Kinetics of thermal decomposition of epoxy resin in nitrogen-oxygen atmosphere

The kinetics of thermal decomposition of epoxy resin are investigated under various heating rates (2, 5, 10, and 20 K/min) and oxygen concentrations (5, 10, and 20%) in the nitrogen-oxygen atmosphere by means of thermogravimetric measurements. Results show that, unlike only one stage of reaction in the inert atmosphere, two reaction stages are involved when oxygen is present in the carrier gas. The initial reaction temperature, in the range of 470-572 K, decreases with increasing oxygen concentration and decreasing heating rate. The rate equations for various oxygen concentrations can be modeled by Arrhenius-type equations, from which kinetic parameters such as activation energy, preexponential factor, and reaction orders for unreacted material and oxygen concentration are determined using Friedman's method. The activation energy is 129.6-151.9 kJ/mol for the first reaction and 103-117.8 kJ/mol for the second reaction, and decreases with increasing oxygen concentration. The cut-off conversion factor between the first and the second reactions is in the range of 0.71-0.74. The complete rate equation, when two-stage reactions are involved, can be obtained by summing the individual weighted rate equations; the weighting factors are determined from the cut-off conversion factor.