An investigation of the thermal degradation of epoxy maleate of bisphenol A

The thermal behavior of epoxy maleate of bisphenol A (EMBA) was investigated by thermogravimetry (TG), derivative thermogravimetry (TDG) and infrared (IR) spectroscopy, in the range of temperatures within 20 and 500degreesC. The kinetic analysis was carried out using both the DTG sim computer software for simulation of DTG curves and the dynamic method for the thermal degradation of polymers at any time. Both TG and DTG curves recorded for 5.5, 9.0, 12.0 and 16.0degreesC min(-1) heating rates show three main decomposition stages. The kinetical parameters were evaluated taking into consideration the maximum rate of decomposition (T-max) as the reference element. The apparent activation energy (Ea) values determined using the dynamic method are 49 kJ mol(-1) for the first stage of decomposition, 106 kJ mol(-1) for the second stage and 159 kJ mol(-1) for the third stage. The kinetical parameters determined in dynamic conditions and data obtained by IR spectroscopy postulate that the thermal degradation mechanism of EMBA involves a scission of the esteric liaison with CO2 elimination in the first stage. This stage is characterized by T-max values placed between 114 (5.5degreesC min(-1) heating rate) and 142degreesC (16.0degreesC min(-1) heating rate). In the second stage with T-max values between 316 and 343degreesC, new scissions of the main polymeric chain take place. The third stage, with T-max values between 363 and 386degreesC is characterized by the presence of parallel competitive reactions of the polymeric fragments formed in the first and the second stage of degradation. The main important products evolved in the third stage are water and higher phenols. (C) 2004 Published by Elsevier B.V.