Non-isothermal degradation kinetics of N,N′-bismaleimide-4,4′-diphenylmethane/barbituric acid based polymers in the presence of hydroquinone

ABSTRACT The non‐isothermal degradation kinetics of the cured polymer samples of N,N′‐bismaleimide‐4,4′‐diphenylmethane/barbituric acid [BMI/BTA = 2/1 (mol/mol)] based polymers in the presence of hydroquinone (HQ) and native BMI/BTA was investigated by the thermogravimetric (TG) technique. By adding 5 wt % HQ into the BMI/BTA polymerization, the activation energy (Ea) of the thermal degradation process increased significantly in comparison with native BMI/BTA. Thus, the thermal stability of the cured polymer sample in the presence of HQ was greatly improved. The thermal degradation process exhibits three distinct stages. The key kinetic parameters associated with these stages were attained via the model‐fitting method. For the sample of native BMI/BTA, the thermal degradation process was primarily controlled by nucleation, followed by the multi‐decay law in the first stage. In contrast, the reaction order model adequately described the thermal degradation kinetics in the second stage. As to the last stage, the complex processes were described satisfactorily by the best‐fitted reaction model. For the sample of BMI/BTA/5 wt % HQ, the degradation process was controlled by the nucleation mechanism, followed by the multi‐molecular decay law in the first stage. In contrast, the second stage was controlled by the mixed mode of the competitive reaction order mechanism and 3‐D diffusion mechanism. In the third stage, the complex processes were also adequately described by the best‐fitted reaction model. All the experimental results illustrated that incorporation of 5 wt % HQ into the BMI/BTA based polymer resulted in the best thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1923–1930, 2013