Kinetics and mechanisms of non-isothermal polymerization of N,N′-bismaleimide-4,4′-diphenylmethane with cyanuric acid

Abstract

Mechanisms and kinetics of non-isothermal polymerization of N,N′-bismaleimide-4,4′-diphenylmethane (BMI) with cyanuric acid (CA) were investigated. Competitive free radical polymerization and aza-Michael addition reaction mechanisms involved in the BMI/CA reaction system were characterized by using DSC, 1H-NMR, electron spin resonance (ESR) and gel permeation chromatography (GPC). Free radical polymerization mechanism predominated in the BMI/CA reaction system. Both model-free and model-fitting methods were used to determine the isoconversional activation energy (Eα) and pre-exponential factor (Aα). The values of Eα and Aα for aza-Michael addition reaction evaluated at α = 0.1 were 86 kJ mol−1 and 2.42 × 1010 min−1, respectively, and the reaction model was f(α) = 1.73(1 - α)α0.11. By contrast, Eα gradually decreased with increasing α (decreased from 88 to 48 kJ mol−1) in the α range 0.15−0.9, which was attributed to the inherent multi-step kinetics in free radical polymerization.