Hydrophobic silicon dioxide aerogel and preparation method thereof

Abstract

The invention relates to a preparation method of hydrophobic silicon dioxide aerogel, and relates to a silicon dioxide aerogel and a preparation method thereof. The method includes steps of taking tetraethoxysilane and methyl triethoxy silane as a common precursor, ethanol as a solvent, water as hydrolysis agent, and hydrolysis as catalyst, ethanol added with carbon fluorinated surfactant as aging fluid; performing supercritical drying process, and obtaining the block-shaped silicon dioxide aerogel with good hydrophobic rate. The preparation method is simple in technique, and able to make samples hydrophobic instead of introducing hexamethyldisilazane and other combustible finishing agent with peculiar smell; the prepared product is low in density, good in hydrophobic property, stable in thermal performance, and excellent in heat insulation performance.

Description

technical field [0001] The invention relates to a silica airgel and a preparation method thereof, in particular to a hydrophobic silica airgel and a preparation method thereof. Background technique [0002] Airgel is a new type of low-density, structure-controllable, lightweight nanoporous amorphous solid material with a spatial network structure composed of colloidal particles or polymer molecules cross-linked with each other. Due to its unique nanoscale pore structure characteristics , so that it has the characteristics of low density, high specific surface area, high porosity, low thermal conductivity, low dielectric constant, etc., and has broad application prospects in high-efficiency heat insulation, catalyst carrier, adsorption, etc. [0003] The preparation of silica airgel generally uses organosilicon precursors (methyl orthosilicate, ethyl orthosilicate, etc.) or inorganic precursors (sodium silicate, silica sol, etc.) as raw materials, using sol-gel The method fo...

AI Technical Summary

Problems solved by technology

The surface of conventionally prepared silica airgel contains a large number of hydrophilic groups of silanol, which makes it easy to absorb moisture in the air, and easy to crack when exposed to water, which affects its thermal, acoustic, electrical properties and practical applications.

[0004] At present, most of the hydroxyl active groups on the surface of silica airgel are inertly replaced by surface post-treatment methods, but the process cycle of this method is prolonged and the process is complicated

For example, the Chinese patent with publication number CN102179230A uses water glass as a raw material and drys it under normal pressure to prepare a magnetic silica airgel with a water contact angle of 110-1200. However, a large amount of organic modifiers (three Methylchlorosilane, hexamethyldisilazane, dimethyldichlorosilane, etc.), the preparation cost is high and the process is complicated

[0005] In the current conventional process, the airgel is hydrophobically modified by adding organosilanes (trimethylchlorosilane, hexamethyldisilazane, dimethyldichlorosilane, etc.) in the aging process. The methyl group (-CH3) replaces the hydroxyl group in Si-OH on the wet gel, but since the wet gel contains a certain amount of water, the water has an important influence on the hydrophobic modification process of the gel, because the organosilane The reactivity of the modifier with water is stronger than the reactivity with Si-OH on the silica gel skeleton, so the modifier will be consumed in large quantities when it reacts with water, which will affect the hydrophobic modification of the gel, and a large amount of modifier must be used. Sexual agent can achieve the purpose

Adding a large amount of flammable, explosive, and odorous silicone modifiers such as trimethylchlorosilane, hexamethyldisilazane, and dimethyldichlorosilane not only brings safety hazards, but also Significantly increase the cost of airgel manufacturing