Physicochemical properties and thermal stability of 2,2′-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride

This investigation delves into the thermal decomposition kinetics and thermal hazards of the water-soluble azo initiator, 2,2 '-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride (AIBI), starting with an examination of phase changes and reactions during AIBI heating. Initially, a thermogravimetric analyser was employed to assess the sample, applying a heat-wait-heat approach to observe exothermic reactions upon heating to the decomposition point. This process revealed reactions initiating around 160 degrees C, a critical temperature for phase transition identified in previous research. However, no noticeable phase change was observed, consistent with earlier reports noting mass loss at this temperature, highlighting the nuanced phase behaviour of AIBI. Further analysis utilised differential scanning calorimetry alongside the isoconversional kinetic analysis via the Flynn-Wall-Ozawa method to investigate AIBI's thermal decomposition. This comprehensive approach revealed a complex decomposition process with an apparent activation energy of approximately 150 kJ mol-1, underscoring the need for careful temperature management during storage and transport to forestall autocatalysis, recommending an ambient temperature below 100 degrees C and incorporating a model-free methodology as a preliminary step allowed for an initial assessment of the reaction's kinetics, providing a broader understanding of the decomposition behaviour. Following this, a model-based approach was employed for advanced verification, such as determining the specific reaction model, f(alpha) and conducting further kinetic calculations. This two-pronged analysis strategy enriched our insight into AIBI's thermal hazard behaviour, enabling a more accurate prediction of thermal hazards and informing safer handling and storage practices. The study confirms the intricate thermal decomposition characteristics of AIBI. It highlights employing both model-free and model-based methodologies for a comprehensive understanding of thermokinetics and safety profiles.