Kinetics of thermal decomposition of styrene-butadiene rubber at low heating rates in nitrogen and oxygen

The kinetics of thermal decomposition of styrene-butadiene rubber have been investigated thermogravimetrically under various heating rates either in nitrogen or mixed with 5-25% oxygen in nitrogen. The results show that in pure nitrogen the reaction involves only one stage, with an initial reaction temperature of 622-661 K and an apparent activation energy at 211 +/- 15 W/mol. The initial reaction temperature decreases, but the reaction rate and its temperature range increase when the heating rate is increased. When oxygen is present, the reaction involves two parallel steps. The fractional conversion at the end of the first reaction is 0.83-0.87, depending on the oxygen concentration. Although the presence of oxygen somewhat delays the start of the initial reaction, the activation energy is reduced significantly, so that its rate becomes faster once reaction commences. The complete rate equation for both stages of reaction was obtained by summing the individual weighted rate equations; the weighting factors were determined from the fractional conversion at the end of the first reaction. Copyright (C) 1997 by The Combustion Institute.