The Study Of Thermal Decomposition And Fire Extinguishing Performance Of The New Clean Extinguishant

With the improvement of international and national environment-protecting requirements,Halon extinguishant agent has been widely banned because of the damage it has taken to the ozone layer,and the existing interim Halon alternatives would also be phased out.Therefore,exploring and developing environmentally friendly,efficient and non-toxic Halon alternative fire-extinguishing agent is one of hotspot and key research point in fire-fighting field.The paper preliminarily screened HFO-1336mzz(1,1,1,4,4,4-hexafluoro-2-butene)as a kind of potential clean fire-extinguishing agent based on its excellent physicochemical properties as fire-extinguishing agent such as environmental friendliness and low boiling point,and explored its fire-extinguishing applicability from the perspectives of thermal decomposition and fire-extinguishing performances.Basing on the high temperature of flame,the paper firstly discussed the thermal decomposition property of HFO-1336mzz using tubular reactor,explored the thermal decomposition products of HFO-1336mzz(Z)and HFO-1336mzz(E)at different temperatures and residence times by GC/MS.The results show that within the temperature range of 200-800?,the thermal decomposition of HFO-1336mzz(Z)or HFO-1336mzz(E)mainly transforms into each other,and the thermal stability of HFO-1336mzz(E)is higher than that of HFO-1336mzz(Z),the substance composition in the system after their decomposition reactions reach to equilibrium at high temperature is both 80%of HFO-1336mzz(E)and 15%of HFO-1336mzz(Z)mainly,while the other products are less.Furthermore,the paper explored the microscopic mechanism of the thermal decomposition process of HFO-1336mzz(Z)and HFO-1336mzz(E)through density functional theory method,calculated five decomposition pathways of HFO-1336mzz(Z)and six decomposition pathways of HFO-1336mzz(E)using Gaussian package.The results show that both HFO-1336mzz(Z)and HFO-1336mzz(E)decompose through homolytic reaction way which has the lowest engry barrier,and C-C bond fracture occurs in this way to generate fire-extinguishing radical CF3·;In addition,the mutual transformation between HFO-1336mzz(Z)and HFO-1336mzz(E)can achieve through a triplet state intermediate,and the energy barrier for HFO-1336mzz(Z)converting to HFO-1336mzz(E)is lower.Finally,based on the thermal decomposition studies,the paper further explored the fire-extinguishing mechanism of HFO-1336mzz(Z)and HFO-1336mzz(E)through density functional theory method,and the results show that the enery barriers of HFO-1336mzz(Z),HFO-1336mzz(E)and their thermal decomposition products CF3C=CH,CF3C=CCF3 and CF3H reacting with free radicals in flame such as OH·,H·,O2 and ·O· are all less than 40 kcal·mol-1,easily occuring addition or capture reactions,and generating fire-extinguishing free radical CF3.to further capture flame free radicals,achieving good chemical extinguishing process.The paper also measured and compared the fire-extinguishing concentrations of HFO-1336mzz(Z),HFO-1336mzz(E)and three kinds of typical HFC extingushing agent,and analyzed the flame shape changes in the fire-extinguishing process for each kind of fire-extinguishing agent.The results show that HFO-1336mzz's fire-extinguishing concentrations are low,showing excellent fire-extinguishing effect,and are comparable to that of HFCs.At the same time,the fire-extinguishing effect of HFO-1336mzz(E)is better than that of HFO-1336mzz(Z).According to the results of thermal decomposition and fire-extinguishing performance research,it can be concluded that HFO-1336mzz can be an alternative product of Halon;In addition,the olefin containing CF3 group has excellent chemical extinguishing effect and could be a new direction for Halon substitute research.