(49b) ¬¬¬¬¬Development of Low-Charring Nanocomposites to Aid in Fundamental Understanding of Nanocomposite Flame-Retardancy

For decades, nanosheets comprised of various different materials have been utilized to construct nanocomposites with enhanced properties including high thermal stability, flammability reduction, and modified mechanical properties. Although research in this field has been actively pursued in the past, there is little understanding as to why these materials exhibit enhanced behavior compared to their pure polymeric counterparts.

Two major mechanisms for enhanced flame-retardancy have been proposed: (1) a physical barrier effect and (2) a catalytic charring effect. As the material burns, a physical barrier of carbonaceous char and stacked nanoparticles forms at the material surface, acting as a physical barrier for radiant, conductive, and convective heat transfer as well as a physical barrier for mass transfer of the fuel to the burning front. Secondly, the presence of nanoparticles can act as a catalyst for charring, increasing the char yield of the material and effectively altering the physical barrier that forms. By utilizing a nanocomposite system with low charring it is possible to observe the physical effects caused by the presence of nanosheets in the polymer matrix. As charring agents are added to the composite, the enhancement of flame-retardancy based on catalyzed charring can be observed.

Furthermore, the research into the field of thermally stable and flame-retardant nanocomposites has only focused on a relatively narrow view of polymers and nanoparticles, so any advancement into new materials is useful to further understand how these systems work. The current research project incorporates α-zirconium phosphate, a material capable of forming atom-thick, nanoscale-width nanosheets, and poly (methyl methacrylate), a widely used polymer in commercial application. Aside from enhanced thermal stability, these materials have altered glass-transition temperatures, excellent optical transparency with UV scattering, and a relatively low char yield, making them an excellent candidate to study the physical barrier effects and catalytic charring effects of polymer nanocomposites.