Fluororubber-coated boron composite particles and a method for producing the same

Abstract

This invention provides fluororubber-coated boron composite particles and their preparation method. The method includes the following steps: Step 1: Add boron powder to a polar solvent and stir for 4-6 hours at a temperature range of 80-100°C. Then, filter, wash, and vacuum dry to obtain pretreated boron powder. Add fluororubber to a good solvent to obtain a fluororubber solution. Step 2: Add the pretreated boron powder to a non-solvent and ultrasonically disperse it. During the ultrasonic dispersion process, mechanical stirring is continuously performed to obtain a dispersion. Step 3: Heat the dispersion to a preset temperature, then add the fluororubber solution to the heated dispersion and stir for 3-6 hours. Then, filter, wash, and vacuum dry to obtain the final product. The mass ratio of fluororubber to boron powder is 1:(10-50). This invention first removes the oxide layer on the surface of the boron powder through pretreatment, improving the activity of the boron powder. Finally, the fluororubber forms a uniform coating on the surface of the boron powder, effectively preventing oxidation and maintaining the activity of the boron powder.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energetic material preparation, and particularly relates to fluorine rubber coated boron composite particles and a preparation method thereof. BACKGROUND

[0002] The mass heat value of boron is 58.74 kJ / g, and the volume heat value is 135.24 kJ / cm 3 , which is one of the most potential high-energy additives. However, the high melting point and high boiling point of boron lead to its difficulty in ignition. In the ignition combustion reaction, boron is not easy to melt and vaporize, and the combustion reaction is mainly layer-by-layer combustion, and the combustion rate is slow; and with the progress of the combustion reaction, the thickness of the oxidation layer will continue to increase, hindering the contact between boron and oxygen, leading to insufficient boron combustion and low energy release rate; in addition, impurities such as B2O3 and H3BO3 on the surface of boron particles are easy to have a gelation reaction with the hydroxyl group of the propellant component HTPB, leading to poor compatibility of boron with HTPB.

[0003] To improve the ignition combustion performance of boron powder and increase the energy release efficiency, the boron powder can be coated and modified to improve its energy release efficiency. Fluorine is the element with the largest electronegativity in the periodic table, so it can create a stronger oxidation environment than oxygen. The fluorination mass heat value and the fluorination volume heat value of boron are 105.01 kJ / g and 245.72 kJ / cm 3 , respectively. In addition, fluorine reacts with boron and boron oxide to form gaseous boron fluoride and oxyfluoride, which can greatly improve the vaporization rate of the oxidation layer on the surface of boron, promote the ignition and combustion of boron. Therefore, the composite material prepared by the fluorine-containing material and the boron powder has a significant energy release advantage. The preparation method of the fluoropolymer / boron powder composite material in the prior art has the following defects: the solvent evaporation method is used for preparation, which is easy to cause uneven coating, and the obtained composite material has the highest oxidation heat of only 8.2 kJ / g, and the energy release efficiency is only 13.9%; PVDF is used to improve the combustion performance of boron powder, but the surface oxidation layer of boron powder is not pretreated and removed, and the surface oxidation layer is an inert material, which reduces the energy density of the material and affects the energy release efficiency of the boron powder. SUMMARY

[0004] In view of the defects and deficiencies of the prior art, the purpose of the present application is to provide fluorine rubber coated boron composite particles and a preparation method thereof, so as to solve the technical problem of low energy release efficiency of fluoropolymer / boron powder composite material in the prior art.

[0005] In order to solve the above technical problems, the technical scheme is adopted as follows:

[0006] A preparation method of fluorine rubber coated boron composite particles comprises the following steps:

[0007] Step 1, the boron powder is added into a polar solvent, stirred at a temperature range of 80-100℃ for 4-6h, then filtered, washed, and vacuum dried to obtain the pretreated boron powder; the fluorine rubber is added into a good solvent to obtain a fluorine rubber solution,

[0008] Step 2, the pretreated boron powder is added into a non-solvent for ultrasonic dispersion, and mechanical stirring is continuously performed during the ultrasonic dispersion to obtain a dispersion liquid;

[0009] Step 3, the dispersion liquid is heated to a preset temperature, then the fluorine rubber solution is added into the heated dispersion liquid and stirred for 3-6h, then filtered, washed, and vacuum dried to obtain the product.

[0010] The fluorine rubber is Viton fluorine rubber, and the mass ratio of the fluorine rubber to the boron powder is 1:(10-50).

[0011] The application also has the following technical features:

[0012] Specifically, the particle size of the boron powder is 1-10μm.

[0013] Further, the polar solvent in step 1 is any one of N,N-dimethylformamide, dimethyl sulfoxide and acetonitrile.

[0014] Further, the mass ratio of the boron powder to the polar solvent in step 1 is 1:(30-40).

[0015] Further, the non-solvent in step 2 includes any one of n-hexane, cyclohexane, n-heptane and n-dodecane.

[0016] Further, the mass ratio of the pretreated boron powder to the non-solvent in step 2 is 1:(40-60).

[0017] Further, the good solvent in step 1 includes any one of acetone, diethyl ether and ethyl acetate, and the mass ratio of the fluorine rubber to the good solvent is 1:(100-500).

[0018] Further, the preset temperature in step 3 is 40-60℃.

[0019] Further, the method comprises the following steps:

[0020] Step 1, 10g of boron powder is added into 400g of acetonitrile, stirred at a temperature range of 80℃ for 6h, then filtered, washed, and vacuum dried to obtain the pretreated boron powder with no oxide layer on the surface; 0.05g of fluorine rubber is added into 20g of acetone to obtain a fluorine rubber solution;

[0021] Step 2, 1.5 g of the pretreated boron powder is added into 80 g of n-dodecane and ultrasonically dispersed, and mechanical stirring is continuously carried out during the ultrasonic dispersion to obtain a dispersion liquid;

[0022] Step 3, the fluororubber solution is added into the heated dispersion liquid and stirred for 3 h, and then filtered, washed and vacuum dried to obtain the fluororubber-coated boron composite particles.

[0023] The present application also protects a fluororubber-coated boron composite particle, which is prepared by the above method.

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

[0025] (1) The present application removes the oxide layer on the surface of the boron powder by pretreating the boron powder coated with the oxide layer to improve the activity of the boron powder; the fluororubber is used to form a uniform coating on the surface of the pure boron powder, which can effectively prevent the oxidation of the boron powder and maintain the activity of the boron powder; when the fluororubber-coated boron powder is ignited and burned, fluorine reacts with boron and boron oxide to generate gaseous boron fluoride and oxyfluoride, which can greatly improve the vaporization rate of the oxide layer on the surface of the boron, promote the ignition and combustion reaction of the boron, and release more heat value through the reaction of fluorine and boron, thereby effectively improving the energy release efficiency of the boron powder.

[0026] (2) The present application uses the solvent / non-solvent method to coat in the liquid phase, which is simple and controllable and can be applied to large-scale preparation.

[0027] (3) The fluororubber-coated boron composite particle provided by the present application has high energy release efficiency and can better meet the requirements of the ignition and combustion test. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a flowchart of the preparation of the fluororubber-coated clean boron composite particle of the present application;

[0029] Figure 2 is a TEM image of the boron powder of Example 1;

[0030] Figure 3 is a TEM image of the fluororubber-coated boron composite particle prepared in Example 1;

[0031] Figure 4 is an XRD image of the boron powder of Example 1;

[0032] Figure 5 is an XRD image of the fluororubber-coated boron composite particle prepared in Example 1;

[0033] Figure 6 is a DSC image of the boron powder and the fluororubber-coated boron composite particle of Example 1.

[0034] The technical solutions of the present application are further described below in combination with examples. DETAILED DESCRIPTION

[0035] In accordance with the above technical solutions, the following specific examples of the present application are given, it should be noted that the present application is not limited to the following specific examples, any equivalent variations made on the basis of the technical solutions of the present application fall within the protection scope of the present application.

[0036] The technical concept of the present application is: using a strong polar solvent to remove the oxide layer on the surface of boron powder in advance to improve the purity of boron powder; then, using a solvent / non-solvent method to prepare fluorine rubber coated clean boron composite particles, wherein a low-boiling-point solvent is selected as a good solvent to dissolve fluorine rubber, a high-boiling-point fluorine rubber poor solvent is selected as a non-solvent to disperse boron powder, by using the boiling point difference of the solvent, under the action of ultrasonic dispersion, by controlling the temperature to remove the good solvent, the fluorine rubber is deposited on the surface of the boron powder to form a better coating layer. Fluorine as an oxidizing agent can react with boron to produce gas, accelerate the gasification rate of boron, promote the ignition combustion efficiency, and increase the heat release.

[0037] The present application protects a preparation method of fluorine rubber coated boron composite particles, comprising the following steps:

[0038] Step 1, micron boron powder with a particle size of 1-10 μm is added to a polar solvent, stirred at a temperature of 80-100°C for 4-6h, then filtered, washed, and vacuum dried to obtain pretreated boron powder; fluorine rubber is added to a good solvent to obtain a fluorine rubber solution,

[0039] Step 2, the pretreated boron powder is added to a non-solvent for ultrasonic dispersion, mechanical stirring is continuously carried out during the ultrasonic dispersion process to obtain a dispersion liquid;

[0040] Step 3, the dispersion liquid is heated to a preset temperature, then the fluorine rubber solution is added to the heated dispersion liquid and stirred for 3-6h, then filtered, washed, and vacuum dried to obtain the fluorine rubber coated boron composite particles;

[0041] The mass ratio of the fluorine rubber to the boron powder is 1:(10-50).

[0042] As a preferred, the polar solvent in step 1 is any one of N,N-dimethylformamide, dimethyl sulfoxide and acetonitrile.

[0043] As a preferred, the mass ratio of the boron powder to the polar solvent in step 1 is 1:(30-40).

[0044] As a preferred, the non-solvent in step 2 includes any one of n-hexane, cyclohexane, n-heptane and n-dodecane.

[0045] As a preferred, the mass ratio of the pretreated boron powder to the non-solvent in step 2 is 1:(40-60).

[0046] Preferably, the good solvent in step 1 is any one of acetone, diethyl ether, ethyl acetate, and the mass ratio of the fluororubber to the good solvent is 1:(100-500).

[0047] Preferably, the preset temperature in step 3 is 40-60℃.

[0048] The amorphous boron powder used in the present application is produced by Yingkou Liaobin Fine Chemical Co., Ltd. Viton fluororubber is FKM26 series, produced by Shandong Dongyue Chemical Co., Ltd. N,N-dimethylformamide, dimethyl sulfoxide, acetone, acetonitrile, diethyl ether, ethyl acetate, etc. are commercially available products of Aladdin Reagent (Shanghai) Co., Ltd., and the purity specifications are all analytical pure.

[0049] Example 1

[0050] According to the above technical solution, as shown in Figure 1 the present embodiment discloses a preparation method of fluororubber-coated boron composite particles,

[0051] comprising the following steps:

[0052] Step 1: 10 g of micron boron powder with a particle size of 1-10 μm is added to 400 g of acetonitrile, stirred at a temperature of 80℃ for 6 h, then filtered, washed, and vacuum dried to obtain pretreated boron powder without an oxidation layer on the surface; 0.05 g of Viton fluororubber is added to 20 g of acetone to obtain a fluororubber solution;

[0053] Step 2: 1.5 g of pretreated boron powder is added to 80 g of n-dodecane for ultrasonic dispersion, and mechanical stirring is continuously performed during the ultrasonic dispersion process to obtain a dispersion liquid;

[0054] Step 3: The fluororubber solution is added to the dispersion liquid heated to 40℃ and stirred for 3 h, then filtered, washed, and vacuum dried to obtain a product of 1.43 g.

[0055] Structure identification:

[0056] Morphology analysis

[0057] As can be seen from Figure 2 and Figure 3 : The raw material boron powder has an irregular shape close to a sphere, and the surface is relatively smooth. After coating with fluoropolymer, the coating layer can be clearly observed on the TEM image, and the coating layer is uniformly coated, effectively protecting the boron powder from further oxidation.

[0058] XRD analysis

[0059] As can be seen from Figure 4 and Figure 5 : The raw material boron powder has an irregular shape close to a sphere, and the surface is relatively smooth. After coating with fluoropolymer, the coating layer can be clearly observed on the TEM image, and the coating layer is uniformly coated, effectively protecting the boron powder from further oxidation.It can be seen that the raw material boron powder has obvious characteristic peaks at 15° and 27°, which are attributed to boric acid and boron oxide, while after the surface of the boron powder is coated with fluoropolymer, the two peaks disappear, indicating that the surface oxide layer of the boron powder is successfully removed, and the fluoropolymer also plays a certain protective role.

[0060] DSC analysis

[0061] As shown in Figure 6 When heated from room temperature to 1200℃ at a heating rate of 10℃ / min, the exothermic quantity of the composite particles is 25999J / g, while the exothermic quantity of the raw material boron powder is only 17949J / g, and the energy release efficiency of the boron powder is increased from 30.5% to 44.3%.

[0062] The fluororubber-coated boron composite particles prepared in this example can be used to prepare propellants.

[0063] Example 2

[0064] The preparation method of the fluororubber-coated boron composite particles disclosed in this example has the same steps as in Example 1, and the only difference is that the amount of fluororubber used is different, in this example, 0.15g of fluororubber is dissolved in 20g of acetone, and finally 1.38g of fluororubber-coated boron composite particles are prepared.

[0065] The structure identification result of this example is the same as that of Example 1.

[0066] Example 3

[0067] The preparation method of the fluororubber-coated boron composite particles disclosed in this example has the same steps as in Example 1, and the only difference is that the amount of fluororubber added is different, in this example, 0.03g of fluororubber is added to 20g of acetone for dissolution, and finally 1.48g of fluororubber-coated boron composite particles are prepared.

[0068] The structure identification result of this example is the same as that of Example 1.

[0069] Example 4

[0070] The preparation method of the fluororubber-coated boron composite particles disclosed in this example has the same steps as in Example 1, and the only difference is that the selection of the non-solvent is different, in this example, 1.5g of pretreated boron powder is added to 80g of n-heptane for ultrasonic dispersion, and finally 1.47g of fluororubber-coated boron composite particles are prepared.

[0071] The structure identification result of this example is the same as that of Example 1.

[0072] Example 5

[0073] The preparation method of fluororubber-coated boron composite particles disclosed in this embodiment is the same as that in Example 1, except that the amount of good solvent is different. In this embodiment, 0.05g of fluororubber is added to 5g of acetone to dissolve, and finally 1.45g of fluororubber-coated boron composite particles are obtained.

[0074] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0075] Example 6

[0076] The preparation method of fluororubber-coated boron composite particles disclosed in this embodiment is the same as that in Example 1, except that the amount of good solvent is different. In this embodiment, 0.05g of fluororubber is dissolved in 10g of acetone, and 1.46g of fluororubber-coated boron composite particles are finally obtained.

[0077] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0078] Example 7

[0079] The preparation method of fluororubber-coated boron composite particles disclosed in this embodiment is the same as that in Example 1, except that the amount of good solvent is different. In this embodiment, 0.05g of fluororubber is dissolved in 15g of acetone, and 1.49g of fluororubber-coated boron composite particles are finally obtained.

[0080] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0081] Example 8

[0082] The preparation method of fluororubber-coated boron composite particles disclosed in this embodiment is the same as that in Example 1, except that the amount of good solvent is different. In this embodiment, 0.05g of fluororubber is dissolved in 25g of acetone, and 1.43g of fluororubber-coated boron composite particles are finally obtained.

[0083] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0084] Example 9

[0085] The preparation method of fluororubber-coated boron composite particles disclosed in this embodiment is the same as that in Example 1, except that the choice of good solvent is different. In this embodiment, 0.05g of fluororubber is dissolved in 20g of ethyl acetate, and 1.40g of fluororubber-coated boron composite particles are finally obtained.

[0086] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0087] Example 10

[0088] The preparation method of fluororubber-coated boron composite particles disclosed in this embodiment is the same as that in Example 1, except that: in this embodiment, the fluororubber solution is added to the dispersion heated to 60°C and stirred, and finally 1.44g of fluororubber-coated boron composite particles are obtained.

[0089] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0090] As can be seen from Examples 1 to 10, the thickness of the coating layer in the obtained composite particles changes with the amount of fluororubber, and the heat of combustion and ignition delay time increase with the increase of fluororubber content. The concentration of fluororubber solution changes with the amount of good solvent, but the uniformity of the coating layer of the obtained composite particles is different when the addition rate is the same. Among them, the uniformity of the coating layer prepared in Example 1 is the best. In addition, the choice of good solvent and non-solvent has no significant effect on the coating effect.

[0091] Comparative Example 1

[0092] The difference from Example 1 is that the boron powder was not pre-treated to remove the film, i.e., step (1) was not performed. The remaining steps are the same as in Example 3.

[0093] Comparative Example 2

[0094] The difference from Example 1 is that the content of fluororubber in step (2) is increased to 0.4g, while the rest of the steps are the same as in Example 3.

[0095] The table below lists the performance parameters of the samples obtained in Example 1, Comparative Example 1, and Comparative Example 2.

[0096]

[0097]

[0098] As can be seen from the table above, the composite particles prepared in Example 1 exhibited the best ignition and combustion performance, with the lowest ignition delay time and a combustion heat of 19.25 kJ·g. -1 It has the longest combustion time and can well meet the needs of solid propellants for metallic fuels. It can be added to solid propellants as a high-energy metallic fuel additive to improve the energy performance of the propellant.

[0099] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0100] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0101] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for producing fluororubber-coated boron composite particles, characterized by comprising the steps of: The method comprises the following steps: ​ Step 1, adding boron powder into a polar solvent, stirring at a temperature range of 80-100 DEG C for 4-6 hours, then performing suction filtration, washing and vacuum drying to obtain pretreated boron powder; adding fluoro rubber into a good solvent to obtain a fluoro rubber solution; Step 2, adding the pretreated boron powder into a non-solvent for ultrasonic dispersion, continuously performing mechanical stirring during the ultrasonic dispersion to obtain a dispersion liquid; Step 3, heating the dispersion liquid to a preset temperature, then adding the fluoro rubber solution into the heated dispersion liquid for stirring for 3-6 hours, then performing suction filtration, washing and vacuum drying to obtain the fluoro rubber coated boron composite particle; The fluoro rubber is Viton fluoro rubber, and the mass ratio of the fluoro rubber to the boron powder is 1:(10-50); The polar solvent in step 1 is any one of N,N-dimethylformamide, dimethyl sulfoxide and acetonitrile; The non-solvent in step 2 is any one of n-hexane, cyclohexane, n-heptane and n-dodecane; The good solvent in step 1 is any one of acetone, diethyl ether and ethyl acetate, and the mass ratio of the fluoro rubber to the good solvent is 1:(100-500).

2. The method for producing a fluororubber-coated boron composite particle according to Claim 1, characterized by, The particle size of the boron powder is 1-10 microns.

3. The method for preparing fluororubber-coated boron composite particles as described in claim 1, characterized in that, The mass ratio of the boron powder to the polar solvent in step 1 is 1:(30-40).

4. The method for preparing fluororubber-coated boron composite particles as described in claim 1, characterized in that, The mass ratio of the pretreated boron powder to the non-solvent in step 2 is 1:(40-60).

5. The method for preparing fluororubber-coated boron composite particles as described in claim 1, characterized in that, The preset temperature in step 3 is 40-60 DEG C.

6. The method for preparing fluororubber-coated boron composite particles as described in claim 1, characterized in that, The method comprises the following steps: Step 1, adding 10 g of boron powder into 400 g of acetonitrile, stirring at a temperature range of 80 DEG C for 6 hours, then performing suction filtration, washing and vacuum drying to obtain pretreated boron powder without an oxide layer; adding 0.05 g of fluoro rubber into 20 g of acetone to obtain a fluoro rubber solution; Step 2, adding 1.5 g of pretreated boron powder into 80 g of n-dodecane for ultrasonic dispersion, continuously performing mechanical stirring during the ultrasonic dispersion to obtain a dispersion liquid; Step 3, adding the fluoro rubber solution into the heated dispersion liquid for stirring for 3 hours, then performing suction filtration, washing and vacuum drying to obtain the fluoro rubber coated boron composite particle.

7. A fluororubber-coated boron composite particle, characterized in that, The fluoro rubber coated boron composite particle is prepared by the method in any one of claims 1-6.

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