A solid rocket engine lining and layered molding method

Abstract

The invention discloses a layered forming method for a solid rocket engine lining, firstly, a bottom layer slurry is uniformly coated on the surface of an insulation layer, and the bottom layer slurry is pre-reacted to obtain a surface-dry bottom layer of the lining layer; then, an intermediate layer slurry is uniformly coated on the surface of the surface-dry bottom layer of the lining layer, and the intermediate layer slurry is pre-reacted to obtain a gelled lining intermediate layer, and in this process, the bottom layer of the lining layer will also reach a gelled state; then, after the surface layer slurry is coated on the surface of the gelled lining intermediate layer, a propellant slurry is poured; finally, the gelled lining bottom layer, the intermediate layer, and the surface layer slurry coated on the surface of the gelled lining intermediate layer are cured and formed together with the propellant slurry to complete the interface bonding. The invention can increase the interface bonding strength by more than 20%, effectively improve the problem of the weak strength layer of the propellant near the interface, and improve the reliability of the interface bonding of the solid rocket engine charge.

Description

Technical Field

[0001] The invention relates to a layered design and molding method for a solid rocket engine lining, and belongs to the technical field of solid rocket engine charge interface bonding. Background Art

[0002] Propellant is the power source of solid rocket engines. Propellant with terminal hydroxyl polybutadiene as adhesive and isophorone diisocyanate as curing agent (hereinafter referred to as IPDI type hydroxybutadiene propellant) is the main type of composite solid propellant in various countries around the world. The most critical issue affecting the application of IPDI type hydroxybutadiene propellant is to achieve reliable interface bonding between propellant / liner / insulating layer, especially the interface bonding between propellant / liner. The failure of bonding will cause the combustion surface of the solid rocket engine to increase abnormally during operation, causing overheating and loss of strength of the shell, leading to burn-through or even explosion.

[0003] Chemical bonding is the most important and effective bonding method at the propellant / liner interface. When the two come into contact, they dissolve and diffuse at the interface to form an interface layer of a certain thickness, accompanied by chemical reactions of active hydrogen groups such as isocyanate (-NCO) and hydroxyl (-OH) to form chemical bonds. Ideally, this will proceed simultaneously with the chemical reactions of the propellant and liner themselves, forming a polymer network structure to connect the two. However, due to the mutual diffusion and side reactions of the components in the propellant, liner and insulation layer, such as the migration of small molecules such as moisture and stearic acid in the insulation layer to the liner and propellant and side reactions with the propellant near the interface, and the diffusion of free curing agent in the propellant to the liner, the molar ratio of -NCO to -OH will deviate from the design, resulting in a low degree of cross-linking and curing in the interface area, and ultimately forming a weak strength layer of the propellant near the interface.

[0004] At present, limited by the understanding of the propellant / liner interface bonding reaction process, in order to ensure that the curing reaction in the interface area proceeds as designed and to eliminate the influence of component migration and side reactions as much as possible, the -NCO to -OH molar ratio designed in the liner system is usually greater than 1 to enhance the anti-interference ability of the curing reaction of the bonding system. This leads to the need for a large number of regular experiments in liner design, continuous adjustment of formulas and processes, and determination of appropriate curing parameters based on experimental results to ensure good bonding performance at the interface. This has the following problems: the effects of the insulation layer and the propellant on the interface bonding are very different, and it is difficult to coordinate the bonding of the liner with a single curing parameter with the insulation layer and the propellant interface, resulting in low interface bonding performance and poor stability, and poor quality stability and reliability of the charge product. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects and provide a solid rocket engine lining layer forming method, firstly, the bottom layer slurry is evenly coated on the surface of the insulation layer, and the bottom layer slurry is pre-reacted to obtain a surface-dry bottom layer of the lining layer; then the middle layer slurry is evenly coated on the surface of the surface-dry bottom layer of the lining layer, and the middle layer slurry is pre-reacted to obtain a gelled lining middle layer, and the bottom layer of the lining layer will also reach a gelled state during this process; then, the surface layer slurry is coated on the surface of the gelled lining middle layer, and the propellant slurry is poured; finally, the gelled lining bottom layer, the middle layer and the surface layer slurry coated on the surface of the gelled lining middle layer are cured and formed together with the propellant slurry to complete the interface bonding. The present invention can increase the interface bonding strength by more than 20%, effectively improve the problem of the weak strength layer of the propellant near the interface, and improve the reliability of the interface bonding of the solid rocket engine charge.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A solid rocket engine lining layer forming method, comprising:

[0008] The liner is divided into a liner bottom layer, a liner middle layer and a liner surface layer in the direction from the thermal insulation layer to the propellant;

[0009] The bottom slurry is evenly coated on the surface of the thermal insulation layer, and the bottom slurry is pre-reacted to obtain a bottom lining layer in a surface dry state;

[0010] The intermediate layer slurry is evenly coated on the surface of the bottom lining layer in a surface-dry state, and the intermediate layer slurry and the bottom lining layer in a surface-dry state are pre-reacted to obtain a gelled intermediate lining layer and a bottom lining layer;

[0011] After coating the surface slurry on the gelled liner intermediate layer, pouring the propellant slurry;

[0012] The gelled lining bottom layer, the lining middle layer and the surface layer slurry coated on the surface of the gelled lining middle layer are solidified together with the propellant slurry to form a lining. The lining bottom layer, the lining middle layer and the lining surface layer are connected as a whole to form an interface bond between the lining and the propellant.

[0013] Furthermore, the solidification parameters of the bottom layer slurry>the solidification parameters of the surface layer slurry>the solidification parameters of the middle layer slurry.

[0014] Further, the curing agent concentration c1 in the liquid phase volume of the surface layer slurry is higher than the curing agent concentration c2 in the liquid phase volume of the propellant slurry;

[0015] c1-c2=0.2mol / L~0.4mol / L.

[0016] Furthermore, the curing parameter of the bottom layer slurry is greater than 3; the curing parameter of the middle layer slurry is 1.05 to 1.2; and the curing parameter of the surface layer slurry is 1.2 to 1.3.

[0017] Furthermore, the pre-reaction temperature of the bottom layer slurry is 50°C to 60°C; the pre-reaction temperature of the middle layer slurry is 65°C to 85°C.

[0018] Furthermore, after being solidified and formed together with the propellant slurry, the thicknesses of the lining bottom layer, the lining middle layer and the lining surface layer in the lining are 0.05mm-0.10mm, 0.35mm-0.80mm and 0.15mm-0.30mm respectively.

[0019] Furthermore, the base layer slurry, the middle layer slurry and the surface layer slurry all adopt a formulation system using terminal hydroxyl polybutadiene as a binder and isophorone diisocyanate as a curing agent.

[0020] Furthermore, the thermal insulation layer is an EPDM thermal insulation layer or a nitrile thermal insulation layer.

[0021] Furthermore, the propellant slurry adopts a formulation system with terminal hydroxyl polybutadiene as a binder and isophorone diisocyanate as a curing agent.

[0022] A solid rocket engine lining is obtained by adopting the above-mentioned solid rocket engine lining layered molding method.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention innovatively proposes a solid rocket engine liner layering molding method, which can increase the interface bonding strength by more than 20%, effectively improve the problem of the propellant weak strength layer near the interface, and improve the reliability of the solid rocket engine charge interface bonding;

[0025] (2) The present invention defines the process parameters such as the curing parameters, pre-reaction temperature and molding thickness of the slurry of each layer of the liner. Under the combination of these parameters, the mechanical properties of the insulation layer / liner / propellant interface can be further optimized;

[0026] (3) In the method of the present invention, the type of the thermal insulation layer, the lining layer and the propellant formulation can be adjusted as needed, and the application range is wide. It is particularly suitable for a lining layer / propellant system with terminal hydroxyl polybutadiene as an adhesive and isophorone diisocyanate as a curing agent, which is conducive to large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a layered molding method for a solid rocket engine liner of the present invention;

[0028] Figure 2This is a fracture surface morphology diagram of the specimen obtained in Comparative Example 1 of the present invention after tensile test;

[0029] Figure 3 This is a fracture surface morphology diagram of the specimen obtained in Example 1 of the present invention after tensile testing. DETAILED DESCRIPTION

[0030] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0031] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0032] The present invention provides a liner layered molding method with simple process, which can effectively eliminate the influence of the migration of propellant, liner and insulation layer components and the cross-linking curing side reaction, thereby significantly improving the interface bonding strength of solid rocket engine charge and ensuring the integrity of the charge structure. Figure 1 As shown, the steps include:

[0033] Step 1: Evenly apply the lining bottom slurry on the surface of the insulation layer at room temperature and pre-react until the surface is dry;

[0034] Step 2, evenly coating the lining middle layer slurry on the surface of the lining bottom layer obtained in step 1, and pre-reacting until gelation;

[0035] Step three, coating the surface of the semi-cured (ie gelled) lining middle layer obtained in step two with lining surface slurry, then pouring the propellant slurry and allowing the lining slurry to solidify and form along with the propellant slurry to complete the interface bonding.

[0036] Furthermore, in the above step 1, the curing parameter of the lining bottom layer slurry is greater than 3, the molding thickness of the lining bottom layer is 0.05 mm to 0.10 mm, and the pre-reaction temperature is 50° C. to 60° C.

[0037] Furthermore, in the above step 2, the curing parameter of the lining middle layer slurry is 1.05-1.2, the molding thickness of the lining middle layer is 0.35mm-0.80mm, and the pre-reaction temperature is 65°C-85°C.

[0038] Furthermore, in the above step three, the curing parameters of the lining surface layer slurry are 1.2 to 1.3, and the forming thickness of the lining surface layer is 0.15 mm to 0.3 mm.

[0039] Furthermore, in the above step three, the curing agent concentration c1 in the liquid phase volume of the surface layer slurry is higher than the curing agent concentration c2 in the liquid phase volume of the propellant slurry, c1-c2=0.2mol / L~0.4mol / L.

[0040] Furthermore, the lining slurry adopts a formulation system with terminal hydroxyl polybutadiene as a binder and isophorone diisocyanate as a curing agent.

[0041] Furthermore, in the above step 1, the insulation layer is an insulation layer material with a specific formula of EPDM insulation layer or nitrile insulation layer.

[0042] Furthermore, in the above step three, the propellant slurry adopts a formulation system with terminal hydroxyl polybutadiene as a binder and isophorone diisocyanate as a curing agent.

[0043] The present invention discloses a layered forming method for a solid rocket engine lining. The lining is finely layered based on the characteristics of the thermal insulation layer and the propellant affecting the interface bonding performance. The lining design is divided into a bottom layer, an intermediate layer and a surface layer. The bottom layer of the lining is a layer rich in isocyanate groups, which can react chemically with small molecules containing active hydrogen in the thermal insulation layer at a relatively fast rate, and the function is to achieve bonding with the thermal insulation layer while effectively preventing small molecules containing active hydrogen from migrating to the interface between the lining and the propellant. The curing speed is controlled by the curing temperature. The pre-reaction temperature of the intermediate layer is 65° C. to 85° C., and gelation is usually achieved in only 1 to 4 hours. Therefore, the intermediate layer of the lining is a fast curing body layer, and the lining body undergoes a chemical reaction to form a polymer network. The network structure is used to avoid the problem of uneven thickness of the lining slurry due to sagging through rapid solidification, and at the same time relieve the stress of the charge combustion chamber; the lining surface layer is a balancing layer. In the existing traditional method, the curing agent content during propellant pouring is higher than that of the lining after pre-curing, and the curing agent in the interface area may migrate from the propellant to the lining layer. In the present invention, the lining surface layer reduces the migration by reducing the difference in curing agent concentration between the lining layer and the propellant. In the present invention, the concentration of the curing agent in the lining surface layer is even higher than that of the propellant curing agent, so that the curing agent in the interface area migrates from the lining layer to the propellant, which is beneficial to ensure that the interface propellant is cured as designed and reaches a curing and cross-linking degree close to that of the propellant body.

[0044] Example 1

[0045] At room temperature, the surface of the EPDM insulation layer is evenly coated with a liner (hereinafter referred to as IPDI type hydroxybutyl liner) bottom layer slurry with terminal hydroxy polybutadiene as an adhesive and isophorone diisocyanate as a curing agent, the curing parameter of which is 3.5, the molding thickness of the liner bottom layer is 0.09mm-0.10mm, and the surface is pre-reacted at 59℃-60℃ until the surface is dry; the IPDI type hydroxybutyl liner middle layer slurry is evenly coated on the surface of the coated liner bottom layer, the curing parameter of which is 1.1, and the molding thickness of the liner middle layer is 0.5 0mm±0.01mm, pre-react at 79℃~80℃ until gelation; evenly coat the surface of the semi-solidified intermediate layer with IPDI type hydroxybutyric acid liner layer slurry, the curing parameter of which is 1.2, and the liner layer forming thickness is 0.15mm~0.16mm, and then pour IPDI type hydroxybutyric acid propellant slurry, the curing agent concentration in the liquid phase volume of the liner layer slurry is 0.2mol / L higher than the curing agent concentration in the liquid phase volume of the propellant slurry, the liner system is cured and formed along with the propellant to complete the interface bonding.

[0046] A rectangular tear-off specimen of propellant / liner / insulation layer was made, and the combined tear-off strength was measured to be 922 kPa. The fracture surface morphology after the tensile test was as follows: Figure 3 shown.

[0047] Example 2

[0048] At room temperature, the surface of the EPDM insulation layer is uniformly coated with IPDI type hydroxybutyric liner bottom layer slurry, the curing parameter of which is 3.5, the molding thickness of the liner bottom layer is 0.05mm~0.06mm, and it is pre-reacted at 59℃~60℃ until the surface is dry; the surface of the coated liner bottom layer is then uniformly coated with IPDI type hydroxybutyric liner middle layer slurry, the curing parameter of which is 1.05, the molding thickness of the liner middle layer is 0.45mm±0.01mm, and it is pre-reacted at 74℃~75℃ until gelation; the surface of the semi-cured middle layer is then uniformly coated with IPDI type hydroxybutyric liner surface layer slurry, the curing parameter of which is 1.2, the molding thickness of the liner is 0.2mm±0.01mm, and then IPDI type hydroxybutyric propellant slurry is poured, the curing agent concentration in the liquid phase volume of the liner surface layer slurry is 0.2mol / L higher than the curing agent concentration in the liquid phase volume of the propellant slurry, the lining system is cured and formed along with the propellant to complete the interface bonding.

[0049] A rectangular tear-off test piece of propellant / liner / insulation layer was made, and the combined tear-off strength was measured to be 876 kPa.

[0050] Example 3

[0051] At room temperature, a layer of isophorone diisocyanate is evenly coated on the surface of the EPDM insulation layer, and the molding thickness is 0.05mm-0.06mm, and it is heated at 59℃-60℃ until the surface is dry; IPDI type hydroxybutyric acid liner middle layer slurry is evenly coated on the coated bottom surface, and the curing parameter is 1.2, the molding thickness of the lining middle layer is 0.60mm±0.01mm, and it is pre-reacted at 84℃-85℃ to gel; IPDI type hydroxybutyric acid liner surface layer slurry is evenly coated on the surface of the semi-cured middle layer, and the curing parameter is 1.25, and the lining molding thickness is 0.15mm-0.16mm, and then IPDI type hydroxybutyric acid propellant slurry is poured, the curing agent concentration in the liquid phase volume of the liner surface layer slurry is 0.25mol / L higher than the curing agent concentration in the liquid phase volume of the propellant slurry, and the lining system is cured and formed along with the propellant to complete the interface bonding.

[0052] A rectangular tear-off test piece of propellant / liner / insulation layer was made, and the combined tear-off strength was measured to be 965 kPa.

[0053] Example 4

[0054] At room temperature, the surface of the nitrile insulation layer is uniformly coated with IPDI type hydroxybutyric liner bottom layer slurry, the curing parameter of which is 4.5, the lining molding thickness is 0.09mm~0.10mm, and it is pre-reacted at 54℃~55℃ until the surface is dry; the surface of the coated bottom layer is then uniformly coated with IPDI type hydroxybutyric liner middle layer slurry, the curing parameter of which is 1.2, the lining molding thickness is 0.4mm±0.01mm, and it is pre-reacted at 65℃~66℃ until gelation; the surface of the semi-cured middle layer is then uniformly coated with IPDI type hydroxybutyric liner surface layer slurry, the curing parameter of which is 1.3, the lining molding thickness is 0.2mm±0.01mm, and then IPDI type hydroxybutyric propellant slurry is poured, the curing agent concentration in the liquid phase volume of the liner surface layer slurry is 0.3mol / L higher than the curing agent concentration in the liquid phase volume of the propellant slurry, the lining system is cured and formed along with the propellant to complete the interface bonding.

[0055] A rectangular tear-off test piece of propellant / liner / insulation layer was made, and the combined tear-off strength was measured to be 903 kPa.

[0056] Comparative Example 1

[0057] At room temperature, a layer of IPDI type hydroxybutane lining slurry is evenly coated on the surface of the EPDM insulation layer. The curing parameter is 1.25, which is the optimal value of the lining curing parameter in the insulation layer / lining / propellant system. The lining molding thickness is 0.75mm~0.76mm. It is pre-reacted at 79℃~80℃ to gelation, and then the IPDI type hydroxybutane propellant slurry is poured. The lining is cured and formed along with the propellant to complete the interface bonding.

[0058] Propellant / liner / insulation layer rectangular tear-off test pieces were made, and the tensile strength of the propellant body was measured to be 1013 kPa according to GJB 770B-2005 "Test Methods for Explosive Powder", and the combined tear-off strength was measured to be 683 kPa according to QJ 916-1985 "Tensile Test Methods for Insulation Layer and Lining Material in Solid Motor Combustion Chamber". It can be seen from the test data of Examples 1 to 3 and Comparative Example 1 that the combined tear-off strength of the propellant / liner / insulation layer test pieces prepared by the liner layer layering molding method of the present invention in Examples 1, 2 and 3 is increased by 239 kPa, 193 kPa and 282 kPa respectively compared with the test piece prepared by the liner layer non-layered molding in Comparative Example 1.

[0059] In addition, the fracture surface morphology of the specimen of comparative example 1 after tensile test is as follows Figure 2 As shown in FIG. 1 , it can be seen that the fracture surface morphology is relatively flat. The fracture of the comparative example 1 specimen is caused by the overall peeling of the near-interface propellant. This is because there is a weak interface layer in the near-interface propellant and the interface bonding strength is poor. The fracture surface morphology of the embodiment 1 specimen after the tensile test is as follows: Figure 3 As shown, it can be seen that under the tensile test, the propellant body of the embodiment 1 specimen underwent a U-shaped fracture, and the strain at the interface failure was greater. This is because the weak interface layer was eliminated in the embodiment 1 specimen, and the liner / propellant interface bonding strength was enhanced.

[0060] Comparative Example 2

[0061] At room temperature, a layer of IPDI type hydroxybutane lining slurry with a curing parameter of 1.25 is evenly coated on the surface of the nitrile insulation layer. This value is the optimal value of the lining curing parameter in the insulation layer / lining / propellant system. The lining molding thickness is 0.7mm±0.01mm. It is pre-reacted at 65℃~66℃ to gelation, and then the IPDI type hydroxybutane propellant slurry is poured. The lining system is cured and formed along with the propellant to complete the interface bonding.

[0062] A rectangular tear-off test piece of propellant / liner / insulation layer was made, and the tensile strength of the propellant body was measured to be 813 kPa, and the combined tear-off strength was 677 kPa. From the test data of Example 4 and Comparative Example 2, it can be seen that the combined tear-off strength of the propellant / liner / insulation layer test piece prepared by the liner layer layering molding method of Example 4 is 226 kPa higher than that of the test piece prepared by the liner layer non-layered molding in Comparative Example 2.

[0063] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0064] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A solid rocket engine lining layer forming method, characterized in that: include: The liner is divided into a liner bottom layer, a liner middle layer and a liner surface layer in the direction from the thermal insulation layer to the propellant; The bottom slurry is evenly coated on the surface of the thermal insulation layer, and the bottom slurry is pre-reacted to obtain a lining bottom layer in a surface dry state; The intermediate layer slurry is evenly coated on the surface of the bottom lining layer in a surface-dry state, and the intermediate layer slurry and the bottom lining layer in a surface-dry state are pre-reacted to obtain a gelled intermediate lining layer and a bottom lining layer; After coating the surface slurry on the gelled liner intermediate layer, pouring the propellant slurry; The gelled lining bottom layer, the lining middle layer and the surface layer slurry coated on the surface of the gelled lining middle layer are solidified together with the propellant slurry to form a lining. The lining bottom layer, the lining middle layer and the lining surface layer are connected as a whole to form an interface bond between the lining and the propellant.

2. A solid rocket engine liner layering molding method according to claim 1, characterized in that: The curing parameters of the bottom layer slurry > the curing parameters of the surface layer slurry > the curing parameters of the middle layer slurry.

3. A solid rocket engine liner layering molding method according to claim 1, characterized in that: The curing agent concentration c1 in the liquid phase volume of the surface layer slurry is higher than the curing agent concentration c2 in the liquid phase volume of the propellant slurry, satisfying: c1-c2=0.2mol / L~0.4mol / L.

4. A solid rocket engine liner layering molding method according to claim 1, characterized in that: The curing parameter of the bottom layer slurry is greater than 3; the curing parameter of the middle layer slurry is 1.05-1.2; and the curing parameter of the surface layer slurry is 1.2-1.

3.

5. A solid rocket engine lining layer forming method according to claim 1 or 4, characterized in that: The pre-reaction temperature of the bottom layer slurry is 50°C to 60°C; the pre-reaction temperature of the middle layer slurry is 65°C to 85°C.

6. A solid rocket engine liner layering molding method according to claim 1, characterized in that: After being solidified and formed together with the propellant slurry, the thicknesses of the lining bottom layer, the lining middle layer and the lining surface layer in the lining are 0.05mm-0.10mm, 0.35mm-0.80mm and 0.15mm-0.30mm respectively.

7. A solid rocket engine liner layering molding method according to claim 1, characterized in that: The base layer slurry, the middle layer slurry and the surface layer slurry all adopt a formula system with terminal hydroxyl polybutadiene as a binder and isophorone diisocyanate as a curing agent.

8. The method for layered molding of a solid rocket engine liner according to claim 1, characterized in that: The heat insulating layer is an EPDM heat insulating layer or a nitrile heat insulating layer.

9. A solid rocket engine liner layering molding method according to claim 1, characterized in that: The propellant slurry adopts a formula system with terminal hydroxyl polybutadiene as a binder and isophorone diisocyanate as a curing agent.

10. A solid rocket engine liner, characterized in that: It is obtained by adopting the solid rocket engine lining layering molding method described in any one of claims 1-9.

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