Deep integration of pyrolysis kinetics and pyrolysis mechanism of polyimide aerogels

Abstract

As novel advanced organic materials, polyimide aerogels (PI-AER) exhibit high porosity and excellent thermal stability. For the general and safe application of PI-AER, it is imperative to clarify their thermal decomposition process. The kinetic parameters of PI-ARE pyrolysis were calculated using different traditional kinetic methods, and the results showed that the PI-AER pyrolysis process conformed to the Fn-like mechanistic function model with an average activation energy of 143.984 kJ/mol. The pyrolysis mechanism function model of the main pyrolysis stages was optimized and reconstructed to obtain the optimal solution f(α). In addition, the concentration changes of pyrolysis products with increasing temperature were monitored by TG-MS and the PI-AER bond breaking mechanism was analyzed. Finally, the TG curves were fitted piecewise to obtain Ea and lnA for the two pyrolysis processes. Combined with the pyrolysis mechanism and two-stage kinetic parameter analysis, the effects of the two pyrolysis stages of PI-AER on the kinetic parameters were elucidated. It was shown that the activation energies of solvent volatilization and desorption and PI-AER main chain were 60.1 kJ/mol and 147.76 kJ/mol, respectively. This study provides fundamental industrial parameters for the application of polyimide aerogels in extreme conditions.