Kinetics of Alder-ene reaction of Tris(2-allylphenoxy)triphenoxycyclotriphosphazene and bismaleimides - a DSC study

Tris(2-allyiphenoxy)triphenoxycyclotriphosphazene was reacted with three bi smaleimides (BMI), viz. bis(4-maleimido phenyl)methane (BMM), bis(4-maleimi do phenyl)ether (BME) and bis(4-maleimido phenyl)sulphone (BMS) via the Ald erene reaction. The differential scanning calorimetric analysis of the blen d manifested two distinct exotherms. The low temperature exothermic reactio n was attributed to the Wagner-Jauregg reaction following the ene reaction and the strong exotherms at around 250-270 degreesC to the cross-linking Di els-Alder reactions of the initially formed adducts. The Kinetic parameters , viz. activation energy (E) and pre-exponential factor (A) of the reaction s were evaluated by Kissinger and Ozawa methods using the variable heating rate method. The kinetic data revealed that the Wagner-Jauregg reaction was disfavoured by electron-withdrawing nature of the BMI. The Diels-Alder rea ction was facilitated by the electron-withdrawing nature of the bismaleimid e. The activation energy for the first exothermic stage decreased and for t he second major step increased on enhancing the stoichiometry of BMI in the blend for a given pair. The activation parameters served to predict the is othermal cure profiles of the blends and deduce the possible network struct ure under the given conditions of cure temperature and stoichiometry. (C) 2 001 Elsevier Science B.V. Ail rights reserved.