Method for eliminating moisture in composite solid propellant

Abstract

The invention discloses a method for eliminating moisture in a composite solid propellant. According to the specific technical scheme, the method comprises the following steps: weighing an adhesive, a plasticizer, a bonding agent, a chain extender and a cross-linking agent into a propellant premixing pot; putting the premixing pot into a water bath oven for heating; uniformly stirring the mixture in the premixing pot, and taking out the mixture from the water bath oven; adding oxazolidine into the premixing pot, and uniformly stirring; adding the spherical aluminum powder into the premixing pot, and uniformly stirring; starting a mixing machine, and pouring the premixed slurry in the premixing pot into a mixing pot of the mixing machine; adding the ammonium perchlorate mixture into a mixing pot of the mixing machine at the same time, heating and stirring; adding a curing agent into a mixing pot of the mixing machine, controlling the temperature of the mixing pot of the mixing machine to be 60 + / -2 DEG C, and stirring for 60-90 minutes to form propellant discharging slurry; and the propellant discharging slurry is poured into a mold to be cured. The oxazolidine substance is added to eliminate moisture in the solid propellant, so that the mechanical property, especially the tensile strength, of the propellant is improved.

Description

Technical Field

[0001] This invention belongs to the field of solid propellant technology, and particularly relates to a method for eliminating moisture in composite solid propellants. Background Technology

[0002] Composite solid propellants are energetic materials formed through chemical reactions, with oxidants, binders, and metallic fuels as the main components. They are the power source for various solid rocket and missile engines, and their performance directly affects the combat effectiveness and reliability of rocket and missile weapons.

[0003] Currently, composite solid propellants are mostly cured using isocyanate curing agents. The isocyanate groups in the curing agent react with the hydroxyl groups in the binder, chain extender, and crosslinking agent to generate urethane groups, ultimately forming a crosslinked cured network, resulting in a composite solid propellant with certain mechanical properties. However, this curing method, where hydroxyl groups react with isocyanates to generate carbon dioxide gas, can lead to porosity and cracks in the finished product. The most effective method for eliminating moisture in composite solid propellants is controlling the moisture content of the raw materials. These raw materials generally need to be dried beforehand, and their moisture content must be strictly monitored during storage. Furthermore, vacuum mixing and vacuum casting during propellant manufacturing can remove the carbon dioxide gas generated by the moisture reaction, reducing the impact of moisture on the propellant. While drying effectively controls porosity and cracks in the final propellant, it consumes significant human and material resources. Materials with high moisture content, such as ADN and GAP, face significant challenges in moisture control, hindering their widespread application in propellants. Summary of the Invention

[0004] To address the above problems, this invention provides a method for eliminating moisture in composite solid propellants, the specific technical solution of which is as follows:

[0005] Step 1: Weigh the adhesive, plasticizer, bonding agent, chain extender, and crosslinking agent into the propellant premixing pot; place the premixing pot in a water bath oven and heat it.

[0006] The second step is to stir the mixture in the premixing pot evenly and remove it from the water bath oven; add oxazolidine to the premixing pot and stir evenly; then add spherical aluminum powder to the premixing pot and stir evenly to form a premixed slurry;

[0007] The third step is to turn on the mixer and pour the premixed slurry from the premixing pot into the mixing pot of the mixer; add the ammonium perchlorate mixture into the mixing pot of the mixer at the same time; control the temperature of the mixing pot of the mixer at 60℃±2℃ and stir for 40 to 60 minutes; at this time, oxazolidine will fully react with the moisture in the raw materials during the stirring process to form alkanolamines or polyols.

[0008] The fourth step is to add the curing agent to the mixing pot of the mixer, control the temperature of the mixing pot at 60℃±2℃, and continue stirring for 60 to 90 minutes to form a propellant discharge slurry; at this time, the polyol or alkanolamine product of the reaction between oxazolidine and water acts as a chain extender and crosslinking agent, and together with the original binder, chain extender, and crosslinking agent, it initially reacts with the curing agent.

[0009] The fifth step involves pouring the propellant slurry into a mold and placing it in an oven at 50-60°C for curing. At this time, the polyol or alkanolamine product of the reaction between oxazolidine and water acts as a chain extender and crosslinking agent, and together with the original adhesive, chain extender, and crosslinking agent, it further reacts with the curing agent to form a thermosetting elastomer with high solids content.

[0010] Furthermore, the oxazolidinone is synthesized from ketones and ethanolamine derivatives, has high sensitivity to water, and contains monocyclic or bicyclic oxazolidinones.

[0011] Furthermore, the monocyclic oxazolidine is 4,4-dimethyloxazolidine or 3-hydroxyethyloxazolidine or a compound having the corresponding oxazolidine structure.

[0012] Furthermore, the bicyclic oxazolidine is 7-ethylbicyclic oxazolidine or a compound with the corresponding oxazolidine structure.

[0013] Furthermore, the amount of oxazolidine added needs to be calculated based on the total moisture content in the propellant.

[0014] Furthermore, the casting method in the fifth step is vacuum casting.

[0015] Furthermore, the amount of curing agent added includes the amount of curing agent required by the propellant and the amount of curing agent consumed by oxazolidine.

[0016] Furthermore, the aluminum powder mentioned in the second step is spherical aluminum powder.

[0017] Furthermore, the ammonium perchlorate mixture mentioned in the third step is prepared by compounding ammonium perchlorates of 40-60 mesh, 100-140 mesh, and 8-11 μm specifications in a certain proportion.

[0018] The principle behind oxazolidine's removal of water is as follows:

[0019] Adding oxazolidine can effectively remove moisture from composite solid propellants and generate β-alcoholic amines; the β-alcoholic amines react with the curing agent in the propellant.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0021] This invention eliminates pores and cracks caused by moisture in solid propellants by adding oxazolidine substances to composite solid propellants and using chemical reactions to eliminate moisture and isocyanate reactions, thereby improving the mechanical properties of the propellants, especially tensile strength. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic diagram illustrating the chemical reaction principle of oxazolidine for removing moisture in a method for eliminating moisture in composite solid propellants provided by this invention.

[0024] Figure 2 A schematic diagram of a cured film for a method of eliminating moisture in a composite solid propellant provided by the present invention; wherein 2a represents the film without oxazolidine; 2b represents the film with 7-ethylbicyclooxazolidine.

[0025] Figure 3 The following are examples of PBT propellant curing conditions for a method to eliminate moisture in a composite solid propellant provided by the present invention: 3a is a composite solid propellant; 3b is a composite solid propellant with added moisture and corresponding moisture-consuming curing agent, but without oxazolidine; 3c is a composite solid propellant with added moisture and corresponding moisture-consuming curing agent, and also with 0.20% 7-ethylbicyclooxazolidine; 3d is a composite solid propellant with added moisture and corresponding moisture-consuming curing agent, and also with 0.73% 4,4-dimethyloxazolidine.

[0026] Specific implementation methods

[0027] The invention will be further described below with reference to the accompanying drawings.

[0028] A method for eliminating moisture in composite solid propellants, the specific technical solution of which is as follows:

[0029] Step 1: Weigh the adhesive, plasticizer, bonding agent, chain extender, and crosslinking agent into the propellant premixing pot; place the premixing pot in a water bath oven and heat it.

[0030] The second step is to stir the mixture in the premixing pot evenly and remove it from the water bath oven; add oxazolidine to the premixing pot and stir evenly; then add aluminum powder to the premixing pot and stir evenly to form a premixed slurry.

[0031] The third step is to turn on the mixer and pour the premixed slurry from the premixing pot into the mixing pot of the mixer; add the ammonium perchlorate mixture into the mixing pot of the mixer at the same time; control the temperature of the mixing pot of the mixer at 60℃±2℃ and stir for 40 to 60 minutes; at this time, oxazolidine will fully react with the moisture in the raw materials during the stirring process to form alkanolamines or polyols.

[0032] The fourth step is to add the curing agent to the mixing pot of the mixer, control the temperature of the mixing pot at 60℃±2℃, and continue stirring for 60 to 90 minutes to form a propellant discharge slurry; at this time, the polyol or alkanolamine product of the reaction between oxazolidine and water acts as a chain extender and crosslinking agent, and together with the original binder, chain extender, and crosslinking agent, it initially reacts with the curing agent.

[0033] The fifth step involves pouring the propellant slurry into a mold and placing it in an oven at 50-60°C for curing. At this time, the polyol or alkanolamine product of the reaction between oxazolidine and water acts as a chain extender and crosslinking agent, and together with the original adhesive, chain extender, and crosslinking agent, it further reacts with the curing agent to form a thermosetting elastomer with high solids content.

[0034] The oxazolidine is synthesized from ketones and ethanolamine derivatives, and is highly sensitive to water, containing monocyclic or bicyclic oxazolidines.

[0035] The monocyclic oxazolidine is 4,4-dimethyloxazolidine or 3-hydroxyethyloxazolidine or a compound with the corresponding oxazolidine structure.

[0036] The bicyclic oxazolidine is 7-ethylbicyclic oxazolidine or a compound with the corresponding oxazolidine structure.

[0037] The amount of oxazolidine to be added needs to be calculated based on the total moisture content in the propellant.

[0038] The fifth step involves vacuum casting.

[0039] The amount of curing agent added includes the amount of curing agent required by the propellant and the amount of curing agent consumed by oxazolidine.

[0040] The aluminum powder mentioned in the second step is spherical aluminum powder.

[0041] The ammonium perchlorate mentioned in the third step is a compound of ammonium perchlorate with specifications of 40-60 mesh, 100-140 mesh, and 8-11 μm in a certain proportion.

[0042] The principle of oxazolidine in removing water is as follows: Figure 1 As shown: Adding oxazolidine can effectively remove moisture from the composite solid propellant and generate β-alcoholic amine; the β-alcoholic amine reacts with the curing agent in the propellant.

[0043] Example 1

[0044] To verify the water removal effect of oxazolidine, a small-scale film experiment was conducted first.

[0045] Propellant film preparation:

[0046] Step 1: Weigh the adhesive (PBT: 3,3-bis(azidomethyl)oxabutane and tetrahydrofuran co-ether), plasticizer (A3: bis(2,2-dinitropropyl)acetal / bis(2,2-dinitropropyl)formal mixture), oxazolidine (7-ethylbicyclooxazolidine), chain extender (TEG: triethylene glycol), and crosslinking agent (TMP: trimethylolpropane) into the propellant premixing pot; place the propellant premixing pot in a 50°C water bath oven and heat for 20 minutes; remove the propellant premixing pot and stir the mixture thoroughly.

[0047] Step 2: Weigh the curing agent (TDI: toluene diisocyanate) into the propellant premixing pot, stir it evenly, put it into a vacuum oven, evacuate the air for 5-10 minutes, pour it into the mold, and put the mold into a 50℃ oven to cure for 7 days.

[0048] Table 1 shows the formulations for preparing the two types of films in Example 1, labeled 1 and 2 respectively:

[0049] Table 1. Formulation and content of the propellant film preparation system in Example 1

[0050]

[0051] from Figure 2 As can be seen from a, in the film without the addition of 7-ethylbicyclooxazolidine, a large bubble formed inside the film. This bubble was formed by carbon dioxide generated from the reaction of water with isocyanate. Figure 2 b. After adding 7-ethylbicyclooxazolidine, no bubbles were generated inside the film. This indicates that water preferentially reacts with 7-ethylbicyclooxazolidine to form a polyol compound, thus avoiding the reaction between water and isocyanate.

[0052] Example 2

[0053] Step 1: Weigh the adhesive (PBT: 3,3-bis(azidomethyl)oxabutane and tetrahydrofuran co-ether), plasticizer (A3: bis(2,2-dinitropropyl)acetal / bis(2,2-dinitropropyl)formal mixture), chain extender (TEG: triethylene glycol), crosslinking agent (TMP: trimethylolpropane), and bonding agent (JH10: diethanolamine borate ester) into the propellant premixing pot; place the premixing pot in a water bath oven and heat it;

[0054] The second step is to stir the mixture in the premixing pot evenly and remove it from the water bath oven; add oxazolidine (7-ethylbicyclooxazolidine or 4,4-dimethyloxazolidine) to the premixing pot and stir evenly; then add spherical aluminum powder to the premixing pot and stir evenly to form a premixed slurry.

[0055] The third step is to turn on the mixer and pour the premixed slurry from the premixing pot into the mixing pot of the mixer; simultaneously add the ammonium perchlorate mixture into the mixing pot of the mixer; control the temperature of the mixing pot of the mixer at 60℃±2℃ and stir for 40 to 60 minutes. During this time, oxazolidine (7-ethylbicyclooxazolidine or 4,4-dimethyloxazolidine) will fully react with the moisture in the raw materials during the stirring process to form alkanolamines or polyols; the ammonium perchlorate mixture is prepared by compounding ammonium perchlorates of 40-60 mesh, 100-140 mesh, and 8-11 μm specifications in a certain proportion.

[0056] The fourth step involves adding the curing agent (TDI: toluene diisocyanate) to the mixing pot of a mixer, controlling the temperature of the mixing pot at 60℃±2℃, and continuing to stir for 60-90 minutes to form a propellant slurry. At this point, the product of the reaction between oxazolidine (7-ethylbicyclooxazolidine or 4,4-dimethyloxazolidine) and water is a polyol or alkanolamine, which acts as a chain extender and crosslinking agent. Together with the original binder (PBT: 3,3-bis(azidomethyl)oxabutane and tetrahydrofuran co-ether), chain extender (TEG: triethylene glycol), and crosslinking agent (TMP: trimethylolpropane), it initially reacts with the curing agent (TDI: toluene diisocyanate).

[0057] The fifth step involves placing the propellant slurry into a vacuum casting mold and then in an oven at 50–60°C for curing. At this point, the polyol or alkanolamine product resulting from the reaction of oxazolidine with water acts as a chain extender and crosslinking agent. Together with the existing binder (PBT: 3,3-bis(azidomethyl)oxabutane and tetrahydrofuran co-ether), chain extender (TEG: triethylene glycol), and crosslinking agent (TMP: trimethylolpropane), it further reacts with the curing agent (TDI: toluene diisocyanate) to form a thermosetting elastomer with high solids content.

[0058] Table 2 shows the four propellant formulations produced in Example 2, labeled as 3, 4, 5, and 6 respectively.

[0059] Table 2. Propellant formulation components and content in Example 2

[0060]

[0061]

[0062] In Example 2, formulation 4 shows the formulation of formulation 3 with the addition of additional water and corresponding water-consuming curing agent, wherein 0.05% water is added and no oxazolidine substances are added, serving as a comparative example with high water content (≥0.05%); formulation 5 shows the formulation of formulation 3 with the addition of additional water, 7-ethylbicyclooxazolidine, and corresponding water-consuming curing agent, wherein 0.05% water, 0.20% 7-ethylbicyclooxazolidine, and 0.48% toluene diisocyanate are added; formulation 6 shows the formulation of formulation 3 with the addition of additional water, 4,4-dimethyloxazolidine, and corresponding water-consuming curing agent, wherein 0.05% water, 0.73% 4,4-dimethyloxazolidine, and 0.48% toluene diisocyanate are added.

[0063] like Figure 3 As shown, 3b is a high-moisture propellant with a water content of not less than 0.05%, and after solidification, the propellant has unevenly distributed reactive pores inside. Similarly, 3c and 3d are propellants with the addition of 7-ethylbicyclooxazolidine and 4,4-dimethyloxazolidine, respectively, and are internally dense without reactive pores, verifying that this method can effectively remove moisture from the propellant.

[0064] Table 3 shows the mechanical properties of the propellant after curing in Example 2. Analysis shows that the addition of 7-ethylbicyclooxazolidine or 4,4-dimethyloxazolidine can remove moisture from the propellant. Compared with propellants with low moisture content (≤0.05%), the tensile strength of the propellant is significantly increased by nearly 100%.

[0065] Table 3 Mechanical properties of four propellants after curing in Example 2

[0066]

[0067]

[0068] Example 3

[0069] Step 1: Weigh the binder (HTPB: hydroxyl-terminated polybutadiene), plasticizer (KZ: diisooctyl sebacate), chain extender (TEG: triethylene glycol), crosslinking agent (JH01: tri-1-(2-methylaziridine)phosphine oxide), bonding agent (JH10: diethanolamine borate ester), and combustion rate catalyst (cattocin, also known as 2,2-bis(ethyl ferrocene)) into the propellant premixing pot; place the premixing pot in a water bath oven and heat it;

[0070] The second step is to stir the mixture in the premixing pot until it is evenly mixed and then remove it from the water bath oven; add oxazolidine (7-ethylbicyclooxazolidine) to the premixing pot and stir until it is evenly mixed; then add spherical aluminum powder to the premixing pot and stir until it is evenly mixed to form a premixed slurry;

[0071] The third step is to turn on the mixer and pour the premixed slurry from the premixing pot into the mixing pot of the mixer; simultaneously add the ammonium perchlorate mixture into the mixing pot of the mixer; control the temperature of the mixing pot of the mixer at 60℃±2℃ and stir for 40 to 60 minutes. At this time, oxazolidine (7-ethylbicyclooxazolidine) will fully react with the moisture in the raw materials during the stirring process to form alkanolamines or polyols; the ammonium perchlorate mixture is prepared by compounding ammonium perchlorates of 40-60 mesh, 100-140 mesh, and 8-11um specifications in a certain proportion.

[0072] The fourth step involves adding the curing agent (IPDI: isophorone diisocyanate) to the mixing pot of a mixer, controlling the temperature of the mixing pot at 60℃±2℃, and continuing to stir for 60-90 minutes to form a propellant slurry. At this point, the product of the reaction between oxazolidine (7-ethylbicyclooxazolidine) and water is a polyol or alkanolamine, which acts as a chain extender and crosslinking agent. Together with the existing binder (HTPB: hydroxyl-terminated polybutadiene), chain extender (TEG: triethylene glycol), and crosslinking agent (JH01: tri-1-(2-methylaziridine)phosphine oxide), the curing agent (IPDI: isophorone diisocyanate) reacts initially.

[0073] The fifth step involves placing the propellant slurry into a vacuum casting mold and then in an oven at 50–60°C for curing. At this point, the polyol or alkanolamine product of the reaction between oxazolidine and water acts as a chain extender and crosslinking agent. Together with the original binder (HTPB: hydroxyl-terminated polybutadiene), chain extender (TEG: triethylene glycol), and crosslinking agent (JH01: tri-1-(2-methylaziridine)phosphine oxide), it further reacts with the curing agent (IPDI: isophorone diisocyanate) to form a thermosetting elastomer with high solids content.

[0074] Table 4 shows the three propellant formulations produced in Example 3, labeled as 7, 8, and 9 respectively. Table 4: Components and Contents of Propellant Formulations in Example 3

[0075]

[0076]

[0077] In Example 3, Serial No. 7 gives a commonly used butyl hydroxyl composite solid propellant formulation; Serial No. 8 gives a formulation of Serial No. 7 with the addition of 7-ethylbicyclooxazolidine and corresponding curing agent, wherein 0.20% 7-ethylbicyclooxazolidine and 0.10% isophorone diisocyanate are added; Serial No. 9 gives a formulation of Serial No. 7 with the addition of 7-ethylbicyclooxazolidine and corresponding curing agent, wherein 0.20% 7-ethylbicyclooxazolidine and 0.21% isophorone diisocyanate are added.

[0078] Table 5 shows the mechanical properties of the propellant after curing in Example 3. The analysis shows that after adding 7-ethylbicyclooxazolidine and the corresponding curing agent, without adding water, 7-ethylbicyclooxazolidine can consume the water in the propellant raw materials and increase the tensile strength of the original propellant. The more curing agent added, the greater the increase in the tensile strength of the propellant.

[0079] Table 5 Mechanical properties of the three propellants after curing in Example 3

[0080]

[0081] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make possible variations and modifications to the technical solutions of the present invention using the disclosed methods and techniques without departing from the spirit and scope of the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, are all within the protection scope of the present invention. Content not described in detail in this specification is common knowledge to those skilled in the art.

Claims

1. A method for removing moisture from composite solid propellants, characterized in that, The specific technical solution is as follows: Step 1: Weigh the adhesive, plasticizer, bonding agent, chain extender, and crosslinking agent into the propellant premixing pot; place the premixing pot in a water bath oven and heat it. The second step is to stir the mixture in the premixing pot evenly and remove it from the water bath oven; add oxazolidine to the premixing pot and stir evenly; then add spherical aluminum powder to the premixing pot and stir evenly to form a premixed slurry; The third step is to turn on the mixer and pour the premixed slurry from the premixing pot into the mixing pot of the mixer; add the ammonium perchlorate mixture into the mixing pot of the mixer at the same time; control the temperature of the mixing pot of the mixer at 60℃±2℃ and stir for 40 to 60 minutes; during the stirring process, oxazolidine reacts fully with the moisture in the raw materials to form alkanolamines or polyols. The fourth step is to add the curing agent to the mixing pot of the mixer, control the temperature of the mixing pot at 60℃±2℃, and continue stirring for 60 to 90 minutes to form the propellant discharge slurry. The fifth step involves pouring the propellant slurry into a mold and placing it in an oven for curing. The product of the reaction between oxazolidine and water is a polyol or an alkanolamine. The polyol or alkanolamine acts as a chain extender and crosslinking agent, reacting with the curing agent along with the original adhesive, chain extender, and crosslinking agent to form a thermosetting elastomer with high solids content.

2. The method for eliminating moisture in a composite solid propellant as described in claim 1, characterized in that, The oxazolidine is synthesized from ketones and ethanolamine derivatives, and includes monocyclic or bicyclic oxazolidines.

3. The method for eliminating moisture in a composite solid propellant as described in claim 2, characterized in that, The monocyclic oxazolidine is 4,4-dimethyloxazolidine or 3-hydroxyethyloxazolidine or a compound with the corresponding oxazolidine structure.

4. The method for eliminating moisture in a composite solid propellant as described in claim 2, characterized in that, The bicyclic oxazolidine is 7-ethylbicyclic oxazolidine or a compound with the corresponding oxazolidine structure.

5. The method for eliminating moisture in a composite solid propellant as described in claim 1, characterized in that, The amount of oxazolidine to be added needs to be calculated based on the total moisture content in the propellant.

6. The method for eliminating moisture in a composite solid propellant as described in claim 1, characterized in that, The fifth step involves vacuum casting.

7. The method for eliminating moisture in a composite solid propellant as described in claim 1, characterized in that, The amount of curing agent added includes the amount of curing agent required by the propellant and the amount of curing agent consumed by oxazolidine.

8. The method for eliminating moisture in a composite solid propellant as described in claim 1, characterized in that, The aluminum powder mentioned in the second step is spherical aluminum powder.

9. The method for eliminating moisture in a composite solid propellant as described in claim 1, characterized in that, The ammonium perchlorate mixture mentioned in the third step is prepared by compounding ammonium perchlorates of 40-60 mesh, 100-140 mesh, and 8-11 μm specifications in a certain proportion.

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