Thermal decomposition of solid azobisisobutyronitrile

Thermal decomposition of AIBN Part C: SADT calculation of AIBN based on DSC experiments

“…For experimental isothermal data at 80, 85, 90 C, this model describes the shape and position of the main peak, but cannot describe the initial range with slow decomposition in the solid phase. The presence of melting for isothermal conditions is in agreement with [9,10], which point to the rapid submelting of the sample in the range between the phase transition temperature of 80 C and 100 C. Gyevi and Tüdös [13] uses X-ray diffractograms for isothermal measurements of AIBN at 85 C and they found that the slow melting and decomposition from the liquid phase exist during the autocatalytical acceleration of the reaction. Therefore, this melting step is reasonable by description of the isothermal decomposition in this range.…”

“…3). Literature values are 135 kJ/mol [9] and 130 kJ/mol [7]. A small sharp exothermal autocatalytic peak at 92 to 115 C on all dynamic measurements has an area of about 1% of the total heat effect.…”

“…Additional effect 2: an endothermal effect at 80 C. This is a solid-solid transition for two different polymorphic modifications of AIBN [9]. This effect is not present in the figures.…”

“…The second step, B ! C, is a reaction of the n-th order [9]. This simple two-step model describes melting and decomposition in the liquid phase for dynamic data with low heating rates well (Fig.…”

“…According to the literature [9,10], submelting is present in the high-temperature polymorphic range and the total reaction rate is therefore 2.5 times higher than in the lowtemperature polymorphic range below 80 C.…”