Polymer/clay aerogel composites with flame retardant agents: Mechanical, thermal and fire behavior

Aerogel is a class of material characterized by its high void content and extreme lightness. Different polymer/clay aerogels have been prepared by a simply freeze-thaw process from a suspension with poly(vinyl alcohol) (PVOH) and clay (Na+-MMT). Low density polymer/clay aerogels modified with flame retardant agents were prepared using a similar approach. The addition of flame retardant agents slightly increased the apparent density of the final composites whereas the compression properties were reduced due to the decrease in the polymer/clay interfacial bonding. An exception was the sample containing Al(OH)3 that exhibited higher modulus and stress at maximum deformation. Regarding thermal properties, the presence of ammonium polyphosphate (APP) or silica gel (SG) significantly slowed the rate of aerogel decomposition at the temperature range from 250 °C to 500 °C while the onset of polymer decomposition was not affected. Fire behavior was analyzed through cone calorimeter suggesting that either the presence of Al(OH)3 or APP reduced the heat release rate of PVOH/clay systems.