Review suggests highly porous gels, which release water to prevent and slow fire, offer an innovative new PIN FR concept. Hydrogels are 3D crosslinked polymeric materials, based on natural or synthetic polymers, which can be prepared as coatings, films, additive particles or slabs, or built into cavities of 3D-printed structures. They are highly porous, so can fix water in their structure. This is released and vaporised in fire, absorbing heat and diluting fire gases. LOI of up to 60% can be achieved. The polymers of hydrogels are generally flammable, but can be modified using silica materials or other PIN FRs to make them into a fire-protective layer. Aerogels are similar polymer structures but without the water (empty pores) and are highly insulating, and can provide a fire protection barrier if flame retarded. This twenty-page review summarises synthesis, applications and flame retardancy of hydrogels and aerogels, based on over 120 studies, concludes that such gels offer a promising new approach to PIN fire safety. Challenges are to avoid too-early water release, to reduce costs and to further research integration of PIN FRs in to the gel structures.
“Next-Gen Flame Retardants: hydrogels & aerogels”, Plastics Engineering“, 1st February 2024, https://www.plasticsengineering.org/2024/02/next-gen-flame-retardants-hydrogels-aerogels-003269/
Hydrogel and aerogel-based flame-retardant polymeric materials: A review”, H. Vahabi et al., J Vinyl Addit Technol. 2024;30:5–25, https://dx.doi.org/10.1002/vnl.22041