Conductive composite material and preparation method thereof

Abstract

The invention belongs to the technical field of conductive composite materials, and particularly relates to a hydrophobic gel conductive composite material and a preparation method thereof. In order to solve the synergistic problem of an electronic equipment protection material in the aspects of flexibility, conductivity and environmental tolerance in an extreme temperature environment, the invention provides a hydrophobic gel conductive composite material which is prepared by the following steps: uniformly mixing butyl methacrylate, short-chain alkyl alcohol with the carbon atom number of 12-16 and a carbon nanotube to obtain a precursor mixed solution; and then adding a cross-linking agent and an initiator, and carrying out in-situ polymerization reaction. The composite material disclosed by the invention has hydrophobicity, excellent stretchability and stable conductivity, keeps structural integrity in an extreme temperature range of-40 DEG C to 120 DEG C, and realizes controllability of material performance. The method is suitable for space probe flexible circuit packaging, expandable antenna protection and other scenes, and has significant engineering application value.

Description

Technical Field

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

[0002] Traditional conductive composite materials face two major technical bottlenecks in achieving functional applications: First, in terms of material system construction, the compatibility control problem between the polymer matrix and the functional phase has not been effectively solved in existing technologies. Especially when using low-molecular-weight liquids as the dispersed phase, phase separation due to interfacial tension mismatch significantly reduces the material's mechanical integrity and environmental stability. Second, in terms of conductivity regulation, the stress transfer efficiency between conventional conductive fillers and flexible matrices is insufficient, making the conductive network prone to breakage during dynamic deformation, severely affecting its reliability as a smart sensing material. It is worth noting that although there have been attempts to construct three-dimensional networks using intrinsically conductive polymers such as polypyrrole, such as the conductive polyacetylene system developed by Japanese chemist Hideki Shirakawa et al., its difficulties in processing and molding, and poor environmental stability, severely restrict its practical application in aerospace. Furthermore, the stringent requirements of aerospace equipment for multifunctional composite materials, such as lightweight design and resistance to extreme environments (withstanding temperature changes from -40℃ to 120℃), further highlight the urgent need to develop new conductive composite materials that combine structural stability and functional durability. Summary of the Invention

[0003] To simultaneously improve the structural stability and functional durability of existing conductive composite materials, especially to overcome the instability of mechanical and electrical properties caused by fluctuations in water content in hydrogel conductive composite materials, and to address the synergistic challenges of flexibility, conductivity, and environmental tolerance in protective materials for electronic devices under extreme temperature environments, this invention provides a hydrophobic conductive composite material with a hydrogel-like structure and its preparation method. This composite material, when applied in extreme environments such as aerospace, exhibits both structural stability and functional durability.

[0004] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, the present invention provides a method for preparing a conductive composite material, comprising the following steps: mixing butyl methacrylate, short-chain alkyl alcohols with 12 to 16 carbon atoms, and carbon nanotubes to form a precursor mixture solution, then adding a crosslinking agent and an initiator to carry out an in-situ polymerization reaction.

[0005] Furthermore, the short-chain alkyl alcohol is selected from at least one of dodecanool (LA), tridecanool, tetradecanool, pentadecanool, or hexadecanool.

[0006] Furthermore, the precursor mixture is prepared above the melting temperature of the short-chain alkyl alcohol.

[0007] Furthermore, the amount of the short-chain alkyl alcohol added is 0.5% to 42.9% of the total volume fraction of the precursor mixture solution.

[0008] Furthermore, the amount of carbon nanotubes added is 0.5% to 5% of the total mass fraction of the precursor mixture solution.

[0009] Furthermore, the initiator is azobisisobutyronitrile (AIBN).

[0010] Preferably, the amount of initiator added accounts for 0.3 to 0.6% of the total mass of the precursor mixture solution.

[0011] Further, the crosslinking agent is selected from at least one of ethylene glycol dimethacrylate (EGDMA), ethylene glycol methacrylate (EGMA), diethylene glycol dimethacrylate (DEGDMA), or triethylene glycol dimethacrylate (TEGDMA).

[0012] Preferably, the amount of crosslinking agent added accounts for 0.8 to 1.5% of the total mass of the precursor mixture solution.

[0013] Furthermore, the in-situ polymerization process includes prepolymerization and polymerization.

[0014] Preferably, the prepolymerization temperature is 80–85°C.

[0015] Preferably, the prepolymerization time is 1 to 1.8 h.

[0016] Furthermore, the polymerization temperature is 58–65°C, and the polymerization time is 24–32 h.

[0017] Secondly, the present invention provides a hydrophobic gel conductive composite material obtained by the above preparation method.

[0018] Beneficial effects: (1) This invention provides a hydrophobic gel conductive composite material, which is obtained by selecting butyl methacrylate with good compatibility and short-chain alkyl alcohols with 12 to 16 carbon atoms as the polymer three-dimensional network matrix and liquid dispersion phase, respectively, and combining them with crosslinking agents and free radical initiators through in-situ polymerization to obtain a hydrogel-like structure. At the same time, one-dimensional conductive materials of carbon nanotubes are introduced to increase the conductivity of the gel material.

[0019] (2) The raw materials selected for the composite material prepared in this invention are all non-hydrophilic materials, so they exhibit hydrophobic and non-hygroscopic properties and have stable and reliable mechanical and electrical properties.

[0020] (3) Experiments have shown that above the melting point of short-chain alkyl alcohols, the interaction between short-chain alkyl alcohols and PBMA increases with increasing temperature, thereby weakening the interaction between PBMA polymers and increasing the stretchability of the gel material. At the same time, the physical binding of carbon nanotubes weakens, and they exhibit a fixed arrangement under the induction of an electric field, thus the conductivity increases exponentially. When the ambient temperature is below the freezing point of short-chain alkyl alcohols, the interaction between alkyl alcohol-PBMA and PBMA-PBMA molecules changes weakly, resulting in the composite material exhibiting rigidity. Moreover, the carbon nanotubes are subject to the dual physical binding of the polymer network and alkyl alcohol, making it difficult for them to be oriented or moved under the induction of an electric field, resulting in electrical properties that are independent of temperature. Therefore, the composite material of this invention has hydrophobicity, excellent stretchability, and stable conductivity, and maintains structural integrity in the extreme temperature range of -40℃ to 120℃, realizing the controllability of material properties.

[0021] (4) The preparation method of the hydrophobic gel conductive composite material prepared by the present invention is simple, reliable, has good hydrophobic effect and strong weather resistance. It is suitable for flexible circuit packaging of space probes, deployable antenna protection and other scenarios. It solves the problem of synergistic effect of electronic device protection materials in terms of flexibility, conductivity and environmental tolerance under extreme temperature environment and has significant engineering application value. Attached Figure Description

[0022] Figure 1 Stress-strain relationship diagrams of PBMA / LA and PBMA / LA / CNTs prepared in Example 2 and Example 3 of this invention; Figure 2 SEM images of PBMA in Comparative Example 1, PBMA / LA with LA volume content of 11.1% in Example 2, and PBMA / LA / CNTs in Example 1 of this invention; Figure 3 The graph shows the conductivity results of PBMA / LA / CNTs prepared in Example 1 of this invention at different temperatures. Figure 4 The electrical signal response diagram of PBMA / LA / CNTs prepared in Example 1 of the present invention under periodic stretching-retraction in a vacuum environment; Figure 5 The graph shows the conductivity stability test results of PBMA / LA / CNTs prepared in Example 1 of the present invention under different environments; Figure 6 The graph shows the conductivity results of PBMA / TD / CNTs prepared in Example 4 of this invention at different temperatures. Detailed Implementation

[0023] To make the technical problems, solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with the embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as understood by one of ordinary skill in the art.

[0024] In one embodiment of the present invention, a method for preparing a conductive composite material is provided, comprising the following steps: mixing butyl methacrylate, short-chain alkyl alcohols with 12 to 16 carbon atoms, and carbon nanotubes to form a precursor mixture solution, then adding a crosslinking agent and an initiator to carry out an in-situ polymerization reaction.

[0025] In this invention, butyl methacrylate is used as the polymer three-dimensional network matrix, and short-chain alkyl alcohols with 12-16 carbon atoms are used as the liquid dispersion phase. An in-situ polymerization reaction is carried out under the action of a crosslinking agent and an initiator to obtain a hydrogel-like composite material. Simultaneously, carbon nanotubes with excellent conductivity and easy dispersion are used to increase the conductivity of the gel material.

[0026] In this invention, a polymer oleogel is designed by mimicking the physical structure of a hydrogel. Polybutyl methacrylate (PBMA) forms the polymer network, and short-chain alkyl alcohols with 12-16 carbon atoms act like water in a hydrogel, aiming to break the entanglement between PBMA molecules through interactions with the PBMA side chains. Without the interaction between PBMA and the short-chain alkyl alcohols, PBMA would simply be a tough polymer, not a gel.

[0027] In this invention, the main purpose of introducing short-chain alkyl alcohols with 12 to 16 carbon atoms is not to increase hydrophobicity, but to introduce a liquid phase into the polymer gel. However, since the reagents selected for the composite material are all hydrophobic materials, the hydrophobic and non-hygroscopic properties of the finished product are guaranteed, thereby providing stable and reliable mechanical and electrical properties.

[0028] In this invention, the purpose of adding carbon nanotubes is to act as a conductive material, not to modify short-chain alkyl alcohols.

[0029] In some specific embodiments of the present invention, the short-chain alkyl alcohol is selected from at least one of dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, or hexadecyl alcohol. The purpose is that if the number of carbon atoms is too low, the alkyl alcohol will dissociate from the polybutyl methacrylate (PBMA) three-dimensional network; while if the number of carbon atoms is too high, the melting point of the alkyl alcohol will also increase, causing the prepared composite material to be a rigid material within its melting point and lose its hydrogel-like properties.

[0030] In some specific embodiments of the present invention, the precursor mixture solution is prepared above the melting temperature of the short-chain alkyl alcohol to ensure that the raw materials are thoroughly and uniformly mixed.

[0031] In some specific embodiments of the present invention, the amount of the short-chain alkyl alcohol added is 0.5 to 42.9% of the total volume fraction of the precursor mixture solution.

[0032] In some specific embodiments of the present invention, the amount of carbon nanotubes added is 0.5-5% by mass fraction of the entire precursor mixture solution.

[0033] In some specific embodiments of the present invention, the initiator is azobisisobutyronitrile (AIBN). The selection of the initiator is determined based on the properties of the raw materials. Since the reagents selected for the composite material are all hydrophobic materials, and in order to ensure the hydrophobicity of the finished product, AIBN, a commonly used initiator suitable for hydrophobic systems, is selected.

[0034] In some preferred embodiments of the present invention, the amount of initiator added accounts for 0.3 to 0.6% of the total mass of the precursor mixture solution.

[0035] In some specific embodiments of the present invention, the crosslinking agent is selected from at least one of ethylene glycol dimethacrylate (EGDMA), ethylene glycol methacrylate (EGMA), diethylene glycol dimethacrylate (DEGDMA), and triethylene glycol dimethacrylate (TEGDMA).

[0036] In some preferred embodiments of the present invention, the amount of crosslinking agent added accounts for 0.8 to 1.5% of the total mass of the precursor mixture solution.

[0037] In some specific embodiments of the present invention, the in-situ polymerization process includes prepolymerization and polymerization. Prepolymerization is to melt-disperse butyl methacrylate, short-chain alkyl alcohols with 12 to 16 carbon atoms, and carbon nanotubes.

[0038] In some preferred embodiments of the present invention, the prepolymerization temperature is 80–85°C.

[0039] In some preferred embodiments of the present invention, the prepolymerization time is 1 to 1.8 h.

[0040] In some specific embodiments of the present invention, the polymerization temperature is 58–65°C, and the polymerization time is 24–32 h.

[0041] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0042] Example 1: Preparation of hydrophobic gel conductive composite material (PBMA / LA / CNTs) (1) Preparation of precursor solution: Weigh 8 mL of butyl methacrylate (about 7.16 g), 1 mL of dodecyl alcohol LA (about 0.83 g), and 0.4 g of carbon nanotubes (CNTs), respectively, and stir evenly in a water bath at 27°C to obtain precursor mixture; (2) Then, 0.04 g of chain initiator AIBN and 0.08 mL of crosslinking agent EGDMA (about 0.084 g) were added to the mixture, and prepolymerization was carried out at a temperature of 85°C for 1.5 h. The prepolymer was obtained after prepolymerization. (3) The prepolymer is transferred to a constant temperature chamber for thermally induced polymerization. The polymerization temperature is 60℃ and the polymerization time is 24h to obtain the composite material PBMA / LA / CNTs. According to the calculation, the CNTs content in the composite material accounts for 4.8% of the mass percentage of the precursor mixture and the LA content accounts for 11.1% of the volume percentage of the precursor mixture.

[0043] Example 2: Preparation of composite materials (PBMA / LA) with different LA contents The amount of LA added in step (1) of Example 1 was adjusted, and no CNTs were incorporated, to investigate the optimal amount of LA incorporation. The volume concentrations of LA in the precursor mixture were 0%, 5.9%, 11.1%, 15.7%, 20%, and 42.9%, respectively. The composite material was named PBMA / LA.

[0044] Example 3: Preparation of composite materials (PBMA / LA / CNTs) with different CNT contents Adjust the amount of CNTs added in step (1) of Example 1 to obtain composite materials PBMA / LA / CNTs with CNTs accounting for 0%, 1.2%, 2.4%, 3.6%, 4.2% and 4.8% of the precursor mixture mass, respectively.

[0045] Comparative Example 1: Preparation of pure PBMA polymer The difference between Comparative Example 1 and Example 1 is that the precursor solution does not contain dodecyl alcohol (LA) and carbon nanotubes (CNTs), while the other steps and components are completely identical, resulting in a pure PBMA polymer material.

[0046] The composite materials prepared in the above experiments were characterized and tested: (1) Tensile properties were tested on PBMA, PBMA / LA, and PBMA / LA / CNTs samples. The results are as follows: Figure 1As shown, with the increase of dodecanoic acid (LA) content, the tensile stress of the PBMA polymer decreases, while the corresponding strain first increases and then decreases. This is very similar to the properties of conventional hydrogels, proving that PBMA / LA has a hydrogel-like structure. With the increase of carbon nanotube (CNT) content, both the tensile stress and strain of the PBMA / LA / CNTs sample continuously decrease, which is because the conductive additive reduces the material's integrity.

[0047] (2) Field emission scanning electron microscopy (FE-SEM) was performed on PBMA / LA samples with a volume content of 11.1% and PBMA / LA / CNTs samples from Example 1. Figure 2 As shown, the addition of LA transforms pure PBMA from a dense and smooth morphology to a rough and porous one. Carbon nanotubes are uniformly distributed within the polymer material.

[0048] (3) The electrical properties of the PBMA / LA / CNTs samples prepared in Example 1 were tested. For example... Figure 3 As shown, when the ambient temperature is below the freezing point of LA (24-26 °C), the conductivity of the composite gel is independent of the ambient temperature; when the ambient temperature is above the melting point of LA, its conductivity increases significantly with increasing temperature.

[0049] (4) The electrical signal response of the PBMA / LA / CNTs sample prepared in Example 1 under cyclic stretching-retraction was tested in a vacuum environment. For example... Figure 4 As shown, the electrical signal exhibits periodic changes with the reciprocating motion of the composite gel, indicating the stability of its electrical properties under vacuum. This demonstrates that the designed material can indeed be applied in the space environment.

[0050] (5) Weather resistance tests were performed on the PBMA / LA / CNTs samples prepared in Example 1. For example... Figure 5 As shown, the electrical properties exhibit high stability whether immersed in water or in a vacuum environment.

[0051] Example 4: Study on the effect of different short-chain alkyl alcohols on the electrical properties of gel complexes Unlike Example 1, dodecanoic acid was replaced with tetradecanoic acid (TD), the precursor solution was prepared at 48°C, and all other conditions remained the same, resulting in the composite material PBMA / TD / CNTs. Electrical performance testing of this sample revealed that the electrical properties remained almost unchanged below 45°C. Above a critical temperature, conductivity increased sharply with increasing ambient temperature. This pattern is almost identical to that of the dodecanoic acid-containing composite material PBMA / LA / CNTs, except that the critical temperature increased from 24°C to 45°C. Figure 6 ).

[0052] In summary, this invention has prepared a series of hydrophobic gel-conductive composite materials using a simple in-situ polymerization technique. These composite materials possess a hydrogel-like microstructure, thus exhibiting good stretchability. When the ambient temperature is below the freezing point of the short-chain alkyl alcohol, the composite material behaves as a rigid material, and its conductivity is temperature-independent. When the ambient temperature is above the melting temperature of the short-chain alkyl alcohol, the composite material transforms into a hyperelastic material, and its conductivity becomes closely related to temperature. More importantly, the composite material no longer contains volatile water, and its mechanical and electrical properties are stable. This characteristic makes the composite material suitable for use in vacuum environments.

Claims

1. A method for preparing a conductive composite material, characterized in that, Includes the following steps: A precursor mixture is prepared by mixing butyl methacrylate, short-chain alkyl alcohols with 12 to 16 carbon atoms, and carbon nanotubes. Then, a crosslinking agent and an initiator are added to carry out an in-situ polymerization reaction.

2. The method for preparing the conductive composite material according to claim 1, characterized in that: The short-chain alkyl alcohol is selected from at least one of dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, or hexadecyl alcohol.

3. The method for preparing the conductive composite material according to claim 2, characterized in that: The amount of the short-chain alkyl alcohol added is 0.5% to 42.9% of the total volume fraction of the precursor mixture solution.

4. The method for preparing the conductive composite material according to claim 1 or 3, characterized in that: The amount of carbon nanotubes added is 0.5% to 5% of the total mass fraction of the precursor mixture solution.

5. The method for preparing the conductive composite material according to claim 4, characterized in that: The initiator is azobisisobutyronitrile; the amount of initiator added accounts for 0.3 to 0.6% of the total mass of the precursor mixture solution.

6. The method for preparing the conductive composite material according to claim 4, characterized in that: The crosslinking agent is selected from at least one of ethylene glycol dimethacrylate, ethylene glycol methacrylate, diethylene glycol dimethacrylate, or triethylene glycol dimethacrylate; the amount of crosslinking agent added is 0.8 to 1.5% of the total mass of the precursor mixture solution.

7. The method for preparing the conductive composite material according to claim 1, characterized in that: The in-situ polymerization process includes prepolymerization and polymerization.

8. The method for preparing the conductive composite material according to claim 7, characterized in that: The prepolymerization temperature is 80–85℃, and the prepolymerization time is 1–1.8 h.

9. The method for preparing the conductive composite material according to claim 7, characterized in that: The polymerization temperature is 58–65℃, and the polymerization time is 24–32 h.

10. The hydrophobic gel conductive composite material obtained by the preparation method according to any one of claims 1 to 9.

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