Self-repairing lightweight high-strength composite material and preparation method thereof

Abstract

The present application relates to the technical field of composite material preparation, in particular to a self-repairing light high-strength composite material and a preparation method thereof. The preparation method comprises the following steps: dissolving polyvinyl alcohol and boric acid in water, adding prepared hydroxyapatite nanowires to obtain a suspension, freezing the suspension into a solid, drying to obtain a white block, and then hot compressing the white block to obtain the self-repairing light high-strength composite material. The raw materials in the preparation method are simple and easy to obtain, green and environmentally friendly, and the process is simple. The self-repairing light high-strength composite material prepared by the method has high modulus, high strength and excellent self-healing ability.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology, specifically to a self-healing lightweight high-strength composite material and its preparation method. Background Technology

[0002] The development of the economy and society requires the support of a large amount of materials, especially lightweight, high-strength materials, which have broad application prospects in various fields. However, during repeated use and processing, materials may fail due to fracture, wear, and distortion, resulting in significant waste and serious economic losses, which is inconsistent with the requirements of the national sustainable development strategy and circular economy. Therefore, how to improve the utilization rate and extend the service life of materials while ensuring their high mechanical properties is a key focus in the field of materials research.

[0003] Self-healing materials based on dynamic covalent bonds can self-repair after performance loss by applying external stimuli, thus extending the material's service life and bringing its performance back to usable standards.

[0004] However, current research on self-healing materials primarily focuses on soft materials such as hydrogels, elastomers, and electrolytes. While soft material systems exhibit high molecular mobility and readily exhibit self-healing behavior, their modulus and strength fall far short of the requirements for structural and engineering materials. Simply incorporating inorganic fillers into soft material systems lacks an ordered microstructure, making it difficult to significantly improve the material's mechanical properties. Furthermore, inorganic fillers can inhibit molecular movement, hindering the development of ideal self-healing behavior. Therefore, obtaining high-modulus, high-strength structural materials while ensuring minimal impact on their self-healing performance has become a pressing issue for leading researchers in this field.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a self-healing lightweight high-strength composite material and its preparation method, aiming to solve the problem of how to enable high-modulus and high-strength structural materials to simultaneously possess excellent self-healing properties.

[0007] Specifically, the technical solution of the present invention is as follows:

[0008] This invention provides a method for preparing a self-healing, lightweight, high-strength composite material, comprising the following steps:

[0009] Preparation of hydroxyapatite nanowires;

[0010] Polyvinyl alcohol and boric acid were dissolved in water, and the hydroxyapatite nanowires were added to obtain a suspension.

[0011] The suspension was frozen into a solid and dried to obtain a white block material.

[0012] The white block material is thermally compressed to obtain the self-healing lightweight high-strength composite material.

[0013] Optionally, the step of preparing hydroxyapatite nanowires includes:

[0014] Calcium chloride solution and sodium hydroxide solution were added to a mixed solution of methanol, water and oleic acid to obtain calcium oleate precursor;

[0015] A sodium dihydrogen phosphate dihydrate solution was added to the calcium oleate precursor, and the mixture was heated to react. After centrifugation and washing, the hydroxyapatite nanowires were obtained.

[0016] Optionally, the temperature of the water is 80–90°C.

[0017] Optionally, the mass ratio of polyvinyl alcohol to water is 1:5.

[0018] Optionally, the mass ratio of boric acid to polyvinyl alcohol is 1:20 to 1:5.

[0019] Optionally, the mass ratio of the hydroxyapatite nanowires to the polyvinyl alcohol is 1:15 to 1:5.

[0020] Optionally, the freezing is performed using a device with bidirectional freezing technology.

[0021] Optionally, the drying is low-temperature vacuum drying, and the drying time is 48-96 hours.

[0022] Optionally, the conditions for the hot compression are: temperature of 80–100°C, pressure of 20–40 MPa, and time of 3–5 h.

[0023] The present invention further provides a self-healing lightweight high-strength composite material prepared by the preparation method of the aforementioned self-healing lightweight high-strength composite material.

[0024] The present invention has the following beneficial effects:

[0025] The self-healing lightweight high-strength composite material preparation method provided by this invention uses readily available and environmentally friendly raw materials, and the process is simple. In the self-healing lightweight high-strength composite material, one-dimensional hydroxyapatite nanowires are the reinforcing phase, polyvinyl alcohol is the toughening phase, and the borate ester bond formed between polyvinyl alcohol and boric acid serves as a dynamic covalent bond, enabling the composite material to simultaneously possess high mechanical properties (maximum flexural modulus > 4 GPa, maximum strength > 150 MPa) and excellent self-healing ability (> 85%), solving the problem that high-modulus and high-strength structural materials cannot simultaneously possess high self-healing performance. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of the hydroxyapatite nanowires prepared in the embodiments of the present invention, with a scale bar of 10 μm;

[0027] Figure 2 This is a scanning electron microscope image of the white block material obtained after freeze-drying in Example 1 of the present invention. The scale bar is 100 μm.

[0028] Figure 3 The mechanical properties of the self-healing lightweight high-strength composite materials prepared in Examples 1-3 of this invention are shown in the figure.

[0029] Figure 4 This is an optical image of the fracture-repair process of the self-healing lightweight high-strength composite material prepared in Example 1 of the present invention. Detailed Implementation

[0030] This invention provides a self-healing lightweight high-strength composite material and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of protection of the invention.

[0031] This invention provides a method for preparing a self-healing, lightweight, high-strength composite material, comprising the following steps:

[0032] Preparation of hydroxyapatite nanowires;

[0033] Polyvinyl alcohol and boric acid were dissolved in water, and the hydroxyapatite nanowires were added to obtain a suspension.

[0034] The suspension was frozen into a solid and dried to obtain a white block material.

[0035] The white block material is thermally compressed to obtain the self-healing lightweight high-strength composite material.

[0036] The step of preparing hydroxyapatite nanowires includes:

[0037] Calcium chloride solution and sodium hydroxide solution were added to a mixed solution of methanol, water and oleic acid to obtain calcium oleate precursor;

[0038] A sodium dihydrogen phosphate dihydrate solution was added to the calcium oleate precursor, and the mixture was heated to react. After centrifugation and washing, the hydroxyapatite nanowires were obtained.

[0039] In a specific embodiment, polyvinyl alcohol and boric acid are dissolved in water to obtain a clear solution. Boric acid can form a self-healing structure with dynamic borate ester bonds between itself and polyvinyl alcohol. Subsequently, hydroxyapatite nanowires are added to the clear organic solution to form a uniformly dispersed white suspension. The white suspension is bidirectionally frozen using a mold to obtain a white block material with a long-range ordered layered structure. The block material is then hot-pressed in a hot press. Through the combination of bidirectional freezing and hot pressing, a self-healing, lightweight, and high-strength composite material is finally obtained.

[0040] In some embodiments, the temperature of the water is 80–90°C.

[0041] In some embodiments, the mass ratio of polyvinyl alcohol to water is 1:5.

[0042] In some embodiments, the mass ratio of boric acid to polyvinyl alcohol is 1:20 to 1:5. Polyvinyl alcohol is the organic phase, and boric acid is added as a crosslinking agent to obtain a self-healing material containing borate ester bonds, eliminating the need for the complex synthesis of other polymeric self-healing materials.

[0043] In some embodiments, the mass ratio of the hydroxyapatite nanowires to the polyvinyl alcohol is 1:15 to 1:5. One-dimensional hydroxyapatite nanowires serve as the reinforcing phase, polyvinyl alcohol as the toughening phase, and the borate ester bond formed between polyvinyl alcohol and boric acid acts as a dynamic covalent bond, enabling the composite material to simultaneously exhibit excellent mechanical properties and good self-healing ability.

[0044] In some embodiments, the freezing process employs a device using bidirectional freezing technology. The device includes a polytetrafluoroethylene mold, a polydimethylsiloxane wedge-shaped block, and a copper pillar. Through bidirectional freezing technology, hydroxyapatite nanowires, polyvinyl alcohol, and boric acid are controllably assembled to obtain a composite material with a long-range ordered layered structure.

[0045] In some embodiments, the drying is low-temperature vacuum drying, and the drying time is 48-96 hours.

[0046] In some embodiments, the conditions for hot compression are: temperature 80–100°C, pressure 20–40 MPa, and time 3–5 hours. Through hot compression, the composite material is further densified.

[0047] In this embodiment of the invention, a self-healing lightweight high-strength composite material is prepared by the method described above. This self-healing lightweight high-strength composite material possesses both excellent mechanical properties and self-healing ability, with a modulus of 4 GPa, a strength of 150 MPa, and can be used as an engineering plastic, exhibiting a self-healing efficiency of 88%.

[0048] The present invention will be further described below with reference to specific embodiments.

[0049] Example 1

[0050] Under magnetic stirring at 500 rpm, calcium chloride solution (1.1 g calcium chloride dissolved in 50 mL deionized water) and sodium hydroxide solution (3.5 g sodium hydroxide dissolved in 50 mL deionized water) were added dropwise to a well-mixed solution of 20 mL methanol, 45 mL deionized water, and 35 mL oleic acid. Each mixture was stirred for 30 min to obtain the calcium oleate precursor. While stirring, sodium dihydrogen phosphate dihydrate solution (1.45 g sodium dihydrogen phosphate dihydrate added to 50 mL deionized water) was added to the above solution, and stirring was continued for 30 min. The resulting solution was transferred to a 500 mL stainless steel reactor lined with polytetrafluoroethylene and placed in an oven at 180 °C for 24 h. After natural cooling, the centrifuge was adjusted to 6000 rpm for 5 min, and the sample was washed three times with water and ethanol respectively. Finally, the product was dispersed in ethanol.

[0051] Dissolve 8g of polyvinyl alcohol in 40g of water at 90℃, stirring slowly until the polyvinyl alcohol is completely dissolved, resulting in a colorless and transparent solution. Add 0.54g of boric acid and stir slowly until completely dissolved, forming another colorless and transparent solution. Next, add 0.8g of hydroxyapatite nanowires and stir at room temperature until a uniformly dispersed white suspension is obtained. Freeze the white suspension to a solid state using a two-dimensional cryogenic technique, and then vacuum dry it at low temperature for 48 hours to obtain a white block material with a long-range ordered layered structure. Hot-compress the white block material in a hot press at 80℃ and 30MPa for 3 hours to obtain a self-healing, lightweight, and high-strength composite material.

[0052] Example 2

[0053] The only difference between the preparation method of this embodiment and that of Example 1 is the addition of 1.6g of hydroxyapatite nanowires.

[0054] Example 3

[0055] The only difference between the preparation method of this embodiment and that of Example 1 is the addition of 0.54g of hydroxyapatite nanowires.

[0056] Structural and morphological characterization

[0057] like Figure 1 As shown in the scanning electron microscope images, the hydroxyapatite nanowires synthesized in the examples have a length of over 100 μm and a diameter of 30-70 nm. Figure 2 The image shown is a scanning electron microscope image of the white block material obtained after freeze-drying in Example 1, which shows that it has a long-range ordered layered structure.

[0058] like Figure 3 As shown, the mechanical properties of the self-healing lightweight high-strength composite materials prepared in Examples 1-3 were tested. Among them, the self-healing lightweight high-strength composite material in Example 1 exhibited the best mechanical properties, with a maximum flexural modulus > 4 GPa and a maximum strength > 150 MPa. In this example, the mass ratio of hydroxyapatite nanowires to polyvinyl alcohol was 1:10, with hydroxyapatite nanowires acting as the reinforcing phase and polyvinyl alcohol as the toughening phase, resulting in the composite material exhibiting excellent mechanical properties simultaneously.

[0059] like Figure 4 As shown, the fracture-repair test results indicate that the self-healing lightweight high-strength composite material prepared in the embodiments of the present invention has good self-healing properties. The borate ester bond formed between polyvinyl alcohol and boric acid in the composite material is a dynamic covalent bond, which endows it with excellent self-healing ability.

[0060] In summary, this invention utilizes a simple and readily available raw material preparation method that is environmentally friendly and easy to implement. In the self-healing, lightweight, and high-strength composite material, hydroxyapatite nanowires serve as the reinforcing phase, polyvinyl alcohol (PVA) as the toughening phase, and the borate ester bond formed between PVA and boric acid acts as a dynamic covalent bond. This results in the composite material possessing both high mechanical properties (maximum flexural modulus > 4 GPa, maximum strength > 150 MPa) and excellent self-healing ability (> 85%).

[0061] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a self-healing, lightweight, high-strength composite material, characterized in that, Including the following steps: Preparation of hydroxyapatite nanowires; Polyvinyl alcohol and boric acid were dissolved in water, and the hydroxyapatite nanowires were added to obtain a suspension. The suspension was frozen into a solid and dried to obtain a white block material. The white block material is hot-compressed to obtain the self-healing lightweight high-strength composite material; The freezing process is performed using a device with bidirectional freezing technology. The white block material is a white block material with a long-range ordered layered structure; The conditions for hot compression are: temperature 80–100℃, pressure 20–40 MPa, and time 3–5 h.

2. The method for preparing the self-healing lightweight high-strength composite material according to claim 1, characterized in that, The steps for preparing hydroxyapatite nanowires include: Calcium chloride solution and sodium hydroxide solution were added to a mixed solution of methanol, water and oleic acid to obtain calcium oleate precursor; A sodium dihydrogen phosphate dihydrate solution was added to the calcium oleate precursor, and the mixture was heated to react. After centrifugation and washing, the hydroxyapatite nanowires were obtained.

3. The method for preparing the self-healing lightweight high-strength composite material according to claim 1, characterized in that, The temperature of the water is 80–90°C.

4. The method for preparing the self-healing lightweight high-strength composite material according to claim 1, characterized in that, The mass ratio of polyvinyl alcohol to water is 1:

5.

5. The method for preparing the self-healing lightweight high-strength composite material according to claim 1, characterized in that, The mass ratio of boric acid to polyvinyl alcohol is 1:20 to 1:

5.

6. The method for preparing the self-healing lightweight high-strength composite material according to claim 1, characterized in that, The mass ratio of the hydroxyapatite nanowires to the polyvinyl alcohol is 1:15 to 1:

5.

7. The method for preparing the self-healing lightweight high-strength composite material according to claim 1, characterized in that, The drying process is low-temperature vacuum drying, and the drying time is 48-96 hours.

8. A self-healing, lightweight, high-strength composite material prepared by the preparation method according to any one of claims 1 to 7.

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