XPS STUDY OF AN INTUMESCENT COATING .2. APPLICATION TO THE AMMONIUM POLYPHOSPHATE PENTAERYTHRITOL ETHYLENIC TERPOLYMER FIRE-RETARDANT SYSTEM WITH AND WITHOUT SYNERGISTIC AGENT

Fire retardancy of polymer may be due to the formation of protective s urface coating, i.e. a swollen char layer (intumescence). The intumesc ent coatings resulting from thermal treatments of the association of a mmonium polyphosphate (APP) and pentaerythritol (PER) with or without zeolite 4A (used as synergistic agent) in a polyethylenic terpolymer ( LRAM3.5) are studied by X-ray photoelectron spectroscopy. The O-1s, P- 2p, C-1s and N-1s spectra are discussed. The formation of pyridinic an d pyrrolic nitrogen and quaternary nitrogen in polyaromatic groups in the intumescent structures is shown. The oxidised nitrogen (nitro grou ps and pyridine N-oxide) are only observed up to 350 degrees C and the n are evolved as NOx species. It is then proposed that the pyridinic f unction, observed only in the case of the system with zeolite at all t emperatures, participates in the improvement of the fire proofing prop erties of the materials. (C) 1997 Elsevier Science B.V.