Polymer composite aerogel fibers and methods of making the same

Abstract

The application discloses a polymer composite aerogel fiber and a preparation method thereof. The application provides a preparation method of the polymer composite aerogel fiber, wherein graphene oxide and polyimide acid are prepared into a mixed solution, and then mixed spinning is carried out, the amphiphilic property and the limited action of the graphene oxide are used to assist in regulating the phase separation process of the polymer aerogel, and the aerogel fiber with a sponge hole structure is obtained. The aerogel fiber has a composite structure of large and small holes, and has excellent effects on heat insulation and adsorption; meanwhile, the structure provides sufficient space, so that the polyimide composite aerogel fiber can be impregnated with phase change materials such as paraffin and polyethylene glycol, and applied to the field of heat management of heating devices.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aerogel preparation, and particularly relates to a polymer composite 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, and has broad application prospects in thermal insulation, pollution adsorption, biological medicine, energy storage and aerospace fields. Compared with bulk aerogel, aerogel fiber has high flexibility and can be easily integrated into various shapes and sizes of applications.

[0003] In the traditional process, the capillary force generated by solvent removal, phase separation stress and strong interaction between polymer chains (such as hydrogen bond and van der Waals force) during phase change or high pressure drying of polymer or high molecular precursor (such as polyimide, chitosan and cellulose) often lead to irreversible shrinkage and densification of polymer chains. For example, during freeze drying of hydrogel, ice crystal growth will squeeze the polymer network, and rapid solvent removal in supercritical drying may cause pore collapse, resulting in deformation of the macrostructure of aerogel, reduction of porosity, sharp reduction of specific surface area and deterioration of mechanical properties. SUMMARY

[0004] In view of the problem that high molecular aerogel material is difficult to prepare in the prior art, the present application provides a preparation method of polymer composite aerogel fiber. By preparing a mixed solution of graphene oxide and polyimide acid and then spinning, the amphiphilic property and confinement effect of graphene oxide are utilized to regulate the phase separation process of high molecular aerogel in the coagulation bath under specific conditions, without freeze drying or supercritical drying, so that aerogel fiber with sponge pore structure is obtained.

[0005] One of the technical solutions of the present application is to provide a preparation method of polymer composite aerogel fiber, specifically comprising: extruding a mixed solution of polymer and graphene oxide, obtaining primary fibers through a coagulation bath, drying the primary fibers, heating in a tube furnace at 1℃ / min to 300℃ for one hour to obtain polymer composite aerogel fiber, and the mass ratio of the polymer to graphene oxide is (5-25):1.

[0006] The polymer in the mixed solution is a 5wt%-15wt% polyimide acid solution.

[0007] Further, the concentration of graphene oxide in the mixed solution is 0.4wt%-2wt%. Graphene oxide as a kind of surfactant can delay the speed of double diffusion of polymer solution and solvent in the coagulation bath. When the concentration of graphene oxide in the mixed solution is 4wt% or more of the polymer, the phase separation is changed from instantaneous phase separation to delayed phase separation. The behavior of the polymer solution phase separation is changed from the appearance of large finger-shaped holes to small sponge holes. At the same time, graphene oxide as a two-dimensional macromolecule has a confinement effect, 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 holes, and the interface between the bulk of graphene oxide and the polymer also realizes the multi-level composite structure of large and small holes.

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

[0009] Further, the drying is at room temperature and normal pressure.

[0010] The second technical solution of the present application provides a polymer composite aerogel fiber prepared by the above method.

[0011] The polymer composite aerogel fiber prepared by the present application has a controllable porous structure. With the increase of the content of graphene oxide, the structure of the aerogel fiber gradually changes from irregular large holes to regular large finger-shaped holes, and finally to a sponge hole structure with large and small holes.

[0012] The present application has the following beneficial effects:

[0013] (1) Using polyimide acid as a polymer raw material, the graphene oxide modified aerogel fiber prepared without freeze-drying or supercritical drying has good thermal conductivity and flexibility.

[0014] (2) The large and small hole composite structure of the prepared aerogel material has excellent effects on heat insulation and adsorption, and 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, and applied in the field of heat management of heating devices.

[0015] (3) Only water is needed as a coagulation bath, and a sponge hole structure aerogel fiber can be prepared without adding a large amount of solvent in the coagulation bath, which reduces the safety hazards in the traditional process. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 SEM image of the polyimide composite aerogel fiber obtained in Example 1.

[0017] Figure 2SEM image of the polyimide composite aerogel fiber obtained in Example 2.

[0018] Figure 3 SEM image of the polyimide composite aerogel fiber obtained in Comparative Example 1.

[0019] Figure 4 SEM image of the polyimide composite aerogel fiber obtained in Comparative Example 3. DETAILED DESCRIPTION

[0020] The following examples are given to further illustrate the application and are not intended to limit the scope of the application. Unless otherwise indicated, parts and percentages are by weight.

[0021] The raw materials used in the present application are all conventional commercially available products unless otherwise specified; the methods used in the present application are all conventional methods in the art unless otherwise specified.

[0022] Sponge pore structure refers to a kind of three-dimensional porous structure with uniform small pores similar to sponge

[0023] The following examples are given to further illustrate the application and are not intended to limit the scope of the application. Unless otherwise indicated, parts and percentages are by weight.

[0024] It should be understood that the described embodiments are only some 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 of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0025] The terms used in the embodiments of the present application are only for the purpose of describing the 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 the plural forms, unless the context clearly indicates otherwise.

[0026] Example 1

[0027] (1) N,N-dimethylacetamide was used as a solvent to prepare a mixed solution of polyimide acid and graphene oxide, the mass ratio of polyimide acid to graphene oxide in the mixed solution was 25:1, and the concentration of polyimide acid was 15wt%, a 23G needle was used to extrude a polyimide acid composite nascent fiber through a coagulation bath, wherein the composition of the coagulation bath was water.

[0028] (2) The polyimide acid composite nascent fiber was dried at room temperature and normal pressure to obtain a polyimide acid composite aerogel fiber.

[0029] (3) Polyimide composite aerogel fibers were thermally imidized to obtain polyimide composite aerogel fibers. The imidization temperature was 300℃, the heating rate was 1℃ per minute, and the imidization time was 1 hour. Figure 1 As shown, the fibers possess a multi-level sponge-like pore structure with varying sizes. The aerogel fibers have a mechanical strength greater than 15 MPa and a thermal conductivity of 0.51 W / m·K. The high thermal conductivity and multi-level porous structure provide sufficient impregnation space for the phase change material, making it a promising candidate for applications in thermal management.

[0030] Example 2

[0031] Example 2 differs from Example 1 in that the ratio of polyimide acid to graphene oxide in the spinning solution is 15:1, and the concentration of graphene oxide is 0.4 wt%. The resulting aerogel fiber has a thermal conductivity of 0.86 W / m·K.

[0032] Example 3

[0033] Example 3 differs from Example 1 in that the ratio of polyimide acid to graphene oxide in the spinning solution is 5:1 and the concentration of polyimide acid is 5 wt%. The resulting aerogel fiber has a thermal conductivity of 1.34 W / m·K.

[0034] Example 4

[0035] Example 4 differs from Example 1 in that the ratio of polyimide acid to graphene oxide in the spinning solution is 5:1 and the concentration of graphene oxide is 2wt%.

[0036] Comparative Example 1

[0037] (1) A 15wt% polyimide solution, with N,N-dimethylacetamide as the solvent, is extruded through a coagulation bath using a 23G needle to obtain nascent polyimide fibers. The coagulation bath is water.

[0038] (2) The polyimide fiber was dried at room temperature and normal pressure to obtain polyimide aerogel fiber.

[0039] (3) Polyimide composite aerogel fibers were thermally imidized to obtain polyimide composite aerogel fibers. The imidization temperature was 300℃, the heating rate was 1℃ per minute, and the imidization time was 1 hour. Figure 3 As shown, the interior of the aerogel fiber at this point consists of irregular large pores. The presence of unevenly distributed large pores larger than 20µm within the fiber significantly weakens the mechanical properties of the aerogel, resulting in low mechanical strength (less than 5MPa), high brittleness, elongation at break of less than 2%, and a lack of flexibility.

[0040] Comparative Example 2

[0041] The 2wt% graphene oxide dispersion solution with solvent of N,N-dimethylacetamide was extruded through a coagulation bath with component of water by a 23G needle, and could not be coagulated.

[0042] Comparative Example 3

[0043] 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. As shown in the figure, the fiber has large and uneven macropores in the interior, and there are many oblong strip-shaped pores around. It can be seen that although the graphene oxide polymer composite has been prepared in the prior art, it cannot be made into aerogel, and even if it is made into aerogel, its structural performance has defects. Because in the traditional freeze-drying or supercritical drying process of graphene oxide polymer composite, on the one hand, the polymer chain itself shrinks, and its stacking with graphene sheets is destroyed, which greatly destroys the three-dimensional network of aerogel and easily collapses. Figure 4

[0044] Comparative Example 4

[0045] (1) The 2wt% graphene oxide dispersion solution with solvent of water was extruded into liquid nitrogen by a 23G needle and freeze-dried to obtain graphene oxide aerogel fibers.

[0046] (2) The polyox graphene aerogel fibers were heat-reduced to obtain reduced graphene oxide aerogel fibers, the heat-reduction temperature was 300℃, the heating rate was 1℃ per minute, and the reduction time was 1 hour.

[0047] The obtained graphene oxide aerogel fibers have very poor strength (less than 5MPa) and large brittleness.

[0048] The above examples illustrate the structure, features and effects of the present application. The above description is only the preferred embodiment of the present application. Any changes made in accordance with the concept of the present application, or modifications of equivalent changes, shall be within the scope of the present application.​

Claims

1. A method for preparing polymer composite aerogel fibers, characterized in that, The polymer and graphene oxide were mixed and extruded, and the resulting nascent fibers were obtained through a coagulation bath. After drying, the nascent fibers were heated in a tube furnace at a rate of 1°C / min to 300°C for one hour to obtain polymer composite aerogel fibers. The mass ratio of the polymer to graphene oxide was (5-25):

1. The polymer in the mixture was a 5wt%~15wt% polyimide solution. The concentration of graphene oxide in the mixture was 0.4wt%-2wt%. The solvent for the polymer and graphene oxide was N,N-dimethylacetamide or N,N-dimethylformamide. The drying was carried out at room temperature and atmospheric pressure.

2. A polymer composite aerogel fiber prepared by the preparation method as described in claim 1.

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