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

The nanocomposite 5%Bentonite/Chitosan (5%Bt/CS) has been prepared and characterized by the means of Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Brunauer, Emmett and Teller method (BET). These techniques confirmed the formation of the 5%Bt/CS, via the intercalation of CS in the interlayer space of Bt leading to the exfoliation of its structure. The non-isothermal degradation process of 5%Bt/CS under air atmosphere was investigated by thermogravimetric analysis (TGA/DTG) and differential scanning calorimetry (DSC), at various heating rates. The appearance of multi-peaks in the DTG curves of 5%Bt/CS, revealed that the nanocomposite underwent a complex degradation mechanism with at least two steps, and greater stability compared to those of neat CS. The thermal degradation steps kinetic parameters were calculated using Kissinger (KIS) and isoconversional Flynn–Wall–Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), Tang and Friedman (FR) methods It was found that the average values of activation energies were Ea = 210.53 kJ/mol for the first step and Ea = 345.28 kJ/mol for the second step. These values were used to match the experimental and simulated y(α) and z(α) master plots. It was found that the modified Sestak-Berggren f(α) = c(1 − α)nαmmodel allowed reproducing qualitatively the Y(α) curves, giving the same maximums, αm, for each value of β, which are consistent with the thermal degradation mechanisms of 5%Bt/CS.