High-strength, flame-retardant, hydrophobic and UV‐shielding cellulose aerogel modified with xylooligosaccharide-derived crosslinker and methyltrimethoxysilane

Cellulose aerogel shows huge potential to substitute petroleum-based building insulation materials because of its renewability and biodegradability. However, it is priority to address its low strength, flammability and hydrophilicity. In this work, we synthesized a xylooligosaccharide-derived flame-retardant crosslinker (XS) and fabricated the high-strength, flame-retardant, hydrophobic and UV‐shielding composite aerogel using XS and methyltrimethoxysilane (MTMS). XS and MTMS reacted with cellulose to form dual chemical crosslinking structure during baking and chemical vapor deposition, respectively. The composite aerogel showed low density (19.58 mg/cm 3 ), high porosity (98.76%) and compressive modulus (742.9 kPa). The high strength made it withstand 14800 times its weight without deformation. The composite aerogel achieved outstanding hydrophobic, UV‐shielding and thermal insulation properties. Its water contact angle, ultraviolet protection factor and thermal conductivity were 144.9 o , 1253.1 and 24.6 mW/(m·K), respectively. The satisfactory hydrophobicity also endowed composite aerogel with continuous oil-water separation capability. The isolation effect of P/N/Si-containing polyaromatic char layer and dilution effect of nonflammable gases endowed composite aerogel with excellent flame retardancy. Its LOI value and UL-94 rating reached 34.9% and V-0, respectively. This study provides new ideas for synthesizing biobased flame-retardant crosslinkers and fabricating multifunctional cellulose aerogels for building insulation application.