Preparation method of high-burning-rate high-oxygen-balance combustible shell

Abstract

This invention discloses a method for preparing a high-burning-rate, high-oxygen-balance combustible shell, comprising the following steps: Step 1, preparation of the shell composite material: 100 parts by mass of photosensitive resin binder, 1-5 parts by mass of photoinitiator, 80-140 parts by mass of solid oxidant, and 1-10 parts by mass of pore-forming agent are mixed uniformly to obtain the shell composite material; Step 2, preparation of the shell preform: The shell composite material is added to the material tank of a photopolymerization 3D printer for photopolymerization molding, with a layer thickness of 0.2-1.5 mm, photopolymerization is performed using a 260 nm-430 nm optomechanical module, with an exposure time of 1-5 s per layer and an exposure intensity of 5-50 mW / cm². 2 The process involves 3D printing to obtain a shell preform; step three, heating to create holes: after cleaning the combustible shell preform, it is placed in an oven and heated to create holes at a temperature of 70-120°C for 2-8 hours. This results in a high-burning-rate, high-oxygen-balance combustible shell. The method for preparing this high-burning-rate, high-oxygen-balance combustible shell achieves a unified balance of high burning rate, high oxygen balance, complete combustion, and structural stability.

Description

Technical Field

[0001] This invention belongs to the field of combustible shell manufacturing technology, and particularly relates to a method for preparing a high-burning-rate, high-oxygen-balance combustible shell. Background Technology

[0002] Combustible shells are used to contain energetic materials in the field of energetic materials, and they disappear through combustion, fragmentation, gasification, etc., as the energetic materials burn or explode, offering good serviceability during use. The formulation and preparation methods of combustible shells are a key research focus in this area. Current combustible shell molding technology requires first processing a mold, then using the mold and press to mold a mixture of polymer binders (such as polysulfone, polyurethane, polyvinyl alcohol formal, etc.) and energetic components (such as nitrocellulose, RDX, octogen, etc.) into a blank, followed by secondary processing on the blank. 3D printing technology has the advantages of rapid manufacturing, high flexibility, and integrated molding, making it a highly efficient manufacturing method. However, current 3D-printed combustible shells still suffer from disadvantages such as low combustion rate and low oxygen balance, resulting in more combustion residue and affecting safety during use. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention discloses a method for preparing a high-burning-rate, high-oxygen-balance combustible shell. By optimizing oxygen supply with an oxidant, constructing interconnected pores with a compound pore-forming agent, and precisely molding using a stepped temperature control process, these three methods work together to achieve a unified high-burning-rate, high-oxygen-balance, complete combustion, and structural stability in the combustible shell. This overcomes the technical difficulties of existing combustible shells, such as low burning rate, insufficient oxygen balance, excessive combustion residue, and difficulty in balancing porosity and strength.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a high-burning-rate, high-oxygen-balance combustible shell includes the following preparation steps: Step 1: Preparation of shell composite material. Mix 100 parts of photosensitive resin binder, 1-5 parts of photoinitiator, 80-140 parts of solid oxidant and 1-10 parts of pore-forming agent evenly according to the mass fraction to obtain shell composite material. Step two, shell preform preparation: The shell composite material is added to the material tank of a photopolymer 3D printer for photopolymerization molding. The layer thickness is 0.2~1.5 mm. Photopolymerization is performed using a 260 nm~430 nm optomechanical module, with an exposure time of 1~5 s per layer and an exposure intensity of 5~50 mW / cm². 2 The shell preform is obtained after 3D printing; Step 3: Heating and drilling. After cleaning the combustible shell blank, place it in an oven and heat it to drill holes. The heating temperature is 70~120℃ and the heating time is 2h~8h. After drilling, a high-burning-rate, high-oxygen-balanced combustible shell is obtained.

[0005] Furthermore, the photosensitive resin adhesive mentioned in step one is composed of one or more of the following: polyurethane-type photosensitive resin adhesive, epoxy-type photosensitive resin adhesive, polyester-type photosensitive resin adhesive, and unsaturated polyester-type photosensitive resin adhesive.

[0006] Furthermore, the solid oxidant mentioned in step one is one or a combination of several of the following: hexanitrohexaazaisopentane, 1,3,5-trinitro-1,3,5-triazacyclohexane, 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane, ammonium perchlorate, and potassium perchlorate.

[0007] Furthermore, the porogen mentioned in step one is a high-temperature decomposition porogen or a solvent-based porogen. The high-temperature decomposition porogen is one or more of ammonium carbonate, sodium bicarbonate, azobisisobutyronitrile, and sodium hydrogen phosphate, and the solvent-based porogen is one or more of benzene, toluene, dichloromethane, and ethyl acetate.

[0008] Furthermore, the photoinitiator mentioned in step one is one or a mixture of several of ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), and phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (XBPO).

[0009] Furthermore, the optomechanical module mentioned in step two is a surface projection digital light processing module.

[0010] Furthermore, the heating rate in step three is 1-5℃ / min.

[0011] Furthermore, the particle size of the solid oxidant ranges from 5 to 100 μm.

[0012] Furthermore, the particle size range of the high-temperature decomposition porogen is 20~100μm.

[0013] The present invention discloses a method for preparing a high-burning-rate, high-oxygen-balance combustible shell. The addition of an oxidant to the combustible shell composite material can greatly improve the combustion rate and oxygen balance of the combustible shell. The addition of a pore-forming agent can create pores in the preform of the combustible shell by heating without changing the geometric dimensions of the combustible shell. During the heating process, the pore-forming agent decomposes or volatilizes, forming a rich pore structure in the preform with a porosity of over 50%. This method ensures the forming accuracy of 3D printing while effectively improving the propagation speed of the flame inside the combustible shell, which can increase the oxygen balance of the combustible shell by more than 10% and the combustion rate by more than 100%.

[0014] In this invention, the porogen does not simply create pores. More importantly, it constructs a connected gradient pore network to directionally regulate the distribution, decomposition sequence, and oxygen release rate of the oxidant. This allows for precise matching between the oxygen release of the oxidant and the thermal decomposition of the matrix. Simultaneously, the pyrolysis products of the porogen undergo a secondary chemical reaction with the oxidant, resulting in secondary oxygen replenishment and activation of the combustion interface. This further enhances the oxygen utilization rate of the system and activates the combustion interface, achieving high-energy, stable, and controllable combustion. While achieving high combustion performance, it also provides multiple unexpected technical effects such as controllable combustion rate, stable combustion, reliable ignition over a wide temperature range, and improved oxygen utilization.

[0015] Conventional high-oxygen formulations tend to cause residues to melt and agglomerate after combustion, clogging pores and hindering subsequent combustion. This patented pore structure, combined with a uniformly distributed oxidant, results in loose and porous residues that are less prone to agglomeration. It continuously releases residual oxygen, significantly improving oxygen balance utilization compared to conventional simple addition methods. This inhibits residue agglomeration and enhances oxygen balance utilization efficiency.

[0016] This invention discloses a method for preparing a high-burning-rate, high-oxygen-balance combustible shell. The formulation and process are highly compatible, and the heating temperature range matches the decomposition / volatilization temperature of the pore-forming agent, the heat resistance temperature of the matrix, and the stability temperature of the oxidant. There are no conflicts between process parameters and the formulation system. The pore-forming process is mild and controllable, with high yield and good performance repeatability. The pore-forming process leaves no harmful solid residues, the combustion products are clean, and the shell combustion efficiency and energy release rate are significantly improved. At the same time, it has good formability and structural strength, and compared with the prior art, it has higher application value and industrial feasibility. Attached Figure Description

[0017] Figure 1 Photograph of the internal pores of the combustible shell prepared for this invention.

[0018] Figure 2 Photograph of the combustible shell prepared for this invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0020] Unless otherwise specified, the terms, methods, or processes used in this document are based on the understanding of those skilled in the art or are implemented using existing methods or processes. Commercially available 3D printing equipment, especially SLA 3D printing (photopolymerization) equipment equipped with a 405nm ultraviolet light source, is applicable to this invention. Example

[0021] A method for preparing a high-burning-rate, high-oxygen-balance combustible shell includes the following steps: Step 1: Preparation of shell composite material. 100 parts by mass of polyurethane photosensitive resin binder, 1 part of ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), 100 parts of ammonium perchlorate with an average particle size of 20 μm, 20 parts of potassium nitrate with an average particle size of 5 μm, and 5 parts of azobisisobutyronitrile with an average particle size of 50 μm are mixed evenly to obtain the shell composite material. Step two, shell preform preparation: The printing composite is added to the material tank of the photopolymer 3D printer for photopolymerization molding, with a layer thickness of 0.2 mm. Photopolymerization is performed using a 260nm optomechanical module, with an exposure time of 1 second per layer and an exposure intensity of 5 mW / cm². 2 After 3D printing, a combustible shell blank is obtained; Step 3: Heating to create holes. After cleaning the printed combustible shell blank, place it in an oven for heating to create holes. The heating temperature is 70℃, the heating time is 8 hours, and the heating rate is 1℃ / min. After the treatment, a high-burning-rate combustible shell is obtained.

[0022] The high-burning-rate, high-oxygen-balance combustible shell prepared in this embodiment was tested for burning rate using an explosion device, and the oxygen balance of the combustible shell material was calculated. The algorithm was as follows: Oxygen balance = (Number of oxygen atoms in the material - Number of oxygen atoms required for all carbon to be oxidized to carbon dioxide - Number of oxygen atoms required for all hydrogen to be oxidized to water) × 1600 / Molar mass of the material. The burning rate of the combustible shell was 15.8 cm / s, which is more than 10 times higher than that of ordinary products, and the oxygen balance was -51.41%, which is more than 10% higher than that of ordinary products. Example

[0023] A method for preparing a high-burning-rate, high-oxygen-balance combustible shell includes the following steps: Step 1: Preparation of shell composite material. 100 parts by mass fraction of epoxy photosensitive resin binder, 5 parts by mass fraction of ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), 80 parts by mass fraction of hexanitrohexaazaisopentane with an average particle size of 50 μm, 20 parts by mass fraction of potassium nitrate with an average particle size of 100 μm, and 5 parts by mass fraction of azobisisobutyronitrile with an average particle size of 100 μm are mixed evenly to obtain the shell composite material. Step two, shell preform preparation: The printing composite is added to the material tank of the photopolymer 3D printer for photopolymerization molding, with a layer thickness of 1.5 mm. Photopolymerization is performed using a 430 nm optomechanical module, with an exposure time of 5 seconds per layer and an exposure intensity of 50 mW / cm². 2 After 3D printing, a combustible shell blank is obtained; Step 3: Heating to create holes. After cleaning the printed combustible shell blank, place it in an oven for heating to create holes. The heating temperature is 120℃, the heating time is 2 hours, and the heating rate is 5℃ / min. After the treatment, a high-burning-rate combustible shell is obtained.

[0024] The high-burning-rate, high-oxygen-balance combustible shell prepared in this embodiment was tested for burning rate using an explosion device, and the oxygen balance of the combustible shell material was calculated. The algorithm was as follows: Oxygen balance = (Number of oxygen atoms in the material - Number of oxygen atoms required for all carbon to be oxidized into carbon dioxide - Number of oxygen atoms required for all hydrogen to be oxidized into water) × 1600 / Molar mass of the material. The burning rate of the combustible shell was 18.7 cm / s, which is more than 10 times higher than that of ordinary products, and the oxygen balance was -49.01%, which is more than 10% higher than that of ordinary products. Example

[0025] A method for preparing a high-burning-rate, high-oxygen-balance combustible shell includes the following steps: Step 1: Preparation of shell composite material. 100 parts by mass of unsaturated polyester photosensitive resin, 3 parts by mass of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 60 parts by mass of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane with an average particle size of 50 μm, 50 parts by mass of potassium nitrate with an average particle size of 80 μm, and 5 parts by mass of ethyl acetate are mixed evenly to obtain the shell composite material. Step two, shell preform preparation: The printing composite is added to the material tank of the photopolymer 3D printer for photopolymerization molding, with a layer thickness of 0.8 mm. Photopolymerization is performed using a 420 nm optomechanical module, with an exposure time of 3 seconds per layer and an exposure intensity of 26 mW / cm². 2 After 3D printing, a combustible shell blank is obtained; Step 3: Heating to create holes. After cleaning the printed combustible shell blank, place it in an oven for heating to create holes. The heating temperature is 100℃, the heating time is 4 hours, and the heating rate is 3℃ / min. After the treatment, a high-burning-rate combustible shell is obtained.

[0026] The high-burning-rate, high-oxygen-balance combustible shell prepared in this embodiment was tested for burning rate using an explosion device, and the oxygen balance of the combustible shell material was calculated. The algorithm was as follows: Oxygen balance = (Number of oxygen atoms in the material - Number of oxygen atoms required for all carbon to be oxidized into carbon dioxide - Number of oxygen atoms required for all hydrogen to be oxidized into water) × 1600 / Molar mass of the material. The burning rate of the combustible shell was 22.5 cm / s, which is more than 10 times higher than that of ordinary products, and the oxygen balance was -57.09%, which is more than 10% higher than that of ordinary products.

[0027] Comparative Example 1: This comparative example differs from Example 3 in that the ethyl acetate content in step 1 is 0, while the other steps and parameters are exactly the same as in Example 3, resulting in a flammable shell.

[0028] Comparative Example 2: This comparative example is another flammable shell manufactured using traditional processes (pressed out using molds), and its components are nitrocellulose sheets.

[0029] Comparative Example 3: This comparative example is another flammable shell manufactured using traditional processes (pressed out using molds), and its component is celluloid.

[0030] Table 1 compares the combustible shells prepared in Examples 1-3 with those prepared by conventional processes. Table 1 shows the comparison of combustion rate and oxygen balance of the combustible shells in the examples and comparative examples.

[0031] Table 1

[0032] As shown in Table 1, compared with common combustible shells, the oxygen balance of the combustible shell obtained by the present invention is improved by more than 10%. In addition, compared with the combustible shells of the present invention with and without pore-forming agents, under the premise of the same oxygen balance, the combustion rate of the combustible shell sample with pore-forming agents is increased by more than 10 times.

[0033] Those skilled in the art should understand that the above description is merely a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-burning-rate, high-oxygen-balance combustible shell, characterized in that, The preparation steps include the following: Step 1: Preparation of shell composite material. Mix 100 parts of photosensitive resin binder, 1-5 parts of photoinitiator, 80-140 parts of solid oxidant and 1-10 parts of pore-forming agent evenly according to the mass fraction to obtain shell composite material. Step two, shell preform preparation: The shell composite material is added to the material tank of a photopolymer 3D printer for photopolymerization molding. The layer thickness is 0.2~1.5 mm. Photopolymerization is performed using a 260 nm~430 nm optomechanical module, with an exposure time of 1~5 s per layer and an exposure intensity of 5~50 mW / cm². 2 The shell preform is obtained after 3D printing; Step 3: Heating and drilling. After cleaning the combustible shell blank, place it in an oven and heat it to drill holes. The heating temperature is 70~120℃ and the heating time is 2h~8h. After drilling, a high-burning-rate, high-oxygen-balanced combustible shell is obtained.

2. The method for preparing a high-burning-rate, high-oxygen-balance combustible shell according to claim 1, characterized in that, The photosensitive resin adhesive mentioned in step one is composed of one or more of the following: polyurethane photosensitive resin adhesive, epoxy photosensitive resin adhesive, polyester photosensitive resin adhesive, and unsaturated polyester photosensitive resin adhesive.

3. The method for preparing a high-burning-rate, high-oxygen-balance combustible shell according to claim 1, characterized in that, The solid oxidant mentioned in step one is one or a combination of several of the following: hexanitrohexaazaisopentane, 1,3,5-trinitro-1,3,5-triazacyclohexane, 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane, ammonium perchlorate, and potassium perchlorate.

4. The method for preparing a high-burning-rate, high-oxygen-balance combustible shell according to claim 1, characterized in that, The porogen mentioned in step one is a high-temperature decomposition porogen or a solvent-based porogen. The high-temperature decomposition porogen is one or more of ammonium carbonate, sodium bicarbonate, azobisisobutyronitrile, and sodium hydrogen phosphate. The solvent-based porogen is one or more of benzene, toluene, dichloromethane, and ethyl acetate.

5. The method for preparing a high-burning-rate, high-oxygen-balance combustible shell according to claim 1, characterized in that, The photoinitiator mentioned in step one is one or a mixture of several of ethyl 2,4,6-trimethylbenzoylphenylphosphonate (TPO-L), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), and phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (XBPO).

6. The method for preparing a high-burning-rate, high-oxygen-balance combustible shell according to claim 1, characterized in that, The optomechanical module mentioned in step two is a surface projection type digital light processing module.

7. The method for preparing a high-burning-rate, high-oxygen-balance combustible shell according to claim 1, characterized in that, The heating rate in step three is 1-5℃ / min.

8. The method for preparing a high-burning-rate, high-oxygen-balance combustible shell according to claim 3, characterized in that, The particle size of the solid oxidant ranges from 5 to 100 μm.

9. The method for preparing a high-burning-rate, high-oxygen-balance combustible shell according to claim 4, characterized in that, The particle size range of the high-temperature decomposition porogen is 20~100μm.

Images