AP-AO composite particle with embedded structure as well as preparation method and application of AP-AO composite particle

Abstract

The invention discloses an AP-AO composite particle with an embedded structure as well as a preparation method and application of the AP-AO composite particle. The preparation method comprises the following steps: dispersing AO in a DMF (Dimethyl Formamide) solution of AP; under stirring, adding ethyl acetate into the suspension; and carrying out vacuum drying after suction filtration to obtain the AP-AO composite particles with the embedded structure. According to the invention, the AO can be embedded and distributed on the AP, the agglomeration phenomenon of the AO is reduced, and the contact area between the AO and the AP is increased; the preparation of the AP-AO composite particles of the embedded structure can promote close contact of AP and AO, the inhibition of AO on AP thermal decomposition and the reduction of the combustion rate of the hydroxyl-terminated polybutadiene composite solid propellant are fully played, and the problems that superfine AO is easy to agglomerate and the effect of reducing AP thermal decomposition and the combustion rate of the hydroxyl-terminated polybutadiene composite solid propellant is poor are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of energetic materials, and particularly relates to an embedded structure AP-AO composite particle, a preparation method thereof, and an application thereof. Background Art

[0002] Composite solid propellants are widely used in fields such as ballistic missiles, rocket launches, and space launch vehicles, and are the main power source. For different uses of solid rocket engines, different requirements are put forward for the burning rate of the propellant. Among them, in the boost stage and cruise stage engines of multi-stage solid rockets, under the requirement of long-term endurance, it is required that the propellant has a low burning rate to achieve a stable release of the propellant energy, reduce the loss of energy during the high-rate release process, increase the endurance time of rocket and missile engines, thereby providing stable and long-term thrust for the engine, and achieving high hit accuracy and strong destruction ability. Among them, ammonium perchlorate (AP) is the most widely used oxidizer in solid propellants, with a proportion as high as 60-90% of the propellant, and its performance directly affects the performance of the propellant. Therefore, it is very important to reduce the thermal decomposition and combustion rate of AP and improve the combustion efficiency.

[0003] At present, a variety of rate reducers have been used to reduce the thermal decomposition of AP and the combustion rate of the propellant. Among them, ammonium oxalate (AO) is the most widely used. At present, a physical mixing method is used to utilize rate reducers such as AO to reduce the thermal decomposition of AP and the combustion rate of hydroxyl-terminated polybutadiene composite solid propellants. However, it is difficult to uniformly mix AP and AO by the physical mixing method. Due to the small particle size of AO, there is a phenomenon of easy agglomeration. Direct addition will result in poor dispersibility, limited contact area with AP, and uneven distribution, thus restricting the role of AO in inhibiting the combustion rate. Therefore, it is particularly necessary to construct AP-AO composite particles to improve the dispersibility of AO, and this method can effectively enhance the rate reduction effect of AO. Summary of the Invention

[0004] Aiming at the problem that the existing technology leads to poor inhibition effect of the rate reducer on the thermal decomposition of AP and the combustion rate of hydroxyl-terminated polybutadiene composite solid propellants, the purpose of the present invention is to provide an embedded structure AP-AO composite particle and a preparation method thereof to solve the problems of easy agglomeration of ultrafine AO and its poor effect in reducing the thermal decomposition of AP and the combustion rate of hydroxyl-terminated polybutadiene composite solid propellants, and verify its inhibition effect in the propellant.

[0005] In the first aspect, the present invention provides a preparation method of an embedded structure AP-AO composite particle, comprising the following steps:

[0006] Step 1: Disperse AO in the DMF solution of AP;

[0007] Step 2: Under stirring conditions, add ethyl acetate to the suspension in Step 1;

[0008] Step 3: After suction filtration, carry out vacuum drying to obtain the embedded structure AP-AO composite particles.

[0009] Preferably, in Step 1, the concentration of the AP DMF solution is 0.8 - 1.0 g / mL.

[0010] Preferably, in Step 1, the particle size of AO is 1 - 10 μm.

[0011] Preferably, in Step 2, the dropping rate of ethyl acetate is 1 - 2 mL / min.

[0012] Preferably, the volume ratio of DMF to ethyl acetate is 1:10.

[0013] Preferably, the vacuum drying temperature is 50 - 80 °C and the time is more than 2 h.

[0014] Preferably, the mass percentage of AP to AO is (99 - 95):(1 - 5).

[0015] In a second aspect, the present invention provides an embedded structure AP-AO composite particle prepared by the method described in the first aspect.

[0016] In a third aspect, the present invention provides an application of the embedded structure AP-AO composite particle described in the second aspect in a hydroxy-terminated polybutadiene composite solid propellant.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) Compared with the traditional physical mixing method, the present invention can embed and distribute AO on AP, reduce the agglomeration phenomenon of AO, and increase the contact area between AO and AP;

[0019] (2) The preparation of the embedded structure AP-AO composite particles can promote the close contact between AP and AO, and fully exert the role of AO in inhibiting the thermal decomposition of AP and reducing the burning rate of the hydroxy-terminated polybutadiene composite solid propellant. Description of the Drawings

[0020] Figure 1 It is the SEM image of AP.

[0021] Figure 2 It is the SEM image of the AP-AO-1% composite particles in Example 1.

[0022] Figure 3 It is the SEM image of the AP-AO-2% composite particles in Example 2.

[0023] Figure 4 It is the SEM image of the AP-AO-3% composite particles in Example 3.

[0024] Figure 5 SEM image of the AP-AO-4% composite particles in Example 4.

[0025] Figure 6 SEM image of the AP-AO-5% composite particles in Example 5.

[0026] Figure 7 SEM image of the ion-polished cross-section of the AP-AO-5% composite particles in Example 5.

[0027] Figure 8 FT-IR spectra of AP and the AP-AO composite particles in Examples 1-5.

[0028] Figure 9 DSC curves of AP and the AP-AO composite particles in Examples 1-5 at a heating rate of 10 °C / min.

[0029] Figure 10 Combustion process diagrams of the propellant without AO (P0), the propellant with AO added by the conventional method (P1), and the propellants with the AP-AO composite particles prepared in Examples 1-5 added (P2-P6). Detailed implementation manners

[0030] The present invention will be described in detail below with reference to specific examples. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made. These all belong to the protection scope of the present invention.

[0031] Example 1

[0032] Step 1: Prepare a 50 mL DMF solution of AP with a concentration of 0.8 g / mL.

[0033] Step 2: Dissolve 0.028 g of AO in the above solution and promote the dispersion of AO by stirring.

[0034] Step 3: Slowly add ethyl acetate to the suspension in Step 2 at a rate of 2 mL / min using a peristaltic pump.

[0035] Step 4: Vacuum-dry the solid particles obtained in Step 3.

[0036] Step 5: In the prepared AP-AO composite particles, since AP undergoes recrystallization and there is loss during the process, the yield is approximately 70%. Therefore, the mass of AP in the obtained AP-AO composite particles is about 2.8 g, the added amount of AO is about 0.028 g, and the mass percentage of AO in the AP-AO composite particles is 1%. The composite particles prepared in this example are named AP-AO-1%.

[0037] Example 2

[0038] Step 1: Prepare a 50 mL DMF solution of AP with a concentration of 0.8 g / mL;

[0039] Step 2: Dissolve 0.057 g of AO in the above solution and promote the dispersion of AO by stirring;

[0040] Step 3: Slowly add ethyl acetate to the suspension in Step 2 at a rate of 2 mL / min through a peristaltic pump; Step 4: Vacuum-dry the solid particles obtained in Step 3;

[0041] Step 5: Obtain AP-AO composite particles. Similarly, name them AP-AO-2%.

[0042] Example 3

[0043] Step 1: Prepare a 50 mL DMF solution of AP with a concentration of 0.8 g / mL;

[0044] Step 2: Dissolve 0.087 g of AO in the above solution and promote the dispersion of AO by stirring;

[0045] Step 3: Slowly add ethyl acetate to the suspension in Step 2 at a rate of 2 mL / min through a peristaltic pump; Step 4: Vacuum-dry the solid particles obtained in Step 3;

[0046] Step 5: Obtain AP-AO composite particles. Similarly, name them AP-AO-3%.

[0047] Example 4

[0048] Step 1: Prepare a 50 mL DMF solution of AP with a concentration of 0.8 g / mL;

[0049] Step 2: Dissolve 0.117 g of AO in the above solution and promote the dispersion of AO by stirring;

[0050] Step 3: Slowly add ethyl acetate to the suspension in Step 2 at a rate of 2 mL / min through a peristaltic pump; Step 4: Vacuum-dry the solid particles obtained in Step 3;

[0051] Step 5: Prepare AP-AO composite particles, and name them AP-AO-4% as above.

[0052] Example 5

[0053] Step 1: Prepare a 50 mL DMF solution of AP with a concentration of 0.8 g / mL.

[0054] Step 2: Dissolve 0.147 g of AO in the above solution, and promote the dispersion of AO by stirring.

[0055] Step 3: Dropwise add ethyl acetate into the suspension in Step 2 at a rate of 2 mL / min through a peristaltic pump.

[0056] Step 4: Vacuum dry the solid particles obtained in Step 3.

[0057] Step 5: Prepare AP-AO composite particles, and name them AP-AO-5% as above.

[0058] To more clearly characterize the morphological structure and thermal decomposition of AP and the composite particles of each example, the raw material AP was recrystallized by the solvent-nonsolvent method: AP was dissolved in a DMF solution, ethyl acetate was added dropwise to precipitate it, and after suction filtration and drying, spherical-like AP was obtained, and its morphology is as Figure 1 shown. FT-IR and DSC are respectively as Figure 8 and Figure 9 shown.

[0059] Figures 2 to 6 is the SEM image of the AP-AO composite particles. The results show that compared with the spherical-like AP, AO particles can be observed adhering to the surface of AP in the AP-AO composite particles, and the AO particles are evenly dispersed on the surface of AP. With the increase of the AO content, the AO content on the surface of AP also increases. Figure 7 is the SEM and EDS images of the cut surface of the AP-AO-5% composite particles in Example 5 cut by ion polishing technology. The cut surface shows the distribution of C element, indicating that AO is embedded and distributed inside AP. In the Figure 8 FT-IR spectra of various AP-AO composite particles, characteristic peaks of AO can be seen, and with the increase of the AO content, the signal peak intensity of AO in the composite particles increases. Figure 9It is the DSC graph of AP and various AP-AO composite particles under the condition of 10 °C / min, which proves that the addition of AO inhibits the low-temperature decomposition of AP and delays the low-temperature decomposition peak of AP by 4-13 °C. To further verify the deceleration effect of AP-AO composite particles in the propellant, the AO not added, the AO added by the common method, and the AP-AO composite particles prepared in Examples 1-5 were made into propellants according to the formulations in Tables 1-3, and their combustion processes were analyzed and burning rate tests were carried out (Table 4). The prepared propellants were named P0, P1, and P2-P6 respectively. The components in the table include AP, aluminum powder (Al), hydroxyl-terminated polybutadiene (HTPB), dioctyl sebacate (DOS), and isophorone diisocyanate (IPDI).

[0060] Table 1 Formulation table of hydroxyl-terminated polybutadiene composite solid propellant (P0) without adding AO

[0061]

[0062]

[0063] Table 2 Formulation table of hydroxyl-terminated polybutadiene composite solid propellant (P1) with AO added by the common method

[0064] Formulation Mass percentage (%) AP 60 AO 3.16 Al 18 HTPB / DOS / IPDI 18.84

[0065] Note: The common method means mixing each component in proportion and stirring evenly.

[0066] Table 3 Formulation table of hydroxyl-terminated polybutadiene composite solid propellant (P2-P6) with the AP-AO composite particles of each example of the present invention added

[0067]

[0068] Table 4 Burning rate results of AP / HTPB composite propellant

[0069] Sample L (mm) u (mm / s) Reduction rate (%) P0 100 1.31 - P1 100 1.04 20.61 P2 100 1.22 6.87 P3 100 1.18 9.92 P4 100 1.15 12.21 P5 100 1.13 13.7 P6 100 1.02 22.14

[0070] Taking the AP-AO-5% (i.e., P6) prepared in Example 5 as an example, the specific experimental process for preparing the hydroxyl-terminated polybutadiene composite solid propellant is as follows: First, weigh a certain mass of HTPB and DOS and premix them for 10-20 min; Second, add the weighed Al to the binder and stir for 10 min to form a uniform slurry; Third, add AP-AO-5% to the premixed slurry in three portions, and stir for 10 min each time after each addition, with a total stirring time of 30 min to ensure the uniformity of the slurry; Then, add a certain mass of IPDI and continue to stir until the mixture is uniform; Next, pour the mixed slurry into a pre-prepared silicone mold and place it in a water bath oven at 60 °C for curing for 7 days; Finally, after it is cured and formed, take out the propellant strip for shaping treatment for subsequent processing and testing use.Figure 10 Table 4 shows the combustion process and burning rate results of the prepared HTPB composite solid propellants. Under the condition of propellant strips with the same length, the combustion time of the P1-P6 propellants with AO added is extended, and the corresponding burning rate results in Table 4 also decrease accordingly, indicating that the addition of AO does reduce the burning rate of the HTPB composite solid propellants. Among them, the propellant strip containing the AP-AO-5% composite particles has the longest combustion time. According to the data in Table 4, its burning rate is 1.02 mm / s, which is about 22.14% lower than that of the P0 propellant without AO added. This shows that the dispersion of AO in the embedded structure AP-AO composite particles is significantly enhanced, increasing the contact area with AP, thus making its effect of reducing the burning rate more remarkable.

[0071] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which does not affect the essence of the present invention.

Claims

1. A method for preparing embedded structure AP-AO composite particles, characterized in that: The steps include: Step 1: Disperse AO in DMF solution of AP; Step 2: Add ethyl acetate to the suspension in step 1 under stirring; Step 3: After filtration, vacuum drying is performed to obtain embedded structure AP-AO composite particles.

2. The method according to claim 1, characterized in that The concentration of AP in DMF solution is 0.8-1.0 g / mL.

3. The method according to claim 1, characterized in that The particle size of AO is 1 to 10 μm.

4. The method according to claim 1, characterized in that The dropping rate of ethyl acetate is 1-2 mL / min.

5. The method according to claim 1, characterized in that The volume ratio of DMF and ethyl acetate was 1:

10.

6. The method according to claim 1, characterized in that The vacuum drying temperature is 50-80°C and the time is more than 2 hours.

7. The method according to claim 1, characterized in that The mass percentage of AP and AO is (99~95):(1~5).

8. An embedded structure AP-AO composite particle prepared by the method according to any one of claims 1 to 7.

9. Use of the embedded structure AP-AO composite particles as claimed in claim 8 in HTPB composite solid propellant.

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