Phosphorus-containing epoxy for flame retardance .4. Kinetics and mechanism of thermal degradation

The kinetics and mechanisms of thermal degradation of a phosphorus-containing epoxy based on bis-(3-glycidyloxy)phenylphosphine oxide (BGPPO) and 4,4'-diaminodiphenylsulfone (DDS) were studied. Two and four stages were found for BGPPO/DDS degradation in nitrogen and air, respectively. The degradation activation energies calculated from the methods of Kissinger, Friedman and Ozawa were obtained. The first stage of degradation, which results from the decomposition of phosphorous groups, showed lower activation energy than the other stages. Furthermore, via FTIR and TG-FTIR investigations, the degradation of this phosphorus-containing epoxy was determined to begin by the breaking of P-Ph bonds, followed by dehydration reactions breaking P-O-C bonds, and elimination of propyl groups. Therefore, the degradation of the epoxy resulted in high char yields and residues with high phosphorus contents. (C) 1996 Elsevier Science Limited.