kinetics of 10%Al₂O₃/CS degradation process, even if this model allowed reproducing qualitatively the Y(α) curves, giving the same maximums, α_m, for each value of β in rang of α (0.15–0.3), which are consistent with the thermal degradation mechanisms of 10%Al₂O₃/CS. Finally, the estimated temperature of degradation is 565 K with a rate constant of 0.172 min⁻¹.