Thermal behaviour of ethylene-propylene rubber/polyurethane/ammonium polyphosphate intumescent formulations - a kinetic study

The paper deals with the thermooxidative degradation of a ethylene-propylene rubber and a fire retardant intumescent ethylene-propylene rubber/polyurethane/ammonium polyphosphate formulation. The invariant kinetic parameters method, applied to thermogravimetric analyses data of these materials, allows to model their degradations. It shows that addition of the intumescent polyurethane/ammonium polyphosphate additive in the formulation increases the thermal stability of the material which thermal behaviour does not imply an ablative process, as generally observed in intumescent polyolefins-based materials. It is proposed that intumescence of the material arises from the reaction of polyphosphate and polyurethane, polyurethane playing the part of an additive and not the part of a polymeric matrix. (C) 1999 Elsevier Science Ltd. All rights reserved.