Thermal Decomposition Behavior of Melaminium Benzoate Dihydrate

Abstract

Crystals of melaminium benzoate dihydrate (MBDH) have been grown from aqueous solution by slow solvent evaporation method at room temperature. Powder X-ray diffraction analysis confirms that MBDH crystallizes in the monoclinic system (C2/c). Thermal decomposition behavior of MBDH has been studied by thermogravimetric analysis at three different heating rates: 10, 15, and 20°C/min. Nonisothermal studies of MBDH revealed that the decomposition occurs in three stages. The values of effective activation energy (Ea) and preexponential factor (ln A) of each stage of thermal decomposition for all heating rates were calculated by model free methods: Arrhenius, Flynn-Wall, Friedman, Kissinger, and Kim-Park methods. A significant variation of effective activation energy (Ea) with conversion (α) indicates that the process is kinetically complex. The linear relationship between the A and Ea values was established (compensation effect). Avrami-Erofeev model (A3), contracting cylinder (R2), and Avrami-Erofeev model (A4) were accepted by stages I, II, and III, respectively. DSC has also been performed.