Facile construction of flame‐retardant, heat‐insulating agar/polyvinyl alcohol composite aerogels via in situ formation of magnesium hydroxide and palygorskite‐assisted strategy

Abstract

AbstractNatural polymer aerogel is a candidate material with broad application prospects in the field of building insulation because of its lightweight, low thermal conductivity, and biodegradability. However, poor mechanical properties and easy combustion greatly limit its development. In this work, magnesium hydroxide (MH) was synthesized in situ in the agar (AG)/polyvinyl alcohol (PVA) composites using magnesium oxide as raw material. Furthermore, the one‐dimensional rod‐like nanoclay palygorskite (Pal) was introduced into the composites. A series of composite aerogels with different ratios of MH and Pal were prepared by a simple freeze‐drying process, and their microstructure, mechanical properties, water resistance, thermal stability, thermal insulation, and flame‐retardant properties were investigated. Cone calorimeter tests showed that MH/Pal synergistic flame retardant had excellent performance in reducing heat release rate and suppressing smoke. The AG/PVA/MH/Pal composite samples had a limiting oxygen index of 37.5% and achieved V‐0 rating in the UL‐94 test. In addition, the introduction of MH and Pal has enabled the AG/PVA composite aerogels to exhibit superior mechanical, thermal insulation, and water stability properties.