HEAT-TRANSFER STUDY OF POLYPROPYLENE-BASED INTUMESCENT SYSTEMS DURINGCOMBUSTION

We have studied the fire behavior and the heat transfer in the intumes cent formulations polypropylene (PP)-ammonium polyphosphate (APP)/pent aerythritol (PER) and PP-Hostaflam AP750 (AP750). We have shown that t he fire proofing properties (LOI, UL-94 and cone calorimeter) of PP wa s strongly improved using the commercial additive AP750 in comparison with the system APP/PER. This is:explained by the protection of the in tumescent coating developed from PP-AP750 which is still efficient at high temperature (450-550 degrees C) and which is developed faster. Th e measurement of temperature profiles in the conditions of the cone ca lorimeter shows that the temperatures reached with PP-AP750 are lower than these obtained with PP-APP/PER. Moreover, the temperature of PP-A P750 always remains lower than the temperature of the beginning of the fast degradation rate of PP which implies that there is never a fast degradation of the polymeric matrix. Finally, the computation of the t emperature of the degradation front (T-d) allows to conclude that low T-d and relatively high displacement rate of the place of the degradat ion front is needed to increase the efficiency of intumescent systems.