Experimental/FEM Optimization of Medium Voltage Rubber Insulated Electric Cables Vulcanized with Steam Water. Differential Scanning Calorimetry (DSC) and Rheometer Experimental Results

The standard industrial process to produce medium voltage electric cables based on EPDM consists of crosslinking by peroxides with high temperature steam (pressurized water vapor). Suboptimal material crosslinking is usually due to a decrease of the temperature along the vulcanization pipe. Temperature variations are connected to variations in steam pressure into pipe system. In the present paper a combined numerical and experimental approach to optimize the production process of medium voltage rubber insulated electric cables vulcanized with steam water is presented. The numerical part, discussed in an accompanying paper, is based on the utilization of Finite Elements and an optimization Genetic Algorithm (GA) approach. Here, attention is focused on the experimental investigation. In particular, the final crosslinking degree is experimentally obtained by means of a DSC determination of non-decomposed peroxide from the external layer to the core of the cable insulation. The final task is to minimize the difference between numerically predicted and experimentally determined crosslinking degree using a steam temperature profile along the pipe to explain the variations. A preliminary evaluation of kinetic reaction constants of rubber cured with peroxides is here provided by means of a previously presented kinetic model.