Effect of Heat Generated in Rubber Compound Vulcanization on the Reaction Kinetics: a Numerical Study

Vulcanization is one of the most important stages in the production of rubber products. Assigning optimum process parameters will allow obtaining high-quality products at the lowest cost. The cost of physical experiments to establish the required parameters can be reduced by theoretical calculation of the vulcanization kinetics. The most significant parameters are the vulcanization duration and temperature changes in various parts of the rubber compound; therefore, the majority of studies are aimed at determining their optimum values. The vulcanization process includes three stages: induction, curing stage, and reversion. The numerical calculation of the first two stages was performed in order to determine the effect of the heat generation in the reaction on the cure course, depending on the product thickness. Plates with a thickness of 2, 5, and 10 mm were considered. A block diagram of the algorithm for calculating the state of cure of a rubber compound is presented. Graphical dependences of the state of cure and temperature for plates of various thicknesses, made of a rubber compound used in the production of truck tires, were obtained for two cases: with and without taking into account the heat generation in the reaction. Data on the vulcanization duration are also given. With an increase in the product thickness, the effect of the heat generation on the vulcanization course increases significantly. Taking into account the heat generated in the reaction leads to a 1.6% change in the vulcanization duration for the 2 mm thick plate, 13% change for the 5 mm thick plate, and 50% change for the 10 mm thick plate. Thus, it is necessary to take into account the thermal effect when calculating the state of cure of rubber compounds, especially for thick items.