Fire resistant cable with ceramifiable layer

Abstract

A fire resistant cable comprising: a conducting element (); a layer, surrounding the conducting element, made of a ceramifiable composition comprising: —a thermoplastic polymer mixture comprising: (a) a copolymer of ethylene with a C-Calpha-olefin, having a density of from 0.860 to 0.910 g/cm, a melt flow index not higher than 3 g/10 min and a melting point of 105° C. at most; (b) an ethylene homopolymer or copolymer of ethylene with a C-Calpha-olefin, having a density of from 0.900 to 0.985 g/cm, a melt flow index not higher than 5 g/10 min and a melting point of at least 110° C.; and (c) a polyethylene grafted with an ethylenically unsaturated monomer; —at least 25 wt % of silica; —a fluxing agent selected from alkaline metal oxides or precursors thereof; —an inorganic hydroxide compound selected from magnesium hydroxide, aluminium hydroxide and mixtures thereof; —a stabilizing agent comprising a hydrated magnesium silicate in an amount of at least 5 wt %; weight percentages being based on the total weight of the ceramifiable composition. Upon exposure to elevated temperatures such as those encountered in case of fire, the ceramifiable composition is transformed into a ceramic material capable of protecting the conducting element from fire and mechanical stresses. The fire resistant cable of the present invention can continue operating under fire conditions for a certain period of time.