Polyurethane insulation foam (PUF) was surface treated with silica (SiO2), by acid and alkali hydrolysis, then lyophilised to generate a silica aerogel at 13 – 33% w/w loading on the foam. The nano-porous structure of the aerogel resulted in improved thermal insulating performance of the PUF, improved resistance to compression and fire performance: self-extinguishing in vertical burn test, peak heat release rate reduced by over 40%. Peak smoke release and smoke optical density were reduced by 46% and 56%. The authors consider that this was because the silica aerogel increased the melt viscosity of the polyurethane in fire and generated a compact silica-rich char.
“Hierarchically porous SiO2/polyurethane foam composites towards excellent thermal insulating, flame-retardant and smoke-suppressant performances”, M-E. Li et al., Journal of Hazardous Materials 375 (2019) 61–69, https://doi.org/10.1016/j.jhazmat.2019.04.065