The effect of intumescents on the burning behaviour of polyester-resin-containing composites

Recently we have shown that the introduction of an intumescent/flame retardant fibre system to a rigid composite comprising a textile reinforcing element (e.g. woven glass fabric layers) and a resin may generate additional char with respect to the additive contributions of all components present when studied using thermogravimetric techniques. This paper presents the results of cone calorimetric experiments of a series of composites comprising a combination of glass reinforcing elements, selected intumescents (based on melamine phosphate), the flame retardant Visil fibre and selected unsaturated polyester resins. Results show that the introduction of the intumescent/Visil can significantly reduce the peak heat release values and in some cases the peak smoke intensities evolved by composite samples exposed to 50 kW m⁻² heat flux. Furthermore, mass loss rates are reduced and residual chars are increased. There is a clear indication that we have established a novel route to increasing the fire resistant properties of rigid composites.