Study on thermal decomposition and combustion mechanism of azobisisobutyronitrile: Combined with TG-DSC-FTIR-GC-MS technology and the ReaxFF molecular dynamics

Abstract

As a typical energetic initiator, the pyrolysis and combustion mechanisms of azobisisobutyronitrile (AIBN) are of great significance for chemical safety and fire/explosion accidents investigation. Addressing the challenge that traditional experimental methods struggle to fully detect intermediates and final products, this study reveals the thermal behavior characteristics of AIBN via TG-DSC-FTIR-GC–MS technology. A significant phenomenon of coupled melting and decomposition was observed. Pyrolysis products such as nitrogen, carbon monoxide, acetic acid, methacrylonitrile, isobutyronitrile, and tetramethylsuccinonitrile were identified. By integrating molecular dynamics with ReaxFF force field, the micro-reaction pathways and product formation mechanisms were analyzed. The reliability of the simulation method was verified by comparing the activation energy (E_a) calculated from DSC with simulated values. The effects of different temperatures (2000–3500 K) and O₂ atmosphere on the initial decomposition, major products, and reaction pathways of AIBN were investigated. Results show that the initial decomposition during pyrolysis is primarily initiated by the N-containing radical C₄H₆N, while the combustion process is driven by oxygen-containing radicals. The participation of oxygen significantly alters the reaction pathways, with O₂-involved reactions accounting for 84.7 % at 2000 K. Furthermore, the formation and decomposition pathways of products such as CO, CO₂, H₂, H₂O, and HCN were clarified, and a complete reaction network for AIBN pyrolysis and combustion was constructed. The mutual validation between experimentally detected products and simulated pathways provides a new experimental-simulation integrated approach for thermal safety assessment and explosion mechanism research of azo-based hazardous chemicals.