COMPARATIVE-STUDY OF THE KINETIC DEGRADATION OF DIFFERENTLY DECRYSTALLIZED COTTON LINTERS USING NONISOTHERMAL DTA CURVES

Cellulose samples of different degree of decrystallization were subjected to differential thermal analysis (DTA) technique under nonisothermal conditions. The samples were prepared by preswelling the cotton linters in 24-Baume NaOH followed by the use of direct or indirect methods to dry the mercerized cotton. The thermal stabilities of the samples were estimated taking into account the values of initial decomposition temperature, maximum decomposition temperature, and activation energy. The activation energy preexponential constant, order of reaction, and other thermodynamic parameters (DELTAH, DELTAS, and DELTAG) associated with each stage were derived by applying integrated peak areas (Satava and Skvara), the Borchart-Daniels general method, and the Prount-Tompkins equation. The results showed that the cellulose pyrolysis process cannot be described as having a single value of E(a) over the entire pyrolysis range. Also, the decrystallization caused by destruction of the formed alkali cellulose complex with a isopropanol-water (WAN) system was found to be the most pronounced change in pyrolytic parameters (i.e., less thermal stability) compared with native and other decrystallized samples. The dependence of E(a) on IR measurements is also discussed.