Three-dimensional porous functional composite material and preparation method thereof

Abstract

This invention discloses a three-dimensional porous functional composite material and its preparation method, comprising a functional film, a thermoplastic film, and a three-dimensional porous foam material, stacked together in a manner of functional film-thermoplastic film-three-dimensional foam-thermoplastic film-functional film. By introducing a thermoplastic film between the two-dimensional and three-dimensional interfaces, and utilizing the rapid plasticization and cooling of the thermoplastic resin during hot pressing, the two-dimensional functional film and the three-dimensional foam are connected, thereby obtaining a porous functional composite material that combines the advantages of both functional composite films and three-dimensional porous materials. For example, bonding an MXene / cellulose nanofiber composite film and a three-dimensional porous foam through the plasticization and cooling curing of the thermoplastic film yields an MXene / three-dimensional porous foam composite material, thereby improving the material's electromagnetic shielding and infrared stealth properties, and providing beneficial thermal insulation properties, thus broadening the material's application areas.

Description

Technical Field

[0001] This invention belongs to the field of functional composite materials technology, specifically relating to a porous functional composite material and its preparation method. Background Technology

[0002] With the development and progress of science and technology in human society, modern industry has increasingly higher requirements for materials. Various functional composite thin film materials with special functions (such as electrical conductivity, thermal conductivity, photothermal properties, electromagnetic shielding, and sensing) have been developed for applications in construction, environmental protection, medical, military, and machinery fields. These functional composite thin film materials have advantages such as dense structure, high content of functional fillers, and excellent mechanical properties. Taking MXene / cellulose nanofiber (CNF) composite films as an example, MXene / CNF films with high MXene content not only possess high electrical conductivity and electromagnetic shielding performance, but also exhibit infrared stealth performance due to their ultra-low infrared emissivity.

[0003] However, dense thin-film materials generally have poorer thermal insulation, sound insulation, and wave absorption capabilities compared to three-dimensional foam materials. For example, MXene / CNF films have relatively poor thermal insulation performance; however, the Stefan-Boltzmann law (…) E = εσT 4 , E Represents thermal radiation energy (W m) -2 ), ε Represents infrared emissivity, σ Represents the Stefan-Boltzmann constant. T The surface temperature (K) represents the radiant energy of a material, which is proportional to the fourth power of the surface temperature. Therefore, poor thermal insulation makes it difficult to isolate heat between the heat source and the sample surface, resulting in a higher surface temperature and thus higher radiant energy, affecting the material's infrared stealth performance. Furthermore, compared to thin-film composites, the three-dimensional porous structure of three-dimensional porous materials inevitably affects their thermal conductivity, electrical conductivity, and mechanical strength. Therefore, obtaining a material that combines the advantages of functional composite films and three-dimensional porous foams remains a challenge in engineering. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a three-dimensional porous functional composite material and its preparation method, which effectively combines the advantages of two-dimensional functional composite films and three-dimensional porous foam materials to obtain a porous functional composite material that has the advantages of both functional composite films and three-dimensional porous materials.

[0005] A three-dimensional porous functional composite material is composed of a functional film, a thermoplastic film, and a three-dimensional porous foam material, which are stacked together in the manner of functional film-thermoplastic film-three-dimensional foam-thermoplastic film-functional film.

[0006] Furthermore, in the aforementioned three-dimensional porous functional composite material, the material selected for the functional film includes, but is not limited to, one of graphene, MXene, carbon nanotubes, cellulose, and silver nanowires. The thickness of the functional film is 20-50 micrometers.

[0007] The aforementioned three-dimensional porous functional composite material further includes, but is not limited to, one of polyethylene film, polypropylene film, thermoplastic polyurethane film, polyvinyl chloride film, and polystyrene film. The thermoplastic film is generally 20–100 micrometers in size.

[0008] The aforementioned three-dimensional porous functional composite material further includes, but is not limited to, one of polyurethane foam, melamine foam, and polystyrene foam.

[0009] The preparation method of the above-mentioned three-dimensional porous functional composite material provided by the present invention includes the following steps:

[0010] (1) Select or prepare functional thin films according to the required functions;

[0011] (2) The functional film, thermoplastic film and three-dimensional porous foam material are stacked horizontally, and the stacking method is from bottom to top as follows: functional film-thermoplastic film-three-dimensional foam-thermoplastic film-functional film;

[0012] (3) The stacked materials are hot-pressed to obtain a three-dimensional porous functional composite material with a "sandwich" structure.

[0013] Due to the structural differences between two-dimensional films and three-dimensional porous foams, it is difficult to effectively bond them together using adhesives or spraying methods to obtain composite materials with good stability. This invention first prepares a functional film and a three-dimensional foam, and then introduces a thermoplastic film between the two-dimensional and three-dimensional interfaces. During hot pressing, the thermoplastic resin rapidly plasticizes and then quickly solidifies during subsequent cooling, effectively connecting the two-dimensional functional film and the three-dimensional foam, thus obtaining a sandwich-structured porous functional composite material. For the functional film, different functional materials can be selected according to different application requirements, and films with different functions can be prepared using different molding processes. The thermoplastic film is placed between the functional film and the porous foam, and undergoes plasticization and cooling curing processes to bond the two-dimensional film and the three-dimensional porous foam.

[0014] In the above method, the materials selected for the functional thin film include, but are not limited to, one or two of graphene, MXene, carbon nanotubes, cellulose, and silver nanowires; when two are selected, the uppermost and lowermost functional thin films are different.

[0015] Furthermore, the methods for preparing functional thin films include, but are not limited to, one of the following: filtration, solution casting, casting, biaxial stretching, blow molding, and spraying.

[0016] In the above method, the thermoplastic film further includes, but is not limited to, one of polyethylene film, polypropylene film, thermoplastic polyurethane film, polyvinyl chloride film, and polystyrene film.

[0017] In the above method, the three-dimensional porous foam includes, but is not limited to, one of polyurethane foam, melamine foam, and polystyrene foam. The foam thickness is 4–6 mm.

[0018] In the above method, the hot pressing temperature is 25–320 °C, the hot pressing time is 0–120 min, and the hot pressing pressure is 0–30 MPa.

[0019] In the above method, the hot pressing is further performed using a flat vulcanizing apparatus.

[0020] The present invention also provides an MXene / three-dimensional porous foam composite material, which has a "sandwich" multi-layer structure, consisting of an MXene / cellulose nanofiber composite film, a thermoplastic film, a three-dimensional porous foam, a thermoplastic film, and an MXene / cellulose nanofiber composite film from top to bottom. The MXene / cellulose nanofiber composite film and the three-dimensional porous foam are bonded together by the plasticizing and cooling curing action of the thermoplastic film.

[0021] The aforementioned MXene / three-dimensional porous foam composite material further includes, but is not limited to, one of polyurethane foam, melamine foam, polystyrene foam, etc., preferably waste polyurethane foam; the foam thickness is 4-6 mm.

[0022] The present invention also provides a method for improving the electromagnetic shielding and infrared stealth performance of MXene / CNF films, wherein MXene / CNF films, thermoplastic films and three-dimensional porous foams are stacked in the manner of MXene / cellulose nanofiber composite film-thermoplastic film-three-dimensional porous foam-thermoplastic film-MXene / cellulose nanofiber composite film and then hot-pressed.

[0023] This invention also provides the application of MXene / three-dimensional porous foam composite materials in the fields of electromagnetic shielding and infrared stealth.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention combines the advantages of two-dimensional functional composite films and three-dimensional porous foam materials to obtain a porous functional composite material that has the advantages of both functional composite films and three-dimensional porous materials.

[0026] 2. This invention significantly improves the electromagnetic shielding and infrared stealth effects of MXene by combining MXene / cellulose nanofiber composite films with three-dimensional porous foam, thus broadening the application fields of MXene / cellulose nanofiber materials. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of sample stacking during the hot pressing process in Example 3.

[0028] Figure 2 This is a SEM image of the side surface of the MXene / CNF membrane.

[0029] Figure 3 SEM image of the side of M20-W-M20 porous composite material.

[0030] Figure 4 The figure shows a comparison of the electromagnetic shielding performance of M20-W-M20 composite material and MC film with the same MXene content in the X-band.

[0031] Figure 5 The graph shows the comparison of infrared emissivity in the near-infrared region between the M20-W-M20 composite material and the MC40 film with the same MXene content.

[0032] Figure 6 The figure shows the comparison results of the thermal conductivity of M20-W-M20 composite material and MC40 film with the same MXene content to characterize the thermal insulation performance of the materials.

[0033] Figure 7 The image shows a comparison of the infrared stealth performance of M20-W-M20 composite material, MC40 film with the same MXene content, and pure WPUF foam. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] A method for preparing a sandwich-structured MXene / waste polyurethane foam composite material, specifically including:

[0037] (1) Preparation of MXene / cellulose nanofiber (CNF) composite film (functional film)

[0038] CNF suspension (2 mg / mL) and MXene suspension (Ti3C2T) x The MXene / CNF mixture (2 mg / mL) was mixed at a mass ratio of 1:4 and then stirred continuously at room temperature for 2 h to obtain a homogeneous MXene / CNF mixture. Subsequently, volumes of 5 mL, 10 mL, 20 mL, and 40 mL of the MXene / CNF mixture were filtered through a vacuum-assisted filter (40 mm diameter filter element) to obtain MXene / CNF membranes, which were labeled as MC5, MC10, MC20, and MC40, respectively, corresponding to the volumes of the MXene / CNF mixture.

[0039] MXene / CNF membrane structure characterization: The cross-sectional morphology of the prepared MXene / CNF composite membrane was characterized using scanning electron microscopy (SEM). The results are as follows: Figure 2 As shown, the MXene / CNF film exhibits a distinct layered structure with tight interlayer bonding.

[0040] (2) Stacking

[0041] The three-dimensional porous foam used was waste flexible polyurethane foam (WPUF) with a pore size of 40 PPI and a height of 5 mm. The thermoplastic film used was thermoplastic polyurethane (TPU) film with a thickness of 10 μm. Then, MXene / CNF films, TPU films, and WPUF, numbered MC5, MC10, or MC20, were used according to… Figure 1 The structure stack shown is, from bottom to top, functional film - thermoplastic polyurethane film - flexible polyurethane foam - thermoplastic polyurethane film - functional film.

[0042] (3) Hot pressing

[0043] The stacked materials were placed in a 2 mm thick square mold, covered with PET film on both sides, and two square iron plates were placed outside the PET films. The whole assembly was then placed in a flat vulcanizing apparatus and hot-pressed at 180 °C and 20 MPa for 20 min. After hot pressing, it was transferred to a flat vulcanizing apparatus at room temperature and cold-pressed at 20 MPa for 10 min to obtain a sandwich-structured porous composite material. Based on the MXene / CNF numbers used, the materials were named M5-W-M5, M10-W-M10, and M20-W-M20, respectively.

[0044] Morphological characterization of composite materials:

[0045] The cross-sectional morphology of the prepared composite material was characterized using SEM. For example... Figure 3As shown, the M20-W-M20 composite material has a dense MXene / CNF film distributed on the outside, while the internal three-dimensional porous foam does not sacrifice its three-dimensional porous structure. The intermediate thermoplastic polyurethane layer is tightly bonded to the MXene / CNF film and the three-dimensional porous foam, indicating that the molten thermoplastic polyurethane successfully combines the two-dimensional MXene / CNF film and the three-dimensional WPUF during the hot pressing process.

[0046] Electromagnetic shielding performance of composite materials:

[0047] The electromagnetic shielding performance of M20-W-M20 composite material and MC40 film with the same MXene content in the X-band was tested.

[0048] The results are as follows Figure 4 As shown, the point electromagnetic shielding performance of the M20-W-M20 composite material with a sandwich structure is significantly better than that of the MC40 film with the same MXene content, indicating that the special structure of the composite material of the present invention prolongs the propagation path of electromagnetic waves and increases the energy consumption of electromagnetic waves.

[0049] Infrared emissivity of composite materials:

[0050] The infrared emissivity in the near-infrared region of the M20-W-M20 composite material and the MC40 film with the same MXene content was tested.

[0051] The results are as follows Figure 5 As shown, after hot pressing by the method of the present invention, the low emissivity advantage of MXene can still be maintained, and the emissivity changes little.

[0052] Characterization of thermal insulation performance of composite materials:

[0053] The thermal conductivity of the M20-W-M20 composite material and the MC40 film with the same MXene content were tested to characterize the thermal insulation performance of the materials.

[0054] The results are as follows Figure 6 As shown, after hot pressing, the thermal conductivity of the M20-W-M20 composite material is much lower than that of the MC40 film with the same MXene content, indicating that the M20-W-M20 composite material with the "sandwich" structure of the present invention has superior thermal insulation performance.

[0055] Infrared stealth performance test of composite materials:

[0056] The infrared stealth performance of M20-W-M20 composite material, MC40 film with the same MXene content and pure WPUF foam was tested using an infrared thermal imager.

[0057] The results are as follows Figure 7As shown, on an 80℃ hot plate, the infrared camera detected a surface temperature of only 30.3℃ for the M20-W-M20 composite material, close to the ambient temperature, indicating superior infrared stealth performance. In contrast, the MC40 film and pure WPUF foam showed relatively higher temperatures, indicating poorer infrared stealth. The excellent infrared stealth performance of the M20-W-M20 composite material is attributed to the combination of MXene's low infrared emissivity and WPUF foam's excellent thermal insulation properties. This demonstrates that the "sandwich" structure composite material prepared in this invention combines the advantages of functional films and three-dimensional porous foam materials, significantly improving the electromagnetic shielding and infrared stealth performance of MXene.

[0058] Example 2

[0059] A method for developing a sandwich-structured graphene oxide / polyurethane foam composite material specifically includes:

[0060] (1) Preparation of graphene oxide (GO) film: Take different volumes of CNF suspension (2 mg / mL) (5 mL, 10 mL, 20 mL, 40 mL) and filter them through vacuum-assisted filtration (filter diameter is 40 mm) to obtain GO film, which is labeled as CNF suspension (2 mg / mL).

[0061] (2) Stacking: The three-dimensional porous foam is flexible polyurethane foam (PUF) with a pore size of 30 PPI and a height of 5 mm. The thermoplastic film is thermoplastic polyurethane (TPU) film with a thickness of 10 μm. Then, GO (GO5, GO10 or GO20), TPU film and PUF are stacked according to... Figure 1 The structure is stacked as shown.

[0062] (3) Hot pressing: The stacked material is placed in a 2 mm thick square mold, covered with PET film on both sides, and then two square iron plates are placed on its upper and lower surfaces. The mold is then placed in a flat vulcanizing apparatus with the temperature set to 160 ℃. It is hot-pressed at 15 MPa for 20 min. After hot pressing, it is transferred to a flat vulcanizing apparatus at room temperature and cold-pressed at 20 MPa for 10 min to obtain a sandwich-structured porous composite material. Depending on the MXene / CNF membrane used, it is named G5-P-G5, G10-P-G10, and G20-P-G20, respectively.

[0063] Example 3

[0064] A method for a sandwich-structured CNT / melamine foam composite material specifically includes:

[0065] (1) Preparation of CNT / cellulose nanofiber (CNF) film: First, 0.5 g of CNT was added to 100 mL of CNF suspension (5 mg / mL), and stirred continuously at room temperature for 0.5 h. Then, the mixture was sonicated at 300 W for 20 min using a cell disruptor to obtain a homogeneous CNT / CNF mixture. Subsequently, the GO / CNF mixture was poured into a 50 mm × 50 mm exfoliation mold and allowed to dry naturally at room temperature to obtain a GO / CNF film.

[0066] (2) Stacking: Flexible melamine foam (MF) with a pore size of 50 PPI and a height of 5 mm was selected for the three-dimensional porous foam. The thermoplastic film was thermoplastic polyvinyl chloride (PVC) film with a thickness of 10 μm. Then, the CNT / CNF film, PVC film, and MF were stacked according to... Figure 1 The structure is stacked as shown.

[0067] (3) Hot pressing: The stacked material is placed into a 2 mm thick square mold, covered with PET film on the top and bottom, and then two square iron plates are placed on the top and bottom surfaces. The mold is placed in a flat vulcanizing apparatus with the temperature set to 180 ℃. It is hot-pressed at 20 MPa for 10 min. After hot pressing, it is transferred to a flat vulcanizing apparatus at room temperature and cold-pressed at 20 MPa for 10 min to obtain a porous composite material with a sandwich structure.

Claims

1. An MXene / three-dimensional porous foam composite material, characterized in that, Its structure is a "sandwich" type multi-layer structure, from top to bottom: MXene / cellulose nanofiber composite film - thermoplastic film - three-dimensional porous foam - thermoplastic film - MXene / cellulose nanofiber composite film. The MXene / cellulose nanofiber composite film and the three-dimensional porous foam are bonded together by the plasticizing and cooling curing effect of the thermoplastic film.

2. The application of the MXene / three-dimensional porous foam composite material of claim 1 in the fields of electromagnetic shielding and infrared stealth.

3. A method for improving the infrared stealth performance of MXene / cellulose nanofiber composite films, characterized in that, The MXene / cellulose nanofiber composite film, thermoplastic film, and three-dimensional porous foam are stacked in the order of MXene / cellulose nanofiber composite film-thermoplastic film-three-dimensional porous foam-thermoplastic film-MXene / cellulose nanofiber composite film and then hot-pressed into shape.

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