Effects of Phenyltrimethoxysilane and Polyvinyl Alcohol on the Properties of Methyltrimethoxysilane-based Silica Aerogels

Abstract

Silica aerogels have attracted great attention owing to their outstanding properties such as ultralow density, high porosity, high surface area, and low thermal conductivities. Their poor mechanical properties and hydrophilicity constrain their practical applications. In this work, phenyltrimethoxysilane (PTMS) and polyvinyl alcohol (PVA) were added into methyltrimethoxysilane (MTMS)-based silica aerogels to enhance their mechanical properties. It was found that PTMS considerably improved the hydrophobicity of MTMS silica aerogels with an increase in water contact angles from 115° to 150°. The addition of PVA considerably increased the hardness, morphology, density, porosity, surface area, and thermal conductivity of MTMS silica aerogels. When PVA concentration was increased from 0 to 2 %, the aerogel hardness, density, and thermal conductivity were also increased from 0 to 14 %, 0.072 to 0.11 g/cm³, and 0.035 to 0.046 W/m.K. In contrast, the aerogel became less porous and the porosity reduced from 97.2 % to 95.72 % and BET surface area decreased from 389 to 43 m²/g.