Fire behavior of simulated low voltage intumescent cables with and without electric current

Abstract

Many circumstances can lead to an electrical fire. It is then helpful to reproduce those circumstances in laboratory conditions to duplicate fire scenarios in order to increase knowledge and to develop safer and flame-retarded materials and electrical systems. Our approach was to develop specific bench scale tests. The mass loss cone calorimeter coupled with Fourier transform infrared was used to mimic a fire scenario on simulated low voltage cable (flame-retarded polymer molded around copper wire) and to characterize the gas phase. The electric current creates an additional heating condition (Joule effect) which can modify the decomposition of the flammable material (e.g. the cable jacket made in thermoplastic), and so its fire behavior in case of fire. It is the reason why we performed the experiments mimicking different fire scenarios with and without electric current. Specific test was also developed to investigate the flame spread and the delamination of the polymer around the wire. The bench scale tests presented in this article were applied on intumescent polymers (ethylene-vinyl acetate containing commercial intumescent additive). The results were discussed with a special emphasis on the influence of electric current on the fire behavior.