Calculation of the Temperature and Extent of Reaction during the Vulcanization of Powdered Rubber

Abstract

Abstract Although vulcanization is a complex series of reactions, the overall result for heat of reaction could be described by an Arrhenius equation and a single activation energy. The activation energy for the vulcanization of powdered rubber recovered from tires was about 106 kJ/mole and the rate of reaction was described by a first-order reaction. With the kinetic parameters determined for the curing reaction by DC, the temperature profiles in rubber sheets were calculated. A numerical method of Dusinberre's generalization was an explicit incremental method applied to one-dimensional conduction and took into account the internal generation of heat due to the cure reaction and the heat transfer through the mold-rubber interface. The last problem was resolved by considering the fact that there was the same heat transfer rate on each part of the interface. This method proved to be as accurate as the implicit Grank Nicholson method, and its great advantage over the latter was that this explicit method needed only a small and inexpensive computer. Experiments pointed out the effect of several parameters on temperature profiles and midplane temperature for rubber sheets. Thus, the sheet thickness, mold temperature, initial rubber temperature, and a single two-step programming of mold temperature were considered. Some importance was given to possible applications. The determination of the time necessary for the midplane temperature to reach particular values such as the mold temperature or its maximum value. It is worth mentioning that our method allowed us to correlate the extent of reaction with the time and, therefore, to predict the time necessary for the extent of the reaction to reach a suitable value with a specified quality of vulcanizate for given operating conditions.