Hydrogel and aerogel-based flame-retardant polymeric materials: A review

Hydrogels are multifunctional engineering materials best known for their promising characteristics such as toughness, flexibility, water absorption capacity, and porosity. These features can support fire protection missions. Application of hydrogels as flame-retardant materials is receiving much attention, such that several research and industrial projects have been devoted to design, manufacturing, and optimization of flame-retardant hydrogels-taking a unique position among advanced multifunctional materials and strategies. Likewise, aerogels (derived from gels) due to their porous structure filled with a gas, usually air, rather than water in the case of hydrogels, have shown superior thermal insulation potential. Correspondingly, they have been used in fire and flame protection applications. In this work, the flame-retardant hydrogels and aerogels along with mechanisms underlying their flame retardancy are reviewed. Besides classifying and interpreting the open literature on flame-retardant hydrogels and aerogels, challenging aspects of future developments ahead of these advanced materials are highlighted. HighlightsBriefly overviewed general features of hydrogels including synthesis and applications.Briefly overviewed principles of flame retardancy and flame-retardant polymers.Reviewed and classified flame-retardant hydrogels and aerogels as advanced materials.Summarized the latest advancements in flame-retardant hydrogels and aerogels.Highlighted future fire protection by flame-retardant hydrogels and aerogels.