Thermal degradation behavior of a flame retardant melamine derivative hyperbranched polyimide with different terminal groups

Abstract

Melamine derivative hyperbranched polyimide (HPI) polymers with different terminal groups were synthesized by emulsion polymerization reactions, followed by stepwise thermal imidization. The non-isothermal behavior of the synthesized HPI polymers was studied by thermogravimetric analysis under a nitrogen atmosphere and the results were compared with the corresponding terminal groups. In this study, we attempted to clarify the effects of different terminal groups on the non-isothermal degradation kinetics. The derived apparent activation energies using Flynn–Wall–Ozawa and Kissinger methods fit well with each other (showing the same trend). Meanwhile, the type of solid state mechanism was determined using the Coats–Redfern and Criado methods proposed for D1 types such as amine–amine terminals, amine–anhydride terminals and anhydride–anhydride terminals, which are one-dimensional diffusions that follow the unimolecular decay law of first order reactions. The E_a showed significant differences at α > 0.7, which indicates the role of different terminal groups towards degradation behavior. From the calculations, the lifetime prediction at 5% mass loss decreases in the following order: anhydride terminated > amine terminated > anhydride–amine terminated which is related to the dissociation energy between the anhydride functional groups and amine functional groups. Hence, the presence of different terminal groups reveals their contributions towards thermal degradation and stability.