A gradient composite fiber membrane of polyvinylidene fluoride and polymethyl methacrylate and a preparation method and application thereof

Abstract

A kind of polyvinylidene fluoride and poly (methyl methacrylate) gradient composite fiber membrane and its preparation method and application, poly (methyl methacrylate) and polyvinylidene fluoride are respectively dissolved in the mixed solution of N, N dimethylformamide and methyl acetate, oil bath stirring, obtain homogeneous transparent spinning solution;The above two kinds of spinning solution are added in needle tube respectively, fixed on microfluidic spinning advance pump, connect infusion hose;Temperature and humidity in spinning bin are controlled, install nylon net on receiver to carry out gradient composite fiber membrane collection, by microfluidic control system, polyvinylidene fluoride and poly (methyl methacrylate) spinning solution pumping is carried out at different change rate, open air valve, and carry out spinning;Gradient composite fiber membrane is taken off from nylon net, and dried to obtain two-component air-blowing poly (methyl methacrylate) and polyvinylidene fluoride gradient composite membrane.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fiber membrane material preparation, and particularly relates to a gradient composite fiber membrane of polyvinylidene fluoride and polymethyl methacrylate and a preparation method and application thereof. BACKGROUND

[0002] With global warming, abnormally high temperatures occur frequently, and high-temperature heat injury becomes a major threat to people's activities in hot weather. In summer, due to strong solar radiation and heat island effect, the temperature of buildings and outer fabrics increases significantly, which not only reduces the thermal comfort of the human body, but also causes fatal danger when the ambient temperature exceeds 37.5℃-38.3℃. With the increase of urbanization rate, the natural environment is gradually replaced by highly artificial reinforced concrete buildings. The dense buildings in the city cause the temperature to rise, which further intensifies the ground object radiation, forming the "urban heat island effect" that the temperature in the city is significantly higher than that in the suburbs. The heat gathered by the buildings is conducted to the indoor through the cement outer wall, and the human body increases the energy consumption of the air conditioning system in order to maintain the thermal comfort at 26℃ in the room. The active cooling equipment such as air conditioner accounts for 40% of the building electricity consumption, 15% of the global electricity, and emits about 10% of the greenhouse gases. Radiative cooling utilizes the "atmospheric window" of 8-13mm to dissipate heat to the cold (about 3K) outer space, while highly reflecting the sunlight of 0.3-2.5mm, realizing the spontaneous cooling of the object surface under the direct sunlight, zero energy consumption and zero pollution.

[0003] Fiber membrane material is a kind of functional material with porous structure, which has the characteristics of comfortable softness and air permeability. On the one hand, its large number of scattering units can carry out strong Mie scattering with sunlight, realizing high reflectivity, and on the other hand, its porous structure can reduce the absorption of non-radiative heat effects such as heat conduction and heat convection of external environment. Human skin is a good infrared emitter, and the emission wavelength basically overlaps with the "atmospheric window" band. In the non-motion state, the heat dissipated by the skin through the radiation path accounts for about 60% of the total heat dissipation of the human body. Clothing plays a crucial role in adjusting the personal thermal comfort under different environmental conditions, however, the design of traditional textiles is mostly based on heat conduction and heat convection, which inevitably blocks the transmission of human body heat radiation, reducing the skin heat dissipation effect. Therefore, it is of great value and practical significance to develop a new type of radiative cooling textile which is environmentally friendly and low in energy consumption, adjusts the spectrum of the inner side fabric, realizes wide spectrum absorption, realizes high-efficiency radiative cooling effect on the outer side, and makes the internal heat conduct to the outside, so that people can have a more comfortable physical and mental feeling when working indoors and outdoors in hot summer. SUMMARY

[0004] The technical problems solved by the present application: the present application provides a preparation method of a polyvinylidene fluoride and polymethyl methacrylate gradient composite fiber membrane and its application, the composite membrane has asymmetric spectral characteristics, the outer side is polyvinylidene fluoride with high selective emissivity in the 8-13 mu m atmospheric window, heat is transmitted to the cold outer space in the form of thermal radiation, the inner side is polymethyl methacrylate with wide spectrum absorption and without high selective emission spectrum, the heat inside is absorbed, and a high-efficiency refrigeration effect is formed. The present application also provides a macro preparation method of a radiation refrigeration fabric.

[0005] Technical scheme: a preparation method of a polyvinylidene fluoride and polymethyl methacrylate gradient composite fiber membrane, comprising the following steps: step 1: dissolving polymethyl methacrylate and polyvinylidene fluoride in a mixed solution of N,N dimethylformamide and methyl acetate respectively, and stirring in an oil bath to obtain homogeneous transparent spinning solution; step 2: adding the two kinds of spinning solution into a needle tube respectively, fixing on a microfluidic spinning push pump, and connecting a liquid infusion hose; step 3: controlling the temperature in the spinning warehouse to be 30-50 DEG C and the humidity to be 20-40%, installing a nylon net on the receiver to collect the gradient composite fiber membrane, and pumping the polyvinylidene fluoride and polymethyl methacrylate spinning solution at different changing push rates through a microfluidic control system, the polyvinylidene fluoride spinning solution is gradually decreased from high-speed pumping to low-speed pumping, the speed is 80 mL / h-0 mL / h, the polymethyl methacrylate spinning solution is gradually increased from low-speed pumping to high-speed pumping, the speed is 0 mL / h-80 mL / h, the air valve is opened to set the air flow pressure to 1-3 bar, and spinning is carried out; step 4: taking the gradient composite fiber membrane from the nylon net, drying in a vacuum oven at 60 DEG C for 12 h, and finally obtaining a two-component air-spraying polymethyl methacrylate and polyvinylidene fluoride gradient composite membrane.

[0006] The oil bath temperature in step 1) is 40-60 DEG C.

[0007] The volume ratio of N,N dimethylformamide and methyl acetate in step 1) is 60:40.

[0008] The mass concentration of polymethyl methacrylate and polyvinylidene fluoride in step 1) is 15%.

[0009] The liquid infusion hose in step 2) is connected to a stirrer and then connected to a spinning needle, and the two kinds of spinning solution are mixed during spinning.

[0010] Preferably, the temperature in the spinning warehouse in step 3) is controlled to be 40 DEG C and the relative humidity is 30%, and the air flow pressure is 2 Bar.

[0011] Preferably, the control of the polyvinylidene fluoride spinning solution in step 3) is recommended to be pumped from 60 mL / h to 0 mL / h at a rate of 1 mL / min decrease, and the polymethyl methacrylate spinning solution is pumped from 0 mL / h to 60 mL / h at a rate of 1 mL / min increase.

[0012] The polyvinylidene fluoride and polymethyl methacrylate gradient composite fiber membrane obtained by the above preparation method.

[0013] Application of the above polyvinylidene fluoride and polymethyl methacrylate gradient composite fiber membrane in woven wearable clothes.

[0014] Beneficial effects: The present application realizes stable and continuous spinning by the two-component air jet spinning method, and the continuous component gradient reduces the delamination phenomenon, so that the prepared fiber membrane has good mechanical properties. The present application realizes the gradient change of fiber diameter while achieving the component gradient, realizes multi-level scattering, and makes the fiber membrane have an extremely high solar reflectivity of 98.3%. The polyvinylidene fluoride and polymethyl methacrylate gradient composite fiber membrane of the present application utilizes the high emission of polyvinylidene fluoride at the atmospheric window of 8-13 μm to radiate heat to the outside, and utilizes the wide and effective absorption of polymethyl methacrylate to the inside heat to effectively absorb and transfer the heat to the outside, thereby further improving the radiation cooling performance and realizing a cooling effect of 4-5℃ in hot weather. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 Scanning electron microscope images of the fiber morphology diameter change of polyvinylidene fluoride with different mass fractions for Comparative Examples 2, 5, and 6.

[0016] Figure 2 Scanning electron microscope images of the fiber morphology diameter change of polymethyl methacrylate with different mass fractions for Comparative Examples 1, 3, and 4.

[0017] Figure 3 Digital camera image of the large-scale preparation sample of Example 1.

[0018] Figure 4 Digital camera image of the mechanical load of the sample of Example 1.

[0019] Figure 5 Tensile stress-strain curves of Example 1 and Comparative Examples 1 and 2.

[0020] Figure 6 Scanning electron microscope images of the fiber diameter gradient change of the sample of Example 1.

[0021] Figure 7 Reflectivity curves of Comparative Example 1, Comparative Example 2, and Example 1.

[0022] Figure 8 Emissivity curve of Example 1.

[0023] Figure 9 Radiative cooling performance of Example 1 and Comparative Example 1 is shown.

[0024] Figure 10 Radiative cooling performance test chart of Example 1. DETAILED DESCRIPTION

[0025] The application will be further described with reference to the following examples. It should be understood that these examples are intended to illustrate the application and are not intended to limit the scope of the application. Furthermore, it should be understood that various modifications and changes can be apparent to those skilled in the art upon reading the contents of this specification, and such modifications and changes are intended to fall within the scope of the appended claims.

[0026] Polyvinylidene fluoride (molecular weight 30w) was purchased from Arkema Company, France; polymethyl methacrylate (molecular weight 10w) was purchased from LG Company, South Korea; methyl acetate (analytical pure, 99%) was purchased from Shanghai Aldrin Biochemical Technology Co., Ltd.; N, N-dimethylformamide (analytical pure, 99.5%) was purchased from Shanghai Titan Science and Technology Co., Ltd.

[0027] Example 1

[0028] Step 1: 8.3 g of polymethyl methacrylate and 8.3 g of polyvinylidene fluoride were respectively dissolved in a mixed solution of 30 mL of N, N-dimethylformamide and 20 mL of methyl acetate, and continuously heated and stirred in a 50°C oil bath for 6 h to obtain a transparent and homogeneous spinning solution with a mass fraction of 15%.

[0029] Step 2: The two spinning solutions were respectively added into 20 mL needle tubes, fixed on a microfluidic spinning advancement pump, connected to a liquid infusion hose, and the stirring device in the spinning needle was started.

[0030] Step 3: The temperature in the spinning warehouse was controlled at 40°C and the humidity was controlled at 30%, and a nylon net was installed on the receiver to collect the gradient composite fiber membrane. Through the microfluidic control system, the polyvinylidene fluoride spinning solution was pumped from 60 mL / h to 0 mL / h at a rate of 1 mL / min, and the polymethyl methacrylate spinning solution was pumped from 0 mL / h to 60 mL / h at a rate of 1 mL / min. The gas valve was opened and the gas flow pressure was set to 2 bar for spinning.

[0031] Step 4: The gradient composite fiber membrane was taken off from the nylon net and dried in a vacuum oven at 60°C for 12 h to finally obtain a bicomponent air-jet polymethyl methacrylate and polyvinylidene fluoride gradient composite membrane.

[0032] Comparative Example 1

[0033] Step 1: 8.3 g of polyvinylidene fluoride was dissolved in a mixed solution of 30 mL N, N dimethylformamide and 20 mL methyl acetate, and stirred in a 50 °C oil bath for 6 h to obtain a transparent and homogeneous spinning solution with a mass fraction of 15%.

[0034] Step 2: The spinning solution was added to a 20 mL needle tube and fixed on a microfluidic spinning pump, and a liquid infusion hose was connected.

[0035] Step 3: The temperature in the spinning tank was controlled at 40 °C and the humidity was controlled at 30%, and a nylon mesh was installed on the receiver to collect the gradient composite fiber membrane. The polyvinylidene fluoride spinning solution was pumped at a speed of 30 ml / h through the microfluidic control system, and the air valve was opened to set the air flow pressure to 2 bar for spinning.

[0036] Step 4: The polyvinylidene fluoride fiber membrane was removed from the nylon mesh and dried in a vacuum oven at 60 °C for 12 h to obtain a single-component air-jet polyvinylidene fluoride fiber membrane.

[0037] Comparative Example 2

[0038] Prepared according to the preparation method of Comparative Example 1, except that the polyvinylidene fluoride was replaced by polymethyl methacrylate to obtain Comparative Example 2.

[0039] Comparative Examples 3, 4

[0040] Prepared according to the preparation method of Comparative Example 1, except that the mass fraction of polymethyl methacrylate was 10% and 20%, respectively, to obtain Comparative Examples 3 and 4.

[0041] Comparative Examples 5, 6

[0042] Prepared according to the preparation method of Comparative Examples 3 and 4, except that the mass fraction of polyvinylidene fluoride was 10% and 20%, respectively, to obtain Comparative Examples 5 and 6.

[0043] Figure 1 Comparative Examples 1, 3, and 4 are shown, because the mass fraction of polyvinylidene fluoride increases from 10% to 20% from left to right, the fiber diameter increases significantly, and the fiber morphology is best when the mass fraction is 15%.

[0044] Figure 2 Comparative Examples 1, 3, and 4 are shown, because the mass fraction of polyvinylidene fluoride increases from 10% to 20% from left to right, the fiber diameter increases significantly, and the fiber morphology is best when the mass fraction is 15%.

[0045] Figure 3 A digital camera image of the large-scale preparation sample of Example 1 is shown. Reliable continuous large-scale preparation can be achieved by double-component air-jet.

[0046] Figure 4 The mechanical load digital camera image of the sample of Example 1 is shown. The composite fiber membrane has excellent mechanical strength by combining the two components of the gas spray and the characteristics of the two polymers.

[0047] Figure 5 The tensile stress-strain curves of Example 1 and Comparative Examples 1 and 2, the mechanical strength of pure polymethyl methacrylate, and the tensile modulus of the composite gradient fiber membrane of Example 1 are shown. The tensile modulus of Example 1 is significantly improved compared to Comparative Examples 1 and 2.

[0048] Figure 6 The scanning electron microscope image of the fiber diameter gradient change of the sample of Example 1 is shown. It can be found that the fiber diameter changes significantly with different components, forming a continuous gradient change, and achieving a gradient change of the scattering unit inside the composite fiber membrane, which is beneficial to more effective multi-stage scattering.

[0049] Figure 7 The reflectivity curves of Comparative Example 1, Comparative Example 2, and Example 1 are shown. Compared with the uniform fiber structure of the single-component fiber membrane of Comparative Examples 1 and 2, the double-component gradient composite fiber membrane of Example 1 has higher reflectivity, significantly reducing the absorption of sunlight, and the total reflectivity is as high as 98.3%.

[0050] Figure 8 The emissivity curve of Example 1 is shown. The double-component structure does not affect the emissivity of the polyvinylidene fluoride on the outside of the fiber membrane, which still has an emissivity as high as 93%, ensuring its high-efficiency radiation cooling performance.

[0051] Figure 9 The radiation cooling performance comparison of Example 1 and Comparative Example 1 is shown. It can be clearly seen that the cooling effect of Example 1 is 1-2℃ lower than that of Comparative Example 1. Because Example 1 considers the internal heat radiation transfer compared to Comparative Example 1, the double-component gradient structure introduces poly-methyl methacrylate with wide-spectrum absorption on the inside, increasing the absorption of internal heat radiation, and maintaining a high-efficiency atmospheric transparent window emission on the outside.

[0052] Figure 10 The radiation cooling performance test graph of Example 1 is shown. In the actual hot summer environment from 10:00 am to 14:00 pm, a significant cooling effect can be observed. The test environment covered with the gradient composite membrane of poly-methyl methacrylate and polyvinylidene fluoride is 4-5℃ lower than the outside natural environment.

Claims

1. A method for producing a gradient composite fiber membrane of polyvinylidene fluoride and polymethyl methacrylate, characterized by, The method comprises the following steps: step 1, dissolving polymethyl methacrylate and polyvinylidene fluoride in a mixed solution of N,N-dimethylformamide and methyl acetate respectively, and stirring in an oil bath to obtain a homogeneous transparent spinning solution; step 2, adding the two spinning solutions into needle tubes respectively, fixing the needle tubes on a microfluidic spinning push pump, and connecting a liquid infusion hose; step 3, controlling the temperature in the spinning bin to be 30-50 DEG C and the humidity to be 20-40 %, installing a nylon net on a receiver to collect the gradient composite fiber membrane, and pumping the polyvinylidene fluoride and polymethyl methacrylate spinning solutions at different changing push rates through a microfluidic control system, the polyvinylidene fluoride spinning solution is gradually decreased from high-speed pumping to low-speed pumping at a speed of 80 mL / h-0 mL / h, and the polymethyl methacrylate spinning solution is gradually increased from low-speed pumping to high-speed pumping at a speed of 0 mL / h-80 mL / h, opening an air valve to set the air flow pressure to be 1-3 bar, and spinning; in step 3), the polyvinylidene fluoride spinning solution is recommended to be pumped from 60 mL / h at a rate of 1 mL / min to 0 mL / h, and the polymethyl methacrylate spinning solution is recommended to be pumped from 0 mL / h at a rate of 1 mL / min to 60 mL / h; step 4, taking the gradient composite fiber membrane off the nylon net, drying in a vacuum oven at 60 DEG C for 12 h, and finally obtaining a two-component air-jet polymethyl methacrylate and polyvinylidene fluoride gradient composite membrane.

2. The production method according to claim 1, characterized by, The oil bath temperature in step 1) is 40-60 DEG C.

3. The preparation method according to claim 1, characterized in that, The volume ratio of N,N-dimethylformamide and methyl acetate in step 1) is 60:

40.

4. The method of claim 1, wherein the method is characterized by, The mass concentration of polymethyl methacrylate and polyvinylidene fluoride in step 1) is 15 %.

5. The preparation method according to claim 1, characterized in that, In step 2), the liquid infusion hose is connected to a stirrer and then connected to a spinning needle, and the two spinning solutions are mixed during spinning.

6. The method of claim 1, wherein, In step 3), the temperature in the spinning bin is controlled to be 40 DEG C, the relative humidity is 30 %, and the air flow pressure is 2 bar.

7. The gradient composite fiber membrane of polyvinylidene fluoride and polymethyl methacrylate obtained by the preparation method in any one of claims 1-6.

8. The use of the gradient composite fiber membrane of polyvinylidene fluoride and polymethyl methacrylate in claim 7 in weaving wearable clothes.

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