Enhanced fire behavior of Casico-based foams

Abstract

The present work deals with the preparation and characterization of improved fire-retardant ethylene-acrylate foams. A commercial formulation, usually employed in the cable industry sector, Casico, was modified using two different synergistic flame retardant (FR) systems: silica/zinc borate micro-sized particles (M) and montmorillonite/graphene nanoplatelets (N). The different composites were prepared by melt-blending and the foams by a compression-molding chemical foaming process (Casico-based foams). All Casico-based foams presented a mainly closed-cell structure. The presence of the nanoparticles system (N) promoted the formation of microcellular foams, with cell sizes lower than 100 μm, and narrow cell distributions. Nevertheless, when both flame retardant systems were added a higher cell collapse was noticed. Due to the foam's Casico-N structure and the presence of the stiff layered nanoparticles an increase of the temperature of β and α relaxations and specific loss modulus was registered for that foam respect to the Casico foam. In a general way, the Casico-based foams presented a thermal decomposition behavior similar to that of unfoamed Casico. Only a slight increase of the thermal stability of the step associated to the ionomer decomposition was observed respect to the Casico. Significant fire behavior improvements were observed for Casico-M-N foam. Specifically, this foam showed the lowest value of PHRR (peak of heat release rate), EHC (effective heat of combustion) and FIGRA (fire index growth rate), having therefore the lowest flammability, even lower than Casico unfoamed material.