Enhancement of transient thermal stability and flame retardancy of hydrophobic silica xerogel composites via carbon family material doping

Abstract

In this study, we investigated the influence of the addition of carbon materials on the heat resistance and flame retardancy of silica xerogels. A mixed dispersion prepared by adding 0.1 to 2.5 wt% each of the carbon materials, graphene oxide (GO), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS), and carbon black (CB) to waterglass (SiO2 6%) was used as the raw material. By adding acid to this dispersion, a sol-gel reaction was carried out and the hydrogel obtained was hydrophobized with hydrochloric acid and a mixed solution of siloxane/isopropylalcohol . Finally, novel carbon-silica xerogel composites (SX-Carbon-X) were prepared via ambient pressure drying. Similarly, glass-fiber-reinforced silica xerogel composite sheets (GFR-SX-Carbon-X) were prepared by impregnating glass fibers with sol. The bulk densities of the samples obtained ranged from 0.204 to 0.217 g/cm3, their thermal conductivities ranged from 0.0187 to 0.0203 W/(m · K). As the amount of carbon material added was increased, the thermal decomposition temperature of the SX-Carbon-X shifted to higher temperatures. In the cone calorimeter test of GFR-SX-Carbon-X, moreover, adding at least 0.5% of the carbon material significantly reduced the combustion time and the peak heat release rate (PHRR), and the flame retardancy improved remarkably.

Keywords

• silica xerogel
• waterglass
• carbon
• thermal stability
• flame retardancy