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

Abstract The 10%Al 2 O 3 /Chitosan nanocomposite (10%Al 2 O 3 /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%Al 2 O 3 /CS by the interaction between functional groups of CS such as NH 2 , OH and CO and Al 2 O 3 . The non-isothermal degradation process of 10%Al 2 O 3 /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 ( α ) = c ( 1 − α ) n α m does not correctly describe the kinetics of 10%Al 2 O 3 /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%Al 2 O 3 /CS. Finally, the estimated temperature of degradation is 565 K with a rate constant of 0.172 min −1 .