The thermal behavior of an acrylic binder resin used in back coatings for textile applications was studied. The influence of the crystalline form of the fire-retardant additive on the thermal behavior was investigated. This resin formed a carbon char during its thermal degradation, so it may be assumed that it acts as a charring agent in intumescent systems with ammonium polyphosphate (APP) as the acid source. Thermogravimetric and spectroscopic analyses of acrylic binder resin/APP mixtures demonstrated the influence of the crystalline form of APP. The degradation mechanism of the binder resin could be described by ring closure and the formation of unsaturations. APP leads to the formation of a phosphocarbon structure that is thermally stable, whatever the crystalline form was of APP. (C) 2004 Wiley Periodicals, Inc.