Solid rocket engine lining interface layer and bonding method and application thereof

Abstract

The invention discloses a solid rocket engine lining interface layer and a bonding method and application thereof, and relates to the technical field of lining interface bonding. The bonding method comprises the following steps: pre-coating bottom layer lining slurry on the surface of an object to be bonded, and pre-curing to form a pre-cured bottom layer lining; coating polymer powder on the surface of the pre-cured bottom lining layer, and completely curing the pre-cured bottom lining layer to form a cured lining layer; and the energetic hydrogel propellant thin slurry is poured on the surface of the curing lining layer, and the energetic hydrogel propellant thin slurry is cured. According to the method, interface bonding of the energetic hydrogel can be achieved through chemical bonding and mechanical embedding, the interface bonding strength is effectively improved, the bonding reliability of the charging interface of the hydrogel solid rocket engine is improved, and the bonding method has the advantages of being simple in step, convenient to operate, easy to implement, firm in bonding and the like.

Description

Technical Field

[0001] This invention relates to the field of liner interface bonding technology, and more specifically, to a solid rocket motor liner interface layer, its bonding method, and its application. Background Technology

[0002] In solid rocket motors, the liner (also known as the cladding layer) is a special adhesive within the combustion chamber that connects the propellant to the insulation layer (including the artificial debonding layer) and / or shell material. Its key function is to firmly bond the propellant, insulation layer (artificial debonding layer), and / or shell material together through interfacial chemical reactions and physical interactions between the liner and the propellant, insulation layer, or shell material, ensuring the integrity of the solid rocket motor's propellant structure throughout its entire lifespan. For commonly used hydroxyl-butadiene propellants and nitrate-plasticized polyether high-energy propellants, a polyurethane curing system is often used to achieve interfacial bonding between the propellant and the insulation layer and / or shell material.

[0003] With the continuous development of new propellants, ammonium nitrate gel propellants are attracting widespread attention as they are expected to meet the needs of rapid response and green, low-cost development of propellants. For the isocyanate curing system commonly used in liner layers, isocyanate ions react with water to release gas, and the migration of water molecules at the bonding interface can lead to debonding at the wet interface. The abundant water and swollen molecular chains in hydrogel propellants limit their affinity and bonding with many adhesives, making it difficult to form effective interfacial adhesion.

[0004] A method for layering and molding a solid rocket motor liner (CN115288882A) discloses a method for layering and molding a solid rocket motor liner, which achieves reliable adhesion of the propellant interface by brushing on multiple layers of liner with different curing parameters. However, for energetic hydrogel propellants, the abundant moisture will react with the isocyanate in the liner and generate bubbles, which not only fails to achieve interface adhesion but also affects the combustion surface of the propellant during operation.

[0005] The Use of nanoparticles for gluing gels (EP2857350A1) discloses a method for bonding a pre-formed hydrogel to another product using nanoparticles or an aqueous solution of nanoparticles. The method achieves a strong interfacial bond by applying stress after applying a nanoparticle composition to the surface of the sample to be bonded. However, this method is not suitable for unformed hydrogel propellant slurry and cannot be cast.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a solid rocket motor liner interface layer, its bonding method, and its application.

[0008] This invention is implemented as follows:

[0009] In a first aspect, the present invention provides a method for bonding an interface layer of a solid rocket motor liner, comprising:

[0010] A base layer slurry is pre-coated onto the surface of the objects to be bonded and then pre-cured to form a pre-cured base layer.

[0011] A polymer powder is coated on the surface of the pre-cured underlayer, and the pre-cured underlayer is then completely cured to form a cured underlayer.

[0012] Energetic hydrogel propellant slurry is poured onto the surface of the cured liner, and the energetic hydrogel propellant slurry is cured.

[0013] In an optional embodiment, the coating thickness of the bottom lining slurry is 0.1mm-5mm;

[0014] Preferably, the coating thickness of the polymer powder is 5 g / m. 2 -200 g / m 2 .

[0015] In an optional embodiment, the pre-curing temperature of the bottom lining slurry is 20-90℃, and the pre-curing time is 2-12h;

[0016] Preferably, the pre-curing temperature of the bottom lining slurry is 40-80℃, and the curing time is 4-6h.

[0017] In an optional embodiment, the curing temperature of the energetic hydrogel propellant slurry is 20-70℃, and the curing time is 5-10 days.

[0018] In an optional embodiment, the raw materials of the bottom lining slurry include a liquid polymer, a polyisocyanate curing agent, an adhesion promoter, a network modifier, a filler, and a curing catalyst in a mass ratio of 100:10-20:4-8:1.5-1.5:4-8:0.1-0.3.

[0019] Preferably, the liquid polymer comprises one or more of hydroxyl-terminated polybutadiene, hydroxyl-terminated polyether, hydroxyl-terminated butadiene-acrylonitrile rubber, and hydroxyl-terminated polyester.

[0020] Preferably, the polyisocyanate curing agent includes one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dimer fatty acid diisocyanate, terephthalimide diisocyanate, and hexamethylene diisocyanate.

[0021] Preferably, the adhesion promoter comprises one or more of tris(2-methyl)aziridine phosphine oxide, isophthaloyl (2-methylaziridine), and 1,3,5-benzentrioyl (2-ethylaziridine);

[0022] Preferably, the network regulator comprises one or more of ethylene glycol, 1,4-butanediol, N,N-bis(2-hydroxypropyl)aniline, and trimethylolpropane;

[0023] Preferably, the filler includes one or more of the following: silica, carbon black, titanium dioxide, zinc oxide, iron oxide, and chromium oxide.

[0024] Preferably, the curing catalyst comprises one or more of iron acetylacetonate, dibutyltin dilaurate, triphenylbismuth, and 2,4,6-tris[(dimethylamino)methyl]phenol;

[0025] Preferably, the curing reaction parameters (molar ratio of isocyanate to hydroxyl groups) in the bottom lining slurry during the curing reaction are 1.1-3.0.

[0026] In an optional embodiment, the polymer powder is a hydroxyl-containing polymer powder;

[0027] Preferably, the polymer powder is one or more of the following: polyvinyl alcohol powder, polyvinyl alcohol and its derivative powder, starch and its derivative powder, cellulose and its derivative powder, hyaluronic acid and its derivative powder, agarose and its derivative powder, or cross-linked products of the above powders.

[0028] In an optional embodiment, the raw materials for the energetic hydrogel propellant slurry include a binder, a crosslinking curing agent, an oxidant, and water in a mass ratio of 10-20:0.2-2:50-80:5-20;

[0029] Preferably, the adhesive comprises one or more of polyvinyl alcohol and its derivatives, carboxymethyl cellulose and its derivatives;

[0030] Preferably, the crosslinking curing agent includes one or more of boric acid, borax, and glutaraldehyde;

[0031] Preferably, the oxidant includes one or more of ammonium perchlorate, ammonium nitrate, hydroxyl ammonium nitrate, dinitramide ammonium, and trinitromethanehydrazine;

[0032] Preferably, the raw materials for the energetic hydrogel propellant slurry further include fuel, wherein the fuel accounts for 0-20% of the energetic hydrogel propellant slurry;

[0033] Preferably, the fuel includes one or more of boron powder and aluminum powder.

[0034] In an optional embodiment, the material to be bonded is an EPDM insulation layer, a nitrile rubber insulation layer, metallic iron, metallic aluminum, or metallic titanium.

[0035] Secondly, the present invention provides a solid rocket motor liner interface layer, which is prepared by the bonding method of the solid rocket motor liner interface layer as described in any of the foregoing embodiments.

[0036] Thirdly, the present invention provides an application of the bonding method for the interface layer of the solid rocket motor liner as described in any of the foregoing embodiments in the preparation of a solid rocket motor.

[0037] The present invention has the following beneficial effects:

[0038] The bonding method for the interface layer of a solid rocket motor liner provided by this invention involves first pre-coating a base liner slurry onto the surface of the material to be bonded, and then pre-curing it to form a pre-cured base liner. At this stage, the pre-cured base liner is not fully cured. After coating its surface with polymer powder, the active groups on the surface of the polymer powder react with the unreacted active isocyanates on the surface of the pre-cured base liner, achieving chemical bonding of the polymer powder within the pre-cured base liner. Simultaneously, during the coating of the polymer powder, some of the polymer powder is embedded in the pre-cured base liner. After the base liner is fully cured (if any unembedded polymer powder is present, it is removed), an energetic hydrogel propellant slurry is poured onto its surface. The water in the energetic hydrogel propellant slurry swells the polymer powder, and the curing agent in the energetic hydrogel propellant slurry further achieves chemical bonding between the energetic hydrogel and the polymer powder. Reliable interface bonding is achieved after the energetic hydrogel propellant slurry is fully cured. This invention can increase the interfacial bonding strength from unmeasurable to over 0.4 MPa, effectively achieving interfacial bonding between energetic hydrogel propellants and rubber insulation layers and / or metal shells, thereby improving the bonding reliability of the propellant interface in hydrogel solid rocket engines. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is an image showing the interfacial bonding morphology of the propellant / liner / insulation layer specimen provided in Embodiment 2 of the present invention. Detailed Implementation

[0041] To make the objectives, 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0042] This invention provides a method for bonding the interface layer of a solid rocket motor liner, comprising the following steps:

[0043] S1. Prepare the bottom lining slurry.

[0044] The raw materials for the bottom lining slurry include liquid polymers, polyisocyanates, adhesion promoters, network modifiers, fillers, and curing catalysts in a mass ratio of 100:10-20:4-8:1.5-1.5:4-8:0.1-0.3.

[0045] Liquid polymers include, but are not limited to, one or more of hydroxyl-terminated polybutadiene (HTPB), hydroxyl-terminated polyether (HTPE), hydroxyl-terminated nitrile butadiene rubber (HTBN), and hydroxyl-terminated polyester (HTCE).

[0046] Polyisocyanate curing agents include, but are not limited to, one or more of toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dimer fatty acid diisocyanate (DDI), terephthalimide diisocyanate (XDI), and hexamethylene diisocyanate (HDI).

[0047] Adhesion promoters include, but are not limited to, one or more of tri(2-methyl)aziridine phosphine oxide (MAPO), isophthaloyl(2-methylaziridine) (HX-752), and 1,3,5-benzentriacyl(2-ethylaziridine) (HX-868).

[0048] Network modifiers include, but are not limited to, one or more of ethylene glycol, 1,4-butanediol, N,N-bis(2-hydroxypropyl)aniline, and trimethylolpropane (TMP).

[0049] The fillers include, but are not limited to, one or more of the following: silica, carbon black, titanium dioxide, zinc oxide, iron oxide, and chromium oxide.

[0050] The curing catalyst includes, but is not limited to, one or more of ferric acetylacetone, dibutyltin dilaurate (DBTDL), triphenylbismuth (TPB), and 2,4,6-tris[(dimethylamino)methyl]phenol.

[0051] S2. Preparation of energetic hydrogel propellant slurry.

[0052] The raw materials for energetic hydrogel propellant slurry include binders, cross-linking curing agents, oxidants, and water in a mass ratio of 10-20:0.2-2:50-80:5-20.

[0053] The adhesive includes, but is not limited to, one or more of polyvinyl alcohol, carboxymethyl cellulose, and gelatin; the crosslinking curing agent includes, but is not limited to, one or more of boric acid, borax, and glutaraldehyde; and the oxidizing agent includes, but is not limited to, one or more of ammonium perchlorate (AP), ammonium nitrate (AN), hydroxyl ammonium nitrate (HAN), ammonium dinitramide (ADN), and trinitromethanehydrazine (HNF).

[0054] In this invention, water and adhesive can be mixed first and then other components can be added, or water and oxidant can be mixed first and then other components can be added.

[0055] Preferably, the raw materials for the energetic hydrogel propellant slurry may include fuel, wherein the fuel accounts for 0-20% of the energetic hydrogel propellant slurry by mass; the fuel includes, but is not limited to, one or more of boron powder and aluminum powder.

[0056] S3. Apply a base coat slurry to the surface of the objects to be bonded and pre-cur it to form a pre-cured base coat.

[0057] The materials to be bonded are EPDM insulation layer, nitrile rubber insulation layer, iron, aluminum or titanium.

[0058] The coating thickness of the bottom lining slurry is 0.1mm-5mm. At this time, it is only necessary to pre-cur the bottom lining slurry to facilitate the subsequent addition of polymer powder. The pre-curing temperature is 20-90℃ and the pre-curing time is 2-12h. Preferably, the pre-curing temperature is 40-80℃ and the pre-curing time is 4-6h.

[0059] Preferably, the curing reaction parameters (molar ratio of isocyanate to hydroxyl groups) are 1.1-3.0.

[0060] S4. Coat the surface of the pre-cured underlayer with polymer powder and allow the pre-cured underlayer to fully cure to form a cured underlayer.

[0061] In this invention, the polymer powder is a hydroxyl-containing polymer powder. Specifically, the polymer powder is one or more of the following: polyvinyl alcohol powder, polyvinyl alcohol and its derivative powder, starch and its derivative powder, cellulose and its derivative powder, hyaluronic acid and its derivative powder, agarose and its derivative powder, or cross-linked products of the above powders.

[0062] Among these, polyvinyl alcohol derivatives refer to copolymers containing polyvinyl alcohol segments, such as polyvinyl butyral (PVB) and ethylene-vinyl alcohol copolymer (EVOH). Starch derivatives refer to physically or chemically modified starch, such as hydroxypropyl starch and dextrin. Cellulose derivatives refer to physically or chemically modified cellulose, such as methylcellulose and hydroxymethylcellulose. Hyaluronic acid derivatives refer to physically or chemically modified hyaluronic acid, such as hydrolyzed hyaluronic acid and hyaluronic acid esters. Agarose derivatives refer to physically or chemically modified agarose, such as agarose pigment and agar gum.

[0063] In this invention, polymer powder is coated onto the surface of the pre-cured underlayer, with a coating thickness of 5 g / m. 2 -200 g / m 2 The active groups on the surface of the coated polymer powder react with unreacted active isocyanates in the underlying liner slurry, achieving chemical bonding of the polymer powder within the underlying liner. Simultaneously, because the pre-cured underlying liner is not fully cured, some polymer powder will be embedded within it. After coating with polymer powder, the pre-cured underlying liner is further cured to ensure complete curing. The curing temperature can be maintained at the pre-curing temperature in step S3, and curing continues for approximately 2-6 days until complete curing. Once the pre-cured underlying liner is fully cured, the unembedded polymer powder on the surface is removed.

[0064] S5. Pour energetic hydrogel propellant slurry onto the surface of the cured liner and cure the energetic hydrogel propellant slurry.

[0065] In this invention, water-swellable polymer powder in an energetic hydrogel is utilized, and a curing agent in the energetic hydrogel is further used to achieve chemical bonding between the energetic hydrogel and the polymer powder. Reliable interfacial bonding can be achieved after the energetic hydrogel propellant slurry is completely cured.

[0066] A slurry of energetic hydrogel propellant is poured onto the surface of the cured liner. This slurry has better fluidity and can adapt to various shapes and spaces. The amount of energetic hydrogel propellant slurry used is not limited and depends on the actual space to be filled. After pouring the slurry, it is cured at 20-70℃ for about 5-10 days until fully cured.

[0067] The solid rocket motor liner interface layer prepared using the above-described bonding method exhibits excellent interfacial bonding performance and can be widely used in the manufacture of solid rocket motors. Therefore, this invention also provides a solid rocket motor comprising the aforementioned solid rocket motor liner interface layer, through which reliable bonding can be achieved between the hydrogel propellant and the solid rocket motor shell / insulation layer.

[0068] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0069] Example 1

[0070] This embodiment demonstrates the interfacial bonding between the EPDM insulation layer and the polyvinyl alcohol energetic hydrogel based on an IPDI underlayer and polyvinyl alcohol powder. The specific method is as follows:

[0071] At room temperature, a base lining slurry with hydroxyl-terminated polybutadiene as the binder and isophorone diisocyanate as the curing agent is uniformly coated onto the surface of the polished EPDM insulation layer. The base lining thickness is 0.6 mm. It is reacted at 80°C for 4 hours to reach the pre-cured state. Then, 20 g / m² of polyvinyl alcohol 1799 powder is uniformly coated onto the surface of the pre-cured base lining. 2 The reaction continued at 80°C until the bottom lining slurry was completely cured. Then, an energetic hydrogel propellant slurry was poured in, using polyvinyl alcohol as a binder, borax as a crosslinking curing agent, ammonium nitrate as an oxidant, and aluminum powder as fuel. After the energetic hydrogel propellant slurry was cured and formed at 50°C, the interface bonding was completed. A propellant / lining / insulation layer pull-off test specimen was made, and the combined pull-off strength was measured to be 0.44 MPa. The fracture mode was mixed fracture.

[0072] Underlayer liner formulation:

[0073]

[0074]

[0075] Energetic hydrogel propellant slurry formulation:

[0076] Formula composition Number of parts by weight Polyvinyl alcohol 15 Borax 1.5 HAN 70 water 15 aluminum powder 15

[0077] Example 2

[0078] This embodiment demonstrates the interfacial bonding between an EPDM insulation layer and a polyvinyl alcohol energetic hydrogel based on an IPDI underlayer and polyvinyl alcohol powder. The specific method is the same as in Example 1, with the main difference being that the energetic hydrogel does not contain aluminum powder filler. The underlayer formulation is the same as in Example 1. The specific method is as follows:

[0079] At room temperature, a base lining slurry with hydroxyl-terminated polybutadiene as the binder and isophorone diisocyanate as the curing agent is uniformly coated onto the surface of the polished EPDM insulation layer. The base lining thickness is 0.6 mm. It is reacted at 80°C for 4 hours to reach the pre-cured state. Then, 20 g / m² of polyvinyl alcohol 1799 powder is uniformly coated onto the surface of the pre-cured base lining. 2 The reaction continued at 80°C until the bottom lining slurry was completely cured. Then, an energetic hydrogel propellant slurry with polyvinyl alcohol as the binder, borax as the crosslinking curing agent, and ammonium nitrate as the oxidant was poured in. After the energetic hydrogel propellant slurry was cured and formed at 50°C, the interface bonding was completed. A propellant / lining / insulation layer pull-off test specimen was made, and the combined pull-off strength was measured to be 0.41 MPa. The fracture mode was mixed fracture.

[0080] Energetic hydrogel propellant slurry formulation:

[0081] Formula composition Number of parts by weight Polyvinyl alcohol 15 Borax 1.5 HAN 70 water 15

[0082] The interface micromorphology of the propellant / liner / insulation layer specimens prepared in Example 2 was observed.

[0083] The specific operating method is as follows: Take the propellant / liner / insulation layer specimen prepared in Example 2, cut the specimen perpendicular to the bonding interface, place it on a sample plate with conductive double-sided adhesive, plate it with gold, and observe it under a scanning electron microscope to obtain the following results. Figure 1 The interface bonding morphology is shown.

[0084] As can be seen from the images, the interface between the propellant / liner / insulation layer in Example 2 is clear and the connection is complete.

[0085] Example 3

[0086] This embodiment demonstrates the interfacial bonding between an EPDM insulation layer and a polyvinyl alcohol (PVA) energetic hydrogel based on an IPDI underlayer and PVA powder. The specific method is the same as in Example 1, with the main difference being a pre-curing time of 6 hours. The underlayer formulation and the energetic hydrogel propellant slurry formulation are also the same as in Example 1. The specific method is as follows:

[0087] At room temperature, a base lining slurry with hydroxyl-terminated polybutadiene as the binder and isophorone diisocyanate as the curing agent is uniformly coated onto the surface of the polished EPDM insulation layer. The base lining thickness is 0.6 mm. It is reacted at 80°C for 6 hours to reach the pre-cured state. Then, 20 g / m² of polyvinyl alcohol 1799 powder is uniformly coated onto the surface of the pre-cured base lining. 2The reaction continued at 80°C until the bottom lining slurry was completely cured. Then, an energetic hydrogel propellant slurry was poured in, using polyvinyl alcohol as a binder, borax as a crosslinking curing agent, ammonium nitrate as an oxidant, and aluminum powder as fuel. After the energetic hydrogel propellant slurry was cured and formed at 50°C, the interface bonding was completed. A propellant / lining / insulation layer pull-off test specimen was made, and the combined pull-off strength was measured to be 0.62 MPa. The fracture mode was intrapropellant fracture.

[0088] Example 4

[0089] This embodiment demonstrates the interfacial bonding between an EPDM insulation layer and a polyvinyl alcohol energetic hydrogel, based on a TDI underlayer and polyvinyl alcohol powder. The specific method is the same as in Example 1, the main difference being that the curing agent is TDI, and the energetic hydrogel propellant slurry formulation is the same as in Example 1. The specific method is as follows:

[0090] At room temperature, a base lining slurry with hydroxyl-terminated polybutadiene as a binder and toluene diisocyanate as a curing agent is uniformly coated onto the surface of the polished EPDM insulation layer. The base lining thickness is 0.6 mm. It is reacted at 80°C for 4 hours to reach a pre-cured state. Then, 20 g / m² of polyvinyl alcohol 1799 powder is uniformly coated onto the surface of the pre-cured base lining. 2 The reaction continued at 80°C until the bottom lining slurry was completely cured. Then, an energetic hydrogel propellant slurry was poured in, using polyvinyl alcohol as a binder, borax as a crosslinking curing agent, ammonium nitrate as an oxidant, and aluminum powder as fuel. After the energetic hydrogel propellant slurry was cured and formed at 50°C, the interface bonding was completed. A propellant / lining / insulation layer pull-off test specimen was made, and the combined pull-off strength was measured to be 0.39 MPa, and the fracture mode was mixed fracture.

[0091] Underlayer liner formulation:

[0092] Formula composition Number of parts by weight HTPB 100 TDI 11.76 MAPO 6 TMP 1 Precipitation silica 6 DBTDL 0.2

[0093] Example 5

[0094] This embodiment demonstrates the interfacial bonding of metallic aluminum and energetic polyvinyl alcohol hydrogel based on an IPDI underlayer and polyvinyl alcohol powder. The specific method is the same as in Embodiment 1, with the main difference being that the object to be bonded is metallic aluminum, and the formulations of the underlayer and energetic hydrogel propellant slurry are the same as in Embodiment 1. The specific method is as follows:

[0095] At room temperature, a base lining slurry with hydroxyl-terminated polybutadiene as a binder and isophorone diisocyanate as a curing agent is uniformly coated onto the surface of a polished aluminum plate. The base lining thickness is 0.6 mm. The mixture is reacted at 80°C for 4 hours to reach a pre-cured state. Then, 20 g / m² of polyvinyl alcohol 1799 powder is uniformly coated onto the surface of the pre-cured base lining. 2The reaction continued at 80°C until the bottom lining slurry was completely cured. Then, an energetic hydrogel propellant slurry was poured in, using polyvinyl alcohol as a binder, borax as a crosslinking curing agent, ammonium nitrate as an oxidant, and aluminum powder as fuel. After the energetic hydrogel propellant slurry was cured and formed at 50°C, the interface bonding was completed. A propellant / lining / aluminum plate pull-off test specimen was made, and the combined pull-off strength was measured to be 0.35 MPa. The fracture mode was mixed fracture.

[0096] Example 6

[0097] This embodiment demonstrates the interfacial bonding between an EPDM insulation layer and a polyvinyl alcohol energetic hydrogel based on an IPDI underlayer and cross-linked polyvinyl alcohol powder. The specific method is the same as in Example 1, the main difference being that the material coated on the surface of the pre-cured underlayer is cross-linked polyvinyl alcohol powder. The underlayer formulation and the energetic hydrogel propellant slurry formulation are the same as in Example 1. The specific method is as follows:

[0098] At room temperature, a base lining slurry with hydroxyl-terminated polybutadiene as the binder and isophorone diisocyanate as the curing agent is uniformly coated onto the surface of the polished EPDM insulation layer. The base lining thickness is 0.6 mm. The mixture is reacted at 80°C for 4 hours to reach a pre-cured state. Then, 20 g / m² of cross-linked polyvinyl alcohol 1799 powder is uniformly coated onto the surface of the pre-cured base lining. 2 The reaction continued at 80°C until the bottom lining slurry was completely cured. Then, an energetic hydrogel propellant slurry was poured in, using polyvinyl alcohol as a binder, borax as a crosslinking curing agent, ammonium nitrate as an oxidant, and aluminum powder as fuel. After the energetic hydrogel propellant slurry was cured and formed at 50°C, the interface bonding was completed. A propellant / lining / insulation layer pull-off test specimen was made, and the combined pull-off strength was measured to be 0.43 MPa. The fracture mode was mixed fracture.

[0099] Example 7

[0100] This embodiment demonstrates the interfacial bonding between an EPDM insulation layer and a polyvinyl alcohol energetic hydrogel based on an IPDI underlayer and cross-linked polyvinyl alcohol powder. The specific method is the same as in Example 1, with the main difference being that starch is coated on the surface of the pre-cured underlayer. The underlayer formulation and the energetic hydrogel propellant slurry formulation are the same as in Example 1. The specific method is as follows:

[0101] At room temperature, a base lining slurry, using hydroxyl-terminated polybutadiene as a binder and isophorone diisocyanate as a curing agent, is uniformly coated onto the surface of the polished EPDM insulation layer. The base lining thickness is 0.6 mm. The mixture is then reacted at 80°C for 4 hours until pre-cured. Finally, 20 g / m² of starch powder is uniformly coated onto the surface of the pre-cured base lining. 2The reaction continued at 80°C until the bottom lining slurry was completely cured. Then, an energetic hydrogel propellant slurry was poured in, using polyvinyl alcohol as a binder, borax as a crosslinking curing agent, ammonium nitrate as an oxidant, and aluminum powder as fuel. After the energetic hydrogel propellant slurry was cured and formed at 50°C, the interface bonding was completed. A propellant / lining / insulation layer pull-off test specimen was made, and the combined pull-off strength was measured to be 0.44 MPa. The fracture mode was mixed fracture.

[0102] Example 8

[0103] This embodiment demonstrates the interfacial bonding between the EPDM insulation layer and the energetic polyvinyl alcohol hydrogel based on an IPDI underlayer and cross-linked polyvinyl alcohol powder. The specific method is the same as in Example 8, with the main difference being that the oxidant in the energetic hydrogel propellant slurry is ammonium perchlorate (AP) and there is no aluminum powder filler. The underlayer formulation is the same as in Example 8, and the specific method is as follows:

[0104] At room temperature, a base lining slurry, using hydroxyl-terminated polybutadiene as a binder and isophorone diisocyanate as a curing agent, is uniformly coated onto the surface of the polished EPDM insulation layer. The base lining thickness is 0.6 mm. The mixture is then reacted at 80°C for 4 hours until pre-cured. Finally, 20 g / m² of starch powder is uniformly coated onto the surface of the pre-cured base lining. 2 The reaction continued at 80°C until the bottom lining slurry was completely cured. Then, an energetic hydrogel propellant slurry was poured in, using polyvinyl alcohol as a binder, borax as a crosslinking curing agent, ammonium perchlorate as an oxidant, and aluminum powder as fuel. After the energetic hydrogel propellant slurry was cured and formed at 50°C, the interface bonding was completed. A propellant / lining / insulation layer pull-off test specimen was made, and the combined pull-off strength was measured to be 0.20 MPa, and the fracture mode was mixed fracture.

[0105] Energetic hydrogel propellant slurry formulation:

[0106] Formula composition Number of parts by weight Polyvinyl alcohol 15 Borax 1.5 AP 70 water 15

[0107] Comparative Example 1

[0108] This comparative example demonstrates the bonding of an EPDM insulation layer to a polyvinyl alcohol energetic hydrogel using an IPDI liner. The specific method is the same as in Example 1, with the main difference being that polymer powder was not coated onto the surface of the pre-cured underlayer liner. The underlayer liner formulation and the energetic hydrogel propellant slurry formulation are the same as in Example 1. The specific method is as follows:

[0109] At room temperature, a lining slurry with hydroxyl-terminated polybutadiene as the binder and isophorone diisocyanate as the curing agent was uniformly coated on the surface of the polished EPDM insulation layer. The bottom lining layer had a thickness of 0.6 mm and was reacted at 80°C for 4 hours to reach a pre-cured state. Then, an energetic hydrogel propellant slurry with polyvinyl alcohol as the binder, borax as the crosslinking curing agent, ammonium nitrate as the oxidant, and aluminum powder as the fuel was poured in. After the energetic hydrogel propellant slurry was cured at 50°C, the interface bonding was completed. A propellant / lining / insulation layer pull-off test specimen was made. If the pull-off strength could not be measured, the interface failure occurred.

[0110] Comparative Example 2

[0111] This comparative example demonstrates the bonding of an EPDM insulation layer to a polyvinyl alcohol energetic hydrogel using an IPDI liner. The specific method is the same as in Example 1, with the main difference being that polymer powder was not coated onto the surface of the pre-cured underlayer liner, and the energetic hydrogel propellant was poured in only after the underlayer liner was fully cured. The formulations of the underlayer liner and the energetic hydrogel propellant slurry are the same as in Example 1. The specific method is as follows:

[0112] At room temperature, a lining slurry with hydroxyl-terminated polybutadiene as the binder and isophorone diisocyanate as the curing agent was uniformly coated on the surface of the polished EPDM insulation layer. The thickness of the bottom lining layer was 0.6 mm. The lining layer was reacted at 80°C until it was completely cured. Then, an energetic hydrogel propellant slurry with polyvinyl alcohol as the binder, borax as the crosslinking curing agent, ammonium nitrate as the oxidant, and aluminum powder as the fuel was poured in. After the energetic hydrogel propellant slurry was cured at 50°C, the interface bonding was completed. A propellant / lining / insulation layer pull-off test specimen was made. If the pull-off strength could not be measured, the interface failure occurred.

[0113] Comparative Example 3

[0114] This comparative example involves directly casting polyvinyl alcohol energetic hydrogel onto the surface of a EPDM insulation layer. The energetic hydrogel propellant slurry formulation is the same as in Example 1. The specific method is as follows:

[0115] At room temperature, an energetic hydrogel propellant slurry containing polyvinyl alcohol as an adhesive, borax as a crosslinking curing agent, ammonium nitrate as an oxidant, and aluminum powder as fuel was poured onto the surface of the polished EPDM insulation layer. After the energetic hydrogel propellant slurry was cured at 50°C, the interface bonding was completed. Propellant / insulation layer pull-off test specimens were made. If the pull-off strength could not be measured, the interface failure occurred.

[0116] Comparative Example 4

[0117] This comparative example involves directly casting polyvinyl alcohol energetic hydrogel onto the aluminum surface. The energetic hydrogel propellant formulation is the same as in Example 1, and the specific method is as follows:

[0118] At room temperature, an energetic hydrogel propellant slurry with polyvinyl alcohol as adhesive, borax as crosslinking curing agent, ammonium nitrate as oxidant, and aluminum powder as fuel was poured onto the polished aluminum surface. After the energetic hydrogel propellant slurry was cured at 50°C, the interface bonding was completed. Propellant / aluminum pull-off test specimens were made. If the pull-off strength could not be measured, the interface failure occurred.

[0119] Comparative Example 5

[0120] This comparative example demonstrates the bonding of an EPDM insulation layer to a polyvinyl alcohol energetic hydrogel using an IPDI liner. The specific method is the same as in Example 1, with the main difference being that polymer powder is coated onto the surface of the pre-cured underlayer liner, and energetic hydrogel propellant slurry is poured in before complete curing, followed by curing. The underlayer liner formulation and the energetic hydrogel propellant slurry formulation are the same as in Example 1, and the specific methods are as follows:

[0121] At room temperature, a lining slurry using hydroxyl-terminated polybutadiene as a binder and isophorone diisocyanate as a curing agent is uniformly coated onto the surface of the polished EPDM insulation layer. The thickness of the bottom lining layer is 0.6 mm. The mixture is reacted at 80°C for 4 hours to reach a pre-cured state. Then, 20 g / m² of polyvinyl alcohol 1799 powder is uniformly coated onto the surface of the pre-cured bottom lining layer. 2 Then, an energetic hydrogel propellant slurry with polyvinyl alcohol as binder, borax as crosslinking curing agent, ammonium nitrate as oxidant, and aluminum powder as fuel was poured. After the energetic hydrogel propellant slurry was cured at 50°C, the interface bonding was completed. A propellant / liner / insulation layer pull-off test specimen was made. The pull-off strength could not be measured and the interface failure occurred. In this comparative example, the mechanical interlocking force with the powder particles made it easy for the hydrogel to debond at the interface due to deformation.

[0122] In summary, the bonding method for the interface layer of a solid rocket motor liner provided by this invention involves first pre-coating a base liner slurry onto the surface of the material to be bonded, and then pre-curing it to form a pre-cured base liner. At this stage, the pre-cured base liner is not fully cured. After coating its surface with polymer powder, the active groups on the surface of the polymer powder react with the unreacted active isocyanates on the surface of the pre-cured base liner, achieving chemical bonding of the polymer powder within the pre-cured base liner. Simultaneously, during the coating of the polymer powder, some of the polymer powder is embedded in the pre-cured base liner. After the base liner is fully cured (if any unembedded polymer powder is present, it is removed), an energetic hydrogel propellant slurry is poured onto its surface. The water in the energetic hydrogel propellant slurry swells the polymer powder, and the curing agent in the energetic hydrogel propellant slurry further facilitates chemical bonding between the energetic hydrogel and the polymer powder. Reliable interface bonding is achieved once the energetic hydrogel propellant slurry is fully cured. This invention can increase the interfacial bonding strength from unmeasurable to over 0.4 MPa, effectively achieving interfacial bonding between energetic hydrogel propellants and rubber insulation layers and / or metal shells, thereby improving the bonding reliability of the propellant interface in hydrogel solid rocket engines.

[0123] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for bonding the interface layer of a solid rocket motor liner, characterized in that, It includes: A base layer slurry is pre-coated onto the surface of the objects to be bonded and then pre-cured to form a pre-cured base layer. A polymer powder is coated on the surface of the pre-cured underlayer, and the pre-cured underlayer is then completely cured to form a cured underlayer. Energetic hydrogel propellant slurry is poured onto the surface of the cured liner, and the energetic hydrogel propellant slurry is cured.

2. The bonding method for the interface layer of the solid rocket motor liner according to claim 1, characterized in that, The coating thickness of the bottom lining slurry is 0.1mm-5mm; Preferably, the coating thickness of the polymer powder is 5 g / m. 2 -200 g / m 2 .

3. The bonding method for the interface layer of the solid rocket motor liner according to claim 1, characterized in that, The pre-curing temperature of the bottom lining slurry is 20-90℃, and the pre-curing time is 2-12h; Preferably, the pre-curing temperature of the bottom lining slurry is 40-80℃, and the pre-curing time is 4-6h.

4. The bonding method for the interface layer of the solid rocket motor liner according to claim 1, characterized in that, The curing temperature of the energetic hydrogel propellant slurry is 20-70℃, and the curing time is 5-10 days.

5. The bonding method for the interface layer of the solid rocket motor liner according to any one of claims 1-4, characterized in that, The raw materials for the bottom lining slurry include a liquid polymer, a polyisocyanate curing agent, an adhesion promoter, a network modifier, a filler, and a curing catalyst in a mass ratio of 100:10-20:4-8:1.5-1.5:4-8:0.1-0.

3. Preferably, the liquid polymer comprises one or more of hydroxyl-terminated polybutadiene, hydroxyl-terminated polyether, hydroxyl-terminated butadiene-acrylonitrile rubber, and hydroxyl-terminated polyester. Preferably, the polyisocyanate curing agent includes one or more of toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dimer fatty acid diisocyanate, terephthalimide diisocyanate, and hexamethylene diisocyanate. Preferably, the adhesion promoter comprises one or more of tris(2-methyl)aziridine phosphine oxide, isophthaloyl (2-methylaziridine), and 1,3,5-benzentrioyl (2-ethylaziridine); Preferably, the network regulator comprises one or more of ethylene glycol, 1,4-butanediol, N,N-bis(2-hydroxypropyl)aniline, and trimethylolpropane; Preferably, the filler includes one or more of the following: silica, carbon black, titanium dioxide, zinc oxide, iron oxide, and chromium oxide. Preferably, the curing catalyst comprises one or more of iron acetylacetonate, dibutyltin dilaurate, triphenylbismuth, and 2,4,6-tris[(dimethylamino)methyl]phenol; Preferably, the curing reaction parameters (molar ratio of isocyanate to hydroxyl groups) in the bottom lining slurry during the curing reaction are 1.1-3.

0.

6. The bonding method for the interface layer of the solid rocket motor liner according to any one of claims 1-4, characterized in that, The polymer powder is a hydroxyl-containing polymer powder; Preferably, the polymer powder is one or more of the following: polyvinyl alcohol powder, polyvinyl alcohol and its derivative powder, starch and its derivative powder, cellulose and its derivative powder, hyaluronic acid and its derivative powder, agarose and its derivative powder, or cross-linked products of the above powders.

7. The bonding method for the interface layer of the solid rocket motor liner according to any one of claims 1-4, characterized in that, The raw materials for the energetic hydrogel propellant slurry include a binder, a crosslinking curing agent, an oxidant, and water in a mass ratio of 10-20:0.2-2:50-80:5-20; Preferably, the adhesive comprises one or more of polyvinyl alcohol and its derivatives, carboxymethyl cellulose and its derivatives; Preferably, the crosslinking curing agent includes one or more of boric acid, borax, and glutaraldehyde; Preferably, the oxidant includes one or more of ammonium perchlorate, ammonium nitrate, hydroxyl ammonium nitrate, dinitramide ammonium, and trinitromethanehydrazine; Preferably, the raw materials for the energetic hydrogel propellant slurry further include fuel, wherein the fuel accounts for 0-20% of the energetic hydrogel propellant slurry; Preferably, the fuel includes one or more of boron powder and aluminum powder.

8. The bonding method for the interface layer of the solid rocket motor liner according to any one of claims 1-4, characterized in that, The material to be bonded is an EPDM insulation layer, a nitrile rubber insulation layer, metallic iron, metallic aluminum, or metallic titanium.

9. A solid rocket motor liner interface layer, characterized in that, It is prepared by the bonding method of the solid rocket motor liner interface layer as described in any one of claims 1-8.

10. The application of the bonding method for the interface layer of the solid rocket motor liner as described in any one of claims 1-8 in the preparation of a solid rocket motor.

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