Heat insulation performance,mechanics and hydrophobic modification of cellulose–SiO2 composite aerogels

Cellulose–SiO₂ composite hydrogel was prepared by combining the NaOH/thiourea/H₂O solvent system and the immersion method with controlling the hydrolysis–fasculation rate of tetraethyl orthosilicate (TEOS). The hydrophobic composite aerogels were obtained through the freeze-drying technology and the cold plasma modification technology. Composite SiO₂ could obviously reduce the thermal conductivity of cellulose aerogel. The thermal conductivity could be as low as 0.026 W/(mK). The thermal insulation mechanism of the aerogel material was discussed. Composite SiO₂ reduced hydrophilicity of cellulose aerogel, but environmental humidity had a significant influence on heat insulation performance. After hydrophobic modification using CCl₄ as plasma was conducted, the surface of composite aerogel was changed from hydrophilic to hydrophobic and water contact angle was as high as 132°. The modified composite aerogel still kept good heat insulation performance. This work provided a foundation for the possibility of applying cellulose–SiO₂ composite aerogel in the insulating material field.