Casting type low-cost thermoplastic solid propellant and preparation method thereof

Abstract

The invention belongs to the technical field of composite solid propellants, and provides a fusion casting type low-cost thermoplastic composite solid propellant and a preparation method of the fusion casting type low-cost thermoplastic composite solid propellant. 10-20% of a thermoplastic elastomer adhesive; 3-20% of a plasticizer; 5-20% of a metal fuel; and 0-5% of an auxiliary agent. The functional additive is at least one of a process additive and a combustion performance regulator, and the metal fuel is spherical aluminum powder or zirconium carbide powder. According to the prepared thermoplastic composite solid propellant, mixing and pouring can be independently carried out, melt mixing and forming can be achieved at the low temperature (95 DEG C), safety is high, waste products can be recycled and repeatedly processed, the used raw materials are common chemical products in the market, and cost is low. And by adopting a similar casting explosive preparation process, casting explosive equipment can be directly applied, the preparation process is relatively mature, and batch manufacturing of the thermoplastic propellants can be rapidly carried out.

Description

Technical Field

[0001] The invention belongs to the technical field of composite solid propellants, and specifically relates to a melt-cast type low-cost thermoplastic solid propellant and a preparation method thereof. The melt-cast type is used as a thermoplastic propellant in melt-cast explosives. Background Art

[0002] Thermoplastic solid propellant is a type of composite solid propellant that uses thermoplastic elastomers as adhesives. It has the characteristics of repeated processing and molding, low scrap rate and low cost. It avoids the limitations of the "applicability period" of traditional thermosetting propellant slurry, can be cured at room temperature in a short time, and has broad application prospects. Summary of the invention

[0003] The present invention provides a melt-cast low-cost thermoplastic solid propellant and a preparation method thereof. The propellant has a reasonable formula composition, simple product production steps, short production cycle, high production efficiency, low raw material cost, and a solid content of more than 80%. It adopts a melt-cast explosive-like preparation process, has high technical maturity, and the prepared propellant has broad application prospects.

[0004] The present invention is realized by the following technical scheme: a melt-cast low-cost thermoplastic solid propellant, comprising the following components in mass percentage: 55%-72% oxidizer; 10%-20% thermoplastic binder; 10%-20% plasticizer; 5%-20% metal fuel; 0-5% auxiliary agent; Wherein: the oxidant is one or a mixture of two or more of ammonium nitrate, ammonium perchlorate, dinitramide, hexachlorobenzene, and octogenin in any proportion; The thermoplastic adhesive is ethylene-vinyl acetate copolymer, and the brand is any one of 28800, 28400, 7470M, 7360M, 633, 710, and 715; The plasticizer is one or a mixture of two or more of dioctyl sebacate, dimethyl phthalate, isopentyl phthalate, diisooctyl sebacate, dibutyl adipate, dibutyl phthalate, diethyl phthalate, butyl benzyl phthalate, and dioctyl adipate in any proportion; The metal fuel is one of aluminum powder and zirconium carbide or a mixture of the two in any proportion; The auxiliary agent is one or a mixture of two or more of talc, stearic acid, octylferrocene, n-butylferrocene and diethylferrocene, carbon black, ferric oxide, catocene and lead sulfide in any proportion.

[0005] Furthermore, it comprises the following components in percentage by weight: 60%-65% oxidant; 10%-15% thermoplastic adhesive; 10%-15% plasticizer; 10%-15% metal fuel; 0-5% auxiliary agent; the thermoplastic adhesive is ethylene-vinyl acetate copolymer, with a grade of 28800.

[0006] The metal fuel is any one of spherical aluminum powder and zirconium carbide powder. The particle size of the spherical aluminum powder is 25 μm, and the particle size of the zirconium carbide is 5 μm.

[0007] The oxidant is ammonium perchlorate AP, and the ammonium perchlorate is composed of three particle size gradations, wherein the first-level ammonium perchlorate particle size is distributed from 5 μm to 15 μm, and the average particle size is 10 μm; the second-level ammonium perchlorate particle size is distributed from 300 μm to 400 μm, and the average particle size is 350 μm; the third-level ammonium perchlorate particle size is distributed from 600 μm to 800 μm, and the average particle size is 700 μm; wherein the AP content of the first-level particle size is 10%-17% of the mass of the thermoplastic propellant, the AP content of the second-level particle size is 15%-25% of the mass of the thermoplastic propellant, and the AP content of the third-level particle size is 25%-40% of the mass of the thermoplastic propellant.

[0008] The method for preparing the melt-cast low-cost thermoplastic solid propellant comprises the following steps: (1) Heating the thermoplastic adhesive; (2) adding the plasticizer and the process aid to the thermoplastic adhesive heated and melted in step (1), and continuing to heat and stir to mix evenly; (3) Add metal fuel and stir for 10 minutes to mix evenly; (4) Finally, add the oxidant in batches and stir to mix evenly; (5) The slurry or strip obtained in step (4) is heated and vacuum-casted, and then allowed to stand for molding to obtain a thermoplastic composite solid propellant.

[0009] The heating temperature in steps (1) to (5) is 90 to 105° C.; in steps (2) to (4), the stirring time is 60 to 110 minutes; in step (5), vacuum pouring is performed into a mold or into an engine, and then the mixture is placed at room temperature to solidify.

[0010] The heating temperature in step (1) is 95°C; the heating temperature in step (2) is 105°C, and the stirring time is 60 minutes.

[0011] The drug slurry of the present invention can be filled into the mold by two methods. One is to first pour the drug slurry into a suitable mold to form a drug strip or a drug block. When filling is required, the drug strip is placed into the mold and heated under vacuum conditions. The drug block is melted and leveled and then solidified at room temperature. The other is to use vacuum pouring into the mold or pouring into the engine during pouring, and then solidifying at room temperature.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: Under a certain solid content, the reasonable gradation of AP can significantly reduce its apparent viscosity and obtain a higher thermoplastic propellant density (>1.6g / cm 3 Thermoplastic propellants prepared using energy-free thermoplastic elastomers as binders have low mechanical sensitivity and high safety in the preparation process.

[0013] The invention optimizes the formula of the thermoplastic propellant by adjusting the gradation of ammonium perchlorate in the thermoplastic propellant, thereby effectively improving the molding processing technology and combustion performance of the propellant.

[0014] The raw materials used to prepare thermoplastic propellants have all been domestically produced, with high technical maturity, low price, good quality consistency, simple preparation process of thermoplastic propellants, good repeatability, and easy to achieve industrial production. Thermoplastic propellants are prepared using a similar melt-cast explosive preparation process. The relevant equipment and processes can be used universally, and the technical maturity growth period is fast, which greatly reduces the cost of propellant production and research and development. Thermoplastic propellants with thermoplastic elastomers as adhesives have repeatable processing properties, which can achieve continuous propellant production and zero scrap rate, thereby improving the production efficiency of propellants and reducing the cost of propellant production. It can greatly shorten the process flow and reduce process costs.

[0015] On the basis of ensuring the normal melt-casting preparation process, the present invention tests out a thermoplastic propellant formula with reasonable viscosity by optimizing the plasticizing system, reasonable particle size distribution, and the influence of stearic acid on the viscosity of the propellant formula, and explores the change law of solid content and thermoplastic elastomer content and the law of mechanical properties, and further optimizes and designs the thermoplastic propellant formula. The melt-casting thermoplastic propellant formula provided by the present invention is sufficient to meet the melt-casting preparation conditions, and can directly refer to the melt-casting explosive production equipment and process, making sufficient preparations for the batch preparation of thermoplastic propellants. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The process flow chart for preparing melt-cast thermoplastic composite solid propellant; Figure 2 It is the viscosity of various plasticizers mixed with EVA; Figure 3 It is the viscosity of various waxes mixed with EVA; Figure 4 This is the surface image after adding stearic acid; Figure 5It is the heating leveling diagram of the propellant slurry; Figure 6 The thermoplastic composite solid propellant obtained in Example 2 of the present invention; Figure 7 These are the appearance diagrams before and after the thermal stability test of Examples 2 and 3 of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0018] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and the disclosure and materials cited therein are hereby incorporated by reference.

[0019] Technical equivalents to the specific embodiments described that are apparent to those skilled in the art using no more than routine experimentation are intended to be encompassed by this application.

[0020] The experimental methods in the following examples are all conventional methods unless otherwise specified. The instruments and equipment used in the following examples are all conventional laboratory instruments and equipment unless otherwise specified; the experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified.

[0021] A melt-cast low-cost thermoplastic solid propellant comprises an oxidizer, a thermoplastic adhesive, a plasticizer, a metal fuel and an auxiliary agent, with the total mass of the solid propellant being 100%.

[0022] Example 1: Composition of thermoplastic composite solid propellant (mass percentage): binder (EVA28800): 21.4%; oxidizer (ammonium perchlorate): 56%; plasticizer (dioctyl sebacate): 7.2%; metal fuel (aluminum powder): 12%; additive (stearic acid): 1%.

[0023] The preparation process comprises: weighing an oxidant, an adhesive, a plasticizer, a metal fuel, and an additive according to the ratio; melting the adhesive in an oil bath under heating, the melting temperature being 95° C.; The remaining weighed components are placed in a beaker and mixed at a mixing temperature of 105°C for 40 to 60 minutes to obtain a slurry; the slurry is directly poured into a mold or into an engine, heated for 2 hours to eliminate bubbles, and then placed at room temperature to solidify.

[0024] Properties of thermoplastic composite solid propellant: density: 1.50g / cm3; melting point: 81~83℃; maximum tensile strength (25℃): 1.20MPa; maximum elongation (25℃): 3.58%; elongation at break (25℃): 6.1%.

[0025] Example 2: Composition of thermoplastic composite solid propellant (mass percentage): binder (EVA633): 15%; oxidizer (first-grade ammonium perchlorate): 15%; oxidizer (second-grade ammonium perchlorate): 20%; oxidizer (third-grade ammonium perchlorate): 30%; plasticizer (dioctyl sebacate): 4%; metal fuel (aluminum powder): 15%; additive (cartosine): 1%. The preparation method is the same as that of Example 1.

[0026] Properties of thermoplastic composite solid propellant: density: 1.66g / cm3; melting point: 84~86℃; maximum tensile strength (25℃): 1.3MPa; maximum elongation (25℃): 3.1%; elongation at break (25℃): 4%.

[0027] Example 3: Composition of thermoplastic composite solid propellant (mass percentage): binder (EVA28400): 13.5%; oxidizer (first-grade ammonium perchlorate): 15%; oxidizer (second-grade ammonium perchlorate): 20%; oxidizer (third-grade ammonium perchlorate): 30%; plasticizer (dioctyl sebacate): 3.5%; metal fuel (aluminum powder): 12%; additive (cartosine): 1%. The preparation method is the same as that of Example 1.

[0028] Thermoplastic composite solid propellant properties: density: 1.68g / cm3; maximum tensile strength (25℃): 1.34MPa; maximum elongation (25℃): 2.8%; elongation at break (25℃): 3.9%.

[0029] Example 4: Composition of thermoplastic composite solid propellant (mass percentage): Binder (EVA710): 12%; Oxidant (ammonium perchlorate with primary particle size): 12%; Oxidant (ammonium perchlorate with secondary particle size): 16%; Oxidant (ammonium perchlorate with tertiary particle size): 28%; Plasticizer (dioctyl sebacate): 3.5%; Metal fuel (aluminum powder): 13.5%; Metal fuel (chromium carbide): 15%; Preparation method is the same as Example 1.

[0030] Properties of thermoplastic composite solid propellant: density: 1.85g / cm3; melting point: 81~83℃; maximum tensile strength (25℃): 1.4MPa; maximum elongation (25℃): 2.31%; elongation at break (25℃): 3.55%.

[0031] Both Example 2 and Example 3 were subjected to thermal stability tests and did not burn or explode after continuous heating at 100°C for 96 hours. After heating for 48 hours, Example 2 lost 2.95% of its mass, while Example 3 lost 0.245% of its mass. After continuous heating for another 48 hours, Example 2 lost 0.045% of its mass, while Example 3 lost 0.005% of its mass.

[0032] The thermal stability test method is based on the 100°C heating method in accordance with GJB5383.13 Pyrotechnic Composition Sensitivity and Stability Test Method.

[0033] The sensitivity of the molten slurry was simulated and tested. Example (2) conducted impact and friction sensitivity tests at 110°C. The impact sensitivity test conditions were 5kg drop hammer, 25cm, and explosion probability was 0; the friction sensitivity test conditions were 90°, 3.92Mpa, and explosion probability was 4%, indicating that the slurry mixing process is highly safe.

[0034] The present invention experimentally designs thermoplastic propellant formulations with different solid contents, and measures the mechanical properties of propellants with different solid contents, as shown in Table 1.

[0035] Table 1 It can be seen from Table 1 that when the solid content reaches 70%, the elongation is only about 3%. The higher the EVA content, the better the mechanical properties. The presence of bubbles in the grain sample may affect the mechanical properties of the sample, but the most important result is the weakening of the force between the molecular chains of the elastomer itself under the action of a large amount of plasticizers. The mechanical properties of the thermoplastic propellant are poor without adding other process additives.

[0036] At the same time, it can be seen from the table that the sample without stearic acid has the best mechanical properties. The content of stearic acid is inversely proportional to the mechanical properties. As the content of stearic acid increases, the mechanical properties of the sample decrease. 5 mPa•s, and the viscosity decreased to 1.39×10 5 mPa•s, indicating that the viscosity decreases more after adding stearic acid, and more EVA can be added under the same conditions. During the test, it was found that when only plasticizer was added, the viscosity would be relatively higher, and the mold would stick during the processing and cooling process, making it difficult to demold, resulting in a rough surface. During the sample preparation process, it was found that the fluidity was better after adding stearic acid, and demolding was simple, and the sample surface was smooth. Figure 4 . Due to its external lubrication characteristics, the surface of the sample after molding can be made smoother, which is conducive to demolding and subsequent processing. In order to improve the processing integrity without affecting the mechanical properties, the content of stearic acid is reduced and the proportion is controlled to about 1%. At the same time, the content of EVA is increased. At this ratio, the viscosity can be reduced and the overall mechanical properties are also slightly affected. A trace amount of stearic acid is added to the formula to improve the processing conditions.

[0037] Figure 5 This is a state change diagram of the propellant slurry gradually leveling under heating conditions. When formulating thermoplastic propellants, it is necessary to ensure that the propellant slurry has fluidity. When the solid content reaches 70%, the insulation temperature is 100°C. It can be seen from the figure that the fluidity of this formula slurry can meet the requirements of casting.

[0038] Figure 6 The powder block for burning rate test and dumbbell-shaped specimen for mechanical test prepared by the formula of Example 2, whether the burning rate catalyst is added will change its color. This thermoplastic propellant specimen is prepared by melt casting. It can be seen from the figure that the prepared propellant specimens have uniform surface, uniform color, no obvious defects, and high uniformity of mixing of each component. It meets the requirement of maintaining structural integrity at a solid content of 80%.

[0039] Figure 7 This is a graph of the changes before and after the test according to the 100°C heating method of GJB 5383.13 pyrotechnics sensitivity and stability test method. As can be seen from the figure, the surface of the propellant will turn black after continuous high-temperature heating for 100 hours, and the blackening signs inside are not obvious, indicating that it mainly reacts with the part in contact with the air. According to the physical and chemical properties of its internal components, its mass loss is basically EVA, and some EVA may react with oxygen in the air under long-term high-temperature heating. In addition, there may be a very small amount of moisture inside the propellant, which will evaporate at high temperature. In addition, the added burning rate catalyst will migrate and oxidize to a certain extent, which has no effect on the normal use of thermoplastic propellants.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A melt-cast low-cost thermoplastic solid propellant, characterized in that: The composition comprises the following components in percentage by weight: 55%-72% oxidant; 10%-20% thermoplastic adhesive; 10%-20% plasticizer; 5%-20% metal fuel; 0-5% auxiliary agent; Wherein: the oxidant is one or a mixture of two or more of ammonium nitrate, ammonium perchlorate, dinitramide, hexachlorobenzene, and octogenin in any proportion; The thermoplastic adhesive is ethylene-vinyl acetate copolymer, and the brand is any one of 28800, 28400, 7470M, 7360M, 633, 710, and 715; The plasticizer is one or a mixture of two or more of dioctyl sebacate, dimethyl phthalate, isopentyl phthalate, diisooctyl sebacate, dibutyl adipate, dibutyl phthalate, diethyl phthalate, butyl benzyl phthalate, and dioctyl adipate in any proportion; The metal fuel is one of aluminum powder and zirconium carbide or a mixture of the two in any proportion; The auxiliary agent is one or a mixture of two or more of talc, stearic acid, octylferrocene, n-butylferrocene and diethylferrocene, carbon black, ferric oxide, catocene and lead sulfide in any proportion.

2. A melt-cast low-cost thermoplastic solid propellant according to claim 1, characterized in that: The invention comprises the following components in percentage by weight: 60%-65% oxidant; 10%-15% thermoplastic adhesive; 10%-15% plasticizer; 10%-15% metal fuel; and 0-5% auxiliary agent. The thermoplastic adhesive is ethylene-vinyl acetate copolymer with the brand number of 28800.

3. A melt-cast low-cost thermoplastic solid propellant according to claim 1 or 2, characterized in that: The metal fuel is any one of spherical aluminum powder and zirconium carbide powder. The particle size of the spherical aluminum powder is 25 μm, and the particle size of the zirconium carbide is 5 μm.

4. A melt-cast low-cost thermoplastic solid propellant according to claim 1 or 2, characterized in that: The oxidant is ammonium perchlorate AP, and the ammonium perchlorate is composed of three particle size distributions. The first-level ammonium perchlorate particle size is distributed from 5μm to 15μm, and the average particle size is 10μm; the second-level ammonium perchlorate particle size is distributed from 300μm to 400μm, and the average particle size is 350μm; the third-level ammonium perchlorate particle size is distributed from 600μm to 800μm, and the average particle size is 700μm; The AP content of the first-level particle size is 10%-17% of the mass of the thermoplastic propellant, the AP content of the second-level particle size is 15%-25% of the mass of the thermoplastic propellant, and the AP content of the third-level particle size is 25%-40% of the mass of the thermoplastic propellant.

5. A method for preparing the melt-cast low-cost thermoplastic solid propellant according to claim 1 or 2, characterized in that: The steps include: (1) Heating the thermoplastic adhesive; (2) adding the plasticizer and the process aid to the thermoplastic adhesive heated and melted in step (1), and continuing to heat and stir to mix evenly; (3) Add metal fuel and stir for 10 minutes to mix evenly; (4) Finally, add the oxidant in batches and stir to mix evenly; (5) The slurry or strip obtained in step (4) is heated and vacuum-casted, and then allowed to stand for molding to obtain a thermoplastic composite solid propellant.

6. The preparation method according to claim 5, characterized in that: The heating temperature in steps (1) to (5) is 90 to 105° C.; in steps (2) to (4), the stirring time is 60 to 110 minutes; in step (5), vacuum pouring is performed into a mold or into an engine, and then the mixture is placed at room temperature to solidify.

7. The preparation method according to claim 6, characterized in that: The heating temperature in step (1) is 95°C; the heating temperature in step (2) is 105°C, and the stirring time is 60 minutes.

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