SYNERGISTIC EFFECT OF ZEOLITE IN AN INTUMESCENCE PROCESS - STUDY OF THE INTERACTIONS BETWEEN THE POLYMER AND THE ADDITIVES

The chemical effect of the zeolite 4A added to the intumescent ammoniu m polyphosphate (APP)-pentaerythritol (PER) system in a fire retardant (FR) ethylene-butyl acrylate-maleic anhydride terpolymer (LRAM3.5)-ba sed formulation has been studied. Thermogravimetric (TG) analysis defi nes the different steps of the degradation of the formulation and show s that the presence of the zeolite leads to an increase in the stabili ty of the material at high temperature (T > 550''C). Spectroscopic cha racterisations, mainly P-31, C-13, H-1 and Al-27 NMR of the solid stat e, demonstrate that there are interactions between the polymer and the additives. In the case of the LRAM3.5-APP-PER formulation, the protec tion arises principally from the additives which make a thermal barrie r between the flame and the material. When zeolite is present it plays an essential role, because it allows the formation of structures stab ilising the polymer which can then participate in the formation of the intumescent protective shield and hence in its own protection. Moreov er, we prove that the FR properties of the protective material obtaine d from the formulations depend on the 'quality' of the intumescent coa ting obtained from the additives. In particular, the presence of the z eolite decreases the size of the amorphous domains of the carbon.