Alginate-chitosan aerogel achieves V-0 flame rating without halogen
Nanjing team blends phosphorylated chitosan with sodium alginate to create a 0.026 g cm⁻³, 0.035 W m⁻¹ K⁻¹ aerogel that passes UL-94 V-0 and shrugs off 200 °C heat
image: Journal of Bioresources and Bioproducts reports a sodium-alginate aerogel doped with 30 % phosphorylated chitosan that records LOI 33.7 %, PHRR 44 % drop and 0.035 W m⁻¹ K⁻¹ conductivity, promising halogen-free insulation.
Credit: School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, China.
A kitchen-sink blend of seaweed slime and shrimp-shell waste has become a fire-proof, feather-light shield. Researchers at Southeast and Nanjing Forestry Universities simply mixed sodium alginate with phosphorylated chitosan (PCS) and freeze-dried the slurry. PCS, made by refluxing chitosan with urea and phosphoric acid, grafts P–N groups onto the alginate chains, forming a 0.026 g cm⁻³ aerogel that traps 98 % air yet blocks flames. In the cone calorimeter, SA-30 PCS delayed ignition to 20 s, slashed peak heat release to 24 kW m⁻² and cut total heat release 45 % versus bare alginate. UL-94 vertical burning awarded the material the top V-0 rating, meaning flames self-extinguish within two seconds and no drips form. Thermal conductivity crept only from 0.0347 to 0.0350 W m⁻¹ K⁻¹, so an 8 mm sheet lets you hold an alcohol-lamp-heated copper plate bare-handed. A quick methyltrichlorosilane vapor bath boosts the water contact angle from 30° to 125°, letting the aerogel float intact for days. Because every atom of phosphorus is covalently bound and the whole scaffold is digestible by chitinase or alginate lyase, the foam offers an eco-exit unlike halogenated foams. The team says roll-to-roll freeze-drying could scale the recipe for fire-safe insulation panels or lightweight linings in protective clothing.
See the article:
DOI
https://doi.org/10.1016/j.jobab.2025.08.004
Original Source URL
https://www.sciencedirect.com/science/article/pii/S236996982500060X
Journal
Journal of Bioresources and Bioproducts