Thermal management coaxial fiber membrane and its preparation method and application

Abstract

The present invention provides a thermal management coaxial fiber membrane, a preparation method and application thereof. The thermal management coaxial fiber membrane of the present invention comprises a low molecular weight PEG membrane core layer and a PVDF shell layer coating the low molecular weight PEG membrane core layer; the thermal management coaxial fiber membrane adopts PVDF solution as the shell layer spinning solution and low molecular weight PEG as the core layer spinning solution through an outer layer high-pressure air flow blowing spinning process. The coaxial fiber membrane of the present invention not only has excellent thermal management performance, but also has guaranteed or even enhanced mechanical properties, excellent flexibility and cyclic stability, and the raw materials used are cheap and easily available, the preparation method is simple, the operation is safe, and it is easy to continuously mass-produce, and has high practical application value in the field of wearable electronic products.

Description

Technical Field

[0001] The present invention relates to the technical field of composite membranes, and in particular to a thermal management coaxial fiber membrane and a preparation method and application thereof. Background Art

[0002] Patent document CN 109056107 A discloses a method for preparing a polyvinylidene fluoride-polyethylene glycol coaxial electrospun fiber, which is prepared by an electrospinning process. The spun fiber is obtained by absorbing and releasing energy using the phase change material polyethylene glycol in the spun fiber, so that the spun fiber can be used to regulate the temperature within a specific temperature range. However, the polyvinylidene fluoride-polyethylene glycol coaxial electrospun fiber needs to be prepared by an electrospinning process, and the production efficiency is low (for example, the flow rate of the outer tube spinning solution is 1.6 mL / h, and the flow rate of the inner tube spinning solution is 107.2 μL / h), and the production process requires a high-voltage electric field, which not only consumes a lot of energy but also poses a safety hazard. Summary of the Invention

[0003] Based on this, it is necessary to provide a thermal management coaxial nanofiber membrane and its preparation method and application.

[0004] The present invention adopts the following technical solutions:

[0005] The present invention provides a thermal management coaxial fiber membrane, which includes a low molecular weight PEG membrane core layer and a PVDF shell layer covering the low molecular weight PEG membrane core layer; the thermal management coaxial fiber membrane adopts PVDF solution as the shell layer spinning solution and low molecular weight PEG solution as the core layer spinning solution through an outer layer high-pressure airflow blowing spinning process.

[0006] In some embodiments, the mass fraction of PEG in the thermal management coaxial fiber membrane is not less than 60%, and the enthalpy value of the fiber membrane is not less than 40 J / g.

[0007] In some embodiments, the fiber size of the thermal management coaxial fiber membrane is 800-3800 nm.

[0008] In some embodiments, the molecular weight of PVDF is 450,000-550,000, and / or the low molecular weight PEG is selected from at least one of PEG400, PEG600, and PEG800.

[0009] The present invention provides a preparation method of the above-mentioned thermal management coaxial fiber membrane, comprising the following steps: preparing a PVDF solution as a shell layer spinning solution; using a low molecular weight PEG as a core layer spinning solution; using a three-axis spinning needle to perform high-pressure airflow blowing and spinning to form coaxial fibers; and drying the collected coaxial fibers to obtain the membrane.

[0010] In some embodiments, in the PVDF solution, the PVDF content is 15 wt %, and the solvent is N,N-dimethylformamide.

[0011] In some embodiments, the sizes of the triaxial spinning needles are 22G-17G-14G, respectively; the low molecular weight PEG solution is connected to the inner layer of the spinning needle; the PVDF solution is connected to the middle layer of the spinning needle; and the high pressure airflow is connected to the outer layer of the spinning needle.

[0012] In some embodiments, the high-pressure air flow blowing spinning process parameters are: the propulsion speed of the PVDF solution is 10 mL / h, the propulsion speed of the low molecular weight PEG solution is 1.5 mL / h, the high-pressure air flow pressure is 1.2 bar, and the distance between the spinning needle and the collecting device is 30 cm.

[0013] In some embodiments, the drying temperature is 45-60°C.

[0014] The application of the above-mentioned thermal management coaxial fiber membrane in the preparation of clothing and wearable electronic devices.

[0015] Compared with the prior art, the core advantages of the present invention are:

[0016] The coaxial fiber membrane of the present invention is prepared by using PVDF solution as the shell layer spinning solution and low molecular weight PEG as the core layer spinning solution through an outer layer high-pressure air flow blowing spinning process. It not only has excellent thermal management performance, but also has guaranteed or even enhanced mechanical properties. It has excellent flexibility and cyclic stability. The raw materials used are cheap and easily available, the preparation method is simple, the operation is safe, and it is easy to continuously and large-scale produce, and is used in the field of wearable (electronic) products.

[0017] The present invention uses solution blown spinning to prepare polyvinylidene fluoride-polyethylene glycol coaxial fiber membrane. The flow rate of the outer tube spinning solution is 10 mL / h, and the flow rate of the inner tube spinning solution is 1.5 mL / h. The production efficiency can be effectively improved (at least 6 times higher than that of electrospinning). At the same time, since the flow rate of the inner tube spinning solution is greatly improved, the prepared coaxial fiber membrane product has a higher core layer content, thereby obtaining a higher enthalpy value. In addition, the present invention uses high-pressure airflow instead of an electric field, which can reduce equipment costs, energy consumption costs and safety hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the coaxial fiber membrane prepared in Example 1 (including fiber diameter frequency analysis).

[0019] Figure 2 TG test graphs of the fiber membranes prepared in Example 1 and Comparative Example 1.

[0020] Figure 3 These are the DSC test graphs of the fiber membrane and PEG800 prepared in Example 1 and Comparative Example 1.

[0021] Figure 4 These are DSC test graphs of the coaxial fiber membranes prepared in Examples 1 to 3.

[0022] Figure 5 The stress-strain curves of the fiber membranes prepared in Example 1 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0023] The technical concept of the present invention is to provide a coaxial high-pressure air blown spinning fiber membrane and its preparation method and application. Among them, the thermal management coaxial high-pressure air blown spinning fiber membrane has excellent thermal management ability, flexibility, cycle stability and mechanical properties.

[0024] The present invention is further described in detail below in conjunction with specific embodiments so that those skilled in the art can understand the present invention more clearly. The following embodiments are only used to illustrate the present invention, but are not limited to limiting the scope of the present invention. Based on the specific embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art; in the embodiments of the present invention, unless specifically specified, the technical means used are conventional means well known to those skilled in the art.

[0025] Sources of key test materials and physical and chemical performance indicators:

[0026] Polyvinylidene fluoride (PVDF), purchased from Arkema (Shanghai) Chemical Co., Ltd., has a molecular weight of 500,000, is a white solid, and has a density of 1.78 g / cm 3 , the glass transition temperature (Tg) is about -35°C, and the crystallinity is usually 50-60%.

[0027] Polyethylene glycol (PEG): purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0028] Implementation Case 1

[0029] This embodiment provides a method for preparing a coaxial high-pressure air flow blown spinning fiber membrane (PVDF-PEG800), comprising the following steps:

[0030] S1, preparation of spinning solution:

[0031] PVDF was dissolved in DMF and stirred at 50° C. for 5 h to obtain a 15 wt% PVDF solution. Subsequently, 10 mL of the PVDF solution was extracted using a 10 mL syringe as the shell spinning solution.

[0032] Load PEG800 into a 10 ml syringe for later use.

[0033] S2, coaxial solution blow spinning:

[0034] At room temperature, a syringe containing a 15wt% PVDF solution, a syringe containing a PEG800 solution, and a high-pressure airflow were connected to a triaxial spinning needle. The selected triaxial spinning needles were 22G-17G-14G (inner diameters of 400, 1017, and 1600 μm, respectively). The syringe containing PEG800 was connected to the inner layer of the spinning needle, the syringe containing a 15wt% PVDF solution was connected to the middle layer of the spinning needle, and the high-pressure airflow was connected to the outer layer of the spinning needle. Among them, the 15wt% PVDF solution was pushed at a speed of 10 mL / h, the PEG800 was pushed at a speed of 1.5 mL / h, and the high-pressure airflow pressure was 1.2 bar. Coaxial fibers were spun at room temperature. The distance between the spinneret and the winding device was about 30 cm, and the spinning collection device rotated at 300 rpm.

[0035] S3, drying the coaxial fiber:

[0036] After spinning and collection, the coaxial fiber was placed in a 45°C oven for 12 h to remove the remaining solvent to obtain the PVDF-PEG800 coaxial nanofiber membrane.

[0037] Implementation Case 2

[0038] This embodiment provides a preparation method of a coaxial high-pressure air flow blown spinning fiber membrane (PVDF-PEG600), which is basically the same as that of embodiment 1, with the only difference being that PEG800 is replaced by PEG600 as the core layer spinning solution.

[0039] Implementation Case 3

[0040] This embodiment provides a preparation method of a coaxial high-pressure air flow blown spinning fiber membrane (PVDF-PEG400), which is basically the same as that of embodiment 1, with the only difference being that PEG800 is replaced by PEG400 as the core layer spinning solution.

[0041] Comparative (Implementation) Example 1

[0042] This comparative example provides a method for preparing a coaxial fiber membrane, which comprises the following steps:

[0043] S1, preparation of spinning solution:

[0044] PVDF was dissolved in DMF and stirred at 50° C. for 5 h to obtain a 15 wt% PVDF solution. Subsequently, 10 mL of the PVDF solution was drawn using a 10 mL syringe as a spinning solution.

[0045] S2, solution blow spinning:

[0046] At room temperature, a syringe filled with a 15wt% PVDF solution and a high-pressure airflow were connected to a triaxial spinning needle. The selected triaxial spinning needles were 22G, 17G, and 14G (inner diameters of 400, 1017, and 1600μm, respectively). The inner layer of the spinning needle was left empty, and the syringe filled with a 15wt% PVDF solution was connected to the middle layer of the spinning needle. The high-pressure airflow was connected to the outer layer of the spinning needle. The 15wt% PVDF solution was fed at a rate of 10mL / h, the high-pressure airflow pressure was 1.2bar, and spinning was carried out at room temperature. The distance between the spinneret and the winding device was approximately 30cm, and the spinning collection device rotated at 300rpm.

[0047] S3, drying fibers:

[0048] After spinning and collection, the coaxial fiber was placed in a 45°C oven for 12 h to remove the remaining solvent to obtain a PVDF fiber membrane.

[0049] The coaxial high pressure air blown spinning nanofiber membrane prepared in the above test example was subjected to DSC test and electron microscope test, and the test results are as follows: Figures 1 to 4 shown.

[0050] Depend on Figure 1 Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the PVDF-PEG800 coaxial high-pressure air-blown fiber membrane (including fiber diameter frequency analysis) show that the PVDF-PEG800 coaxial fiber membrane has a dense fiber structure, with an average fiber diameter of 1536.22nm and a coefficient of variation of 0.38. Furthermore, TEM images demonstrate that the PVDF-PEG800 coaxial high-pressure air-blown fiber membrane has an excellent coaxial structure, with an extremely high PEG content in the core layer, which lays the foundation for high enthalpy and excellent thermal management performance.

[0051] Depend on Figure 2 Data analysis shows that further analysis and calculation of the Tg results show that the mass fraction of PEG in the PVDF-PEG800 coaxial fiber membrane is 66.53%.

[0052] Depend on Figure 3 Data analysis shows that: in comparison with Example 1, there is no phase change within the test range, while the PVDF-PEG800 coaxial high-pressure air flow blown spinning fiber membrane composite material in Example 1 exhibits very excellent thermal management performance, with an enthalpy value of 43.13 J / g.

[0053] Depend on Figure 4 Data analysis indicates that the coaxial high-pressure airflow-spun nanofiber membrane exhibits excellent scalability. Depending on the application scenario, excellent thermal management performance can be achieved by replacing PEG with different molecular weights. The coaxial high-pressure airflow-spun nanofiber membranes prepared in Examples 1, 2, and 3 all exhibited high thermal conductivity values, reaching 43.13 J / g, 43.85 J / g, and 46.16 J / g, respectively.

[0054] Depend on Figure 5 Data Analysis: Compared to Comparative Example 1, the mass fraction of the polymer matrix (PVDF) in Example 1 was reduced by 66.53%, the tensile strength was reduced by 52.09%, and the elongation at break was increased by 23.46%. In other words, compared to Comparative Example 1, the high-pressure air blown spun fiber membrane of Example 1 exhibited improved mechanical properties despite a reduced polymer matrix.

[0055] In fact, the thermal management coaxial high-pressure airflow blowing spinning fiber membrane of the present invention is prepared by using PEG of different molecular weights and PVDF of specific molecular weight through a high-pressure airflow blowing spinning process with specific process parameters, which can achieve a PEG mass fraction in the composite membrane of not less than 60% and a fiber membrane enthalpy value of not less than 40 J / g.

[0056] In addition, it is worth mentioning that the inventors further explored the effects of different spinning process types and process parameters on the prepared PVDF-PEG coaxial fiber membranes, and the statistical results are shown in the following table:

[0057]

[0058] It is important to note that the above embodiments are intended only to further illustrate and describe the technical solutions of the present invention and are not intended to further limit the technical solutions of the present invention. The methods of the present invention are merely preferred implementations and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a thermal management coaxial fiber membrane, characterized in that: The steps include: preparing a PVDF solution as a shell spinning solution; Low molecular weight PEG was used as the core spinning solution; A triaxial spinning needle is used to perform high-pressure air blow spinning to form coaxial fibers; The collected coaxial fibers are dried to obtain; The molecular weight of PVDF is 450,000 to 550,000, and the low molecular weight PEG is selected from at least one of PEG400, PEG600, and PEG800. The PVDF content in the PVDF solution is 15 wt%, and the solvent is N,N-dimethylformamide. The sizes of the triaxial spinning needles are 22G, 17G, and 14G respectively. The low molecular weight PEG is connected to the inner layer of the spinning needle, the PVDF solution is connected to the middle layer of the spinning needle, and the high-pressure airflow is connected to the outer layer of the spinning needle. The high-pressure air blowing spinning process parameters are as follows: the propulsion speed of the PVDF solution is 10 mL / h, the propulsion speed of the low molecular weight PEG solution is 1.5 mL / h, the high-pressure air flow pressure is 1.2 bar, and the distance between the spinning needle and the collecting device is 30 cm.

2. The method for preparing the thermal management coaxial fiber membrane according to claim 1, characterized in that: The drying temperature is 45-60°C.

3. A thermal management coaxial fiber membrane, characterized in that: The thermal management coaxial fiber membrane comprises a low molecular weight PEG membrane core layer and a PVDF shell layer covering the low molecular weight PEG membrane core layer; The thermal management coaxial fiber membrane is prepared by the preparation method of the thermal management coaxial fiber membrane according to claim 1 or 2.

4. The thermal management coaxial fiber membrane according to claim 3, characterized in that The fiber size of the thermal management coaxial fiber membrane is 800-3800 nm.

5. Use of the thermal management coaxial fiber membrane according to any one of claims 3 to 4 in the preparation of clothing and wearable electronic devices.

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