| Azo compounds are the materials easily showing self-reactive performance, which are commonly used in solution radical polymerization. If the phase change endothermic process overlaps decomposition exothermic process, it will go against the reaction kinetics and thermal hazards studies. In this paper, the two azo compounds which have overlapping phenomenon,2,2’-Azobis(isobutyronitrile)(AIBN),1,1’-Azobis(cyclohexane-l-carbonitrile)(ACCN), and their samples in different solvents are studied.Firstly, thermal decomposition characteristics of AIBN and ACCN in solid phase and solvents were measured by dynamic DSC, and the affect of phase change endothermic process on decomposition exothermic process were analysed by comparing kinetic parameters. Secondly, isothermal decomposition kinetics of AIBN and ACCN in soild phase were studied by using DSC. Thirdly, thermal decomposition characteristics of AIBN and ACCN in solid phase and solvents under adiabatic conditions were measured by using ARC, and their thermal stabilities were compared. Finally, based on Semenov model, thermal hazards of AIBN and ACCN in solvents were quantitatively assessed respectively by using thermodynamic parameters of ARC.The results show that AIBN decomposition reaction mechanism is a pseudo-autocatalytic reaction under isothermal conditions. Under dynamic and adiabatic conditions, the decompositions of AIBN and ACCN accompany phase change, and the decomposition reaction of ACCN in solid phase is the most complex in the samples of AIBN and ACCN in solid phase and in different solvents. For AIBN, the aniline does not interfere with the decomposition reaction mechanism, and it could be described as Mampel Power principle G(a)=a2/3. The self-accelerating decomposition temperatures of AIBN and ACCN in solvents are in the range of25～35℃,45～55℃, respectively. Therefore, if AIBN and ACCN need to be used in solvents in some processes, the temperature must be strictly controlled to avoid thermal explosions. |
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