A boron nitride nanoplatelet-modified spinnable organic-inorganic hybrid polyborazylene and a preparation method thereof

Abstract

The application discloses a boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene and a preparation method thereof, and comprises the following steps: 1, amino functionalization of commercial boron nitride nanosheet (BNNS); 2, preparation of the organic-inorganic hybrid polyborazylene: the amino functionalized BNNS is doped into polyborazylene monomers, the chemical bond of the two is realized by deamination reaction, and then the preparation of the organic-inorganic hybrid polyborazylene is completed through a polymerization reaction. The application first synthesizes an organic-inorganic hybrid polyborazylene precursor which has high ceramic yield, excellent processing performance and can be used for preparing high-crystalline boron nitride material; the chemical doping method is adopted to realize the uniform dispersion of the boron nitride nanosheet in the polyborazylene. The application provides the possibility for further regulating the microstructure of the boron nitride material and preparing high-performance boron nitride ceramic material and boron nitride ceramic fiber. The preparation process of the application is simple and can be used for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and particularly relates to a boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene and a preparation method thereof, and also relates to a boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene and a synthesis method thereof. BACKGROUND

[0002] The trace doping of inorganic nanofillers can significantly affect the microstructure and performance of polymer matrix materials, but there are still few studies on the doping of inorganic nanofillers into boron nitride precursors (polyborazylene).

[0003] Boron nitride ceramic materials have excellent high-temperature resistance, ablation resistance, chemical corrosion resistance and wave transmission performance, and have wide application prospects in the fields of aviation, aerospace, energy and catalysis. The polymer precursor method (PDCs) is widely used in the preparation of boron nitride ceramic materials due to the advantages of designable precursor molecular structure, high purity of ceramic products, and realization of uniform product structure and composition by controlling the uniform distribution of components in the precursor polymer. Among them, the design and synthesis of suitable precursors are the key technologies for preparing boron nitride ceramic materials suitable for different application fields, and have attracted much attention in recent years.

[0004] At present, a large number of studies have been carried out on the preparation of boron nitride ceramic materials by the polymer precursor conversion method. Various forms of polyborazylene precursors have been synthesized, and the ceramic conversion process has been controlled in many ways. However, the boron nitride ceramic materials prepared by the current method all have the problems of difficult control of the amorphous to crystalline transition process during the preparation process, low crystallinity of the boron nitride ceramic materials, and difficult microstructure control of the boron nitride ceramic materials, which affects the thermodynamic, electrical and mechanical properties of the boron nitride ceramic materials.

[0005] Therefore, it is urgent to design and synthesize a spinnable polyborazylene precursor that can be used to prepare high-crystallinity boron nitride materials, so as to provide the possibility for the microstructure control of boron nitride ceramic materials and the preparation of high-performance boron nitride ceramic fibers and ceramic materials. SUMMARY

[0006] In view of the problems of difficult control of the amorphous to crystalline transition process during the preparation process, low crystallinity of the boron nitride ceramic materials and difficult microstructure control of the boron nitride ceramic materials of the boron nitride ceramic materials prepared by the prior art, the application provides a boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene and a preparation method thereof, and also provides a boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene and a preparation method thereof. The preparation process is simple and can be used for large-scale production. The boron nitride ceramic material prepared has high crystallinity, which provides the possibility for further microstructure control of boron nitride materials, preparation of high-performance boron nitride ceramic fibers and ceramic materials, and enrichment of the types of boron nitride precursors.

[0007] The content of the present application aims to solve the problem that the crystallinity of the boron nitride ceramic material prepared at present is low, and the molecular structure of the precursor in the polymer precursor conversion method can be adjusted, and a spinnable organic-inorganic hybrid polyborazylene is synthesized by chemical doping method, and the technical principle of the present application is:

[0008] (1) Preparation of modified boron nitride nanosheet:

[0009]

[0010] (2) Preparation of organic-inorganic hybrid polyborazylene:

[0011]

[0012] The purpose of the present application is realized by the following technical scheme:

[0013] A preparation method of a spinnable organic-inorganic hybrid polyborazylene modified by boron nitride nanosheet, comprising the following steps:

[0014] (1) Preparation of modified boron nitride nanosheet:

[0015] The boron nitride nanosheet (BNNS) is mixed with the modifier according to the mass ratio of 6:1, and then placed in a high-energy ball mill for ball milling, and then the obtained powder is washed, filtered, dried, and dispersed in a solvent according to the mass-volume ratio of 2g:10mL to obtain a modified BNNS dispersion liquid;

[0016] The modified BNNS dispersion liquid, wherein the size of the BNNS is 100nm-10μm, and the thickness is 10nm-20nm;

[0017] The modifier is an amino group-containing compound selected from one or a mixture of NH2R1, NHR1R2 (R1, R2=CH3, CH2CH3, CH2CH2CH3 or other alkyl) amine compounds and other amino-containing compounds, and the mixing ratio is arbitrary;

[0018] The solvent is selected from toluene, xylene, chlorobenzene;

[0019] (2) Preparation of organic-inorganic hybrid polyborazylene:

[0020] The modified BNNS dispersion solution obtained in the above step is added into the borazane oligomer solution at a mass ratio of 0.1%-0.5% at room temperature, the concentration of the borazane oligomer solution is 10 mg / mL-100 mg / mL, and the modified BNNS is doped into the borazane oligomer by chemical bonds and physical methods under low temperature; the temperature is slowly increased to high temperature for preservation, and the organic-inorganic hybrid polyborazane is obtained after cooling to room temperature;

[0021] The borazane is selected from one or a mixture of several of borane, cyclotriborazane, trichlorocyclotriborazane, alkylaminoborane or ammonia borane, and the mixture is in any ratio.

[0022] The oligomer is selected from one of dimer, trimer and tetramer.

[0023] The preservation under low temperature is at a temperature of 60-160 DEG C for 1-5 hours.

[0024] The slow increase of the temperature to high temperature is to increase the temperature to 180-300 DEG C for 1-15 hours.

[0025] In the present application:

[0026] The ball milling in step (1) is performed for 12-48 hours at a rotating speed of 400-1000 r / min.

[0027] The modified BNNS dispersion solution in step (1) has a BNNS size of 400 nm-2 microns and a thickness of 10-20 nm.

[0028] The borazane in step (2) is an organic polymer with a B-N-B six-membered ring structure in the main chain, and is selected from one or a mixture of several of borane, cyclotriborazane, trichlorocyclotriborazane, alkylaminoborane and ammonia borane.

[0029] The present application also relates to a boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazane, which is prepared by the above method.

[0030] (1) the boron nitride nanosheet and the polyborazane are chemically bonded;

[0031] (2) high ceramic yield, specifically, the ceramic yield is greater than or equal to 65%;

[0032] (3) excellent spinnability, E η= 1.0 kJ / mol.

[0033] The application also relates to a BN ceramic material, which is prepared from the boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene above by melt spinning and precursor conversion, and has the following technical indexes:

[0034] (1) high crystallinity, specifically, the crystallinity is > 90%;

[0035] (2) excellent mechanical properties, > 1.0 GPa;

[0036] (3) high density, specifically, the density is > 2.0 g / cm 3 .

[0037] Compared with the prior art, the application has the following advantages:

[0038] 1. The boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene has the modified boron nitride nanosheet chemically bonded with the polyborazylene, realizes the uniform dispersion of the modified boron nitride nanosheet, can be converted into the high-crystallinity boron nitride ceramic material, and has high ceramic yield and good spinnability.

[0039] 2. The preparation method of the boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene has a simple preparation process, raw materials are easy to obtain, and the reaction process is controllable. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained according to the structures shown in the drawings without creative labor.

[0041] Figure 1 is an optical photograph of the synthesized hybrid precursor;

[0042] Figure 2 is an FT-IR graph of the hybrid polyborazylene precursor;

[0043] Figure 3 is a viscosity-shear rate curve graph of the embodiment 3 and the comparative example 1 of the application;

[0044] Figure 4These are SEM images of the spun fibers before pyrolysis in Example 4 of this invention (where A and B are surface and cross-sectional images of the fibers before pyrolysis, respectively, and C is an enlarged view of the area marked by the red circle in B, where the presence of modified boron nitride nanosheets can be observed).

[0045] Figure 5 The images show XRD patterns of boron nitride ceramic fibers prepared from the hybrid polyboronazine precursor and the non-BNNS-doped polyboronazine precursor in Example 1 of this invention. Detailed Implementation

[0046] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0047] The following examples and comparative examples were all carried out according to the above-described method for preparing organic-inorganic hybrid polyboronazine precursors doped with modified boron nitride nanosheets, the difference being the size and addition ratio of the modified boron nitride nanosheets used; all operations such as sample addition and transfer were performed in an argon glove box, and the argon gas used was high-purity argon gas with a purity ≥99.99%; the protective atmosphere in all examples and comparative examples was nitrogen gas, and the nitrogen gas used had a purity ≥99.9%; other chemical reagents used, unless otherwise specified, were obtained through conventional commercial channels.

[0048] Example 1:

[0049] A method for preparing spinnable organic-inorganic hybrid polyboronazine modified with boron nitride nanosheets includes the following steps:

[0050] (1) Preparation of modified boron nitride nanosheets:

[0051] Boron nitride nanosheets and urea were placed in a high-energy ball mill at a mass ratio of 6:1 and ball-milled for 12 hours. The resulting powder was then washed, filtered, dried, and dispersed in toluene to obtain a modified BNNS (mBNNS) toluene dispersion.

[0052] Depend on Figure 1 It can be seen that the size of mBNNS is 2μm;

[0053] (2) Preparation of organic-inorganic hybrid polyboronazine:

[0054] At room temperature, a mBNNS toluene dispersion was added at a mass ratio of 0.1% to a poly[2-propylamino-4,6-bis(methylamino)borazine-tris(methylamino)borazine] (PPMAB) oligomer solution and kept at 60°C for 5 h to allow the modified BNNS to be incorporated into the borazane oligomer through chemical bonding. The temperature was then slowly increased to 180°C and kept at that temperature for 15 h. After cooling to room temperature, the organic-inorganic hybrid polyborazane was obtained.

[0055] The apparent viscosity of the organic-inorganic hybrid polyborazylene synthesized in this embodiment decreases with the increase of the shear rate, showing the shear thinning behavior of a pseudoplastic fluid;

[0056] It can be seen that the crystallinity of the BN ceramic fiber prepared by using the organic-inorganic hybrid polyborazylene synthesized by the synthesis method in this embodiment as a raw material is greatly improved. Figure 5

[0057] Example 2:

[0058] A preparation method of a boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene, comprising the following steps:

[0059] (1) Preparation of modified boron nitride nanosheets:

[0060] The boron nitride nanosheets and urea are placed in a high-energy ball mill at a mass ratio of 6:1 for 12 h, and then the obtained powder is washed, filtered, and dried, and is dispersed in toluene to obtain a modified BNNS (mBNNS) toluene dispersion;

[0061] It can be seen that the size of the mBNNS is 2 μm. Figure 1

[0062] (2) Preparation of an organic-inorganic hybrid polyborazylene:

[0063] The mBNNS toluene dispersion is added to a poly[2-propylamino-4,6-bis(methylamino) borazine-tris(methylamino) borazine] (PPMAB) oligomer solution at a mass ratio of 0.1% at room temperature, and is incubated at 160°C for 5 h, so that the modified BNNS is doped into the borazylene oligomer by chemical bonds and Van der Waals forces; the temperature is slowly increased to 300°C, and is incubated for 15 h, and after cooling to room temperature, an organic-inorganic hybrid polyborazylene is obtained.

[0064] The apparent viscosity of the organic-inorganic hybrid polyborazylene synthesized in this embodiment decreases with the increase of the shear rate, showing the shear thinning behavior of a pseudoplastic fluid;

[0065] The crystallinity of the BN ceramic fiber prepared by using the organic-inorganic hybrid polyborazylene synthesized by the synthesis method in this embodiment as a raw material is greatly improved.

[0066] Example 3:

[0067] A preparation method of a boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene, comprising the following steps:

[0068] (1) Preparation of modified boron nitride nanosheets:

[0069] ​​Boron nitride nanosheets and urea were placed in a high-energy ball mill at a mass ratio of 6:1 and ball-milled for 12 hours. The resulting powder was then washed, filtered, dried, and dispersed in toluene to obtain a modified BNNS (mBNNS) toluene dispersion.

[0070] Depend on Figure 1 It can be seen that the size of mBNNS is 2μm;

[0071] (2) Preparation of organic-inorganic hybrid polyboronazine:

[0072] At room temperature, a mBNNS toluene dispersion was added at a mass ratio of 0.5% to a poly[2-propylamino-4,6-bis(methylamino)borazine-tris(methylamino)borazine] (PPMAB) oligomer solution and kept at 160°C for 5 h to allow the modified BNNS to be incorporated into the borazane oligomer through chemical bonding. The temperature was then slowly increased to 180°C and kept at that temperature for 15 h. After cooling to room temperature, the organic-inorganic hybrid polyborazane was obtained.

[0073] Depend on Figure 3 It can be seen that the apparent viscosity of the organic-inorganic hybrid polyboronazine synthesized in this embodiment decreases with increasing shear rate, exhibiting the shear-thinning behavior of a pseudoplastic fluid.

[0074] The crystallinity of BN ceramic fibers prepared using the organic-inorganic hybrid polyboronazine synthesized by the method in this embodiment is greatly improved.

[0075] Example 4:

[0076] A method for preparing spinnable organic-inorganic hybrid polyboronazine modified with boron nitride nanosheets includes the following steps:

[0077] (1) Preparation of modified boron nitride nanosheets:

[0078] Boron nitride nanosheets and urea were placed in a high-energy ball mill at a mass ratio of 6:1 and ball-milled for 36 hours. The resulting powder was then washed, filtered, dried, and dispersed in toluene to obtain a modified BNNS (nBNNS) toluene dispersion.

[0079] Depend on Figure 1 It can be seen that the size of nBNNS is 400 nm;

[0080] (2) Preparation of organic-inorganic hybrid polyboronazine:

[0081] At room temperature, nBNNS toluene dispersion was added to poly[2-propylamino-4,6-bis(methylamino)borazine-tris(methylamino)borazine] (PPMAB) oligomer solution at a mass ratio of 0.1%, and kept at 60°C for 5 h to allow the modified BNNS to be doped into the borazane oligomer through chemical bonding. The temperature was then slowly increased to 180°C and kept at that temperature for 15 h. After cooling to room temperature, the organic-inorganic hybrid polyborazane was obtained.

[0082] The apparent viscosity of the organic-inorganic hybrid polyboronazine synthesized in this embodiment decreases with increasing shear rate, exhibiting the shear-thinning behavior of a pseudoplastic fluid.

[0083] The crystallinity of BN ceramic fibers prepared using the organic-inorganic hybrid polyboronazine synthesized by the method in this embodiment is greatly improved.

[0084] This embodiment also provides a BN fibril (BN ceramic material) such as Figure 4 As shown, modified BNNS was successfully incorporated into BN fibrils. The organic-inorganic hybrid polyboronazine synthesized by the method in this embodiment was used as raw material and obtained by melt spinning.

[0085] Example 5:

[0086] A method for preparing spinnable organic-inorganic hybrid polyboronazine modified with boron nitride nanosheets includes the following steps:

[0087] (1) Preparation of modified boron nitride nanosheets:

[0088] Boron nitride nanosheets and 15 N-labeled urea was ball-milled in a high-energy ball mill at a mass ratio of 6:1 for 12 hours. The resulting powder was then washed, filtered, dried, and dispersed in toluene to obtain modified BNNS. 15 NH2-mBNNS) toluene dispersion;

[0089] (2) Preparation of organic-inorganic hybrid polyboronazine:

[0090] At room temperature, 15 NH2-mBNNS toluene dispersion was added to a poly[2-propylamino-4,6-bis(methylamino)borazine-tris(methylamino)borazine] (PPMAB) oligomer solution at a mass ratio of 0.1%. The mixture was kept at 60°C for 5 hours to allow the modified BNNS to be incorporated into the borazane oligomer through chemical bonding. The temperature was then slowly increased to 180°C and kept at that temperature for 15 hours. After cooling to room temperature, the organic-inorganic hybrid polyborazane was obtained.

[0091] Comparative Example 1:

[0092] The difference from Examples 1-5 is that no modified boron nitride nanosheets were added in step (2).

[0093] By Figure 5 It can be seen that the crystallinity of the boron nitride ceramic material prepared by converting the precursor prepared under the condition is low.

[0094] The FT-IR characterization of the organic-inorganic hybrid polyborazylene synthesized in Example 3 and Comparative Example 1 was compared with the molecular structure, and the results are shown in Figure 2 .

[0095] It can be seen that the molecular structure of the precursor obtained in the example is not much different from that of the comparative example, indicating that the types of chemical bonds in the hybrid polyborazylene precursor structure doped with modified BNNS have not changed, only the comparative example has changed.

[0096] Although the present application has been illustrated and described with reference to specific embodiments, it is realized that many other changes and modifications can be made therein without departing from the spirit and scope of the present application. Therefore, it is intended that the appended claims encompass all such changes and modifications as fall within the scope of the present application.

Claims

1. A method for preparing boron nitride nanoplatelet-modified spinnable organic-inorganic hybrid polyborazylene, characterized by: The method comprises the following steps: (1) Preparation of modified boron nitride nanosheets: The boron nitride nanosheets BNNS and the modifier are mixed in a mass ratio of 6:1, and then placed in a high-energy ball mill for ball milling. The obtained powder is then washed, filtered, and dried. The powder is dispersed in a solvent in a mass-volume ratio of 2g:10mL to obtain a modified BNNS dispersion; The modified BNNS dispersion, wherein the size of the BNNS is 100nm-10μm, and the thickness is 10nm-20nm; The modifier is urea; The solvent is selected from toluene, xylene, and chlorobenzene; (2) Preparation of organic-inorganic hybrid polyborazylene: The modified BNNS dispersion obtained in the previous step is added to a borazylene oligomer solution in a mass ratio of 0.1%-0.5% at room temperature, the concentration of the borazylene oligomer solution is 10mg / mL-100mg / mL, and the modified BNNS is doped into the borazylene oligomer by chemical bonds and physical methods under low temperature. Slowly warm up to high temperature and cool to room temperature to obtain organic-inorganic hybrid polyborazylene; The borazylene is selected from one or a mixture of cyclo-borazylene, trichloro-cyclo-borazylene, alkylamine borane, or ammonia borane, and the mixture is in any ratio; The oligomer is selected from one of dimer, trimer, and tetramer; The low-temperature preservation is at a temperature of 60℃-160℃ for 1h-5h; The slow warming to high temperature is to warm up to 180℃-300℃ for 1h-15h.

2. The method for preparing a spinnable organic-inorganic hybrid polyboronazine modified with boron nitride nanosheets according to claim 1, characterized in that: The ball milling in step (1) is for 12h-48h at a rotation speed of 400r / min-1000r / min.

3. The preparation method of a spinable organic-inorganic hybrid polyborazane modified by boron nitride nanosheets according to claim 1, characterized in that: The modified BNNS dispersion in step (1), wherein the size of the BNNS is 400nm-2μm, and the thickness is 10nm-20nm.

4. A boron nitride nanoplatelet-modified spinnable organic-inorganic hybrid polyborazylene, characterized by: The preparation method of the boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene according to any one of claims 1-3, wherein the boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene has the following technical indexes: the modified boron nitride nanosheet and the polyborazylene are combined by chemical bond, the ceramic yield is ≥65%, the spinnability E η =1.0 kJ / mol.

5. A BN ceramic material characterized by: The boron nitride nanosheet modified spinnable organic-inorganic hybrid polyborazylene of claim 4 is used as raw material, and is prepared by melt spinning and precursor conversion method, and has the following technical indexes: crystallinity > 90%, mechanical property > 1.0 GPa, and density ≥ 2.0 g / cm 3 .

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