Facile preparation of a phenyl-reinforced flexible silica aerogel with excellent thermal stability and fire resistance

Abstract

How to improve the thermal stability and flame resistance of a silica aerogel while enhancing its mechanical properties and hydrophobicity is a major challenge. In this work, phenyltriethoxysilane (PTES) was introduced into a binary silicon source system formed by methyltriethoxysilane (MTES) and dimethyldiethoxysilane (DEDMS), and a phenyl-enhanced flexible aerogel was prepared by a simple sol–gel process and ambient pressure drying, avoiding long time solvent exchange and surface modification. The results show that the prepared aerogel exihibits low density (0.082 g cm⁻³), high porosity (94.2%) and high specific surface area (162.1 m² g⁻¹). A membrane-like structure derived from PTES strengthens the original flexible skeleton and makes the aerogel framework change from a spherical particulate structure to a non-particulate structure. Compared with common flexible silica aerogels, the phenyl-enhanced flexible silica aerogel shows more excellent mechanical properties and hydrophobility (a contact angle as high as 159.8°), and the maximum degradation rate temperature in N₂ conditions is improved by over 150 °C, reaching up to 742.9 °C. Moreover, the enhanced silica aerogel even exhibits outstanding flame resistance. With the excellent hydrophobility, mechanical properties, oil–water separation capacity, thermal stability, and flame resistance, the phenyl-enhanced flexible silica aerogel can be applied in some extreme conditions with high temperature and high humidity.