ABSTRACT This work presents a comprehensive numerical model to optimize mechanical properties of thick rubber vulcanized items, comprising medium and high voltage electric cables and three-dimensional devices. Several vulcanization systems are considered, including peroxides and accelerated sulfur. For peroxides, both a genetic algorithm (GA) and an alternating tangent (AT) approach are adopted to determine the optimal final mechanical properties (tensile strength) of rubber items. The use of a mixture of peroxides is also considered, demonstrating that balanced mixtures may help in reducing the curing time and/or in increasing the optimal tensile strength in both core and skin of thick devices. For sulfur vulcanization, a mathematical kinetic model is presented to predict the cross-linking density of vulcanized rubber. The model is conceived to fit experimental rheometer data, and it is suitable to have an estimate of cross-linking degree at fixed temperature. The model requires a parametric calibration by means of only three kinetic constants, successively implemented in Finite Element (FE) software, specifically developed to perform thermal analyses on two-dimensional geometries. As an example, an extruded cylindrical thick EPDM item is considered and meshed through four-noded isoparametric plane elements. Several FE simulations are repeated changing both exposition time, tc, and external curing temperature, Tc, to evaluate for each (tc, Tc) couple the corresponding mechanical properties of the item at the end of the thermal treatment.
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