Basic Ingredients of Intumescent Compositions

This chapter overviews the typology and evolution of flame retardants for building structures, their chemical composition and the functional contribution of the main components of the intumescent system to the fire-retardant mechanism. Approaches to the development of the most widely used materials based on the intumescent triad, including ammonium polyphosphate (APP), melamine (MA) and pentaerythritol (PE), are considered. The main groups of the required ingredients of these intumescent compositions are classified in detail, in accordance with the ideas about the functional contribution of each of them to the process of thermolytic synthesis of heat-insulating charring coatings: acid donors (ammonium phosphates), char formers (pentaerythritol, cellulose) and porophores (melamine, urea, guanidine and chloroparaffins). On the basis of a critical analysis of literary sources and experimental data obtained by the authors on the properties of substances that traditionally constitute intumescent materials, a hypothesis has been put forward that established ideas about the functional contribution of the discussed components of intumescent systems and the nature of the processes are inaccurate. The results of authors’ own research are presented, which allow to review and clarify the role of the main ingredients in the synthesis of charred layer. The authors experimentally confirmed and theoretically substantiated the new data on the behavior of pentaerythritol during thermolysis of the triad intumescent system of melamine–pentaerythritol–ammonium polyphosphate, which exclude pentaerythritols esterification by phosphoric acids under the considered conditions. It is shown that today there is no coherent concept that could be the scientific and technological foundation for creating fire-retardant intumescent compositions and could unambiguously describe the physicochemical nature of the processes of thermolytic synthesis of charred heat-insulating layers of intumescent coatings.