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 ~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.