Mechanism of fire retardancy of polyurethanes using ammonium polyphosphate

Abstract

ABSTRACT:In this work, we studied the mechanism of the fire retardancy of ammonium polyphosphate (APP) in polyurethane (PU). Indeed, according to the limiting oxygen index test, the efficiency of APP in PU coating was proven. On the one hand, thermogravimetric analyses showed that the addition of APP to PU accelerates the decomposition of the matrix but leads to an increase in the amount of high-temperature residue, under an oxidative or inert atmosphere. This stabilized residue acts as a protective thermal barrier during the intumescence-fire retardancy process. On the other hand, spectroscopic analysis of the charring materials using infrared spectroscopy, MAS NMR of the solid state, and ESR enables better understanding of the carbonization process and, consequently, of the intumescence phenomenon. It has been shown that the char resulting from PU consists of an aromatic carbonaceous structure which condenses and oxidizes at high temperature. In the presence of APP, a reaction between the additive and the polymer occurs, which leads to the formation of a phosphocarbonaceous polyaromatic structure. Moreover, this char is strongly paramagnetic. The presence of large radical species, such as a polyaromatic macromolecule trapping free radicals, was demonstrated. Both of these characteristics help to explain the fire-retardant performance of PU/APP.

Investigation of fire behavior of rigid polyurethane foams containing fly ash and intumescent flame retardant by using a cone calorimeter

“…The IFR addition into the PUR and PUR/FA accelerated the decomposition processes11, 72 and PUR/IFR and PUR/FA/IFR composites decomposed early in comparison with PUR and PUR/FA. The reason for an early decomposition of PUR/IFR and PUR/FA/IFR is due to the intumescent flame retardant addition.…”

Effects of expandable graphite and dimethyl methylphosphonate on mechanical, thermal, and flame‐retardant properties of flexible polyurethane foams

“…In the first place, DMMP was decomposed to phosphoric acid at about 180°C, which further degenerated to metaphosphoric acid and polymetaphosphoric acid. These products could act as a catalyst for urethane bond breaking, so T 1stage and T 1max decreased slightly. Moreover, DMMP dehydrated to coke residue and the products covered FPUF substrate, which made thermal conductivity and decomposition rate decreased.…”

Melamine amino trimethylene phosphate as a novel flame retardant for rigid polyurethane foams with improved flame retardant, mechanical and thermal properties

“…This may be attributed to the decomposition of MATMP itself and the catalytic decomposition of the RPU caused by phosphorus‐containing acid formed during the thermal decomposition of MATMP. The same behavior can also be observed in case of APP filled polyurethane in the literature . Compared with the untreated RPU foam, the residue at 750 °C of flame‐retardant RPU foams are higher, which can be explained by the fact that the phosphorus‐containing acid can promote the char formation at higher temperatures.…”