Study On The Thermal Stability Of Azo Initiators

Azo initiators are a general term for a class of azo compounds used as initiators.Due to the existence of azo groups(—N=N—),azo initiators are highly hazardous to heat,easily decompose and explode when exposed to heat,and their hazard categories are classified and labelled by global chemicals(GHS).)Is defined as an explosive substance.If the conditions of use,storage and transportation are improperly controlled,heat accumulation,impact,friction,electric sparks,open flames,etc.are very prone to combustion and explosion accidents.It is of great significance to conduct thermal stability studies on azo initiators.This paper selects two typical oil-soluble azo initiators,2,2-azobisisobutyronitrile and diisopropyl azodicarboxylate;2,2-azobis(2-methylpropylimid)Two typical water-soluble azo initiators,dihydrochloride and 4,4-azo(4-cyanovaleric acid),have carried out a series of thermal stability studies for the research objects.First,use the explosion-proof differential calorimetry scanner(DSC)to set different heating rates(?)and upper temperature limits according to the standard program to perform programmed heating and constant temperature testing at a certain temperature.The research results show that there is an endothermic-exothermic coupling phenomenon in the thermal decomposition process of the selected sample materials,and the exothermic heat is much greater than the endothermic heat;with the acceleration of the heating rate,the endothermic peak and the exothermic peak both move towards the high temperature area Moving to different degrees,the decomposition rate increases;the constant temperature test at a specific temperature found that the heat flow curve of the sample material is in the form of a "bell".With the increase of time,the decomposition rate first increases,reaches the peak and then decreases,showing A typical autocatalytic feature.Secondly,according to the analysis and test data,three methods are used to calculate the activation energy,the exponential factor and the related mechanism function expressions and undetermined parameters,so as to obtain the pyrolysis kinetic relationship,and based on this,the adiabatic maximum temperature of typical azo compounds Simulation and prediction of ramp rate time(TMRad),self-accelerating decomposition temperature(SADT)and safe storage period are carried out.The relevant research results have guiding significance for the production,storage and transportation methods and conditions of typical azo compounds.Finally,the vacuum stability equipment is used to monitor and analyze the pressure changes during the thermal decomposition of typical azo compounds,and the functional relationship describing the internal pressure changes of the equipment is obtained,and the corresponding activation energy and pre-exponential factors are obtained.The risk control of such compounds provides guidance.