XPS STUDY OF AN INTUMESCENT COATING APPLICATION TO THE AMMONIUM POLYPHOSPHATE PENTAERYTHRITOL FIRE-RETARDANT SYSTEM

Fire retardancy of polymers may be due to the formation of a protective surface coating, i.e. a swollen charred layer (intumescence). An intumescent coating resulting from thermal treatments of the association of ammonium polyphosphate (APP) and pentaerythritol (PER) is studied by X-ray photoelectron spectroscopy. The O 1s, P 2p, C 1s and N 1s spectra are discussed. In the formation of the intumescent material the presence is shown of nitrogen in pyrrole and pyridine type structures of aromatic phosphate esters. A degradation mechanism is suggested which involves a reaction with O2 via the formation of carbonyl and carboxylic groups.