CN114933735B

CN114933735B - Preparation method of polymer-based heat-insulating aerogel material

Info

Publication number: CN114933735B
Application number: CN202210525453.0A
Authority: CN
Inventors: 翁志焕; 蹇锡高; 宋世聪; 王锦艳; 张守海; 刘程
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2022-05-16
Filing date: 2022-05-16
Publication date: 2023-02-14
Anticipated expiration: 2042-05-16
Also published as: CN114933735A

Abstract

The invention belongs to the technical field of aerogel, and discloses a preparation method of a polymer-based heat-insulating aerogel material. According to the method, chloromethylated polysulfone is dissolved in N-methyl pyrrolidone or dimethyl sulfoxide, three-dimensional mesh porous wet gel is prepared through the in-situ composite reaction of chloromethyl and amine curing agent, and the obtained wet gel is aged, replaced by solvent, freeze-dried and cured at high temperature to obtain the heat-insulating aerogel material. The heat-insulating aerogel material prepared by the invention has lower density, heat conductivity coefficient and good heat-insulating property, simultaneously solves the problems of powder falling and slag falling of the aerogel, has certain flexibility and compressive strength, can be used as a heat-insulating protective material of an aerospace aircraft, and has certain effects on overall weight reduction, efficiency improvement and cost reduction.

Description

Preparation method of polymer-based heat-insulating aerogel material

Technical Field

The invention belongs to the technical field of aerogel, and particularly relates to a preparation method of an aerogel heat insulation material.

Background

The aerogel is a solid nano material with a three-dimensional network framework and formed by mutual polymerization of colloidal particles or polymer monomers, and has excellent performances of ultralow density, low thermal conductivity, high specific surface area, high porosity and the like. The porosity of aerogel materials is more than 90%, and the nano porous structure in the aerogel materials can enable the aerogel to have excellent heat insulation and sound insulation, adsorption and catalysis and other performances, so that the aerogel has wide application prospects in the fields of battery energy, industrial high-temperature kilns, aerospace and the like.

In the literature and patent reported so far, various aerogels are prepared based on different precursors, and the currently commonly used aerogel thermal insulation materials are mainly divided into: oxide aerogel insulation (Ceramics International,2016,42 (1): 874-882), carbon aerogel insulation (Materials Letters,2011,65 (23/24): 3454-3456), carbide aerogel insulation (Journal of Sol-Gel Science and Technology,2018,86 (5): 383-390), and polymer aerogel insulation (Chemical Engineering Journal,2020,385 123963. Most of the existing polymer aerogel materials are prepared by adopting an ice template method, and although the existing polymer aerogel materials can reach corresponding standards, the requirements on the preparation operation process are high. There is a report in literature that a thermal insulation aerogel is prepared by using chitosan as a precursor and using a two-way freezing ice mold method, although the thermal insulation aerogel has a low thermal conductivity, the ice mold plate is easily broken due to uneven heating during the formation process, and the overall performance of the aerogel is finally affected, so that the cost is high and mass production is difficult (Journal of Hazardous Materials,2021, 403. Therefore, a method for preparing heat insulation materials with excellent performance by a simple process and low cost is needed. On the basis, the invention provides a new idea for preparing an aerogel heat insulation material, namely preparing three-dimensional reticular porous aerogel through in-situ composite reaction of chloromethyl and amino.

Disclosure of Invention

The invention aims to provide a heat-insulating aerogel material and a preparation method thereof.

The invention provides an aerogel heat-insulating material prepared by using Chloromethyl Modified Polysulfone (CMPSF) as a polymer-based aerogel precursor and an amine curing agent as a cross-linking agent in a manner of cross-linking chloromethyl on a modified polysulfone structural unit and the amine curing agent.

In order to achieve the above object, the present invention provides the following preparation scheme:

a preparation method of a polymer-based heat-insulating aerogel material comprises the following steps:

(1) Weighing chloromethylated polysulfones (CMPSF) with different masses, dissolving the chloromethylated polysulfones (CMPSF) in N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO) under stirring to obtain a CMPSF solution with the mass fraction of 1-5 wt%, pouring the CMPSF solution into a mold, dropwise adding an amine curing agent into the solution, and placing the obtained mixed solution in a vacuum oven at 25 ℃ for standing to form gel to obtain a composite wet gel;

(2) And (2) aging, solvent replacement, freeze drying and high-temperature curing the wet gel obtained in the step (1) to obtain the heat-insulating aerogel material.

In the present invention, the chloromethylated polysulfone (CMPSF) in step (1) is prepared from Polysulfone (PSF) by chloromethylation degree DCM of preferably 1.59-3.52 mmol/g; the mass fraction of the chloromethylated polysulfone solution is more preferably 2 to 4wt%, and the most preferred mass fraction is 3wt%. The amine curing agent is preferably triethylene tetramine, polyether amine D230 or polyether amine D600. The equivalent ratio of chloromethyl group in CMPSF to amino group in curing agent is 1:1.

in the invention, the wet gel aging temperature in the step (2) is preferably 30-50 ℃; the aging time is preferably 12 to 36 hours; the solvent for solvent replacement is absolute ethyl alcohol and deionized water, namely, the absolute ethyl alcohol is used for replacement for 1 to 2 days, and then the deionized water is used for replacement for 1 to 2 days, preferably, the absolute ethyl alcohol is used for replacement for 24 hours, and then the deionized water is used for replacement for 24 hours; the gel freezing method adopts liquid nitrogen freezing; the pressure of freeze drying is 1-10 Pa, the temperature is-50 to-44 ℃, and the time is 2-3 days; the high-temperature post-curing temperature is 80-100 ℃, the curing time is 12-24 h, and preferably the high-temperature post-curing temperature is 100 ℃ and the curing time is 24h.

The density of the heat-insulating aerogel prepared by the invention is 0.04-0.09 g/cm ³ The specific surface area is 104 to 192m ² The thermal conductivity is 0.032-0.052W/(mK) at normal temperature and pressure.

The invention has the beneficial effects that: compared with the prior art, the invention provides a new preparation idea of the heat-insulating aerogel, namely, the purpose of preparing the three-dimensional porous reticular aerogel is achieved by in-situ crosslinking of chloromethyl and amine curing agents. The preparation process is simple and convenient, the obtained aerogel heat insulation material has low density and heat conductivity and good heat insulation performance, and the defects of powder falling and slag falling of the traditional aerogel are overcome. The aerogel has certain flexibility and compressive strength, can be used as a heat insulation protective material of an aerospace aircraft, and has certain effects on overall weight reduction, efficiency improvement and cost reduction.

Drawings

FIG. 1 is a scanning electron microscope image of the prepared thermal insulating aerogel.

Detailed Description

The following provides specific embodiments of a thermal insulating aerogel material and methods of making the same. It is to be noted that: the following examples are intended only to illustrate the present invention in more detail, and do not narrow the scope of the present invention. Modifications and adaptations of the present invention are within the scope of the invention as claimed and are contemplated by the present invention.

The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.

Example 1

The embodiment provides an aerogel thermal insulation material, and a preparation method thereof comprises the following steps:

(1) CMPSF with DCM =2.02mmol/g weighed 3g was dissolved in 100mL N-methylpyrrolidone and stirred at room temperature for 20min to obtain the precursor solution. Pouring the precursor solution into a polytetrafluoroethylene square mold, then slowly dropwise adding 0.8mL of polyetheramine D230 (the equivalent ratio of chloromethyl group to amino group is 1:1) into the precursor solution, carrying out ultrasonic treatment for 5min, and then placing the precursor solution into a vacuum oven at 25 ℃ for standing and gelling.

(2) And (3) placing the wet gel obtained in the step (1) in a vacuum oven at 40 ℃ for aging for 24h. Then demoulding, replacing the solvent by absolute ethyl alcohol, replacing the ethyl alcohol once every 8 hours for 24 hours, and then replacing the solvent by deionized water again. Changing the deionized water every 8h, taking out the gel after 24h, placing the gel in a plastic container, freezing for 20min by using liquid nitrogen, and freeze-drying under the pressure of 5Pa for 48h. Finally, the aerogel material is obtained after post-curing for 24 hours at the temperature of 100 ℃.

Referring to fig. 1, which is a scanning electron microscope image of the thermal insulating aerogel prepared by example, it was found that the aerogel had a three-dimensional network porous structure, which is also a cause of low density and thermal conductivity of the aerogel.

Example 2

(1) CMPSF with DCM =2.02mmol/g was dissolved in 100mL of N-methylpyrrolidone (mpk) and stirred at room temperature for 20min to obtain a precursor solution. Pouring the precursor solution into a polytetrafluoroethylene square mold, then slowly dropwise adding 1.6mL of polyetheramine D230 (the equivalent ratio of chloromethyl group to amino group is 1:2) into the precursor solution, carrying out ultrasonic treatment for 10min, and then placing the precursor solution into a vacuum oven at 25 ℃ for standing and gelling.

(2) And (2) placing the wet gel obtained in the step (1) in a vacuum oven at 50 ℃ for aging for 48h. Then demoulding, replacing the solvent by absolute ethyl alcohol solution, replacing the ethyl alcohol solution every 8h for 24h, and then replacing the solvent by deionized water again. Changing deionized water every 8h, taking out the gel after 24h, placing the gel in a plastic container, freezing for 20min by using liquid nitrogen, and then carrying out freeze drying under the pressure of 5Pa for 48h. Finally, post-curing the aerogel material at 100 ℃ for 24 hours to obtain the aerogel material.

Example 3

(1) CMPSF with DCM =2.02mmol/g was dissolved in 100mL of N-methylpyrrolidone (mpk) and stirred at room temperature for 20min to obtain a precursor solution. Pouring the precursor solution into a polytetrafluoroethylene square mold, then slowly dropwise adding 0.4mL of polyetheramine D230 (the equivalent ratio of chloromethyl group to amino group is 1.

(2) And (3) placing the wet gel obtained in the step (1) in a vacuum oven at 60 ℃ for aging for 72h. Then demoulding, replacing the solvent by absolute ethyl alcohol, replacing the ethyl alcohol once every 8 hours for 24 hours, and then replacing the solvent by deionized water again. Changing deionized water every 8h, taking out the gel after 24h, placing the gel in a plastic container, freezing for 20min by using liquid nitrogen, and then carrying out freeze drying under the pressure of 5Pa for 48h. Finally, the aerogel material is obtained after post-curing for 24 hours at the temperature of 100 ℃.

Example 4

in step (1) of examples 1 to 3 above, the CMPSF with a chloromethyl group content of DCM =2.02mmol/g was replaced by CMPSF with a chloromethyl group content of DCM =1.59mmol/g in the same amount, the equivalence ratio of CMPSF with a chloromethyl group content of DCM =1.59mmol/g to polyetheramine D230 was the same as in the corresponding examples, and after sonication for 5min, the mixture was placed in a vacuum oven at 25 ℃ for gel formation. Other process steps are the same as the corresponding examples.

Example 5

in step (1) of examples 1 to 3 above, the CMPSF with a chloromethyl group content of DCM =2.02mmol/g was replaced by CMPSF with a chloromethyl group content of DCM =3.52mmol/g in the same amount, the equivalence ratio of CMPSF with a chloromethyl group content of DCM =3.52mmol/g to polyetheramine D230 was the same as in the corresponding examples, and after sonication for 5min, the mixture was placed in a vacuum oven at 25 ℃ to form a gel. Other process steps are the same as the corresponding examples.

Example 6

In step (1) of examples 1 to 5 above, the mass concentration of chloromethylpolysulfone CMPSF (DCM =1.59 to 3.52 mmol/g) used was varied, and the mass of CMPSF used was 1.5g, 2g, 4g, 5g, and 6g, respectively. The equivalent ratio of CMPSF with chloromethyl content of DCM = 1.59-3.52 mmol/g to polyetheramine D230 is the same as that of the corresponding example, and the CMPSF and the polyetheramine D230 are placed in a vacuum oven at 25 ℃ for standing and colloid forming after ultrasonic treatment for 5 min. Other process steps are the same as the corresponding examples.

Example 7

In step (1) of examples 1 to 6 above, the crosslinking agent polyetheramine D230 used was replaced with triethylenetetramine. The equivalent ratio of CMPSF (DCM = 1.59-3.52 mmol/g) and triethylene tetramine with different mass concentrations is the same as that of the corresponding embodiment, and the mixture is placed in a vacuum oven at 25 ℃ for standing and gelling after ultrasonic treatment for 5 min. Other process steps are the same as the corresponding examples.

Example 8

In step (1) of examples 1 to 6 above, the crosslinking agent polyetheramine D230 used was replaced with polyetheramine D600. The equivalent ratio of CMPSF (DCM = 1.59-3.52 mmol/g) with different mass concentrations to polyetheramine D600 is the same as that of the corresponding example, and the mixture is placed in a vacuum oven at 25 ℃ for standing and gel forming after ultrasonic treatment for 5 min. Other process steps are the same as the corresponding examples.

Example 9

In step (1) of examples 1 to 3 above, the solution N-methylpyrrolidone used was replaced with dimethyl sulfoxide. CMPSF (DCM =2.02 mmol/g) and polyetheramine D230 were used in the same amounts as in the corresponding examples, and after sonication for 5min they were placed in a vacuum oven at 25 ℃ and allowed to stand to gel. Other process steps are the same as the corresponding examples.

To determine the best process step for the present invention, the CMPSF aerogels of the above examples were subjected to performance testing with the following results:

1. determination of solvent and optimal DCM content in precursor solution

For example, the mass fraction of CMPSF with DCM = 1.59-3.52 mmol/g is 3wt%, and the amino equivalent ratio of chloromethyl group of CMPSF to polyetheramine D230 is 1:1, the aging temperature is 40 ℃, and the aging time is 24 hours. At other times, the effect of two solvents and different DCM content on aerogel performance was investigated. The test results are given in table 1 below.

TABLE 1 Effect of two solvents on aerogel Performance

As shown in Table 1, the density and thermal conductivity of the aerogel are lower than those of the aerogel when the solvent is N-methylpyrrolidone, and the density and thermal conductivity of the aerogel are lowest when DCM =2.02mmol/g, so that N-methylpyrrolidone is used as the solvent, and the chloromethyl content is DCM =2.02mmol/g in the subsequent study of the invention.

2. Determination of optimum concentration of precursor solution

In the case of CMPSF with DCM =2.02mmol/g, the solvent is N-methylpyrrolidone, the mass fraction is 1 to 5wt%, the amino equivalent ratio of chloromethyl group of CMPSF to polyetheramine D230 is 1:1, the aging temperature is 40 ℃, and the aging time is 24 hours. The influence of different concentrations of CMPSF solutions on the overall performance of the aerogel was explored.

TABLE 2 Effect of different concentrations of precursor solutions on aerogel Performance

Mass fraction (wt%)	Density (g/cm 3)	Thermal conductivity (W/mK)
			1	0.031	0.036
2	0.037	0.033
			3	0.046	0.032
4	0.057	0.034
			5	0.072	0.041

As can be seen from Table 2, the aerogel has the lowest thermal conductivity at a mass fraction of 3wt% with only the CMPSF concentration being varied, and for thermal insulation materials, a lower thermal conductivity means better thermal insulation. The mass fraction range of the CMPSF is 1-5 wt%, wherein the mass fraction is preferably 2-4 wt%, and the best mass fraction is 3wt%.

3. Determination of optimum curing agent

By taking CMPSF with DCM =2.02mmol/g as an example, the solvent is N-methylpyrrolidone, the mass fraction is 3wt%, and the curing agents are triethylene tetramine, polyether amine D230 and polyether amine D600. The equivalent ratio of chloromethyl group to amino group of the curing agent of CMPSF is 1:1, the aging temperature is 40 ℃, and the aging time is 24 hours. The effect of varying concentrations of curing agent on the overall performance of the aerogel was explored at other times.

TABLE 3 Effect of different curing agents on aerogel Performance

Mass fraction (wt%)	Density (g/cm) ³ )	Thermal conductivity (W/mK)
			Triethylene tetramine	0.053	0.039
Polyetheramine D230	0.046	0.032
			Polyetheramine D600	0.048	0.037

As can be seen from Table 3, when polyetheramine D230 is used as the curing agent, the density and thermal conductivity of aerogel are lower than those of the other two curing agents, so in the present invention, polyetheramine D230 is preferably used as the curing agent.

4. Determination of the optimum equivalent ratio of chloromethyl to amino

In the case of CMPSF with DCM =2.02mmol/g, the solvent is N-methylpyrrolidone, the mass fraction is 3wt%, and the curing agent is polyetheramine D230. The CMPSF has an amino equivalent ratio of chloromethyl to curing agent of 1:0.5 to 2, the aging temperature is 40 ℃, and the aging time is 24 hours. At other times, the effect of different equivalent ratios of chloromethyl to amino groups on the overall performance of the aerogel was explored.

TABLE 4 influence of different equivalent ratios of chloromethyl and amino groups on aerogel performance

Chloromethyl to amino equivalent ratio	Density (g/cm) ³ )	Thermal conductivity (W/mK)
			1：0.5	0.047	0.034
1：1	0.046	0.032
			1：1.5	0.051	0.038
1：2	0.063	0.042

As can be seen from Table 4, under other conditions, the equivalent ratio of chloromethyl to amino is 1: the density and thermal conductivity of the aerogel is lowest at 1 hour, so the chloromethyl to amino equivalent ratio is preferably 1:1.

5. effect of different aging temperatures on aerogel Performance

In the case of CMPSF with DCM =2.02mmol/g, the solvent is N-methylpyrrolidone, the mass fraction is 3wt%, and the curing agent is polyetheramine D230. The equivalent ratio of chloromethyl group to amino group of the curing agent of CMPSF is 1:1, the aging temperature is 30-70 ℃, and the aging time is 24 hours.

TABLE 5 Effect of different aging temperatures on aerogel Performance

Aging temperature (. Degree. C.)	Density (g/cm) ³ )	Thermal conductivity (W/mK)
			30℃	0.049	0.035
40℃	0.046	0.032
			50℃	0.048	0.034
60℃	0.052	0.037
			70℃	0.055	0.043

As can be seen from Table 5, the aging temperature range of the present invention was selected to be 30 to 70 ℃ in the case where only the aging temperature was changed. When the aging temperature is 30-50 ℃, the density and the thermal conductivity of the aerogel are relatively close, so in the invention, the aging temperature is preferably 30-50 ℃, and the optimal aging temperature is 40 ℃.

6. Effect of different aging times on aerogel Performance

In the case of CMPSF with DCM =2.02mmol/g, the solvent is N-methylpyrrolidone, the mass fraction is 3wt%, and the curing agent is polyetheramine D230. The equivalent ratio of chloromethyl group to amino group of the curing agent of CMPSF is 1:1, the aging temperature is 40 ℃, and the aging time is considered to be 12-72 h.

TABLE 6 Effect of different aging times on aerogel Performance

Aging time (h)	Density (g/cm) ³ )	Thermal conductivity (W/mK)
			12h	0.048	0.034
24h	0.046	0.032
			36h	0.050	0.035
48h	0.057	0.041
			60h	0.062	0.045
72h	0.071	0.049

As can be seen from Table 6, the aerogel has stable density and thermal conductivity when the aging time is 12-36 h under the condition of only changing the aging time, and the lower thermal conductivity indicates that the aerogel has better thermal insulation performance, so the aging time is preferably 12-36 h, and the optimal aging temperature is 24h.

Through performance tests of aerogels prepared under different conditions, the optimal preparation process is determined, namely the DCM content of CMPSF is 2.02mmol/g, the solvent is N-methylpyrrolidone, the mass fraction is 3wt%, the curing agent is polyetheramine D230, and the amino equivalent ratio of chloromethyl of CMPSF to the curing agent is 1:1, the aging temperature is 40 ℃, and the aging time is 24 hours.

Claims

1. A preparation method of a polymer-based heat-insulating aerogel material is characterized by comprising the following steps:

(1) Dissolving chloromethylated polysulfone CMPSF in N-methyl under stirringObtaining a CMPSF solution with the mass fraction of 1 to 5wt% in pyrrolidone or dimethyl sulfoxide; then pouring the CMPSF solution into a mold, dropwise adding an amine curing agent, and placing the obtained mixed solution at 25 ^o C, standing in vacuum to form gel to obtain composite wet gel; wherein, the molar ratio of chloromethyl in CMPSF and amino in the curing agent is 1:1;

(2) Aging, solvent replacement, freeze drying and high-temperature curing of the composite wet gel obtained in the step (1) to obtain a heat-insulating aerogel material;

the aging temperature of the composite wet gel is 30 to 50 ^o C, aging for 12 to 36h; the solvent for solvent replacement is absolute ethyl alcohol and deionized water, namely, the ethanol solvent is used for replacing 1~2 days, and then the deionized water is used for replacing 1~2 days; the freezing is performed by adopting liquid nitrogen, the pressure of the freezing drying is 1 to 10Pa, and the temperature is-50 to-44 ^o C, the time is 2~3 days; the curing temperature after high temperature is 80 to 100 ^o And C, curing for 12 to 24h.

2. The process according to claim 1, wherein the CMPSF in step (1) has a chloromethylation degree DCM of 1.59 to 3.52mmol/g.

3. The preparation method according to claim 1 or 2, wherein the amine curing agent in step (1) is triethylene tetramine, polyether amine D230 or polyether amine D600.