HYbrid ComPOsites POlymer NanoTAlc for FlAMe Retardancy – Hypopotaam

The high fire hazards posed by polymeric materials both in historical times and to the present days are a consequence of their organic composition. In order to improve their flame retardant (FR) properties, flame retardant, and in particular mineral fillers, may be added to the polymeric matrix. Among the existing mineral filler, metallic hydroxide and nanoparticles are the most studied. The first class is non toxic, low cost solution but in order to be efficient, additives have to be used at high loading leading to problems during processing and also regarding the mechanical properties of the resulting composites. At the opposite, nanoparticules are used at low levels but the fire performances achieved are not satisfactory to comply with standards. In this frame, the aim of HYPOPOTAAM is to develop novel hybrid inorganic-organic materials exhibiting enhanced flame retardancy using innovative concepts. The main innovative approaches consist first in the use of talc-like hybrids (TLH) with the following chemical formula: Mg3(RSi)4O8(OH)2 where R stands for the organic moiety as mineral fillers. Those systems differ from previous ones reported in the literature (such as for example clays or layered double hydroxides and could in ourd case gives its FR properties since in the case of TLH, the organic moieties that gives the functionality to the mineral filler) are covalently bonded to the framework. Moreover, a great variety of compositions can be obtained by considering not only the organoalkoxysilane used as precursors but also the metal cations. Secondly, innovative process will be develop and consists to generate and to functionalize the nanofiller directly in the polymer. This very innovative approach, also known as reactive extrusion is based on the dispersion of inorganic precursors and on the creation of the inorganic structure in the molten polymer during processing through hydrolysis-condensation reactions (classically called sol-gel in the inorganic chemistry). Using this approach, it is expected ensuring a good dispersion of the fillers. As a conclusion, it is expected using the good compositions of precursors (organic moieties and metal cations) and the good processing methodology, to develop a polymer/TLH composites presenting morphology in the way of promoting the fast accumulation of inorganic at the surface upon heating and the formation of a cohesive char. These new materials should thus present high fire performance and could be used for rail way applications. In particular, the material should be used as electrical parts for rolling stocks (single and two levels) and high and very high speed trains.