Casting and Curing Process Optimization of Epoxy Resin used in Electromagnetic track brakes

Abstract

Liquid epoxy resin vacuum casting systems contain an epoxy and a hardener, which are used to manufacture crosslink three dimensional network called thermoset material. Their applications include vacuum and vacuum/pressure casting in the manufacture of both advanced and conventional enameled copper coil winding. The combination of high mechanical properties with high resistivity and relatively low dissipation factors are the important properties of epoxy resin that provides advantages in electrical and electronic insulation. Due to its good insulation properties, liquid epoxy resin is convenient as a secondary insulation to cast under vacuum into enameled copper coil in magnetic track rail brakes. The aim of using liquid epoxy resin is to protect enameled copper coil from touching each other and thermo-mechanical aging, and also to act as a secondary electrical insulation material during operation. The vacuum casting of liquid epoxy resin provides some advantages such as ensuring void free casting, reliable electrical insulation with lowest partial discharge and excellent bonding and mechanical fixation. The effects of curing conditions such as time and temperature on the physical properties of an epichlorohydrin derivate anhydride cured epoxy system have been investigated. The cure kinetics and thermal behavior was monitored experimentally. The main purpose of the work is to decrease the curing time in order to achieve higher productivity of magnetic track brakes without losing the quality. For this purpose, the thermal and mechanical properties such as; viscosity, glass transition temperature (Tg), Modulus of Elasticity, thermal coefficient of expansion, decomposition temperature and water absorption by using rheometer, Differential Scanning Calorimeter (DSC), Dynamic Mechanical Analysis (DMA), Thermal Mechanical Analysis (TMA), Thermal Gravimetric Analysis (TGA) have been investigated respectively. Additionally, FTIR Spectrometer was used to determine structural changes and to monitor the evolution of functional group for various times cured samples at isothermal temperature. These analysis represents an important step in configuration of curing conditions (Temperature and Time), which can save considerable costs during process of production. The obtained results were interpreted through good correlations between different techniques in terms of curing time/temperature/properties relationships. Finally, the obtained results exhibited that a gradual scientific methodology based on different measurement methods was really helpful to determine an acceptable level of curing. Besides, this methodology will be used as an instrument in Knorr Bremse for the further development.