Zeolites: New Synergistic Agents for Intumescent Fire Retardant Thermoplastic Formulations—Criteria for the Choice of the Zeolite

The adduct of zeolites in intumescent formulations of thermoplastic polymers (additives: ammonium polyphosphate and pentaerythritol) leads to a great improvement in their fire retardant performance. A classification of different groups (A, X, Y, Mordenite and ZSM-5) is presented. The influence of the physicochemical properties of the zeolites is discussed. TG analyses reveal that the zeolite may act as a catalyst for the development of the intumescent carbonaceous material and stabilize the carbonaceous residue resulting in the degradation of the intumescent shield. Characterized by MAS-NMR ²⁷Al and ²⁹Si, it is proposed that alumino- and silicophosphate species formed are catalysts active for the synthesis of a protective carbon-based material.