| Some chemicals are relatively unstable,such as flammable solids,oxidizing substances and organic peroxides.When such substances are subjected to thermal stimulation,impurities or impact and other mechanical effects,the probability of accidents such as combustion and explosion will increase.Therefore,studying the thermal decomposition characteristics and impact sensitivity of unstable substances under the effect of impurities has certain reference significance for providing safety guidance for its production,transportation and storage.In this paper,the thermal decomposition characteristics and impact sensitivity of benzoyl peroxide（BPO）,azobisisobutyronitrile（AIBN）and ammonium perchlorate（AP）under the effect of impurities are studied.For BPO,on the one hand,containing appropriate water is beneficial to the safe storage and transportation of BPO,but on the other hand,water has a certain promotion effect on its decomposition,and changes decomposition mechanism under isothermal conditions.The activation energy ranges of dry and wet BPO under isothermal and dynamic conditions are obtained by using Friedman iso-conversion method.It is proved that the reaction mechanisms under two conditions are different.Based on the model fitting method,a two-step continuous reaction of"autocatalytic+n-stage"is established for the solid phase decomposition of dry and wet BPO;a three-step continuous reaction of"autocatalytic+autocatalytic+n-stage"is established for the melting and decomposition process.Through the impact sensitivity experiment,it is found that when the ambient temperature is 40℃,the water will significantly reduce the impact sensitivity of BPO.As the temperature increases,this trend gradually decreases.The expression of impact sensitivity for dry BPO is H50=(7.009-2.690×10-2T0)1.596,and the expression of wet BPO is H50=(18.20-6.291×10-2T0)8.410.For AIBN,Na2S2O3 can promote the decomposition of AIBN.The activation energy ranges of AIBN and AIBN with Na2S2O3 under isothermal and dynamic condition are obtained by using Friedman iso-conversion method.It is proved that the reaction mechanisms under isothermal and dynamic conditions are different,and the decomposition under solid phase is a multi-step reaction.Based on the model fitting method,a parallel reaction model of"n-stage"and"autocatalytic+autocatalytic"is established for the solid phase decomposition kinetics of AIBN and AIBN with Na2S2O3;a three-step continuous reaction model of"autocatalytic+autocatalytic+n-stage"is established for the melting and decomposition process.When the ambient temperature is 40℃,AIBN with Na2S2O3 is more sensitive to impact by promoting the thermal decomposition of AIBN;however,as the ambient temperature increases,the melting of Na2S2O3 reduces the energy conversion efficiency,which causes the impact sensitivity of AIBN to decrease.The impact sensitivity expression of AIBN is H50=(15.63-4.296×10-2T0)1.642,and the expression of AIBN with Na2S2O3is H50=(10.32-3.430×10-2T0)1000/（621.1-1.12T）0</sup>.For AP,DSC results show that the decomposition is multi-step,and its high temperature decomposition is gas phase reaction.Friedman method is used to calculate the range of activation energy under dynamic condition,which proves that the contribution of high temperature decomposition is large.Based on the model fitting method,a"autocatalytic+autocatalytic（gas phase）"continuous reaction model was established for AP.The impact sensitivity test results show that AP has low impact sensitivity due to its high hot spot temperature,but ferric oxide will increase impact sensitivity of AP.This paper studies the thermal decomposition characteristics and impact sensitivity of BPO,AIBN,and AP under the influence of impurities,and has certain reference significance for the production,transportation,and storage of unstable chemicals. |
