阅读说明：本技术 改性二氧化硅气凝胶的制备方法及改性二氧化硅气凝胶 (Preparation method of modified silica aerogel and modified silica aerogel ) 是由 翁朝阳 于 2020-05-25 设计创作，主要内容包括：本发明属于气凝胶领域,涉及二氧化硅气凝胶技术领域,具体是改性二氧化硅气凝胶的制备方法及二氧化硅气凝胶,本发明采用巯基改性纤维作为补强材料,在制备二氧化硅气凝胶时采用含碳碳不饱和双键修饰剂修饰,巯基和碳碳不饱和双键在紫外光照射下发生“巯基-烯”点击化学反应,获得纤维补强二氧化硅气凝胶,在较低的纤维含量下二氧化硅气凝胶就具有较好的力学性能,同时较大程度的保持了二氧化硅气凝胶的低密度和低导热系数等性能。(The invention belongs to the field of aerogel, relates to the technical field of silicon dioxide aerogel, and particularly relates to a preparation method of modified silicon dioxide aerogel and the silicon dioxide aerogel.)

1. The preparation method of the modified silicon dioxide aerogel is characterized by comprising the following steps,

s1, ultrasonically dispersing the sulfhydryl modified fiber into absolute ethyl alcohol, adding ethyl orthosilicate, uniformly stirring, adding water, uniformly stirring, adding acid, uniformly stirring for hydrolysis, adding alkali, uniformly stirring, and condensing to obtain wet gel;

s2, carrying out aging and absolute ethyl alcohol replacement on the wet gel obtained in the step S1 for 2 times, soaking the wet gel into a carbon-carbon unsaturated double bond modifier solution for 15-30 hours, taking out the wet gel, soaking the wet gel into a photoinitiator solution, irradiating by ultraviolet light, taking out the wet gel, and drying the wet gel at normal pressure to obtain the modified silicon dioxide aerogel.

2. The method according to claim 1, wherein the fibers in step S1 are at least one selected from the group consisting of glass fibers, ceramic fibers, polyimide fibers, polyamide fibers, polyester fibers, and silicon carbide fibers.

3. The preparation method according to claim 1, wherein the weight ratio of the mercapto-modified fiber, the absolute ethyl alcohol, the ethyl orthosilicate, and the water in step S1 is 1: 150-2000: 20-200: 15-150.

4. The method according to claim 1, wherein the carbon-carbon unsaturated double bond modifier in step S2 is at least one selected from the group consisting of dimethylvinylchlorosilane, tetramethyldivinyldisilazane, and 3- (methacryloyloxy) propyldimethylchlorosilane.

5. The method according to claim 1, wherein a solvent of the carbon-carbon unsaturated double bond modifier solution in step S2 is n-hexane, and a concentration of the carbon-carbon unsaturated double bond modifier is 10-200 g/L.

6. The method according to claim 1, wherein the photoinitiator in step S2 is at least one selected from benzoin dimethyl ether, benzoin ethyl ether, and benzoin butyl ether.

7. The method according to claim 1, wherein the concentration of the photoinitiator in the photoinitiator solution in step S2 is 1-5 g/L.

8. The method according to claim 1, wherein the dominant wavelength of the ultraviolet light in the ultraviolet light irradiation in step S2 is 365nm, the light intensity is 1-10 mW/cm, and the irradiation time is 1-20 minutes.

9. The method according to claim 1, wherein the drying at normal pressure in step S2 is performed at normal pressure at 40 ℃ for 1-5 hours, at 80 ℃ for 1-5 hours, and at 120 ℃ for 1-5 hours.

10. Modified silica aerogel, characterized by being obtained by the preparation method according to any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of aerogel, and relates to a preparation method of modified silicon dioxide aerogel and the modified silicon dioxide aerogel.

Background

The silicon dioxide aerogel is a novel nano porous material, more than 95% of the volume of the silicon dioxide aerogel is filled with air, so the silicon dioxide aerogel has the characteristics of low density, low heat conductivity coefficient, high porosity, large specific surface area and the like, is a novel material with a very large application prospect, has the defect of low strength, needs supercritical drying or freeze drying in the preparation process, and has high cost, long period and low productivity. Therefore, the method for improving the mechanical strength of the silica by adopting a modification means can dry the silica at normal pressure, and is a development direction of silica aerogel, wherein one means is to adopt fiber reinforcement modification. CN110127706A adopts glass fiber, CN110256101A adopts PI chopped fiber, CN108640643A adopts reinforced fiber such as aramid fiber and carbon fiber, CN108467276A adopts electrostatic spinning nanofiber, CN107986745A adopts polyester fiber, CN107673730A adopts cellulose, CN109422520A adopts silicon carbide fiber, and CN107337423A adopts nanocellulose. However, in the above method, the fibers and the silica aerogel have physical effects, the acting force is not strong, the reinforcing effect is not high, and if the reinforcing effect is good, a large amount of fibers are required, so that the low density and low thermal conductivity of the silica aerogel can be affected.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a preparation method of modified silica aerogel, which obtains the modified silica aerogel formed by chemically bonding modified fibers and silica aerogel through the 'mercapto-alkene' click chemical reaction between mercapto-modified fibers and vinyl hydrophobic modified silica aerogel, and can realize lower fiber content and higher reinforcing effect.

The invention also aims to provide the modified silica aerogel, which integrates the fiber reinforcement effect and the performance of the silica aerogel, has the characteristics of better mechanical property, lower density, lower heat conductivity coefficient and the like, and avoids the defect that the density and the heat conductivity coefficient of the silica aerogel are obviously increased due to high fiber content.

The technical scheme of the invention is as follows:

the preparation method of the modified silicon dioxide aerogel comprises the following steps,

s1, ultrasonically dispersing the sulfhydryl modified fiber into absolute ethyl alcohol, adding ethyl orthosilicate, uniformly stirring, adding water, uniformly stirring, adding acid, uniformly stirring for hydrolysis, adding alkali, uniformly stirring, and condensing to obtain wet gel;

s2, carrying out aging and absolute ethyl alcohol replacement on the wet gel obtained in the step S1 for 2 times, soaking the wet gel into a carbon-carbon unsaturated double bond modifier solution for 15-30 hours, taking out the wet gel, soaking the wet gel into a photoinitiator solution, irradiating by ultraviolet light, taking out the wet gel, and drying the wet gel at normal pressure to obtain the modified silicon dioxide aerogel.

Preferably, the fiber in step S1 is selected from at least one of glass fiber, ceramic fiber, polyimide fiber, polyamide fiber, polyester fiber, and silicon carbide fiber.

Inorganic fibers such as mercapto group-modified glass fibers, ceramic fibers, and silicon carbide fibers can be treated with a mercapto group-containing silane coupling agent.

Organic fibers such as polyimide fibers, polyamide fibers and polyester fibers can be modified by a mercaptosilane sol-gel method to obtain modified sulfydryl on the surface of the fibers, which is reported in the major paper 2012 of the university of east China, namely polyester fibers and polyamide fibers surface sulfydryl modification and chemical silvering fiber preparation. The other treatment method is to treat the fiber with alkali to obtain hydroxyl on the surface of the fiber, and then react with a mercaptosilane coupling agent, and is reported in a research on mercaptomodified PET fiber and chemical silvering electromagnetic shielding cloth in a journal printing and dyeing auxiliary published in 3 months 2011.

Preferably, the weight ratio of the mercapto-modified fiber, the absolute ethyl alcohol, the ethyl orthosilicate and the water in the step S1 is 1: 150-2000: 20-200: 15-150. More preferably, the weight ratio of the sulfhydryl modified fiber, the absolute ethyl alcohol, the ethyl orthosilicate and the water is 1: 400-1200: 50-150: 30-120.

Preferably, the carbon-carbon unsaturated double bond modifier in step S2 is at least one selected from the group consisting of dimethylvinylchlorosilane, tetramethyldivinyldisilazane, and 3- (methacryloyloxy) propyldimethylchlorosilane. More preferably, it is selected from dimethylvinylchlorosilane or tetramethyldivinyldisilazane.

Preferably, in the step S2, the solvent of the carbon-carbon unsaturated double bond modifier solution is n-hexane, and the concentration of the carbon-carbon unsaturated double bond modifier is 10-200 g/L.

Preferably, the photoinitiator in step S2 is selected from at least one of benzoin dimethyl ether, benzoin ethyl ether, and benzoin butyl ether.

Preferably, the concentration of the photoinitiator in the photoinitiator solution in the step S2 is 1-5 g/L.

Preferably, in the step S2, the dominant wavelength of the ultraviolet light in the ultraviolet light irradiation is 365nm, the light intensity is 1-10 mW/cm, and the irradiation time is 1-20 minutes.

Preferably, the drying under normal pressure in step S2 is performed at normal pressure and at 40 ℃ for 1-5 hours, at 80 ℃ for 1-5 hours, and at 120 ℃ for 1-5 hours.

Modified silica aerogel prepared by the preparation method according to any one of the above embodiments.

The invention has the beneficial effects that: the modified silica aerogel disclosed by the invention has the advantages that through the sulfydryl-alkene click chemical reaction, the modified fibers and the silica aerogel are bonded together through chemical bonds, a higher reinforcing effect is achieved under the condition of lower fiber content, the mechanical strength is higher, meanwhile, the higher mechanical strength can effectively resist the shrinkage and collapse of the silica aerogel caused by the volatilization of an organic solvent, and the influence on the density and the heat conductivity coefficient of the silica aerogel is smaller.

Detailed Description

The technical solution of the present invention is further illustrated and described by the following detailed description.

Unless otherwise specified, the parts in the following embodiments are parts by weight.