Polytrifluorochloroethylene chemically coated boron powder and preparation method thereof

Abstract

The invention discloses polytrifluorochloroethylene chemically-coated boron powder and a preparation method thereof.The polytrifluorochloroethylene chemically-coated boron powder is obtained by chemically connecting polytrifluorochloroethylene and boron powder through polydopamine, and the preparation method comprises the steps that the surface of polytrifluorochloroethylene is coated with polydopamine; hydrophilic groups rich in the surface of the polydopamine and an oxide layer on the surface of the boron powder are subjected to a condensation polymerization reaction, part of the oxide layer on the surface of the boron powder is removed before the boron powder is ignited and combusted, the capacity of polytrifluorochloroethylene for removing the oxide layer on the surface of the boron powder is further enhanced, and the purpose of improving the ignition and combustion performance of the boron powder is achieved.

Description

Technical Field

[0001] The invention relates to the field of polymers, and in particular to polychlorotrifluoroethylene chemically coated boron powder and a preparation method thereof. Background Art

[0002] At present, the main method for developing energetic materials with higher energy density is to add highly active metal powder to the energetic materials to increase the energy density of the energetic materials. The selection of highly active metal powder is mainly based on the calorific value of the highly active metal. The theoretical volume calorific value of boron (131.60 kJ / cm 3 ) and theoretical mass calorific value (59.28kJ / g), which are 1.66 times and 1.9 times that of aluminum respectively. In theory, boron can further improve the energy level of energetic materials compared to the currently widely used aluminum. In practical applications, due to the physical properties of boron's high melting point and high boiling point, and the surface sticky oxide layer (B203, H3BO3, etc.) hindering oxygen diffusion, these all lead to poor ignition performance and low combustion efficiency of boron, affecting its energy performance.

[0003] Related studies have found that the adverse effects of the boron surface oxide layer on the ignition and combustion of boron can be reduced by changing the oxidation environment of boron, thereby improving the ignition and combustion performance of boron. Patent document CN111423289A discloses a boron-based composite material used as a combustible or combustion-supporting agent, specifically grinding boron powder with aluminum powder and polytetrafluoroethylene in a grinder. The resulting composite powder can reduce the reaction threshold of boron, improve energy utilization, and solve the acidity of boron powder and improve its process problems with HTPB. Sun Yuxiang used a physical grinding and mixing method to prepare a boron / polytetrafluoroethylene mixed powder. When the amount of polytetrafluoroethylene was between 0.1% and 1% of the mass of boron, the combustion efficiency of the mixed sample would be greatly improved, and the specific impulse of the boron-containing propellant would also be significantly improved (Research on the Combustion Performance of Boron and the Combustion Performance of Boron-containing Propellants [D]. Beijing: Beijing Institute of Technology, 2017). Pan Wen et al. used RDX as the main explosive, added boron powder and fluorine-containing binder F 2603 , a direct mixing method was used to prepare boron-containing explosives. The study found that the hydrofluoric acid, fluorine element and other substances produced by the decomposition of the fluorine-containing binder consumed the boron oxide film, effectively improving the oxidation completeness of the boron powder during the explosion process, thereby increasing the energy release of the explosion reaction of the boron-containing explosive (Effect of fluorine-containing binder on the completeness of the reaction of boron powder during the explosion process [J]. Initiators, 2022(5):41–45).

[0004] The above study only used the physical and mechanical mixing method to prepare the boron complex. This method has the problem that the coating will desorb under certain conditions. During the ignition and combustion process, it may not be able to effectively destroy the oxide layer on the surface of the boron powder and improve the combustion performance of the boron powder. In addition, only the physical and mechanical mixing method is used. During the preparation stage of the boron powder, mechanical mixing is difficult to effectively destroy the oxide layer on the surface of the boron powder. Summary of the invention

[0005] The purpose of the present invention is to provide a poly(chlorotrifluoroethylene) chemically coated boron powder and a preparation method thereof in view of the above technical problems. The inventors of the present invention coated polydopamine on the surface of poly(chlorotrifluoroethylene) and used the hydrophilic groups rich in the surface of polydopamine, such as hydroxyl groups and amine groups, to react with the oxide layer on the surface of the boron powder to produce a polycondensation reaction. This not only firmly coated the poly(chlorotrifluoroethylene) on the surface of the boron powder in the form of covalent bonds, but also removed part of the oxide layer on the surface of the boron powder before the boron powder was ignited and burned, further enhancing the ability of poly(chlorotrifluoroethylene) to remove the oxide layer on the surface of the boron powder, thereby achieving the purpose of improving the ignition and combustion performance of the boron powder.

[0006] The technical solution of the present invention is as follows:

[0007] First, the present invention provides a polychlorotrifluoroethylene chemically coated boron powder, wherein the polychlorotrifluoroethylene and the boron powder are chemically connected using polydopamine.

[0008] Second, the present invention provides a method for preparing polytrifluorochloroethylene chemically coated boron powder, the preparation method comprising the following steps:

[0009] S1: polychlorotrifluoroethylene is extracted with acetone and then dried, polychlorotrifluoroethylene is added to a Tris-HCl solution of dopamine, stirred at a temperature of 30°C to 50°C for self-polymerization, and washed and dried to obtain polydopamine-modified polychlorotrifluoroethylene;

[0010] S2: adding polydopamine-modified polychlorotrifluoroethylene and boron powder into a Tris-HCl solution, stirring at a temperature of 30° C. to 50° C. to carry out a surface grafting modification reaction, and washing and drying to obtain polychlorotrifluoroethylene chemically coated boron powder.

[0011] The concentration of the Tris-HCl solution is 5-20 mmol / L, and the pH is 8-9. Preferably, the concentration is 10 mmol / L, and the pH is 8.5.

[0012] The concentration of dopamine in the Tris-HCl solution of dopamine is 0.5 to 2.5 g / L, preferably 1.5 to 2.5 g / L.

[0013] The particle size of the polychlorotrifluoroethylene is 1 to 10 μm, preferably 1 to 5 μm.

[0014] The mass ratio of the polydopamine-modified polychlorotrifluoroethylene to the boron powder is 1 to 10:100, preferably 5 to 10:100.

[0015] The particle size of the boron powder is 0.5-10 μm, preferably 1-5 μm.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: polychlorotrifluoroethylene and boron powder are connected by using polydopamine, and the hydroxyl and amine groups on the surface of polydopamine react with the oxide layer on the surface of the boron powder to remove part of the oxide layer on the surface of the boron powder before the boron powder is ignited and burned, thereby further enhancing the ability of polychlorotrifluoroethylene to remove the oxide layer on the surface of the boron powder, thereby achieving the purpose of improving the ignition and combustion performance of the boron powder. DETAILED DESCRIPTION

[0017] Example 1

[0018] Preparation of modified polytrifluorochloroethylene: Extract polytrifluorochloroethylene with a particle size of 3 μm with acetone for 24 hours and vacuum dry it at 40°C for 6 hours. Add the dried polytrifluorochloroethylene into a Tris-HCl solution with a dopamine concentration of 2 g / L (Tris concentration is 10 mmol / L, pH=8.5), stir at 40°C for 24 hours to perform a self-polymerization reaction, and then wash and dry the product to obtain modified polytrifluorochloroethylene.

[0019] Polytrifluorochloroethylene chemically coated boron powder: 5 g of modified polytrifluorochloroethylene and 100 g of boron powder with a particle size of 3 μm were added to a Tris-HCl solution (Tris concentration was 10 mmol / L, pH = 8.5), stirred for 24 h at 40°C for surface grafting modification, and then the product was washed and dried to obtain polytrifluorochloroethylene chemically coated boron powder.

[0020] Example 2

[0021] Preparation of modified polytrifluorochloroethylene: Extract polytrifluorochloroethylene with a particle size of 5 μm with acetone for 24 hours and vacuum dry it at 40°C for 6 hours. Add the dried polytrifluorochloroethylene into a Tris-HCl solution with a dopamine concentration of 2 g / L (Tris concentration is 10 mmol / L, pH=8.5), stir at 40°C for 24 hours to perform a self-polymerization reaction, and then wash and dry the product to obtain modified polytrifluorochloroethylene.

[0022] Polytrifluorochloroethylene chemically coated boron powder: 7.5 g of modified polytrifluorochloroethylene and 100 g of boron powder with a particle size of 5 μm were added to a Tris-HCl solution (Tris concentration was 10 mmol / L, pH = 8.5), stirred for 24 h at 40°C for surface grafting modification, and then the product was washed and dried to obtain polytrifluorochloroethylene chemically coated boron powder.

[0023] Example 3

[0024] Preparation of modified polytrifluorochloroethylene: Extract polytrifluorochloroethylene with a particle size of 1 μm with acetone for 24 hours and vacuum dry it at 40°C for 6 hours. Add the dried polytrifluorochloroethylene to a Tris-HCl solution with a dopamine concentration of 2.5 g / L (Tris concentration is 10 mmol / L, pH=8.5), stir at 40°C for 24 hours to perform a self-polymerization reaction, and then wash and dry the product to obtain modified polytrifluorochloroethylene.

[0025] Polytrifluorochloroethylene chemically coated boron powder: 10 g of modified polytrifluorochloroethylene and 100 g of boron powder with a particle size of 3 μm were added to a Tris-HCl solution (Tris concentration was 10 mmol / L, pH = 8.5), stirred for 24 h at 40°C for surface grafting modification, and then the product was washed and dried to obtain polytrifluorochloroethylene chemically coated boron powder.

[0026] Example 4

[0027] Preparation of modified polytrifluorochloroethylene: Extract polytrifluorochloroethylene with a particle size of 7 μm with acetone for 24 hours and vacuum dry it at 40°C for 6 hours. Add the dried polytrifluorochloroethylene into a Tris-HCl solution with a dopamine concentration of 1 g / L (Tris concentration is 10 mmol / L, pH=8.5), stir at 40°C for 24 hours to perform a self-polymerization reaction, and then wash and dry the product to obtain modified polytrifluorochloroethylene.

[0028] Polytrifluorochloroethylene chemically coated boron powder: 3 g of modified polytrifluorochloroethylene and 100 g of boron powder with a particle size of 7 μm were added to a Tris-HCl solution (Tris concentration was 10 mmol / L, pH = 8.5), stirred for 24 h at 40°C for surface grafting modification, and then the product was washed and dried to obtain polytrifluorochloroethylene chemically coated boron powder.

[0029] Comparative Example 1

[0030] The polytrifluorochloroethylene with a particle size of 3 μm was extracted with acetone for 24 h and vacuum dried at 40°C for 6 h. 5 g of dried polytrifluorochloroethylene and 100 g of boron powder with a particle size of 3 μm were taken, and 2 L of anhydrous ethanol was used as a process control agent, and ball milled under nitrogen protection. After ball milling, the ethanol solvent was removed by filtration, and polytrifluorochloroethylene modified boron powder was obtained after vacuum drying.

[0031] Test Case

[0032] The combustion performance of the pure boron powder and the boron powders prepared in Examples 1-4 and Comparative Example 1 was tested by DSC method, the heating rate was 10°C / min, and the test temperature range was 50-1000°C.

[0033] The ignition performance of pure boron powder and the boron powder prepared in Examples 1-4 and Comparative Example 1 was tested. The test method was as follows: take an appropriate amount of sample and place it on the sample stage of the laser ignition instrument. The instrument parameters were set to frequency 1000 Hz; duty cycle 3%; number of pulses 1000; pulse train light; power 40 W; pulse energy 40 mJ; and pulse width 30 μs.

[0034] Table 1 Combustion performance and ignition performance test data

[0035] sample Combustion performance / ℃ Ignition delay time / ms Pure Boron 681 54 Example 1 512 34 Example 2 515 36 Example 3 521 40 Example 4 529 44 Comparative Example 1 537 49

[0036] It can be seen from the data in Table 1 that, compared with pure boron powder and physically modified boron powder, the polytrifluorochloroethylene chemically coated boron powder of the present invention has a lower combustion temperature and a shorter ignition delay time.

Claims

1. A polytrifluorochloroethylene chemically coated boron powder, characterized in that: Polychlorotrifluoroethylene and boron powder were chemically linked using polydopamine.

2. A method for preparing the polytrifluorochloroethylene chemically coated boron powder according to claim 1, characterized in that: The preparation method comprises the following steps: S1: polychlorotrifluoroethylene is extracted with acetone and then dried, polychlorotrifluoroethylene is added to a Tris-HCl solution of dopamine, stirred at a temperature of 30°C to 50°C for self-polymerization, and washed and dried to obtain polydopamine-modified polychlorotrifluoroethylene; S2: adding polydopamine-modified polychlorotrifluoroethylene and boron powder into a Tris-HCl solution, stirring at a temperature of 30° C. to 50° C. to carry out a surface grafting modification reaction, and washing and drying to obtain polychlorotrifluoroethylene chemically coated boron powder.

3. The method for preparing polytrifluorochloroethylene chemically coated boron powder according to claim 2, characterized in that: The concentration of the Tris-HCl solution is 5-20 mmol / L, and the pH is 8-9.

4. The method for preparing polytrifluorochloroethylene chemically coated boron powder according to claim 2, characterized in that: The concentration of dopamine in the Tris-HCl solution of dopamine is 0.5-2.5 g / L.

5. The method for preparing polytrifluorochloroethylene chemically coated boron powder according to claim 2, characterized in that: The particle size of the polychlorotrifluoroethylene is 1 to 10 μm.

6. The method for preparing polytrifluorochloroethylene chemically coated boron powder according to claim 2, characterized in that: The mass ratio of polydopamine-modified polychlorotrifluoroethylene to boron powder is 1-10:

100.

7. The method for preparing polytrifluorochloroethylene chemically coated boron powder according to claim 2, characterized in that: The particle size of the boron powder is 0.5-10 μm.