CN110256101A - PI chopped strand enhances flexible silicon dioxide silica aerogel composite material and preparation method thereof - Google Patents

Abstract

The invention discloses a PI chopped fiber reinforced flexible silica airgel composite material and a preparation method thereof, belonging to the technical field of high-performance porous materials. It includes polyimide fibers filled inside the silica airgel porous structure to obtain a flexible and reinforced composite material, and the composite material can recover to 60% to 80% of its original length under 50% compression deformation. The preparation method designed in the present invention uses deionized water as a solvent, polyimide chopped fibers as a reinforcing phase, and controls the viscosity of the sol through a surfactant, so that chopped fibers of different lengths can be uniformly dispersed, and the replacement process is optimized to produce The obtained composite material not only has good mechanical properties, but also has good thermal insulation properties.

Description

PI chopped fiber reinforced flexible silica airgel composite material and preparation method thereof

technical field

The invention relates to an airgel material and belongs to the technical field of high-performance porous materials, in particular to a PI chopped fiber reinforced flexible silica airgel composite material and a preparation method thereof.

Background technique

Airgel is a new type of nano-porous super thermal insulation material with low density and low thermal conductivity. The unique nano-network structure endows it with good thermal insulation performance. At the same time, due to the high porosity, high specific surface area and extremely small acoustic impedance of airgel, compared with traditional lightweight sound insulation materials, the energy loss of sound waves propagating in its pores is accelerated, showing Better sound insulation performance. Therefore, airgel has great application potential as a lightweight thermal insulation and noise reduction material; however, the mechanical properties of aerogel limit the expansion of its application.

Surfactants can adsorb on the interface, greatly reduce the interfacial tension, and change the interface chemical properties of the solvent system. At the same time, surfactants will also self-polymerize in the solution to form various forms of molecularly ordered assemblies, such as micelles, reverse micelles, vesicles, and liquid crystals. These ordered molecular assemblies exhibit a variety of application functions. Among them, based on the solubilization of micelles and other ordered molecular assemblies, micelles are derived to catalyze, form microemulsions, and serve as chemical reaction media and microreactors. That is, an appropriate amount of surfactant can enable the hydrophobic trifunctional silicon source to undergo hydrolysis and condensation reactions in the water system, delay the phase separation during the gel process, and obtain a silica airgel with a more continuous skeleton structure .

In recent years, organic fibers with higher toughness and superior comprehensive performance have gradually entered the field of vision of researchers. Organic fibers are used as a reinforcing phase to improve the mechanical properties of aerogels, especially for chopped fibers, which are easier to add. By reinforcing the flexible airgel with chopped fibers as the reinforcing phase, this kind of composite material is more "elastic", thus having the function of damping vibration and noise reduction.

Chinese invention patent (application publication number: CN106311155A, application publication date: 2017-01-11) discloses a modified cellulose aerogel that can purify urine and its preparation method, which mainly uses traditional organic fibers such as cotton Short-fiber fiber-reinforced silica aerogels, because the temperature resistance of traditional organic fibers is 200 ° C to 300 ° C, the heat resistance of composite fibers is poor.

Chinese invention patent (application publication number: CN108503327A, application publication date: 2018-09-07) discloses a low-cost airgel insulation material, its preparation method and its application. It is mixed with an organic solvent to obtain a blended material, and the blended material is molded and dried to obtain an airgel thermal insulation material. Due to the poor bonding effect between the fiber and the airgel in the organic fiber reinforced silica airgel, the composite material is prone to separation between the matrix and the fiber during the compression process, and the phenomenon of powder and slag falling occurs.

Chinese invention patent (application publication number: CN101973752A, application publication date: 2011-02-16) discloses glass fiber reinforced silica airgel composite material and its preparation method, by combining glass fiber and silica airgel Formation, but because only a single length of chopped fibers can be added, it is impossible to achieve effective regulation of mechanical, thermal and sound insulation properties of composite materials.

Contents of the invention

In order to solve the above technical problems, the present invention provides a PI chopped fiber reinforced flexible silica airgel composite material and a preparation method thereof. The preparation method uses deionized water as a solvent and polyimide chopped fiber as a reinforcement. phase, the viscosity of the sol is controlled by a surfactant, so that chopped fibers of different lengths can be uniformly dispersed, and the replacement process is optimized. The composite material not only has good mechanical properties, but also has good thermal insulation performance.

To achieve the above purpose, the present invention discloses a PI chopped fiber reinforced flexible silica airgel composite material, which includes polyimide fibers filled inside the silica airgel porous structure to obtain a flexible reinforced composite The composite material can recover to 60% to 80% of its original length under 50% compression.

Further, the length of the polyimide fiber is 1mm-10mm.

Further, the thermal conductivity of the composite material is between 0.020-0.027W/(m·K).

Preferably, the hydrophobic angle of the composite material reaches 171°.

Preferably, the composite material can recover to 60%-80% of its original length under 50% compression deformation.

Preferably, for a composite material with a thickness of 1 cm and a density of 60 mg/cm ³ , the sound transmission loss between 500 and 1600 Hz is about 20 dB.

Preferably, the initial decomposition temperature of the composite material is as high as 550°C.

In order to better realize the technical purpose of the present invention, the present invention also discloses a preparation method of the above-mentioned composite material, which includes the following steps:

1) Preparation of micelles or microemulsions: take an acidic catalyst and deionized water and mix to obtain an acidic solution, then add a surfactant, and stir to obtain micelles or microemulsions;

2) Preparation of sol: adding a trifunctional silicon source to the micelles or microemulsions in step 1), and then adding a basic catalyst to obtain a mixed solution, sealing and standing to obtain a sol;

3) Add reinforcement phase: measure the viscosity value of the sol described in step 2), add polyimide fibers of different lengths at the corresponding viscosity value and stir evenly, seal, and wait for the gel;

4) Aging and replacement: After gelling, add deionized water, take it out after aging, place in deionized water, seal and let stand, wait for the end of the first replacement; continue to add ethanol to complete the second replacement;

5) Drying: the wet gel replaced in step 4) is placed in an airtight container, and treated with a drying medium in a critical state to obtain an airgel material.

Further, the kinematic viscosity of the sol in step 3) is 20-50 mm ² /s, which corresponds to the addition of polyimide fibers with a length of 1-10 mm. Among them, through viscosity control, chopped fibers of various lengths can be evenly dispersed to control the relationship between heat insulation and sound insulation. And the polyimide fiber has the excellent characteristics of high strength, high and low temperature resistance and corrosion resistance, which can be used as a reinforcing phase to improve the mechanical properties of the flexible airgel, and can be better combined with the airgel matrix to make it more flexible. It has "elasticity" and good high temperature resistance, and the good toughness of polyimide fiber further enhances the sound insulation performance of airgel composites.

Preferably, the sol described in step 3) is placed in a water bath at 40-80°C, and its viscosity value is observed.

Further, the trifunctional silicon source molecule in step 2) contains a non-polar group that does not participate in hydrolytic condensation and three alkoxy groups that participate in hydrolytic condensation reaction, and the trifunctional silicon source is removed from step 1). The volume ratio of ionized water is 1:(1.5~6).

Preferably, the trifunctional silicon source includes at least one of methyltriethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane or ethyltrimethoxysilane.

Preferably, the trifunctional silicon source is methyltriethoxysilane.

Further, the basic catalyst in step 2) includes ammonia water or sodium hydroxide, and the pH value of the mixed solution is 7-8.

Preferably, the ammonia water concentration is 1-6.5 mol/L.

Further, the pH value of the acid solution in step 1) is 3-4, and the acid catalyst includes at least one of hydrofluoric acid, hydrochloric acid, nitric acid, acetic acid or oxalic acid.

Further, the surfactant includes anionic surfactant, cationic surfactant or amphoteric surfactant.

Preferably, the surfactant is cetyltrimethylammonium bromide.

Further, after gelling in step 4), add deionized water, take it out after aging at 40-80°C, place it in deionized water at 40-80°C, seal it and let it stand until the first replacement is completed; continue to add ethanol Complete the second replacement;

Further, the drying medium in step 5) is ethanol or carbon dioxide.

The beneficial effects of the present invention are mainly reflected in the following aspects:

1. The preparation method designed in the present invention uses deionized water as the solvent system, which effectively reduces the cost of raw materials and makes the production process more safe and controllable;

2. The preparation method designed in the present invention adopts a trifunctional silicon source, which greatly improves the mechanical properties of the airgel itself, and has intrinsic hydrophobic properties, reduces the introduction of impurities, and simplifies the process flow;

3. The preparation method designed by the present invention uses the organic chopped fiber-polyimide fiber with excellent characteristics of high strength, high and low temperature resistance and corrosion resistance as the reinforcing phase of the flexible airgel to improve the mechanical properties of the flexible airgel, And the fiber is tightly combined with the airgel matrix without pretreatment, which solves the problem of powder and slag falling off the airgel composite material;

4. The preparation method designed by the present invention uses surfactants to slow down the phase separation of the trifunctional silicon source in the gel process, and the chopped fibers of different lengths are evenly distributed in the gel by controlling the viscosity of the sol, thereby being able to adjust heat insulation and The relationship between sound insulation;

5. The fiber-reinforced airgel prepared by the present invention is a flexible and lightweight material with superhydrophobicity, low density, heat insulation and sound insulation, etc. Good application prospects.

Description of drawings

Fig. 1 is the preparation schematic diagram of the design airgel composite material of the present invention;

Fig. 2 is the scanning electron microscope microscopic topography figure of the airgel composite material sample prepared in Example 1 of the present invention;

Fig. 3 is the scanning electron microscope microscopic topography figure of the airgel composite material sample prepared in Example 1 of the present invention;

Fig. 4 is the thermogravimetric curve of the airgel composite material sample prepared in Example 1 of the present invention;

Fig. 5 is the hydrophobic performance test figure of the airgel composite material sample prepared in Example 1 of the present invention;

Fig. 6 is the compression performance test diagram of the airgel composite material sample prepared in Example 1 of the present invention;

Fig. 7 is a test chart of the sound insulation performance of the airgel composite material sample prepared in Example 1 of the present invention.

Detailed ways

The invention discloses a method for preparing a PI chopped fiber reinforced flexible silica airgel composite material, which comprises the following steps:

1) Prepare micelles or microemulsions: add 30mL deionized water to a beaker, then add an acidic catalyst to make the solution pH = 3-4, stir for 5 minutes, add 0.1-5g surfactant, and stir for 20-60 minutes;

2) Preparation of sol: Add silicon source according to the volume ratio of silicon source and deionized water as 1: (0.5~6), continue stirring at room temperature for 3~5 hours, and then add a certain amount of molar concentration of 1~6.5mol/L ammonia water until the solution pH=7~8, and continue to stir for 0.5~1h;

3) Add reinforcement phase: place the sol in a water bath at 40-80°C, and observe its viscosity value through a viscometer. When the kinematic viscosity of the sol is 20-50mm ² /s, add 0.01-0.2g 10mm polyimide fiber, and stir well, wait for the gel;

4) Aging and replacement: The wet gel is aged at 40-80°C for two days, and then replaced with deionized water in a water bath at 40-80°C for 8-12 hours to remove surfactants and other unreacted substances, and after replacement Finally, replace it with ethanol 3 times at room temperature, each time for 8-12 hours;

5) Drying: Put the replaced wet gel into a container that can withstand high temperature and high pressure, and seal it. Add ethanol or carbon dioxide into the airtight container, and raise the temperature to the critical state of boosting the pressure to the drying medium. Continue to replace, and then lower the temperature and pressure to obtain a complete aerogel.

In order to better explain the present invention, the main content of the present invention is further clarified below in conjunction with specific examples, but the content of the present invention is not limited to the following examples.

Example 1

Add 30mL deionized water to the beaker, then add acetic acid to make the solution pH=3~4, stir for five minutes, add 0.4g cetyltrimethylammonium bromide CTAB, stir for 20min, then add 7.5mL methyl triethyl ammonium bromide Oxysilane MTES, continue to stir at room temperature for 4h. Then add a certain amount of ammonia water with a molar concentration of 1 mol/L until the pH of the solution is 7, and continue stirring for 1 h. Put the sol in a water bath at 60°C, and observe its viscosity value through a viscometer. When the kinematic viscosity of the sol is 20mm ² /s, add 0.1g of polyimide fiber with a length of 3mm, and stir evenly, and wait for the gel . The wet gel was aged at 60 °C for two days, followed by replacement with deionized water for 8 h in a 60 °C water bath to remove surfactants and other unreacted substances. After replacement, replace with ethanol 3 times at room temperature, 12 hours each time. Finally, the SiO ₂ airgel was obtained by supercritical drying with CO ₂ .

Example 2

Add 30mL deionized water to the beaker, then add acetic acid to make the solution pH=3~4, stir for five minutes, add 0.2g cetyltrimethylammonium bromide CTAB, stir for 20min, then add 7.5mL methyl triethyl ammonium bromide Oxysilane MTES, continue to stir at room temperature for 4h. Then add a certain amount of ammonia water with a molar concentration of 1mol/L until the pH of the solution is 7, continue to stir for 1 hour, place the sol in a water bath at 60°C, and observe the viscosity value with a viscometer until the viscosity of the sol is 25mm ² /s , add 0.1g of polyimide fibers with a length of 5mm, and stir evenly, and wait for the gel. The wet gel was aged at 60 °C for two days, followed by replacement with deionized water for 8 h in a 60 °C water bath to remove surfactants and other unreacted substances. After replacement, replace with ethanol 3 times at room temperature, 12 hours each time. Finally, the SiO ₂ airgel was obtained by supercritical drying with CO ₂ .

Example 3

Add 30mL deionized water to the beaker, then add acetic acid to make the solution pH=3~4, stir for five minutes, add 0.1g cetyltrimethylammonium bromide CTAB, stir for 20min, then add 7.5mL methyl triethyl Oxysilane MTES, continue to stir at room temperature for 4h. Then add a certain amount of ammonia water with a molar concentration of 1mol/L until the pH of the solution is 7, continue stirring for 1 hour, place the sol in a water bath at 60°C, and observe the viscosity value with a viscometer until the viscosity of the sol is 30mm ² /s , add 0.1g of polyimide fibers with a length of 7mm, and stir evenly, and wait for the gel. The wet gel was aged at 60 °C for two days, followed by replacement with deionized water for 8 h in a 60 °C water bath to remove surfactants and other unreacted substances. After replacement, replace with ethanol 3 times at room temperature, 12 hours each time. Finally, the SiO ₂ airgel was obtained by supercritical drying with CO ₂ .

Example 4

Add 30mL deionized water to the beaker, then add acetic acid to make the solution pH=3~4, stir for five minutes, add 0.8g cetyltrimethylammonium bromide CTAB, stir for 20min, then add 7.5mL methyl triethyl ammonium bromide Oxysilane MTES, continue to stir at room temperature for 4h. Then add a certain amount of ammonia water with a molar concentration of 1mol/L until the pH of the solution is 7, continue to stir for 1 hour, place the sol in a water bath at 60°C, and observe the viscosity value with a viscometer until the viscosity of the sol is 20mm ² /s , add 0.1g of polyimide fibers with a length of 3mm, and stir evenly, and wait for the gel. The wet gel was aged at 60 °C for two days, followed by replacement with deionized water for 8 h in a 60 °C water bath to remove surfactants and other unreacted substances. After replacement, replace with ethanol 3 times at room temperature, 12 hours each time. Finally, the SiO ₂ airgel was obtained by supercritical drying with CO ₂ .

Example 5

Add 30mL deionized water to the beaker, then add acetic acid to make the solution pH=3~4, stir for five minutes, add 0.2g cetyltrimethylammonium bromide CTAB, stir vigorously for 20min, then add 10mL methyl trimethoxy base silane MTMS, and continued to stir at room temperature for 4 h. Then add a certain amount of ammonia water with a molar concentration of 1mol/L until the pH of the solution is 7, continue stirring for 1 hour, place the sol in a water bath at 60°C, and observe the viscosity value with a viscometer until the viscosity of the sol is 20mm ² /s , add 0.1g of polyimide fibers with a length of 3mm, and stir evenly, and wait for the gel. The wet gel was aged at 60 °C for two days, followed by replacement with deionized water for 8 h in a 60 °C water bath to remove surfactants and other unreacted substances. After replacement, replace with ethanol 3 times at room temperature, 12 hours each time. Finally, the SiO ₂ airgel was obtained by supercritical drying with CO ₂ .

In conjunction with Figure 1, it can be known that the preparation method designed by the present invention uses deionized water as the solvent system, adopts a trifunctional silicon source, and adds organic chopped fibers-polyimide fibers with excellent characteristics of high strength, high and low temperature resistance and corrosion resistance , to improve the mechanical properties of the flexible aerogel for the reinforcing phase of the flexible aerogel; and the added surfactant is beneficial to slow down the phase separation of the trifunctional silicon source during the gelation process, and the chopped strands of different lengths can be made by controlling the viscosity of the sol The fibers are evenly distributed in the gel, making it possible to adjust the relationship between thermal and acoustic insulation.

It can be seen from Fig. 2 and Fig. 3 that the airgel composite material designed in the present invention, due to the addition of polyimide fibers, the fibers are tightly combined with the airgel matrix without pretreatment, which solves the problem of airgel composite The problem of material falling powder and slag.

It can be seen from Fig. 4 that the airgel composite material designed in the present invention has good thermal insulation performance, and the thermal conductivity can be adjusted between 0.020-0.027W/(m·K).

It can be seen from Fig. 5 that the airgel composite material designed in the present invention has superhydrophobicity, and the hydrophobic angle reaches 171°.

It can be seen from Fig. 6 that the airgel composite material designed in the present invention has certain flexibility, and can recover to 64% of the original length under 50% compression deformation.

It can be seen from Fig. 7 that the airgel composite material designed by the present invention has good sound insulation performance. For a material with a thickness of 1 cm and a density of 60 mg/cm ³ , the sound transmission loss between 500 and 1600 Hz is about 20 dB.

The above embodiments are only the best examples, rather than limiting the implementation of the present invention. In addition to the above-mentioned embodiments, the present invention also has other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the present invention.

Claims (10)

1. A kind of PI chopped fiber reinforced flexible silica airgel composite material, it comprises that polyimide fiber is filled in the interior of silica airgel porous structure, obtains the composite material that flexibility strengthens, and described composite material is in It can recover to 60% to 80% of its original length under 50% compression. 2. The PI chopped fiber reinforced flexible silica airgel composite material according to claim 1, characterized in that: the length of the polyimide fiber is 1 mm to 10 mm. 3. The PI chopped fiber reinforced flexible silica airgel composite material according to claim 1 or 2, characterized in that: the thermal conductivity of the composite material is between 0.020-0.027W/(m·K). 4. A method for preparing composite material according to any one of claims 1 to 3, comprising the steps of: 1) Preparation of micelles or microemulsions: take an acidic catalyst and deionized water and mix to obtain an acidic solution, then add a surfactant, and stir to obtain micelles or microemulsions; 2) Preparation of sol: adding a trifunctional silicon source to the micelles or microemulsions in step 1), and then adding a basic catalyst to obtain a mixed solution, sealing and standing to obtain a sol; 3) Add reinforcement phase: measure the viscosity value of the sol described in step 2), add polyimide fibers of different lengths at the corresponding viscosity value and stir evenly, seal, and wait for the gel; 4) Aging and replacement: After gelling, add deionized water, take it out after aging, place in deionized water, seal and let stand, wait for the end of the first replacement; continue to add ethanol to complete the second replacement; 5) Drying: the wet gel replaced in step 4) is placed in an airtight container, and treated with a drying medium in a critical state to obtain an airgel material. 5. according to the preparation method of the PI chopped fiber reinforced flexible silica airgel composite material of claim 4, it is characterized in that: the kinematic viscosity value of the sol described in step 3) is ²⁰ ～50mm/s, corresponding to Add polyimide fibers with a length of 1-10mm. 6. according to the preparation method of the PI chopped fiber reinforced flexible silica airgel composite material of claim 4 or 5, it is characterized in that: the trifunctional silicon source molecule described in step 2) comprises a non-hydrolytic condensation that does not participate in A polar group and three alkoxy groups participating in the hydrolysis condensation reaction, the volume ratio of the trifunctional silicon source to the deionized water in step 1) is 1:(1.5-6). 7. according to the preparation method of the described PI chopped fiber reinforced flexible silica airgel composite material of claim 6, it is characterized in that: the basic catalyst described in step 2) comprises ammonia or sodium hydroxide, and the mixed solution The pH value is 7-8. 8. according to the preparation method of the described PI chopped fiber reinforced flexible silica airgel composite material of claim 4 or 5, it is characterized in that: the pH value of the acidic solution described in step 1) is 3～4, and described The acid catalyst includes at least one of hydrofluoric acid, hydrochloric acid, nitric acid, acetic acid or oxalic acid. 9. according to the preparation method of the PI chopped fiber reinforced flexible silica airgel composite material of claim 4 or 5, it is characterized in that: the surfactant comprises anionic surfactant, cationic surfactant or amphoteric surface active agent active agent. 10. The preparation method of PI chopped fiber reinforced flexible silica airgel composite material according to claim 4 or 5, characterized in that: the drying medium in step 5) is ethanol or carbon dioxide.