Study On Thermal Hazards Of Three Azo Initiators Mixed With Impurities

The-N=N-structure of the azo compound,which is a kind of self-reactive material.It is easily broken under high temperature and pressure to form free radicals.As impurities inevitably be doped in the process of production and transportation,the thermal stability of azo compounds will be affected,leading to the occurrence of accidents and disasters.Therefore,three azo compounds[oil-soluble azo compounds:azodiisobutyronitrile?AIBN?,azodiisoheptanitrile?ABVN?,water-soluble azo compounds:azodiisobutylamidine hydrochloride?AIBA?]and doped with different impurities were selected to study the thermal hazard.Firstly,the thermal decomposition characteristics of three pure azo compounds were conducted by differential scanning calorimeter?DSC?to acquire thermokinetic parameters.DSC was still used to screen the impurities,and the impurities which have a significant influence on the thermal decomposition of azo compounds were selected.Based on the proportion of impurities which have the greatest influence on the thermal stability,isothermal experiments of AIBN mixtures and dynamic DSC experiments of ABVN and AIBA mixtures were carried out.Then,the decomposition models are established and kinetic parameters of azo compunds are calculated by the Friedman method and Thermal Safety Software?TSS?.Finally,the thermal decomposition characteristics of pure azo compounds and mixtures were employed by accelerating rate calorimeter?ARC?.Combining decoupled dynamic and adiabatic data,the kinetic model of ABVN and ABVN mixed system doped with Fe?NO₃?₃impurities was established.The results show that AIBN,ABVN and their mixtures are coupling of heat absorption and generation.It is further proved by the“interruption and re-scanning”method that the kinetic model of ABVN is N-order.It is verified that AIBN and AIBA are self-catalytic substances.Three impurities were selected:Fe?NO₃?₃,Na₂S₂O₃ and Na₂SO₄.When the impurity content is about 18³1%,it had a great impact on the thermal decomposition of azo compounds.In addition,the curves of ABVN and ABVN mixed system doped with Fe?NO₃?₃impurities obtained by simulated the N-order model are basically consistent with the experiments curves.It means that the decomposition process can be better reflected by the dynamic and adiabatic calorimetry mode at the same time.Based on the above models,the safety assessment parameters such as Time to Maximum Rate under adiabatic conditions(TMR_ad)and?Self Accelerating Decomposition Temperature?SADT are obtained.The obtained parameters play a guiding role for safe production and transportation and are useful for determining a proactive emergency response procedure associated with industrial applications on azo compounds during thermal upsets.