NEW INSIGHTS IN THERMAL DECOMPOSITION OF AZOBISISOBUTYRONITRILE

摘要

Recently the results of interlaboratory investigation of AIBN thermal decomposition have been reported in a series of papers [l]-[4]. The main topic was: can we use small-scale tests to evaluate kinetic parameters allowing predicting thermal behavior in industry scale (Self-Accelerating Decomposition Temperature in particular)? 2,2'-azobisisobutyronitrile (AIBN) have been selected as an object since it is widely used chemical compound, posing certain thermal hazard. AIBN has been extensively studied in literature (e.g. [5], [6]), but the mechanism of its decomposition was not entirely clarified. It is interesting to note that all the participants of the AIBN interlaboratory investigation have used the same experimental raw data, but they proposed different kinetic models to predict experimental SADT. In these models the initial and key step is the solid-state AIBN decomposition. In present study the accelerating rate calorimetry (ARC) have been used to derive the kinetic parameters of AIBN decomposition. The total process of AIBN decomposition is shown to be complex comprising the following events: solid-state decomposition of the low-temperature phase, decomposition of the high-temperature form, melting, liquid-state decomposition and ignition. From the analysis of the initial region of self-heating rate-temperature curve the decomposition process in solid-state found to follow the 1st order with E_a=179.8±1.7 kJ/mol and lg(A, s~(-1))=22.0±0.3. Thermal behavior of the 3-dimensional AIBN charge has been simulated using CISP Thermal Safety Software v 2.4.3 (Cheminform [4]) by numerical solution of the thermal balance equation and compared with the experimental BAM data [1]. Thermophysical parameters, necessary for modeling of heat balance have been determined experimentally. Comparison of the experimental and simulated data reveals that the solid-state AIBN decomposition kinetic parameters evaluated with accelerating rate calorimetry allows successful predicting of the AIBN self-accelerating decomposition temperature (SADT). The impact of the involved parameters, i.e., heat effect, heat capacity, heat conductivity, charge density and heat transfer coefficient on the simulated SADT value is discussed.