CN111232992B

CN111232992B - Aerogel modification method

Info

Publication number: CN111232992B
Application number: CN202010034403.3A
Authority: CN
Inventors: 沈晓冬; 孔勇; 江国栋
Original assignee: Nanjing Tech University
Current assignee: Nanjing Tech University
Priority date: 2020-01-14
Filing date: 2020-01-14
Publication date: 2022-04-26
Anticipated expiration: 2040-01-14
Also published as: CN111232992A

Abstract

The invention belongs to the field of preparation of new materials, and particularly relates to a modification method of aerogel. According to the invention, organic steam and aerogel surface hydroxyl groups are chemically grafted, and then groups in the modifier are crosslinked on the surface of the aerogel through ultraviolet illumination and high-temperature heat treatment to form macromolecules so as to protect an aerogel network structure, so that the mechanical property and the hydrophobic property of the aerogel are improved.

Description

Aerogel modification method

Technical Field

The invention belongs to the field of preparation of new materials, and relates to a modification method of an aerogel material.

Background

The aerogel has the structural characteristics of low density, high specific surface area, large porosity and the like, has excellent heat insulation, adsorption, catalysis and other performances, and is widely applied to the fields of industrial production, building energy conservation, aerospace and the like. But the defects of poor mechanical property and powder falling of the aerogel greatly limit the SiO₂Application of aerogel. In order to solve the problem of poor mechanical properties of aerogels, researchers have conducted a large number of studies on polymer crosslinked reinforced silica aerogels [ chem.mater.2010,22, 2790-2803; chem.mater.2005,17, 1085-; j Mater Chem 16: 3046-3054; acc Chem Res 40: 874-884]The method comprises the steps of grafting amino on the surface of the silica wet gel, grafting a high molecular monomer on the amino, polymerizing the high molecular monomer to form a polymer macromolecule, increasing the silica wet gel, and drying to obtain the enhanced silica aerogel. The method can obviously improve the mechanical property of the silica aerogel, but has complex reaction steps, needs a plurality of organic solvents, has relatively poor environmental friendliness and is not suitable for large-scale industrial production.

Disclosure of Invention

The invention provides a modification method of aerogel materials for overcoming the defects of the prior art, which is a method for directly modifying the prior aerogel products to increase the mechanical property of the aerogel products and endowing the aerogel products with a hydrophobic function.

The technical scheme of the invention comprises the following steps: the aerogel modification method comprises the following specific steps:

(1) after the aerogel is subjected to heat treatment, removing adsorbed water vapor and unhydrolyzed alkoxy groups;

(2) reacting the aerogel subjected to the heat treatment in the step (1) with modifier steam at the temperature of 20-60 ℃ for 4-24 hours to graft the modifier on the surface of the aerogel;

(3) irradiating the surface-grafted aerogel obtained in the step (2) with ultraviolet light to enable the modifier to be crosslinked;

(4) and (4) carrying out heat treatment on the aerogel obtained in the step (3) at 200-250 ℃ for 4-24 hours, and further crosslinking and strengthening the aerogel to obtain the modified aerogel.

Preferably, the aerogel in step (1) is an aerogel containing hydroxyl groups on the surface, such as a silica aerogel, an alumina aerogel, a zirconia aerogel or a titania aerogel.

Preferably, the heat treatment temperature in the step (1) is 200-300 ℃, and the heat treatment time is 1-3 hours.

Preferably, the modifier in the step (2) is one or more of vinylmethyldichlorosilane, vinyldimethylchlorosilane or mercaptopropylmethyldimethoxysilane.

Preferably, the ultraviolet intensity of the ultraviolet illumination in the step (3) is 100-200 mW/cm²(ii) a The time of ultraviolet irradiation is 10-30 minutes.

Preferably, the modified aerogel obtained in the step (4) is typically characterized in that the density is increased by 5-50%, the strength is improved by 6-30 times, and the thermal conductivity is increased by 15-30% compared with the unmodified aerogel.

Has the advantages that:

the aerogel modification method provided by the invention has the following characteristics:

(1) the aerogel product is directly modified instead of wet gel, a solvent is not needed, and the aerogel product is good in environmental friendliness and high in flexibility.

(2) The method can be used for modifying various aerogels, has wide applicability, and can be used for aerogels with hydroxyl groups on the surfaces.

(3) The modifier is crosslinked through ultraviolet illumination and high-temperature heat treatment after grafting, and the problems of poor mechanical property, poor water resistance and powder falling of the aerogel are solved.

Drawings

FIG. 1 is a schematic representation of the hydrophobic properties of the modified silica aerogel prepared in example 1.

Detailed Description

Example 1

Treating the silica aerogel at 200 ℃ for 3 hours, and then reacting the silica aerogel with vinylmethyldichlorosilane steam at 20 ℃ for 24 hours to graft the vinylmethyldichlorosilane on the surface of the silica aerogel; grafted silica aerogel having a strength of 100mW/cm²Ultraviolet irradiation is carried out for 30 minutes to enable the vinyl on the modifier to be crosslinked, and then heat treatment is carried out for 24 hours at 200 ℃ to enable the vinyl to be further crosslinked, so that the modified silica aerogel is obtained. The density of the modified silicon oxide aerogel is increased by 50 percent, the strength is improved by 30 times, the thermal conductivity is increased by 30 percent, and the water contact angle is 120 degrees.

Referring to the drawings, FIG. 1 is a schematic representation of the hydrophobic properties of the modified silica aerogel prepared in example 1. A macromolecular protective layer is formed on the surface of silica aerogel particles through grafting, polymerization and crosslinking, so that the problems of poor mechanical property and powder falling of the silica aerogel are solved, and the hydrophobic property of the silica aerogel is endowed by methyl groups in the modifier.

Example 2

Treating the alumina aerogel at 250 ℃ for 1 hour, and then reacting the alumina aerogel with vinyldimethylchlorosilane steam at 40 ℃ for 4 hours to graft the vinyldimethylchlorosilane on the surface of the alumina aerogel; grafted alumina aerogel with a strength of 200mW/cm²Ultraviolet irradiation is carried out for 10 minutes to enable the vinyl on the modifier to be crosslinked, and then heat treatment is carried out for 4 hours at 250 ℃ to enable the vinyl to be further crosslinked, so that the modified alumina aerogel is obtained. The density of the modified alumina aerogel is increased by 5 percent, the strength is improved by 6 times, the thermal conductivity is increased by 15 percent, and the water contact angle is 120 degrees.

Example 3

Treating the zirconia aerogel at 300 ℃ for 1 hour, and reacting the treated zirconia aerogel with mixed steam of vinyldimethylchlorosilane and mercaptopropylmethyldimethoxysilane at 60 ℃ for 12 hours to graft the vinyldimethylchlorosilane and the mercaptopropylmethyldimethoxysilane on the surface of the zirconia aerogel; the strength of the grafted zirconia aerogel is 100mW/cm²And (3) performing ultraviolet irradiation for 20 minutes to crosslink the vinyl and the mercaptopropyl on the modifier, and then continuing to perform heat treatment at 250 ℃ for 12 hours to further crosslink the vinyl and the mercaptopropyl to obtain the modified zirconia aerogel. The density of the modified zirconia aerogel is increased by 30 percent, and the strength is improved by 20 timesThe thermal conductivity is increased by 20 percent, and the water contact angle is 125 degrees.

Example 4

Treating the titanium oxide aerogel at 250 ℃ for 2 hours, and then reacting the titanium oxide aerogel with vinylmethyldichlorosilane steam at 60 ℃ for 8 hours to graft the vinylmethyldichlorosilane on the surface of the titanium oxide aerogel; the strength of the grafted titanium oxide aerogel is 150mW/cm²And (3) ultraviolet irradiation is carried out for 30 minutes to enable the vinyl on the modifier to be crosslinked, and then heat treatment is carried out for 8 hours at 230 ℃ to enable the vinyl to be further crosslinked, so that the modified titanium oxide aerogel is obtained. The density of the modified titanium oxide aerogel is increased by 25 percent, the strength is improved by 11 times, the thermal conductivity is increased by 20 percent, and the water contact angle is 125 degrees.

Example 5

Treating the silica aerogel at 250 ℃ for 2 hours, and then reacting the silica aerogel with vinylmethyldichlorosilane and mercaptopropylmethyldimethoxysilane (the mass ratio is 1: 1) steam at 40 ℃ for 16 hours to graft the vinylmethyldichlorosilane and the mercaptopropylmethyldimethoxysilane on the surface of the silica aerogel; grafted silica aerogel having a strength of 100mW/cm²Ultraviolet irradiation is carried out for 20 minutes to enable the vinyl on the modifier to be crosslinked, and then heat treatment is carried out for 12 hours at 220 ℃ to enable the vinyl to be further crosslinked, so that the modified silica aerogel is obtained. The density of the modified silicon oxide aerogel is increased by 30 percent, the strength is improved by 18 times, the thermal conductivity is increased by 25 percent, and the water contact angle is 120 degrees.

Claims

1. The aerogel modification method comprises the following specific steps:

(4) and (4) carrying out heat treatment on the aerogel obtained in the step (3) at 200-250 ℃ for 4-24 hours to obtain the modified aerogel.

2. Modification process according to claim 1, characterized in that the aerogel in step (1) is a silica aerogel, an alumina aerogel, a zirconia aerogel or a titania aerogel.

3. The modification method according to claim 1, wherein the heat treatment temperature in the step (1) is 200 to 300 ℃ and the heat treatment time is 1 to 3 hours.

4. The modification process according to claim 1, characterized in that the modifier in step (2) is one or more of vinylmethyldichlorosilane, vinyldimethylchlorosilane, or mercaptopropylmethyldimethoxysilane.

5. The modification method according to claim 1, wherein the ultraviolet intensity of the ultraviolet irradiation in the step (3) is 100 to 200mW/cm²(ii) a The time of ultraviolet irradiation is 10-30 minutes.

6. The modification method according to claim 1, wherein the density of the modified aerogel obtained in the step (4) is increased by 5-50%, the strength is improved by 6-30 times, and the thermal conductivity is increased by 15-30% compared with that of the unmodified aerogel.