A thermally insulating porous micro-nano fiber membrane and a preparation method thereof

Abstract

The invention discloses a heat-insulating porous micro-nano fiber membrane and a preparation method thereof. The method comprises the following steps: 1) adding an oil phase to a continuous phase under stirring, and stirring until completely emulsified to obtain a microemulsion, wherein the oil phase contains ethanol, acetic acid, hexadecyltrimethylammonium bromide and liquid paraffin, and the continuous phase contains polyimide, polysulfoneamide and N,N-dimethylacetamide; 2) electrostatic spinning the microemulsion to obtain a micro-nano fiber membrane; 3) calcining the micro-nano fiber membrane to obtain the heat-insulating porous micro-nano fiber membrane. The present invention first prepares a micro-nano fiber membrane by electrostatic spinning of a microemulsion, and then calcining it, volatilizing the organic solvent and the liquid paraffin components therein to form a porous structure, and the prepared porous micro-nano fiber membrane has a low thermal conductivity and excellent heat insulation effect.

Description

[Technical field]

[0001] The present application relates to the technical field of fiber membrane materials, and in particular to a thermally insulating porous micro-nano fiber membrane and a preparation method thereof. [Background technology]

[0002] The flexible thermal insulation materials commonly used in thermal protective clothing on the market are mostly fiber felt materials, such as aramid felt, flame-retardant cotton fiber felt, etc. However, the thermal insulation layer of this type of material is too thick, and the thermal conductivity is generally 0.05-0.08W / (m·k). The thermal conductivity is high, so that workers are still threatened by high temperatures when working in extreme environments. At the same time, because the thermal insulation layer material is too thick and has poor air permeability, the high-temperature and high-humidity microclimate will cause heat stress reactions in workers and even threaten their lives.

[0003] The thermal insulation mechanism of thermal insulation materials is to utilize the pore structure of the material itself, increase the proportion of static air in the material, increase the solid-gas interface, increase the tortuous heat transfer path, etc., to achieve the purpose of reducing heat transfer and reducing heat loss. Therefore, thermal insulation materials generally have the characteristics of small pore size and high porosity.

[0004] Electrospinning fiber membrane materials have the characteristics of small pore size, high porosity, low density, low specific surface area, etc., and have great development prospects in the fields of air filtration, waterproof and moisture permeability, and thermal insulation. However, the thermal insulation performance of this type of material needs to be further improved, and the thermal conductivity of the material needs to be further reduced. [Summary of the invention]

[0005] The purpose of the present invention is to provide a method for preparing a thermally insulating porous micro-nano fiber membrane in view of the shortcomings and problems of the prior art. The method can prepare a porous micro-nano fiber membrane with very low thermal conductivity and excellent thermal insulation performance.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for preparing a thermally insulating porous micro-nano fiber membrane, the preparation method comprising the following steps:

[0008] 1) adding the oil phase to the continuous phase under stirring, and stirring until completely emulsified to obtain a microemulsion, wherein the oil phase contains ethanol, acetic acid, hexadecyltrimethylammonium bromide and liquid paraffin, and the continuous phase contains polyimide (PI), polysulfoneamide (PSA) and N,N-dimethylacetamide (DMAC);

[0009] 2) electrospinning the microemulsion to obtain a micro-nano fiber membrane;

[0010] 3) calcining the micro-nano fiber membrane to obtain the thermally insulating porous micro-nano fiber membrane.

[0011] In the present invention, the porous micro-nano fiber membrane refers to a fiber membrane with a porous structure and a fiber size in the micrometer and nanometer levels.

[0012] In some embodiments, the mass ratio of the ethanol, acetic acid, cetyltrimethylammonium bromide and liquid paraffin in the oil phase is 1:1-5:1-5:3-15.

[0013] Preferably, the ethanol is anhydrous ethanol.

[0014] In some embodiments, the mass ratio of the oil phase to the continuous phase is 1:6-12.

[0015] In some embodiments, the preparation method further includes the step of preparing the continuous phase: dissolving the polyimide and the polysulfoneamide in the N,N-dimethylacetamide to obtain a polyimide solution and a polysulfoneamide solution, respectively, and mixing the polyimide solution and the polysulfoneamide solution to obtain the continuous phase.

[0016] In some embodiments, the mass concentration of the polyimide solution is 13% to 19%.

[0017] In some embodiments, the mass concentration of the polysulfoneamide solution is 8% to 20%, preferably 12%.

[0018] In some embodiments, the mass ratio of the polyimide solution to the polysulfoneamide solution is 4-7:3-6.

[0019] Preferably, the molecular weight of the polyimide is 40,000.

[0020] In some embodiments, the adding is done dropwise.

[0021] In some embodiments, in step 2), the electrospinning is received by a roller, the rotation speed of the roller is 100 to 1200 rpm, and the receiving distance of the roller is 12 to 16 cm.

[0022] In some embodiments, in step 2), the electrospinning speed is 0.8 to 1.4 mL / h.

[0023] In some embodiments, in step 2), the voltage of the electrospinning is 16 to 25 kV.

[0024] In some embodiments, in step 3), the calcination is performed in a tube furnace.

[0025] In some embodiments, the calcination is specifically as follows: firstly heating to 140-150°C at a rate of 1-10°C / min, and calcining for 0.5-1h; then heating to 250-300°C at a rate of 1-10°C / min, and calcining for 2-3h.

[0026] The present invention also provides a heat-insulating porous micro-nano fiber membrane prepared by the above-mentioned preparation method.

[0027] Furthermore, the thermal conductivity of the thermally insulating porous micro-nano fiber membrane is less than 0.018 W / (m·K), and has excellent thermal insulation performance.

[0028] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art.

[0029] The present invention uses an N,N-dimethylacetamide solution containing polyimide and polysulfoneamide as a continuous phase, and then adds an oil phase containing ethanol, acetic acid, hexadecyltrimethylammonium bromide and liquid paraffin into the continuous phase to prepare a microemulsion. The microemulsion is then used as a raw material for electrostatic spinning to first prepare a micro-nano fiber membrane, in which the size of fibers is at the micrometer and nanometer levels. The micro-nano fiber membrane is then calcined, and the organic solvent and liquid paraffin components in the fiber membrane are volatilized after calcination, leaving a porous structure in the fiber membrane, and finally a porous micro-nano fiber membrane is obtained. The membrane has a rich porous structure and a high porosity, can contain more still air, and can greatly reduce heat loss, so that the thermal insulation performance is significantly improved and the thermal conductivity is significantly reduced.

[0030] The thermally insulating porous micro-nano fiber membrane provided by the present invention has excellent thermal insulation performance, and its thermal conductivity can be as low as 0.018 W / (m·K).

Brief Description of the Drawings

[0031] Figure 1 This is a cross-sectional SEM image of the porous micro-nano fiber membrane prepared in Example 1 of the present invention.

[0032] Figure 2 It is the cross-sectional SEM picture of the porous micro-nano fiber membranes prepared in Examples 2 to 5 of the present invention before and after calcination.

[0033] Figure 3 This is a thermal imaging picture of the porous micro-nano fiber membrane prepared in Example 4 of the present invention after being placed on a platform at 90° C. for 10 minutes.

[0034] Figure 4 This is a thermal image of the porous micro-nano fiber membrane prepared in Example 4 of the present invention after being placed on ice for 10 minutes.

[0035] Figure 5This is a thermocouple diagram of the porous micro-nano fiber membrane prepared in Example 4 of the present invention. [Specific implementation method]

[0036] The technical solution of the present invention is described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solution of the present invention, but the present invention is not limited to the scope of the examples.

[0037] The polyimide in the following examples was purchased from Dongguan Zhanyang Polymer Materials Co., Ltd. with a molecular weight of 40,000, and the polysulfoneamide was purchased from Shanghai Tespandex Co., Ltd.

[0038] Example 1

[0039] This embodiment provides a porous micro-nano fiber membrane, and the preparation method thereof is as follows:

[0040] The first step: dissolve 4.39g of polyimide (PI) powder in 20g of N,N-dimethylacetamide (DMAC), stir evenly, and obtain a PI solution with a mass fraction of 18wt%; dissolve 5.45g of polysulfoneamide staple fiber in 40g of DMAC, stir until fully dissolved, and obtain a PSA solution with a mass fraction of 12wt%.

[0041] Step 2: Take 6.6 g of PI solution and 4.4 g of PSA solution, mix and stir evenly to obtain a PI / PSA mixed solution as a continuous phase.

[0042] Step 3: Add 0.9 g of hexadecyltrimethylammonium bromide (CTAB) to a mixed solution of 0.9 g of anhydrous ethanol and 0.9 g of acetic acid, mix and stir, then add 2.7 g of liquid paraffin to the mixed liquid, mix and stir, as the oil phase.

[0043] Step 4: With the mass ratio of oil phase to continuous phase being 1 / 11, take 1g of oil phase and add it dropwise into the above continuous phase while stirring. After the oil phase is added, continue magnetic stirring. After sufficient stirring, a microemulsion is obtained as the spinning solution for electrospinning.

[0044] Step 5: Pour the spinning solution into a syringe for electrospinning. The electrospinning parameters are: voltage 22 kV, receiving distance 15 cm, spinning speed 1 mL / h, roller receiving device, and rotation speed 500 rpm. PI / PSA micro-nano fiber membrane was obtained by electrospinning.

[0045] Step 6: calcine the PI / PSA micro-nano fiber membrane in a tubular furnace filled with nitrogen. The calcination process is: starting from room temperature (25°C), heating to 150°C at a rate of 1°C / min, calcining for 1 hour, and then heating to 300°C at a rate of 2°C / min, calcining for 2 hours. A porous micro-nano fiber membrane is obtained.

[0046] The cross-sectional SEM image of the porous micro-nanofiber membrane is Figure 1 , it can be seen that it has a rich porous structure.

[0047] Example 2

[0048] This embodiment provides a porous micro-nano fiber membrane, and the preparation method thereof is as follows:

[0049] The first step: dissolve 8.19g of polyimide (PI) powder in 40g of N,N-dimethylacetamide (DMAC), stir evenly, and obtain a PI solution with a mass fraction of 17wt%; dissolve 5.45g of polysulfoneamide staple fiber in 40g of DMAC, stir until fully dissolved, and obtain a PSA solution with a mass fraction of 12wt%.

[0050] Step 2: Take 5.6 g of PI solution and 2.4 g of PSA solution, mix and stir evenly to obtain a PI / PSA mixed solution as a continuous phase.

[0051] Step 3: Add 0.9 g of hexadecyltrimethylammonium bromide (CTAB) to a mixed solution of 0.9 g of anhydrous ethanol and 0.9 g of acetic acid, mix and stir, then add 2.7 g of liquid paraffin to the mixed liquid, mix and stir, as the oil phase.

[0052] Step 4: With the mass ratio of oil phase to water continuous phase being 1 / 6, take 1.33 g of oil phase and add it dropwise into the above continuous phase while stirring. After the oil phase is added, continue magnetic stirring. After sufficient stirring, a microemulsion is obtained as the spinning solution for electrospinning.

[0053] Step 5: Pour the spinning solution into a syringe for electrospinning. The electrospinning parameters are: voltage 16 kV, receiving distance 15 cm, spinning speed 1 mL / h, roller receiving device, and rotation speed 500 rpm. PI / PSA micro-nano fiber membrane was obtained by electrospinning.

[0054] Step 6: calcine the PI / PSA micro-nano fiber membrane in a tubular furnace filled with nitrogen. The calcination process is: starting from room temperature (25°C), heating to 150°C at a rate of 1°C / min, calcining for 1 hour, and then heating to 300°C at a rate of 2°C / min, calcining for 2 hours. A porous micro-nano fiber membrane is obtained.

[0055] The cross-sectional SEM images of the porous micro-nano fiber membrane before and after calcination are shown in Figure 2. Figure 2 As shown in a1 and a2, it can be seen that the fiber membrane forms an obvious pore structure after calcination.

[0056] Example 3

[0057] This embodiment provides a porous micro-nano fiber membrane, and the preparation method thereof is as follows:

[0058] The first step: dissolve 8.19g of polyimide (PI) powder in 40g of N,N-dimethylacetamide (DMAC), stir evenly, and obtain a PI solution with a mass fraction of 17wt%; dissolve 5.45g of polysulfoneamide staple fiber in 40g of DMAC, stir until fully dissolved, and obtain a PSA solution with a mass fraction of 12wt%.

[0059] Step 2: Take 5.6 g of PI solution and 2.4 g of PSA solution, mix and stir evenly to obtain a PI / PSA mixed solution as a continuous phase.

[0060] Step 3: Add 0.9 g of hexadecyltrimethylammonium bromide (CTAB) to a mixed solution of 0.9 g of anhydrous ethanol and 0.9 g of acetic acid, mix and stir, then add 2.7 g of liquid paraffin to the mixed liquid, mix and stir, as the oil phase.

[0061] Step 4: With the mass ratio of oil phase to continuous phase being 1 / 8, take 1g of oil phase and add it dropwise into the above continuous phase while stirring. After the oil phase is added, continue magnetic stirring. After sufficient stirring, a microemulsion is obtained as the spinning solution for electrospinning.

[0062] Step 5: Pour the spinning solution into a syringe for electrospinning. The electrospinning parameters are: voltage 16 kV, receiving distance 15 cm, spinning speed 1 mL / h, roller receiving device, and rotation speed 500 rpm. PI / PSA micro-nano fiber membrane was obtained by electrospinning.

[0063] Step 6: calcine the PI / PSA micro-nano fiber membrane in a tubular furnace filled with nitrogen. The calcination process is: starting from room temperature (25°C), heating to 150°C at a rate of 1°C / min, calcining for 1 hour, and then heating to 300°C at a rate of 2°C / min, calcining for 2 hours. A porous micro-nano fiber membrane is obtained.

[0064] The cross-sectional SEM images of the porous micro-nano fiber membrane before and after calcination are shown in Figure 2. Figure 2 As shown in b1 and b2, it can be seen that the fiber membrane forms an obvious pore structure after calcination.

[0065] Example 4

[0066] This embodiment provides a porous micro-nano fiber membrane, and the preparation method thereof is as follows:

[0067] The first step: dissolve 8.19g of polyimide (PI) powder in 40g of N,N-dimethylacetamide (DMAC), stir evenly, and obtain a PI solution with a mass fraction of 17wt%; dissolve 5.45g of polysulfoneamide staple fiber in 40g of DMAC, stir until fully dissolved, and obtain a PSA solution with a mass fraction of 12wt%.

[0068] Step 2: Take 5.6 g of PI solution and 2.4 g of PSA solution, mix and stir evenly to obtain a PI / PSA mixed solution as a continuous phase.

[0069] Step 3: Add 0.9 g of hexadecyltrimethylammonium bromide (CTAB) to a mixed solution of 0.9 g of anhydrous ethanol and 0.9 g of acetic acid, mix and stir, then add 2.7 g of liquid paraffin to the mixed liquid, mix and stir, as the oil phase.

[0070] Step 4: With the mass ratio of oil phase to water phase being 1 / 10, take 0.8 g of oil phase and add it dropwise into the above continuous phase while stirring. After the oil phase is added, continue magnetic stirring. After sufficient stirring, a microemulsion is obtained as the spinning solution for electrospinning.

[0071] Step 5: Pour the spinning solution into a syringe for electrospinning. The electrospinning parameters are: voltage 16 kV, receiving distance 15 cm, spinning speed 1 mL / h, roller receiving device, and rotation speed 500 rpm. PI / PSA micro-nano fiber membrane was obtained by electrospinning.

[0072] Step 6: calcine the PI / PSA micro-nano fiber membrane in a tubular furnace filled with nitrogen. The calcination process is: starting from room temperature (25°C), heating to 150°C at a rate of 1°C / min, calcining for 1 hour, and then heating to 300°C at a rate of 2°C / min, calcining for 2 hours. A porous micro-nano fiber membrane is obtained.

[0073] The cross-sectional SEM images of the porous micro-nano fiber membrane before and after calcination are shown in Figure 2. Figure 2 As shown in c1 and c2, it can be seen that the fiber membrane forms an obvious pore structure after calcination.

[0074] In Example 4, the PI / PSA micro-nano fiber membrane was post-calcined to remove the non-volatile solvent and liquid paraffin to obtain a porous micro-nano fiber membrane. The micro-nano fiber membrane before and after calcination was placed on a heating platform at 90°C and heated for 10 minutes. The temperatures of the heating platform (position 1), the micro-nano fiber membrane before calcination (position 2), and the micro-nano fiber membrane after calcination (position 3) were tested respectively. The results are as follows: Figure 3As shown, the photos of the micro-nano fiber membrane before and after calcination are as follows Figure 3 As shown in the upper right corner. It can be seen that the surface temperature of the porous micro-nano fiber membrane obtained after calcination is lower than that of the micro-nano fiber membrane before calcination, and both are lower than the position where the micro-nano fiber membrane is not placed. It can be seen that the porous micro-nano fiber membrane has excellent thermal insulation performance compared with the pre-calcined one.

[0075] In Example 4, the PI / PSA micro-nano fiber membrane was treated after calcination to remove the non-volatile solvent and liquid paraffin to obtain a porous micro-nano fiber membrane. The micro-nano fiber membrane before and after calcination was placed on ice for 10 minutes, and the temperatures of the ice surface (position 1), the micro-nano fiber membrane before calcination (position 2), and the micro-nano fiber membrane after calcination (position 3) were tested respectively. The results are as follows: Figure 4 As shown, the photos of the micro-nano fiber membrane before and after calcination are as follows Figure 4 As shown in the upper right corner. It can be seen that the surface temperature of the porous micro-nano fiber membrane obtained after calcination is higher than that of the micro-nano fiber membrane before calcination, and both are higher than the position where the micro-nano fiber membrane is not placed. It can be seen that the porous micro-nano fiber membrane has excellent cold insulation performance compared with the pre-calcination.

[0076] In Example 4, the PI / PSA micro-nano fiber membrane was post-calcined to remove the non-volatile solvent and liquid paraffin to obtain a porous micro-nano fiber membrane. The micro-nano fiber membrane before and after calcination was placed on a heating platform at 90°C, and the change in the membrane surface temperature was observed by a thermocouple. Figure 5 It can be seen that the porous micro-nano fiber membrane obtained after calcination heats up more slowly than before calcination, and the stable temperature reached on the surface of the porous micro-nano fiber membrane is lower than the stable temperature reached on the surface of the micro-nano fiber membrane before calcination. The porous micro-nano fiber membrane has excellent thermal insulation properties.

[0077] In Example 4, the PI / PSA micro-nano fiber membrane was treated after calcination to remove the non-volatile solvent and liquid paraffin to obtain a porous micro-nano fiber membrane. The thermal conductivity of the micro-nano fiber membrane before and after calcination in Example 4 was tested. The thermal conductivity before calcination was 0.023W / (m·K), and the thermal conductivity of the porous micro-nano fiber membrane after calcination was reduced to 0.018W / (m·K). Both are lower than the thermal conductivity of air (0.026W / (m·K).

[0078] Example 5

[0079] This embodiment provides a porous micro-nano fiber membrane, and the preparation method thereof is as follows:

[0080] The first step: dissolve 8.19g of polyimide (PI) powder in 40g of N,N-dimethylacetamide (DMAC), stir evenly, and obtain a PI solution with a mass fraction of 17wt%; dissolve 5.45g of polysulfoneamide staple fiber in 40g of DMAC, stir until fully dissolved, and obtain a PSA solution with a mass fraction of 12wt%.

[0081] Step 2: Take 5.6 g of PI solution and 2.4 g of PSA solution, mix and stir evenly to obtain a PI / PSA mixed solution as a continuous phase.

[0082] Step 3: Add 0.9 g of hexadecyltrimethylammonium bromide (CTAB) to a mixed solution of 0.9 g of anhydrous ethanol and 0.9 g of acetic acid, mix and stir, then add 2.7 g of liquid paraffin to the mixed liquid, mix and stir, as the oil phase.

[0083] Step 4: With the mass ratio of oil phase to water phase being 1 / 12, take 0.667 g of oil phase and add it dropwise into the above continuous phase while stirring. After the oil phase is added, continue magnetic stirring. After sufficient stirring, a microemulsion is obtained as the spinning solution for electrospinning.

[0084] Step 5: Pour the spinning solution into a syringe for electrospinning. The electrospinning parameters are: voltage 16 kV, receiving distance 15 cm, spinning speed 1 mL / h, roller receiving device, and rotation speed 500 rpm. PI / PSA micro-nano fiber membrane was obtained by electrospinning.

[0085] Step 6: calcine the PI / PSA micro-nano fiber membrane in a tubular furnace filled with nitrogen. The calcination process is: starting from room temperature (25°C), heating to 150°C at a rate of 1°C / min, calcining for 1 hour, and then heating to 300°C at a rate of 2°C / min, calcining for 2 hours. A porous micro-nano fiber membrane is obtained.

[0086] The cross-sectional SEM images of the porous micro-nano fiber membrane before and after calcination are shown in Figure 2. Figure 2 As shown in d1 and d2, it can be seen that the fiber membrane forms an obvious pore structure after calcination.

[0087] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0088] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A method for preparing a thermally insulating porous micro-nano fiber membrane, It is characterized in that The preparation method comprises the following steps: 1) adding the oil phase to the continuous phase under stirring, and stirring until completely emulsified to obtain a microemulsion, wherein the oil phase contains ethanol, acetic acid, hexadecyltrimethylammonium bromide and liquid paraffin, and the continuous phase contains polyimide, polysulfoneamide and N,N-dimethylacetamide; 2) electrospinning the microemulsion to obtain a micro-nano fiber membrane; 3) calcining the micro-nano fiber membrane to obtain the thermally insulating porous micro-nano fiber membrane; The mass ratio of ethanol, acetic acid, hexadecyltrimethylammonium bromide and liquid paraffin in the oil phase is 1:1-5:1-5:3-15; The mass ratio of the oil phase to the continuous phase is 1:6-12; The preparation method further comprises the step of preparing the continuous phase: dissolving the polyimide and the polysulfoneamide in the N,N-dimethylacetamide to obtain a polyimide solution and a polysulfoneamide solution, respectively, and mixing the polyimide solution and the polysulfoneamide solution to obtain the continuous phase; The mass ratio of the polyimide solution to the polysulfoneamide solution is 4-7:3-6; The thermal conductivity of the thermally insulating porous micro-nano fiber membrane is less than 0.018 W / (m·K).

2. A method for preparing a thermally insulating porous micro-nano fiber membrane according to claim 1, It is characterized in that The mass concentration of the polyimide solution is 13% to 19%; and / or the mass concentration of the polysulfoneamide solution is 8% to 20%.

3. The method for preparing a thermally insulating porous micro-nano fiber membrane according to claim 1, It is characterized in that In step 1), the adding method is dropwise addition; and / or, in step 2), the electrospinning is received by a roller, the rotation speed of the roller is 100 to 1200 rpm, and the receiving distance of the roller is 12 to 16 cm; and / or, in step 2), the spinning speed of the electrospinning is 0.8 to 1.4 mL / h; and / or, in step 2), the voltage of the electrospinning is 16 to 25 kV.

4. The method for preparing a thermally insulating porous micro-nano fiber membrane according to claim 1, It is characterized in that In step 3), the calcination is carried out in a tubular furnace; and / or, in step 3), the calcination is specifically: firstly heating to 140-150°C at a rate of 1-10°C / min, and calcining for 0.5-1h; then heating to 250-300°C at a rate of 1-10°C / min, and calcining for 2-3h.

5. A thermally insulating porous micro-nanofibrous membrane prepared by the method for preparing a thermally insulating porous micro-nanofibrous membrane according to any one of claims 1 to 4.

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