Preparation And Properties Of Silica Elastomeric Aerogels From Organosilane Precursors

As human activity scope expanding gradually,the requirements of facing high temperature environments such as polar and marine are more and more strong.Therefore,seeking a kind of low density,low thermal conductivity and high strength elasticity insulation material attracts extensive attention of the whole society.Elasticity of silica aerogel is connected by nanoparticles into a unique three-dimensional network structure of low density porous material,widely used in the thermal field.However,the poor elasticity and low intensity of silica aerogel limits its application.To solve above problems,methyltrimethoxysilane(MTMS)respectively composed with n-octyltriethoxysilane(n-Octyl)and vinyltriethoxysilane(VTES)composite organosilane precursor were prepared,thus good elastic performance and high strength elasticity silica aerogel is obtained through ambient pressure drying technology.This paper research content mainly includes the following two parts.(1)Using n-Octyl and MTMS as compound organosilane precursors,the Octyl groups were introduced in the aerogel three-dimensional frame structure.Research showed that the more n-Octyl groups were introduced,the more uniform the micromorphology and pore structure distribution of the aerogel became when the molar ratio of n-Octyl to MTMS was in the range of 0～0.100.The uniform morphology and pore structure distribution made the aerogel obtain good elastic properties.When the amount of n-Octyl introduced was 0.100,the aerogel withstood a maximum strain of 60% and a maximum compressive strength of 0.148 MPa.At the same time,the aerogel had a low thermal conductivity,which was 0.025 W/(m·K)in the air atmosphere at 25 ℃.In addition,because its internal contained a large number of organic groups,the aerogel had good hydrophobicity and oil absorption such as motor oil,pump oil,gasoline and vegetable oil,and the hydrophobic angle was 141°and had a good adsorption capacity for a variety of organic reagents with adsorption between 6 to 8.(2)Using VTES and MTMS composite organosilane precursor,vinyl groups were introduced in the aerogel three-dimensional frame structure to obtain VTES/MTMS-based silica aerogel.Research showed that as the amount of VTES introduced increased,the maximum stress that the aerogel withstood increased and then decreased when the molar ratio of VTES to MTMS was in the range of 0 to0.084.The uniform morphology and pore structure distribution made the aerogel obtain good elastic properties.When the amount of n-Octyl introduced was 0.060,the aerogel withstood a maximum strain of 55% and a maximum compressive strength of0.571 MPa.After stress and strain tests for 40 times,the maximum compressive strength value was only fell by 5%,the stability was good.At the same time,the aerogel had a low thermal conductivity,which was 0.024 W/(m·K)in the air atmosphere at 25 ℃.