Natural mineral fire retardant fillers for polyethylene

In this article, we study the behaviour of common and low cost mineral fillers into a polyethylene matrix when exposed to mass loss calorimeter conditions. The different systems are made of linear low‐density polyethylene (LLDPE), with 50 wt% of calcium carbonate (CaCO₃), magnesium carbonate or talc treated with stearic acid or nontreated. These systems were exposed to an external heat flux of 50 kW/m ² and their burning behaviours were compared. Significant decrease of heat release rate peaks (PkHRR) was obtained with all these mineral fillers; however, even better results were obtained when particles were treated with stearic acid. Indeed, the system with CaCO₃‐treated stearic acid leads to a surprising intumescent behaviour. A rheological study showed no impact of stearic acid on the viscosity of the system and did not explain the appearance of the intumescent phenomenon. However, scanning electron microscopy (SEM) shows that stearic acid enhances the dispersion of particles into the polymer and acts as a dispersive agent. The results also show that the aspect ratio of the particles, the cation nature of the carbonates and the polarity of the polymer matrix have an effect on the appearance or not on the intumescent phenomenon. Copyright © 2010 John Wiley & Sons, Ltd.