Polymer composite aerogel fiber and preparation method thereof

Abstract

The invention discloses a polymer composite aerogel fiber and a preparation method thereof. The invention provides a preparation method of a polymer composite aerogel fiber, which comprises the following steps: preparing graphene oxide and polyimide acid into a mixed solution, then carrying out mixed spinning, and carrying out auxiliary regulation and control on a phase separation process of polymer aerogel by utilizing the amphipathy and confinement effect of the graphene oxide, so as to obtain the aerogel fiber with a sponge hole structure. The aerogel fiber has a large-pore and small-pore composite structure which has an excellent effect on heat insulation and adsorption, and meanwhile, the structure also provides sufficient space, so that the polyimide composite aerogel fiber can be impregnated with phase-change materials such as paraffin and polyethylene glycol to be applied to the fields of heat management of heating devices and the like.

Description

Technical Field

[0001] The invention relates to the technical field of aerogel preparation, and in particular to a polymer composite aerogel fiber and a preparation method thereof. Background Art

[0002] Aerogel is a new type of material with high porosity, low density, large specific surface area and good thermal insulation performance, while aerogel fiber combines the advantages of aerogel and fiber materials. It is a lightweight, porous, flexible and multifunctional material with broad application prospects in thermal insulation, pollution adsorption, biomedicine, energy storage and aerospace. Compared with bulk aerogel, aerogel fiber is highly flexible and weavable, and can be more easily integrated into applications of various shapes and sizes.

[0003] In traditional processes, polymers or polymer precursors (such as polyimide, chitosan, cellulose, etc.) often experience irreversible shrinkage and densification of polymer chains due to capillary forces, phase separation stress, and strong interactions between polymer chains (such as hydrogen bonds and van der Waals forces) generated by solvent removal during phase change or high-pressure drying. For example, when hydrogels are freeze-dried, ice crystal growth squeezes the polymer network, and rapid solvent release during supercritical drying may cause pore collapse, ultimately causing macroscopic structural deformation of the aerogel, decreased porosity, a sharp decrease in specific surface area, and deterioration of mechanical properties. Summary of the invention

[0004] In view of the difficulty in preparing polymer aerogel materials in the prior art, the present invention provides a method for preparing polymer composite aerogel fibers, by preparing graphene oxide and polyimide acid into a mixed solution and then mixing and spinning them, utilizing the amphiphilicity and confinement effect of graphene oxide under specific conditions to regulate the phase separation process of the polymer aerogel in a coagulation bath, without the need for freeze drying or supercritical drying, to obtain aerogel fibers with a sponge pore structure.

[0005] One of the technical solutions of the present invention is to provide a method for preparing a polymer composite aerogel fiber, specifically, comprising: preparing a polymer and graphene oxide into a mixed solution and then extruding it, obtaining a spun fiber through a coagulation bath, drying the spun fiber and heating it in a tubular furnace at 1°C / min to 300°C for one hour to obtain a polymer composite aerogel fiber, wherein the mass ratio of the polymer to the graphene oxide is (5-25):1.

[0006] The polymer in the mixed solution is a polyimide acid solution with a concentration of 5wt% to 15wt%.

[0007] Furthermore, the concentration of graphene oxide in the mixed solution is 0.4wt%-2wt%. Graphene oxide, as a surfactant, can slow down the speed of double diffusion of polymer solution and solvent in coagulation bath. When the concentration of graphite oxide in the mixed solution accounts for 4wt% and above of the polymer. The phase separation is changed from instantaneous phase separation to delayed phase separation. The phase separation behavior of polymer solution is changed from the appearance of large finger-like pores to small sponge pores. At the same time, graphene oxide has a confinement effect as a two-dimensional macromolecule, which further hinders the movement of polymer chain segments and the double diffusion of solvent and non-solvent, which further promotes the generation of small pores. At the same time, the interface and phase separation between the graphene oxide body and the polymer also realize a multi-level composite structure of large and small pores.

[0008] Furthermore, the solvent of the polymer solution and the graphene oxide dispersion is N,N-dimethylacetamide or N,N-dimethylformamide.

[0009] Furthermore, the drying is carried out at room temperature and normal pressure.

[0010] The second technical solution of the present invention is to provide a polymer composite aerogel fiber prepared by the above method.

[0011] The polymer composite aerogel fiber prepared by the present invention has an adjustable porous structure. As the content of graphene oxide increases, the structure of the aerogel fiber gradually changes from irregular large pores to regular large finger-like pores and finally to a sponge pore structure of large and small pores.

[0012] The beneficial effects of the present invention are: (1) The graphene oxide-modified aerogel fibers prepared using polyimide acid as the polymer raw material without freeze drying or supercritical drying have good thermal conductivity and flexibility.

[0013] (2) The composite structure of large and small pores of the prepared aerogel material has excellent effects on thermal insulation and adsorption. At the same time, this structure also provides sufficient space for the polyimide composite aerogel fiber to be impregnated with phase change materials such as paraffin and polyethylene glycol for application in the fields of thermal management of heating devices.

[0014] (3) Only water is needed as the coagulation bath, and aerogel fibers with sponge pore structure can be prepared without adding a large amount of solvent to the coagulation bath, which reduces the safety hazards in the traditional process. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the SEM image of the polyimide composite aerogel fiber obtained in Example 1.

[0016] Figure 2 This is the SEM image of the polyimide composite aerogel fiber obtained in Example 2.

[0017] Figure 3 This is the SEM image of the polyimide composite aerogel fiber obtained in Comparative Example 1.

[0018] Figure 4 This is the SEM image of the polyimide composite aerogel fiber obtained in Comparative Example 3. DETAILED DESCRIPTION

[0019] The following examples are used to further illustrate the present invention, and their purpose is to illustrate the present invention and should not be construed as limiting the scope of the present invention. Unless otherwise specified, all parts by weight and weight percentages are used below.

[0020] The raw materials used in the present invention, unless otherwise specified, are conventional commercially available products; the methods used in the present invention, unless otherwise specified, are conventional methods in the art.

[0021] Sponge pore structure refers to a type of three-dimensional porous structure with uniform small pores similar to a sponge. The embodiments of the present invention are further described below with reference to a plurality of embodiments.

[0022] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0023] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0024] Example 1 (1) Using N,N-dimethylacetamide as solvent, polyimide acid and graphene oxide are prepared into a mixed solution, the mass ratio of polyimide acid to graphene oxide in the mixed solution is 25:1, and the concentration of polyimide acid is 15wt%. The polyimide acid composite primary fibers are obtained by extruding through a coagulation bath with a 23G needle, wherein the coagulation bath consists of water.

[0025] (2) The polyimide acid composite nascent fibers are dried at room temperature and normal pressure to obtain polyimide acid composite aerogel fibers.

[0026] (3) The polyimide acid composite aerogel fiber is thermally imidized to obtain the polyimide composite aerogel fiber. The imidization temperature is 300°C, the heating rate is 1°C per minute, and the imidization time is 1 hour. Figure 1As shown in the figure, there is a multi-level sponge pore structure with a composite size inside the fiber. The mechanical strength of the aerogel fiber is greater than 15Mpa, and the thermal conductivity is 0.51W / m·K. The high thermal conductivity and the composite porous structure provide sufficient impregnation space for phase change materials, which has good application prospects in the field of thermal management.

[0027] Example 2 The difference between Example 2 and Example 1 is that the ratio of polyimide acid to graphene oxide in the composition of the spinning solution is 15:1, and the concentration of graphene oxide is 0.4wt%. The thermal conductivity of the obtained aerogel fiber is 0.86 W / m·K.

[0028] Example 3 The difference between Example 3 and Example 1 is that the ratio of polyimide acid to graphene oxide in the composition of the spinning solution is 5:1 and the concentration of polyimide acid is 5wt%. The thermal conductivity of the obtained aerogel fiber is 1.34 W / m·K.

[0029] Example 4 Example 4 is different from Example 1 in that the ratio of polyimide acid to graphene oxide in the composition of the spinning solution is 5:1 and the concentration of graphene oxide is 2 wt %.

[0030] Comparative Example 1 (1) A 15 wt% polyimide acid solution, wherein the solvent is N,N-dimethylacetamide, is extruded through a coagulation bath using a 23G needle to obtain polyimide acid primary fibers, wherein the coagulation bath is water.

[0031] (2) Drying the polyimide acid fiber at room temperature and normal pressure to obtain the polyimide acid aerogel fiber.

[0032] (3) The polyimide acid composite aerogel fiber is thermally imidized to obtain the polyimide composite aerogel fiber. The imidization temperature is 300°C, the heating rate is 1°C per minute, and the imidization time is 1 hour. Figure 3 As shown. At this time, the inside of the aerogel fiber is irregular macropores. There will be uneven macropores larger than 20µm inside the fiber, which greatly weakens the mechanical properties of the aerogel, resulting in low mechanical strength (less than 5MPa), high brittleness, elongation at break less than 2%, and no flexibility.

[0033] Comparative Example 2 A 2 wt % graphene oxide dispersion, with N,N-dimethylacetamide as solvent, was extruded through a coagulation bath consisting of water using a 23G needle, but failed to coagulate.

[0034] Comparative Example 3 Comparative Example 3 is different from Example 1 in that the ratio of polyimide acid to graphene oxide in the composition of the spinning solution is 100:1. Figure 4 As shown in the figure. It can be seen from the figure that the inside of the fiber is a large and uneven macropore with many long and flat strip-shaped pores around it; it can be seen that although graphene oxide polymer composites have been prepared in the prior art, they cannot be made into aerogels, and even if aerogels are made, their structural properties are also defective. Because in the traditional freeze-drying or supercritical drying process of graphene oxide polymer composites, on the one hand, the polymer chain itself shrinks, and its stacking with the graphene sheets is destroyed, which greatly destroys the three-dimensional network of the aerogel and is easy to collapse.

[0035] Comparative Example 4 (1) A 2 wt% graphene oxide dispersion, with water as solvent, was extruded into liquid nitrogen using a 23G needle and freeze-dried to obtain graphene oxide aerogel fibers.

[0036] (2) The poly-graphene oxide aerogel fiber is thermally reduced to obtain reduced graphene oxide aerogel fiber, the thermal reduction temperature is 300°C, the heating rate is 1°C per minute, and the reduction time is 1 hour.

[0037] The obtained graphene oxide aerogel fiber has very poor strength (less than 5MPa) and is quite brittle.

[0038] The above embodiments describe in detail the structure, features and effects of the present invention. The above are only preferred embodiments of the present invention. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which do not exceed the scope covered by the specification, should be within the protection scope of the present invention.

Claims

1. A method for preparing a polymer composite aerogel fiber, characterized in that: The polymer and graphene oxide are prepared into a mixed liquid and then extruded, and the nascent fibers are obtained through a coagulation bath. The nascent fibers are dried and heated to 300° C. at 1° C. / min for one hour in a tubular furnace to obtain polymer composite aerogel fibers, wherein the mass ratio of the polymer to the graphene oxide is (5-25):

1.

2. The preparation method according to claim 1, characterized in that: The polymer in the mixed solution is a polyimide acid solution with a concentration of 5wt% to 15wt%.

3. The preparation method according to claim 1, characterized in that: The concentration of graphene oxide in the mixed solution is 0.4wt%-2wt%.

4. The preparation method according to claim 1, characterized in that: The solvent of the polymer and graphene oxide is N,N-dimethylacetamide or N,N-dimethylformamide.

5. The preparation method according to claim 1, characterized in that: The drying is carried out at room temperature and normal pressure.

6. A polymer composite aerogel fiber prepared by the preparation method according to any one of claims 1 to 5.

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