PET (Polyethylene Terephthalate)-based directional moisture-conducting electrospun fibrous membrane and preparation method thereof

Abstract

The invention belongs to the technical field of occupational health individual protection, and particularly relates to a PET (Polyethylene Terephthalate)-based directional moisture-conducting electrospun fibrous membrane and a preparation method thereof. The method comprises the following steps: preparing a PET (Polyethylene Terephthalate)-based spinning solution, determining the influence of spinning parameters on a fiber microstructure and dust catching performance, and preparing an efficient dust catching micro-nano fiber filter membrane; hydrophilic and hydrophobic nano-particles / groups are added into a PET spinning solution, and a hydrophilic and hydrophobic micro-nanofiber filter membrane is spun; the hydrophobic / dust-catching / hydrophilic multi-layer composite bionic fiber filter material is constructed by adopting a laminating spinning method and taking an efficient dust-catching fiber filter material as a core layer. The PET-based one-way moisture-conducting electrospun fiber filter membrane prepared by the preparation method disclosed by the invention has a remarkable one-way water molecule transport characteristic and an efficient and low-resistance dust collection effect, can effectively improve the wearing comfort of an individual dustproof material in a humid and hot high-dust environment, and is very wide in application.

Description

Technical Field

[0001] The invention belongs to the technical field of occupational health individual protection, and specifically relates to a PET-based directional moisture-conducting electrospun fiber membrane and a preparation method thereof. Background Art

[0002] Currently, pneumoconiosis is still the most serious occupational disease in my country, accounting for 90% of the total number of occupational diseases. As of the end of 2022, my country has reported a total of 922,000 cases of occupational pneumoconiosis, of which coal workers' pneumoconiosis cases accounted for nearly half, and the number of new cases of coal workers' pneumoconiosis each year remains high. The disease is irreversible and is showing a trend of becoming younger, and has become a serious public health problem in my country.

[0003] The filter material in the individual protective respiratory equipment for dust in coal mines focuses on two performance parameters: dust filtration efficiency and breathing resistance. The filter material is composed of multiple layers of functional fiber materials, which effectively capture dust through inertial impact, interception, diffusion, gravity sedimentation and electrostatic effect. However, the hot and humid environment underground greatly affects the electrostatic adsorption and dust capture effect of the filter material. At the same time, water vapor exhaled by the human body and in the surrounding environment easily condenses on the fiber surface, hindering the air flow movement inside the fiber filter material, resulting in a sharp increase in breathing resistance. Therefore, the hot and humid environment underground restricts the dust filtration efficiency of the filter material to a certain extent. How to improve the dust filtration performance while increasing the moisture permeability of the filter material to reduce breathing resistance has become a key issue restricting the individual protection effect of dust underground. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a polyethylene terephthalate (PET)-based directional moisture-conducting electrospun fiber membrane and a preparation method thereof. The present invention selects PET as the substrate of the electrospun fiber material, adds hydrophilic and hydrophobic nanoparticles / groups, prepares modified hydrophilic micro-nano fiber filter membranes and hydrophobic micro-nano fiber filter membranes, and prepares gradient wetting-type bionic fiber filter materials through layered spinning, so as to achieve efficient dust capture while effectively promoting the unidirectional passage of water, thereby improving the wearing comfort of the human body.

[0005] The first purpose of the present invention is to provide a PET-based directional moisture-conducting electrospun fiber membrane, which includes selecting PET as the base material of the electrospun fiber material, adding hydrophilic and hydrophobic nanoparticles / groups, preparing modified hydrophilic micro-nano fiber filter membranes and hydrophobic micro-nano fiber filter membranes, using PET / G-OH membrane as the core layer, PET / PVP / G-OH membrane as the inner layer, and PET / SiO2 / FPU membrane as the outer layer, and adopting a layered spinning method to prepare a gradient wettability multilayer composite fiber membrane with hydrophobic outer layer / dust-catching core layer / hydrophilic inner layer through a one-step spinning method.

[0006] The second object of the present invention is to provide a method for preparing the above-mentioned PET-based directional moisture-conducting electrospun fiber membrane, comprising the following steps:

[0007] 1) Preparation of PET spinning solution;

[0008] 2) Preparation of core layer PET / G-OH spinning solution;

[0009] 3) Preparation of inner layer PET / PVP / G-OH spinning solution;

[0010] 4) Preparation of outer layer PET / SiO2 / FPU spinning solution;

[0011] 5) A one-step electrospinning method is used to prepare a multilayer composite nanofiber filter membrane with a gradient wetting property, from the inner layer, the core layer to the outer layer, layer by layer, to achieve a transition from hydrophilic to hydrophobic.

[0012] Furthermore, the preparation of the PET spinning solution in step 1) is: adding PET to a mixed solution of dichloromethane (DCM) and trifluoroacetic acid (TFA) in a volume ratio of 4:1, and stirring in a water bath at room temperature until completely dissolved to prepare a PET spinning solution, wherein the concentration of the PET spinning solution is 8wt%.

[0013] Furthermore, the preparation of the core layer spinning solution in step 2) is as follows: hydroxylated graphene (G-OH) is dispersed and added to a PET spinning solution to prepare a PET / G-OH spinning solution, and ultrasonically stirred to form a uniform core layer spinning solution. The mass volume ratio of the mixed solution of PET, G-OH, DCM and trifluoroacetic acid is 0.5:0.01:4:1 (g / L / L).

[0014] Furthermore, in step 3), the inner layer spinning solution is prepared by adding polyvinyl pyrrolidone (PVP) to the PET / G-OH spinning solution to prepare a hydrophilic layer spinning solution, and the mass ratios of PVP added to the PET / G-OH spinning solution are 1%, 3% and 5% respectively.

[0015] Furthermore, in step 4), the outer layer spinning solution is prepared by adding SiO2 nanoparticles and fluorinated polyurethane (FPU) to the PET spinning solution to prepare a hydrophobic layer spinning solution, wherein the mass ratio of SiO2 nanoparticles added to the PET spinning solution is 1%, and the mass ratio of FPU is 0.5%, 1% and 2%.

[0016] Furthermore, in step 5), each spinning solution is placed in a 5 mL syringe, the injection pump speed is 1 mL / h, the spinning voltage is 18 kV, the distance between the needle and the collector is 15 cm, the drum speed is 150 r / min, the temperature is 23±3°C, and the relative humidity is 30±5%.

[0017] Furthermore, in step 5), PVP with different mass ratios was introduced to construct a hydrophilic gradient, and the mass ratios of PVP from the inside to the outside were 5%, 3%, and 1%, and the spinning time of each layer was 8 minutes.

[0018] Furthermore, in step 5), a hydrophobic gradient is constructed by introducing FPU of different mass ratios, wherein the mass ratio of FPU from inside to outside is 0.5%, 1%, and 2%, and the spinning time of each layer is 4 minutes.

[0019] Furthermore, in step 5), the electrospinning time of the three-layer gradient wetting filter membrane is 1 hour in total, and the composite ratio between each layer is 2 / 2 / 1.

[0020] For further explanation, the present invention also provides a specific method for preparing a PET-based directional moisture-conducting electrospun fiber membrane, comprising the following steps:

[0021] a. PET was added to a mixed solution of dichloromethane (DCM) and trifluoroacetic acid (TFA) in a volume ratio of 4:1, and stirred in a water bath at room temperature until completely dissolved to prepare a PET spinning solution, wherein the concentration of the PET spinning solution was 8wt%;

[0022] b. 0.5 mg of hydroxylated graphene (G-OH) was added to an 8 wt % PET spinning solution, and the mixed solution was ultrasonically treated for 30 min to prepare a PET / G-OH spinning solution;

[0023] Step 2, adding polyvinyl pyrrolidone (PVP) in mass ratios of 1%, 3%, and 5% respectively to the above PET / G-OH spinning solution to prepare hydrophilic layer spinning solutions (PET / PVP-1 / G-OH, PET / PVP-3 / G-OH, PET / PVP-5 / G-OH);

[0024] Step 3, adding SiO2 nanoparticles with a mass ratio of 1% and fluorinated polyurethane (FPU) with different mass ratios (0.5%, 1%, and 2%) to 8wt% PET spinning solution to prepare three electrospinning solutions of PET / SiO2 / FPU-0.5, PET / SiO2 / FPU-1, and PET / SiO2 / FPU-2;

[0025] Step 4: A one-step electrospinning method is used to prepare a multilayer composite nanofiber filter membrane with a gradient wetting property layer by layer to achieve a transition from hydrophilic to hydrophobic.

[0026] In step 4 of the aforementioned PET-based directional moisture-conducting electrospun fiber membrane and preparation method thereof, each spinning solution is placed in a 5 mL syringe and pushed out at a rate of 1 mL / h using a syringe pump. The voltage is set to 18 kV, the distance between the needle and the collector is maintained at 15 cm, the drum speed is 150 r / min, the temperature is maintained at 23±3°C, and the relative humidity is 30±5%.

[0027] In step 4 of the aforementioned PET-based directional moisture-conducting electrospun fiber membrane and its preparation method, the PET / PVP / G-OH membrane is the inner layer, the PET / G-OH membrane is the middle layer, and the PET / SiO2 / FPU fiber membrane is the outer layer.

[0028] In step 4 of the aforementioned PET-based directional moisture-conducting electrospun fiber membrane and preparation method thereof, PVP in different mass ratios is introduced to construct a hydrophilic gradient, with the PVP mass ratio from inside to outside being 5%, 3%, and 1%, and the spinning time for each layer being 8 minutes.

[0029] In step 4 of the aforementioned PET-based directional moisture-conducting electrospun fiber membrane and preparation method thereof, a hydrophobic gradient is constructed by introducing FPU of different mass ratios, wherein the FPU mass ratio from inside to outside is 0.5%, 1%, and 2%, and the spinning time of each layer is 4 minutes.

[0030] In the aforementioned PET-based directional moisture-conducting electrospun fiber membrane and preparation method thereof, step 4, the electrospinning time of the three-layer gradient wetting filter membrane is 1 hour in total, and the composite ratio between the layers is 2 / 2 / 1.

[0031] The beneficial effects of the present invention are: preparing a PET-based spinning solution, clarifying the influence of spinning parameters on fiber microstructure and dust-collecting performance, and preparing a high-efficiency dust-collecting micro-nano fiber filter membrane; adding hydrophilic and hydrophobic nanoparticles / groups to the PET spinning solution to spin hydrophilic and hydrophobic micro-nano fiber filter membranes; using a layered spinning method, using a high-efficiency dust-collecting fiber filter material as the core layer to construct a hydrophobic / dust-collecting / hydrophilic multi-layer composite bionic fiber filter material. The PET-based unidirectional moisture-conducting electrospun fiber filter membrane prepared by the present invention has a significant unidirectional water molecule transport characteristic and a high-efficiency and low-resistance dust collection effect, can effectively improve the wearing comfort of individual dust-proof materials in a hot and humid environment with high dust content, and has a very wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0033] Figure 1 is a microscopic scanning electron microscope image of the intermediate layer PET / G-OH nanofiber filter membrane prepared by the present invention;

[0034] Figure 2 It is a microscopic scanning electron microscope image of the inner layer PET / PVP / G-OH nanofiber filter membrane prepared by the present invention;

[0035] Figure 3 It is a microscopic scanning electron microscope image of the outer layer PET / SiO2 / FPU nanofiber filter membrane prepared by the present invention;

[0036] Figure 4The filtration efficiency of the PET-based directional moisture-conducting electrospun fiber membrane prepared by the present invention on NaCl and DEHS particles at a flow rate of 20-85 L / min;

[0037] Figure 5 The piezoresistance of the PET-based directional moisture-conducting electrospun fiber membrane prepared by the present invention to NaCl and DEHS particles at a flow rate of 20-85 L / min;

[0038] Figure 6 This is a diagram showing the wettability changes of the inner and outer layers of the PET-based directional moisture-conducting electrospun fiber membrane prepared by the present invention;

[0039] Figure 7 The invention relates to terahertz imaging of moisture inside the PET-based directional moisture-conducting electrospun fiber membrane prepared by the invention. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0041] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0042] Example 1: A PET-based directional moisture-conducting electrospun fiber membrane and a preparation method thereof, the specific steps are:

[0043] First, PET was added to a mixed solution of dichloromethane (DCM) and trifluoroacetic acid (TFA) (volume ratio of 4:1) and stirred in a water bath at room temperature until completely dissolved to prepare an 8 wt % PET spinning solution. 0.5 mg of hydroxylated graphene (G-OH) was added to the PET solution and ultrasonically treated for 30 minutes to prepare a PET / G-OH spinning solution; secondly, polyvinyl pyrrolidone (PVP) was added to the above-mentioned PET / G-OH spinning solution in mass ratios of 1%, 3%, and 5%, respectively, to prepare hydrophilic layer spinning solutions (PET / PVP-1 / G-OH, PET / PVP-3 / G-OH, PET / PVP-5 / G-OH); then, SiO2 nanoparticles with a mass ratio of 1% and fluorinated polyurethane (FPU) with different mass ratios (0.5%, 1%, and 2%) were added to the 8wt% PET spinning solution to prepare three electrospinning solutions of PET / SiO2 / FPU-0.5, PET / SiO2 / FPU-1, and PET / SiO2 / FPU-2; finally, a one-step electrospinning method was used to prepare a multilayer composite nanofiber filter membrane with a gradient wetting type from the inner layer, the core layer to the outer layer, layer by layer, to achieve a transition from hydrophilic to hydrophobic.

[0044] like Figure 1-3 As shown, Figure 1is a microscopic scanning electron microscope image of the intermediate layer PET / G-OH nanofiber filter membrane prepared by the present invention; Figure 2 It is a microscopic scanning electron microscope image of the inner layer PET / PVP / G-OH nanofiber filter membrane prepared by the present invention; Figure 3 It is a microscopic scanning electron microscope image of the outer layer PET / SiO2 / FPU nanofiber filter membrane prepared by the present invention.

[0045] Example 2: A dust filtration capacity test of a PET-based directional moisture-conducting electrospun fiber membrane, the specific steps are as follows:

[0046] Under the environment of temperature 25℃ and relative humidity 30%, the filtration performance of nanofiber membrane was estimated by LZC-K1 filter material comprehensive tester, and the simulated particle diameter of the device was 0.3-10μm NaCl and DEHS aerosol particles. The prepared PET-based directional moisture-conducting electrospun fiber membrane was cut into squares (14cm×14cm) and placed on the filter table. The aerosol particles were set to pass through the nanofiber membrane at air flow rates of 20, 40, 60, and 85L / min. The difference in the number of particles upstream and downstream of the fiber membrane was counted, and the filtration efficiency of the nanofiber membrane at different spinning times was calculated according to the formula. Figure 4 As shown, as the air flow rate through the nanofiber membrane increased from 20 L / min to 85 L / min, the filtration efficiency of an electrospun fiber membrane for NaCl and DEHS aerosol particles decreased from 99.61% and 99.33% to 97.19% and 95.59%, respectively, indicating that the filtration efficiency of the electrospun fiber membrane decreased with the increase of air flow rate.

[0047] Example 3: Dust filtration piezoresistance test of a PET-based directional moisture-conducting electrospun fiber membrane, the specific steps are as follows:

[0048] The filtration performance of the nanofiber membrane was measured by the LZC-K1 filter material comprehensive tester at a temperature of 25°C and a relative humidity of 30%. The simulated particles of the device were NaCl and DEHS aerosol particles with a diameter of 0.3-10 μm. The prepared PET-based directional moisture-conducting electrospun fiber membrane was cut into squares (14 cm × 14 cm) and placed on the filter table. The aerosol particles were set to pass through the nanofiber membrane at an air flow rate of 85 L / min. The resistance value of the airflow was obtained by the sensor, and the duration of each filtration test was 3 minutes. Figure 5 As shown, as the air flow rate through the nanofiber membrane increased from 20 L / min to 85 L / min, the piezoresistance of an electrospun fiber membrane to NaCl and DEHS aerosol particles increased from 94.6 Pa and 102.3 Pa to 276.1 Pa and 282.9 Pa, respectively, indicating that the piezoresistance of the electrospun fiber membrane increased with the increase of air flow rate.

[0049] Example 4: A wettability test of a PET-based directional moisture-conducting electrospun fiber membrane, the specific steps are as follows:

[0050] The water contact angle of the nanofiber membrane was measured using a contact angle meter (KRUSSDSA25, Kruss, Germany) at room temperature and 45% humidity. A 2 μL water droplet (or silicone oil) was fixed on the surface of the nanofiber membrane for 1 min using a micro-syringe, and the contact angle of each nanofiber membrane was measured. The flow rate of the fixed liquid was 0.1 μL / s, and the distance from the nozzle to the substrate was tested to be 2 ± 0.2 cm. Figure 6 As shown in the figure, the inner layer PET / PVP / G-OH membrane exhibits hydrophilic properties, and the contact angle continues to decrease until it reaches 0° with time; the outer layer PET / SiO2 / FPU fiber membrane exhibits extremely strong hydrophobicity, with a contact angle of approximately 135.2°, which remains basically unchanged for a long time.

[0051] The directional moisture permeability of PET-based electrospun fiber membrane was tested by terahertz spectral imaging technology. At room temperature and 100% humidity, the saturated PET-based electrospun fiber membrane (4cm×4cm) was placed in the terahertz time-domain reflection light path. The terahertz spectrum information of the fiber membrane was collected every 2 minutes, and the peak-to-peak change was used to compile the moisture reflection imaging spectrum of the PET-based electrospun fiber membrane. Figure 7 As shown, after humidification, the surface of the fiber membrane shows water marks that gradually transition from purple to red due to different moisture contents. When the water content is high, it is close to purple, and when the water content is low, it is close to red. This shows that during the humidification process, moisture adheres to the membrane surface and continuously accumulates to form small water droplets of different sizes, eventually forming a discontinuous blue-green interwoven area.

Claims

1. A PET-based directional moisture-conducting electrospun fiber membrane, characterized in that: PET was selected as the base material of electrospun fiber material, and hydrophilic and hydrophobic nanoparticles / groups were added to prepare modified hydrophilic micro-nano fiber filter membranes and hydrophobic micro-nano fiber filter membranes. PET / G-OH membrane was used as the core layer, PET / PVP / G-OH membrane was used as the inner layer, and PET / SiO2 / FPU membrane was used as the outer layer. The layered spinning method was adopted to prepare a gradient wettability multilayer composite fiber membrane with hydrophobic outer layer / dust-catching core layer / hydrophilic inner layer through a one-step spinning method.

2. A method for preparing a PET-based directional moisture-conducting electrospun fiber membrane, comprising the following steps: 1) Preparation of PET spinning solution; 2) Preparation of core layer PET / G-OH spinning solution; 3) Preparation of inner layer PET / PVP / G-OH spinning solution; 4) Preparation of outer layer PET / SiO2 / FPU spinning solution; 5) A one-step electrospinning method is used to prepare a multilayer composite nanofiber filter membrane with a gradient wetting property, from the inner layer, the core layer to the outer layer, layer by layer, to achieve a transition from hydrophilic to hydrophobic.

3. The method for preparing a PET-based directional moisture-conducting electrospun fiber membrane according to claim 2, characterized in that: The step 1) of preparing the PET spinning solution is as follows: adding PET to a mixed solution of dichloromethane (DCM) and trifluoroacetic acid (TFA) in a volume ratio of 4:1, and stirring in a water bath at room temperature until completely dissolved, to prepare a PET spinning solution, wherein the concentration of the PET spinning solution is 8 wt%.

4. The method for preparing a PET-based directional moisture-conducting electrospun fiber membrane according to claim 2, characterized in that: The preparation of the core layer spinning solution in step 2) is as follows: hydroxylated graphene (G-OH) is dispersed and added to a PET spinning solution to prepare a PET / G-OH spinning solution, and then ultrasonically stirred to form a uniform core layer spinning solution. The mass volume ratio of the mixed solution of PET, G-OH, DCM and trifluoroacetic acid is 0.5:0.01:4:1 (g / L / L).

5. The method for preparing a PET-based directional moisture-conducting electrospun fiber membrane according to claim 2, characterized in that: In the step 3), the inner layer spinning solution is prepared by adding polyvinyl pyrrolidone (PVP) to the PET / G-OH spinning solution to prepare a hydrophilic layer spinning solution, and the mass ratios of PVP added to the PET / G-OH spinning solution are 1%, 3% and 5% respectively.

6. The method for preparing a PET-based directional moisture-conducting electrospun fiber membrane according to claim 2, characterized in that: In step 4), the outer layer spinning solution is prepared by adding SiO2 nanoparticles and fluorinated polyurethane (FPU) to the PET spinning solution to prepare a hydrophobic layer spinning solution, wherein the mass ratio of SiO2 nanoparticles added to the PET spinning solution is 1%, and the mass ratio of FPU is 0.5%, 1% and 2%.

7. The method for preparing a PET-based directional moisture-conducting electrospun fiber membrane according to claim 2, characterized in that: In step 5), each spinning solution is placed in a 5 mL syringe, the injection pump speed is 1 mL / h, the spinning voltage is 18 kV, the distance between the needle and the collector is 15 cm, the drum speed is 150 r / min, the temperature is 23±3°C, and the relative humidity is 30±5%.

8. The method for preparing a PET-based directional moisture-conducting electrospun fiber membrane according to claim 2, characterized in that: In step 5), PVP with different mass ratios was introduced to construct a hydrophilic gradient, and the mass ratio of PVP from inside to outside was 5%, 3%, and 1%, and the spinning time of each layer was 8 min.

9. The method for preparing a PET-based directional moisture-conducting electrospun fiber membrane according to claim 2, characterized in that: In step 5), a hydrophobic gradient is constructed by introducing FPU of different mass ratios, wherein the mass ratio of FPU from inside to outside is 0.5%, 1%, and 2%, and the spinning time of each layer is 4 minutes.

10. The method for preparing a PET-based directional moisture-conducting electrospun fiber membrane according to claim 2, characterized in that: In step 5), the electrospinning time of the three-layer gradient wetting filter membrane is 1 hour in total, and the composite ratio between each layer is 2 / 2 / 1.

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