Bulk-shaped hydrophobic flexible silicon dioxide aerogel and preparation method thereof
A technology of hydrophobic silica and silica, applied in the direction of silica, silica, etc., can solve the problems of difficulty in obtaining bulk material, difficulty in forming bulk, shrinkage and cracking of skeleton, etc., and achieves short cycle and high porosity. , the effect of low cost
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[0026] One aspect of the present invention provides a method for preparing a bulk hydrophobic silica aerogel. In the preparation method, firstly, the trialkoxysilane containing vinyl functional group is reacted with thiol, and then alcohol is used as a solvent, and two-step acid-base catalysis is adopted to prepare wet gel through sol-gel, and then dry under normal pressure to obtain lumps Silica aerogel. Specifically, as an example, the preparation method of the present invention may include the following steps.
[0027](1) After mixing the vinyl group-containing trialkoxysilane and the thiol in a stoichiometric ratio, the C-S bond-containing trialkoxysilane is prepared by heating or adding an initiator or ultraviolet irradiation. The stoichiometric ratio here refers to the stoichiometric ratio of the addition reaction of thiol and vinyl group. If the heating method is adopted, the heating temperature may be 40-80° C., and the heating time may be 1-5 hours. If an initiator...
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[0040] Example 1
[0041] Weigh vinyltrimethoxysilane and 1,2-ethanedithiol in a stoichiometric ratio (molar ratio of 2:1) and mix them, and stir and react at 60°C for 4 h to obtain trimethoxysilane containing C-S bonds; 16.0 g of Trimethoxysilane containing C-S bond, 80.0g of ethanol was mixed with 5ml, 0.1mol·L -1 The hydrochloric acid was stirred for 2h; then 5ml was added, 1mol·L -1 The urea aqueous solution was stirred for 5min and left to stand to obtain a gel;
[0042] The gel obtained above was soaked in ethanol at 60°C for 48h, and then dried at 80°C under normal pressure for 2h to obtain a flexible silica aerogel. The above flexible silica aerogel has a density of 0.16 g cm -3 , the porosity is 91.1%, and the BET specific surface area is 200m 2 ·g -1 , the contact angle between distilled water and the surface is 138°, the pore size distribution is 10-500nm, the compressive modulus is 0.37MPa, the flexural modulus is 0.05MPa, and the thermal conductivity is 0.036...
Example Embodiment
[0043] Example 2
[0044] Weigh vinyltrimethoxysilane in a stoichiometric ratio (molar ratio of 2:1) and mix with 1,8-octanedithiol, and irradiate with ultraviolet light for 2 h to obtain trimethoxysilane containing C-S bonds; 2.1 g containing C-S bonds are mixed. of trimethoxysilane, 10.0g of ethanol was mixed with 0.7ml, 0.05mol·L -1 The hydrochloric acid was stirred for 2h; then 0.7ml, 1mol·L was added. -1 The ammonia water was stirred for 5min, and the gel was obtained by standing;
[0045] The gel obtained above was soaked in ethanol at 40°C for 24h, and then dried at 50°C under normal pressure for 48h to obtain a flexible silica aerogel. The above flexible silica aerogel has a density of 0.18 g cm -3 , the porosity is 90.0%, and the BET specific surface area is 240m 2 ·g -1 , the contact angle formed by distilled water and the surface is 148°, the pore size distribution is 10-200nm, the compressive modulus is 0.55MPa, the flexural modulus is 0.15MPa, and the thermal...
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