Multi-crosslinked, ecofriendly flame-retardant starch-based composite aerogels with high compression-resistance

To achieve ecofriendly aerogels with high mechanics and fire resistance, naturally-occurring pea starch was employed as the major substrate, and starch-based composite aerogels were fabricated by freeze-drying method. The corresponding hydrogels were obtained through successive gelatinization/dissolution of pea starch and polyvinyl alcohol (PVA), formation of precursor hydrogels via cyclic freeze-thawing, followed by treatment with borax aqueous solution. Borax treatment not only results in aerogels with high mechanics, but also endows the aerogels flame-retardant property. The final aerogels show high compression-resistance, with a maximum specific compressive modulus achieved at similar to 44 MPa and the yield strength 665 kPa, owing to the formation of a multi-crosslinked hybrid network. The maximum limiting oxygen index (LOI) of the aerogels exceeds 34. The peak heat release rate, the heat release capacity, and the total heat release decrease 74.5%, 76.2%, and 73.8% after borax treatment. Moreover, the obtained aerogels demonstrate good thermal stability and thermal insulation. The good performance is conducive for practical application.