This work presents a comprehensive numerical model to optimize mechanical properties of thick rubber vulcanized items, comprising medium and high voltage electric cables and 3D devices. Several vulcanization systems are considered, including peroxides and accelerated sulphur. 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 a 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 sulphur vulcanization, a mathematical kinetic model is presented to predict the crosslinking density of vulcanized rubber. The model is conceived to fit experimental rheometer data, and it is suitable to have an estimate of crosslinking degree at fixed temperature. The model requires a parametric calibration by means of only three kinetic constants, successively implemented in a Finite Element software, specifically developed to perform thermal analyses on 2D 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.

A comprehensive numerical model for the interpretation of crosslinking with peroxides and sulphur: chemical mechanisms and optimal vulcanization of real items

MILANI, GABRIELE;
2012-01-01

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 3D devices. Several vulcanization systems are considered, including peroxides and accelerated sulphur. 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 a 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 sulphur vulcanization, a mathematical kinetic model is presented to predict the crosslinking density of vulcanized rubber. The model is conceived to fit experimental rheometer data, and it is suitable to have an estimate of crosslinking degree at fixed temperature. The model requires a parametric calibration by means of only three kinetic constants, successively implemented in a Finite Element software, specifically developed to perform thermal analyses on 2D 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.
2012
vulcanization; kinetic model; peroxides; accelerated sulfur; crosslinking; mathematical model
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/687094
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