Enhancing Flame-Retardant Properties of Polyurethane Aerogels Doped with Silica-Based Particles

In this work, polyurethane (PUR) aerogels doped with different SiO₂ particles, derived from a renewable source, were successfully synthesized, and the effects of SiO₂ content on the properties of PUR aerogels were investigated. Specifically, three types of SiO₂-based particles obtained from rice husk through different procedures were evaluated to enhance the thermal stability of the composites with special attention given to flame-retardant properties. With the optimal SiO₂ particles, obtained through acid digestion, the influence of their content between 0.5 and 3 wt.% on the physicochemical characteristics of the synthesized aerogels was thoroughly examined. The results showed that increasing the doping agent content improved the lightness, thermal stability, and flame-retardant properties of the resulting PUR aerogels, with the best performance observed at a 2 wt.% doping level. The doped aerogel samples with non-modified SiO₂ particles significantly enhanced the fire safety performance of the material, exhibiting up to an eightfold increase in flame retardancy. However, modification of the SiO₂ particles with phytic acid did not slow down the combustion velocity when filling the aerogels. This research highlights the promising potential of doped PUR/SiO₂ aerogels in advancing materials science and engineering applications for withstanding high temperatures and improving fire safety.