SYNERGISTIC EFFECT OF ZEOLITE IN AN INTUMESCENCE PROCESS - STUDY OF THE CARBONACEOUS STRUCTURES USING SOLID-STATE NMR

This work deals with the chemical effect of zeolite 4A added to the in tumescent ammonium polyphosphate (APP)-pentaerythritol (PER) system [f ire retardant (FR) polyethylene-based formulation]. The study of the t hermal behaviour of the system using thermogravimetric (TG) analysis s hows that the presence of the zeolite leads to an increase in the stab ility of the material at high temperature (T > 500 degrees C). Chemica l analysis and cross-polarisation dipolar-decoupled magic-angle spinni ng (CP-DD-MAS)C-13 NMR reveals that the materials resulting from the t hermal treatment of the APP-PER and APP-PFR/4A systems are formed by c arbonaceous and phosphocarbonaceous species and that the zeolite enhan ces the stability of the phosphocarbonaceous species. DD-MAS P-31 NMR indicates that this stability may be due to an absence of pyrophosphat e species in the heat-treated APP-PER/4A system. Micro-Raman spectrosc opy and H-1 NMR of the solid state provides information on the structu re of the carbonaceous material. Thermal treatment led to the formatio n of a 'turbostatic carbon' with a local structure of this 'carbon spe cies', with the zeolite permitting retention of the comparatively unor ganised carbon species in the high-temperature range. Moreover, a low- resolution solid-state H-1 NMR study of the spin-lattice and spin-spin relaxations of the samples allows an evaluation of the size of the sl ow relaxation domains using the Goldman-Shen procedure. It is shown th at the zeolite hinders the formation of small molecules in the polyaro matic network. Finally, the relationship between the formation of a co herent macromolecular network and the improved FR performance of the A PP-PER/4A system is proposed.