A skin-core structure polyimide aerogel fiber and a preparation method thereof
By preparing polyimide aerogel fibers with a sponge-like pore structure, the problem of loose bonding in traditional core-sheath aerogel fibers was solved, enabling efficient and low-cost continuous production and improving the mechanical properties of the fibers.
Patent Information
- Application Number
- CN202510202703.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-24
- Publication Date
- 2026-01-02
- Estimated Expiration
- 2045-02-24
AI Technical Summary
Existing methods for preparing core-sheath structured aerogel fibers are cumbersome, costly, and the skin and core layers are not tightly bonded, resulting in poor interfacial compatibility and affecting fiber performance.
A core-skin structure polyimide aerogel fiber is used. The fiber core has a sponge-like pore structure and the skin has long strip-shaped pores. By controlling the residence time and solvent composition in the phase separation bath, a continuous core-skin structure aerogel fiber is prepared. External stress can be better transmitted to the fiber interior, avoiding stress concentration.
It enables continuous production of aerogel fibers, which have uniform pore size, low density, and high porosity, and improve the tensile properties, bending resistance, and compression resistance of the fibers.
Smart Images
Figure CN120099661B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of aerogel preparation, and a skin-core structure polyimide aerogel fiber and a preparation method thereof. BACKGROUND
[0002] Aerogel is a new type of material with high porosity, low density, large specific surface area and good thermal insulation performance. Aerogel fiber, which combines the advantages of aerogel and fiber material, is a lightweight, porous and flexible multifunctional material with wide application prospects in thermal insulation, pollution adsorption, biomedicine, energy storage and aerospace. Compared with bulk aerogel, aerogel fiber has high flexibility and can be easily integrated into various shapes and sizes of applications. However, due to its high porosity and large pore structure, aerogel fiber inevitably has low tensile strength and compression strength and is relatively soft and difficult to resist bending. Therefore, in some application scenarios, a dense skin layer is often added to the aerogel fiber.
[0003] The existing methods for preparing skin-core structure are usually coaxial spinning and coating sizing. Coaxial spinning usually uses a coaxial spinning needle to inject different spinning solutions into the skin layer and the core layer, and then coagulates them in the same coagulation bath to prepare aerogel fibers with different skin-core structures. Coating sizing is to coat other thermoplastic resins on the prepared aerogel fiber by sizing or manual coating. Since the skin layer and the core layer are two or more different materials, it is inevitable that there will be gaps caused by poor combination between the inner aerogel fiber and the outer skin layer, defects caused by poor interfacial compatibility, etc., which greatly weaken the excellent performance that the aerogel fiber should have. SUMMARY
[0004] In view of the defects of the existing aerogel fibers with skin-core structure that require coaxial spinning or coating sizing, the present application provides a skin-core structure polyimide aerogel fiber and a preparation method thereof, which overcomes the problems of traditional skin-core structure aerogel fibers, such as complicated process, discontinuity, high cost and many defects.
[0005] One of the technical solutions of the present application is to provide a skin-core structure polyimide aerogel fiber. The fiber core has a sponge pore structure, and the skin layer has a long strip-shaped pore structure. The length direction of the long strip-shaped pore structure is distributed along the circumferential direction of the fiber. The fiber diameter is 200-300 µm, and the skin layer thickness is 3 µm-12 µm.
[0006] The long strip hole structure distributed in the circumferential direction can better disperse the stress and bending moment brought by the outside of the fiber, and the continuous skin-core structure enables the external stress to be better transmitted to the inside of the fiber, avoiding stress concentration and interface effect caused by defects at the skin-core interface, and the orientation of the long strip hole structure in the circumferential direction enables the long strip hole structure to have higher compression resistance in the radial direction, so that the fiber has stronger modulus and higher compression stress.
[0007] The second technical solution of the present application provides the preparation method of the aerogel fiber, and specifically, the method comprises the following steps: 10wt%-15wt% polyimide acid solution is subjected to phase separation in a phase separation bath to form a gel fiber with a skin-core structure, and the gel fiber is dried to obtain the aerogel fiber; the phase separation bath is a mixed solution of a solvent of the polyimide acid and a non-solvent, and the mass fraction of the solvent of the polyimide acid is 40%-60%; the coagulation bath is a non-solvent of the polyimide acid; and the time of the phase separation bath is 15s-45s.
[0008] Further, the drying is freezing drying, supercritical drying, or normal temperature and pressure drying after coagulation in the coagulation bath.
[0009] Further, the solvent is one or more of DMF, DMAC, NMP, and DMSO, and the non-solvent is one or more of water, ethanol, isopropanol, methanol, diethyl ether, ethyl acetate, ethylene glycol, and glycerol.
[0010] In the phase separation bath, the solvent in the fiber diffuses from inside to outside, and the non-solvent diffuses from outside to inside. In the initial stage of phase separation, the high molecular chains on the outside first contact the non-solvent, resulting in high chain entanglement and slow and difficult movement of the high molecular chains. In a short time, the pores on the outside are more dense, and the content of the solvent on the inside is higher. The high molecular chains form a loose porous structure. With the extension of the phase separation time, the solvent on the inside diffuses outward, so that the entangled chains in the skin layer are separated and become a loose porous structure. At the same time, the skin layer of the fiber is extruded into a long strip hole structure distributed in the circumferential direction due to the formation of the internal porous structure. Therefore, by adjusting the residence time of the viscose fiber in the phase separation bath, aerogel fibers with different thicknesses of the skin layer and continuous skin-core structures can be obtained. Further, the residence time in the phase separation bath is 15s-45s.
[0011] In some embodiments of the present application, polyimide acid is used as a polymer solution to prepare a polyimide aerogel fiber. After drying, the polyimide acid aerogel fiber needs to be moved to a tube furnace for imidization at 300℃ for one hour to obtain a polyimide aerogel fiber.
[0012] The beneficial effects of the present application are that: by regulating the phase separation behavior of the fiber in the phase separation bath, the aerogel fiber with continuous skin-core structure is prepared in one step. And the prepared aerogel has uniform pore size, low density, high porosity, good tensile properties, bending properties and compression properties. BRIEF DESCRIPTION OF DRAWINGS
[0013] Figure 1 SEM image of the polyimide aerogel fiber obtained in Example 1;
[0014] Figure 2 SEM image of the polyimide aerogel fiber obtained in Example 2;
[0015] Figure 3 SEM image of the polyimide aerogel fiber obtained in Example 3;
[0016] Figure 4 Comparison chart of the skin layer thickness of the polyimide aerogel fibers obtained in Example 2, Example 1 and Example 3. DETAILED DESCRIPTION
[0017] Non-solvent induced phase separation is a common basic scientific principle in the field of high polymer film materials. Its process flow is to dissolve the polymer in the solvent to form a homogeneous solution, then slowly add a reagent (called extractant) with stronger mutual solubility with the solvent to extract the solvent, form a two-phase structure with polymer as the continuous phase and solvent as the dispersed phase, and then remove the solvent by normal pressure drying to obtain a polymer with certain pore structure. In the traditional wet spinning process, the skin and core of the fiber often show obvious structural differences, forming the structure characteristics of dense outside and loose inside. By comprehensively regulating the residence time of the gel fiber in the phase separation bath, the skin-core structure aerogel fiber with small pores outside and large pores inside can be realized.
[0018] The following examples are used to further illustrate the present application, and the purpose is to illustrate the present application, and should not be interpreted as limiting the scope of the present application. The following uses weight parts and weight percentage unless otherwise specified.
[0019] The raw materials used in the present application, such as no special instructions, are conventional commercial products; the methods used in the present application, such as no special instructions, are conventional methods in the art.
[0020] The following examples are used to further illustrate the present application, and the purpose is to illustrate the present application, and should not be interpreted as limiting the scope of the present application. The following uses weight parts and weight percentage unless otherwise specified.
[0021] It should be clear that the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.
[0022] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.
[0023] Example 1
[0024] (1) A 15wt% polyimide N,N-dimethylacetyl solution was extruded through a 25G needle and wet-spun through a phase separation bath and a coagulation bath to obtain polyimide nascent fibers. The phase separation bath consisted of N,N-dimethylacetyl solution and water in a 1:1 mass ratio, the coagulation bath was water, and the residence time of the gel fibers in the phase separation bath was 30s.
[0025] (2) Dry the polyimide nascent fiber at room temperature and normal pressure to obtain polyimide aerogel fiber.
[0026] (3) Polyimide aerogel fibers were thermally imidized to obtain polyimide aerogel. The imidization temperature was 300℃ and the imidization time was 1h. Figure 1 As shown, the fiber core has a sponge-like pore structure, and the skin has an elongated pore structure, with the length of the elongated pore structure distributed along the circumference of the fiber.
[0027] (4) The fiber diameter is 200µm, the skin thickness is 5.4µm, the tensile strength is 25.8MPa, the tensile modulus is 288MPa, the elongation at break is 27.5%, and the compressive modulus at 30% strain is 1.31MPa.
[0028] Example 2
[0029] Example 2 differs from Example 1 in that the phase separation bath consisted of an N,N-dimethylacetyl solution and water in a 6:4 mass ratio, and the residence time of the gel fibers in the phase separation bath was 45 s. The skin thickness was 3.5 µm, the tensile strength was 18.6 MPa, the tensile modulus was 255 MPa, the elongation at break was 12.5%, and the compressive modulus at 30% strain was 0.85 MPa. The obtained polyimide aerogel fibers are as follows: Figure 2 As shown.
[0030] Example 3
[0031] Example 3 differs from Example 1 in that the phase separation bath consisted of an N,N-dimethylacetyl solution and water in a mass ratio of 4:6, and the residence time of the gel fibers in the phase separation bath was 15 seconds. The resulting polyimide aerogel fibers are as follows: Figure 3The skin thickness is 12.1 pm, the tensile strength is 24.2 MPa, the tensile modulus is 352 MPa, the elongation at break is 15.5%, and the compression modulus at 30% strain is 1.74 MPa. The comparison of the skin thickness of the fibers in the three examples is shown in FIG. 4, from left to right, they are Example 2, Example 1, and Example 3. It can be seen that as the residence time of the phase separation bath is prolonged, the skin thickness of the aerogel fibers becomes thinner, and the internal structure is more uniform. Figure 4 The skin thickness is 12.1 pm, the tensile strength is 24.2 MPa, the tensile modulus is 352 MPa, the elongation at break is 15.5%, and the compression modulus at 30% strain is 1.74 MPa. The comparison of the skin thickness of the fibers in the three examples is shown in FIG. 4, from left to right, they are Example 2, Example 1, and Example 3. It can be seen that as the residence time of the phase separation bath is prolonged, the skin thickness of the aerogel fibers becomes thinner, and the internal structure is more uniform.
[0032] Example 4
[0033] The only difference from Example 1 is that a 10 wt% polyimide acid solution is used. The fiber diameter is 300 pm, and the skin thickness is 3 pm.
[0034] Comparative Example 1
[0035] The only difference from Example 1 is that the residence time of the gel fibers in the phase separation bath is 120 s. The obtained polyimide aerogel fibers have uniform pore structure and size on the outside and inside, without obvious skin-core structure, and the tensile modulus is very low, only about 200 MPa, and the compression modulus at 30% strain is only 0.62 MPa. The obtained long and small strip-shaped pores on the outside and the round and large sponge pores on the inside in the non-examples.
[0036] Comparative Example 2
[0037] (1) A 15 wt% water-soluble polyimide acid aqueous solution is directly extruded into liquid nitrogen with a 25G needle, and after quick freezing, it is moved to a freeze dryer for freeze-drying to obtain a polyimide acid aerogel fiber.
[0038] (2) The polyimide acid aerogel fiber is imidized to obtain a polyimide aerogel, the imidization temperature is 300°C, and the imidization time is 1 h. The obtained polyimide aerogel fiber has uniform pore structure and size on the outside and inside, without obvious skin-core structure.
Claims
1. A method for preparing a core-sheath polyimide aerogel fiber, characterized by, A 10wt%-15wt% polyimide acid solution is first subjected to phase separation in a phase separation bath to form a gel fiber with a skin-core structure, and after the gel fiber is shaped and dried, an aerogel fiber is obtained; the shaping and drying is first subjected to coagulation in a coagulation bath and then subjected to normal temperature and pressure drying; the phase separation bath is a mixed solution of a solvent and a non-solvent of the polyimide acid, and the mass fraction of the solvent of the polyimide acid is 40%-60%; the coagulation bath is a non-solvent of the polyimide acid; the time of the phase separation bath is 15s-45s, the solvent is DMAC, and the non-solvent is water.
2. A core-sheath polyimide aerogel fiber prepared according to the method of claim 1, wherein, The core has a sponge hole structure, and the skin layer has a long strip-shaped pore structure, and the length direction of the long strip-shaped pore structure is distributed along the circumferential direction of the fiber.
3. The fiber according to claim 2, characterized in that, The diameter of the aerogel fiber is 200-300µm, and the thickness of the skin layer is 3µm-12.1µm.