Flow aging response material for filling and sealing adiabatic gap of solid rocket engine

Abstract

The invention provides a flow aging response material for encapsulating an adiabatic gap of a solid rocket engine, the encapsulating material is prepared by mixing epoxy-terminated polyether and a low-molecular-weight polyamide curing agent, and molecular chains of the epoxy-terminated polyether and the low-molecular-weight polyamide curing agent in the components contain a large number of groups capable of easily forming reversible hydrogen bonds. Before filling, the filling and sealing material is subjected to strong shearing to destroy super-hydrogen bonds in a filling and sealing material system, so that the super-hydrogen bonds of the filling and sealing material are destroyed without being recombined under the strong shearing effect, the system has extremely low viscosity and can adapt to slit filling and sealing, the strong shearing effect disappears after the filling and sealing material is filled into a slit, and the internal super-hydrogen bonds are recombined; the system forms a semi-gel state, so that the flowability disappears quickly. According to the invention, the effect of flow aging response is realized through a strong shearing effect and a timeliness coupling effect formed by a super hydrogen bond, namely the physical characteristics of extremely high flowability during perfusion and rapid disappearance of the flowability after perfusion.

Description

Technical Field

[0001] This invention relates to the field of solid rocket motor technology, specifically to a flow-aging response material for filling the thermal gap of a solid rocket motor and its application method. Background Technology

[0002] Large solid rocket motors have numerous thermal insulation gaps in their insulation coatings, which are sealed and thermally protected using potting bonding. Since the potting process involves propellant, it must be performed at ambient temperature and pressure, avoiding strong electrical currents to mitigate safety risks. Furthermore, the gaps are small, typically less than 3mm, requiring the potting material to have good flowability during injection (0-3h). Once injected into the gaps, it must lose its flowability before complete curing (0-24h) to prevent leakage and potting defects, thus meeting the flow aging response requirement. The potting material needs to exhibit two opposing flowability characteristics before and after entering the gaps, possessing completely opposite flowability under the same chemical state. Clearly, conventional materials or formulations alone cannot address this issue. In addition, potting materials also need to meet the following requirements: room temperature curing, low density to reduce negative weight, no volatile solvent components, good flexibility, good adhesion to thermal insulation materials, and good ablation resistance. Currently commonly used potting materials such as silicone systems, polyurethane systems, acrylate systems, and epoxy resin systems cannot meet the above requirements.

[0003] Based on the above, for the thermal protection of the insulation gap of large solid rocket engines, it is necessary to develop special functional materials combined with special construction techniques to meet the contradictory process and performance requirements of the flow aging response of the filling material in this environment. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and to provide a flow-aging response material for filling the thermal gaps of solid rocket motors.

[0005] This invention provides the following technical solution:

[0006] This invention provides a flow-aging response material for filling the thermal insulation gap of a solid rocket motor, comprising component A and component B. Component A is an end-terminated epoxy polyether, and component B is a low molecular weight polyamide curing agent. The mass ratio of component A to component B is 100:80-200.

[0007] This potting material adopts a terminal epoxy polyether and polyamide curing structure. Through flexible molecular segments, rigid crosslinking, and super hydrogen bonding structure, it achieves high flexibility, low bulk strength, high elongation, and weak creep after curing.

[0008] Furthermore, the terminal epoxy polyether structure is as follows:

[0009]

[0010] Where R1 is H or CH3, and m = 4-10.

[0011] Furthermore, the low molecular weight polyamide curing agent is formed by the condensation polymerization of dimer acid and polyamine, with the following structural formula:

[0012]

[0013] The number of nitrogen atoms (N) in the structural formula of low molecular weight polyamide curing agents is determined by the type of polyamine: N=2 for ethylenediamine, N=3 for diethylenetriamine, and R2 for C. 34 Alkyl segments, n is between 1 and 2.

[0014] Furthermore, the potting material also includes one or more of a diluent, an accelerator, and a reinforcing filler.

[0015] Furthermore, the accelerator is an amine accelerator, including but not limited to DMP-30 and DBMA, and the amount added is 0.5%-2% of the total mass; the accelerator is mainly used to adjust the curing cycle of the material.

[0016] Furthermore, the diluent is an epoxy diluent, including but not limited to A100 and 5316, and the amount added is 2%-7% of the total mass; the diluent is mainly used to adjust the initial viscosity during material potting.

[0017] Furthermore, the reinforcing filler is modified carbon black and modified silica, including but not limited to A380, HL-380, modified N330 and modified N220, and the addition amount is 1%-4% of the total mass; the reinforcing filler is mainly used to adjust the strength, ablation resistance and creep resistance of the material after curing.

[0018] The present invention also provides a method for using the above-mentioned potting material. Before potting, the material is fully mixed according to the formula ratio using a mixing device with strong shear. Component A is terminal epoxy polyether, and component B is low molecular weight polyamide curing agent. The mass ratio of component A to component B is 100:80-200.

[0019] Furthermore, depending on performance and application requirements, one or more of the following may be added: accelerator, diluent, and reinforcing filler. The accelerator is an amine accelerator, added at 0.5%-2% of the total mass; the diluent is an epoxy diluent, added at 2%-7% of the total mass; and the reinforcing filler is modified carbon black and modified silica, added at 1%-4% of the total mass.

[0020] The flow-aging response method based on superhydrogen bond formation endows potting materials with opposite flow characteristics before and after potting. Specifically, before potting, a strong shearing action is applied to the potting material to disrupt the superhydrogen bonds within the system. Under this strong shearing, the broken superhydrogen bonds do not have time to recombine, resulting in an extremely low viscosity suitable for slot filling. Once the material is poured into the slot, the strong shearing action disappears, the internal superhydrogen bonds recombine, and the system forms a semi-gel-like state, causing the flow characteristics to rapidly disappear. This coupling effect of strong shearing and the time-dependent formation of superhydrogen bonds achieves the physical properties of extremely high flowability during potting and rapid loss of flowability after potting.

[0021] The present invention has the following beneficial effects:

[0022] 1. The potting material of the present invention achieves low viscosity during potting through the principle of shear thinning, so as to meet the requirement of full filling of the gap. After potting, it rapidly thickens through hydrogen bond recombination to meet the requirement of non-sagging and avoid the risk caused by gap defects.

[0023] 2. The potting material of the present invention solves the contradiction between high fluidity and rapid thickening during potting through the time-aged superhydrogen bond structure, thus meeting the application requirements of potting the gaps in the insulation layer of solid rocket engines.

[0024] 3. The potting material of the present invention has good adhesion to the insulation layer, low strength, and high elongation, and plays a role in protecting the insulation layer and insulation gap during engine operation.

[0025] 4. The potting material of the present invention has ultra-flexibility and good filling properties during the curing process and after curing, thus reducing the risk of engine failure. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The thermal insulation gap potting compound provided in this embodiment of the invention is made by mixing terminal epoxy polyether and low molecular weight polyamide curing agent. The terminal epoxy polyether is component A and the low molecular weight polyamide curing agent is component B, with a mass ratio of 100:80-200.

[0028] The material composition meets the requirements for room temperature curing, and the curing process will not release a large amount of heat.

[0029] The structure of the terminal epoxy polyether is as follows:

[0030]

[0031] Where R1 is H or CH3, and m = 4-10.

[0032] Low molecular weight polyamide curing agent is formed by the condensation polymerization of dimer acid and polyamine, with the following structural formula:

[0033]

[0034] The number of nitrogen atoms (N) in the structural formula of low molecular weight polyamide curing agents is determined by the type of polyamine: N=2 for ethylenediamine, N=3 for diethylenetriamine, and R2 for C. 34 Alkyl segments, n is between 1 and 2.

[0035] The terminal epoxy polyether and low molecular weight polyamide curing agent in the components contain a large number of groups that easily form reversible hydrogen bonds on their molecular chains; the main groups forming reversible hydrogen bonds in the terminal epoxy polyether are epoxy groups (-CH(O)CH-) and hydroxyl groups (-OH); the main groups forming reversible hydrogen bonds in the low molecular weight polyamide curing agent are amide groups (-CO-NH-) and amine groups (-NH2 or -NH-);

[0036] The formation of reversible hydrogen bonds in the formulation can be mainly categorized into the following four types:

[0037] a. The amide group (NH) of the polyamide and the O on the terminal epoxy polyether hydroxyl group;

[0038] b. The hydroxyl groups (OH) on the terminal epoxy polyether and the carbonyl oxygen (C=O) on the amide group of the polyamide;

[0039] c. The (NH) on the terminal amine group of the polyamide and the O on the terminal hydroxyl group of the epoxy polyether;

[0040] d. The amide group (NH) of one polyamide molecule reacts with the carbonyl oxygen (C=O) of another polyamide molecule.

[0041] Among them, the reversible hydrogen bond states formed under conditions a and b are the most typical and strongest states after the formulation of the present invention is mixed; the hydrogen bond state formed under condition c exists both before and after the formulation reaction.

[0042] The following figure shows several typical hydrogen bond states of the formulation after mixing:

[0043]

[0044] However, in order to ensure good gap filling effect and efficiency, the hydrogen bonds are broken under strong shear after the formula is mixed, and the viscosity is reduced.

[0045] After the formulated material is injected into the gap, it loses its strong shearing effect, and the hydrogen bonds between molecules are rapidly assembled and formed, resulting in a rapid increase in viscosity. It achieves a non-sagging effect in a short time, which can effectively avoid cavity defects in the insulation gap.

[0046] After the formulation material is injected into the gap, the terminal epoxy polyether and the low molecular weight polyamide curing agent begin to react and cure in three steps at room temperature.

[0047] The first step of the curing reaction is the reaction of the primary amine group (-NH2) on the polyamide with the epoxy group, which opens the three-membered ring and generates a secondary amine and a secondary hydroxyl group, as shown in the following reaction formula;

[0048] R-NH2+CH2(O)CH-R′→R-NH-CH2-CH(OH)-R′

[0049] The second step of the curing reaction involves the secondary amine group (-NH-) generated in the previous step reacting with an epoxy group to generate a tertiary amine and another secondary hydroxyl group, as shown in the following reaction formula;

[0050] R-NH-CH2-CH(OH)-R′+CH2(O)CH-R″→RN(CH2-CH(OH)-R″)-CH2-CH(OH)-R′

[0051] The third step of the curing reaction involves the large number of hydroxyl groups (-OH) generated in the reaction catalyzing the ring-opening of epoxy groups under the curing agent conditions to generate ether bonds, as shown in the following reaction formula;

[0052] R-OH+CH2(O)CH-R′→RO-CH2-CH(OH)-R′

[0053] Through the repeated reactions described above, a dense three-dimensional cross-linked network structure is eventually formed. At the same time, there are a large number of hydrogen bonds between the components, which effectively improves the impact resistance and toughness of the material. The structural diagram is shown below.

[0054]

[0055] The present invention will be further illustrated below through specific embodiments:

[0056] Example 1:

[0057] This embodiment provides a flow-aging-responsive material for filling the thermal gaps of a solid rocket motor:

[0058] First, a preferred formulation and its structure are provided. In the formulation, component A is a terminal epoxy polyether, wherein R1 is H, m=4, and there are a large number of hydroxyl groups (-OH) in the molecular chain segment, which helps to form superhydrogen bonds.

[0059] Component B in the formulation is a low molecular weight polyamide curing agent, wherein N=2, n=1, and contains a large number of flexible segments, wherein the amide group (-CO-NH-) and amine group (-NH2 or -NH-) are the main groups for forming hydrogen bonds;

[0060] When the formulation is mixed according to the mass ratio of components A to B of 100:115, a large number of reversible hydrogen bonds will form between the hydroxyl groups (-OH), amide groups (-CO-NH-), and amine groups (-NH2 or -NH-) in the liquid state.

[0061] The method of using the formula is to use a mixing device with strong shear to fully mix the ingredients according to the formula ratio before infusion. During the mixing process, the strong shear action makes the hydrogen bond breaking rate greater than the recombination rate.

[0062] The principle and requirement of the formulation for injection is to maintain a thinned state under strong shear mixing to facilitate injection into narrow gaps and achieve full filling.

[0063] After the formula is injected into the gap, the disappearance of strong shear force causes the superhydrogen bonds between molecules in the formula to recombine rapidly, which causes the viscosity of the adhesive to increase rapidly in the gap, reaching a state of non-flow, non-sagging and non-creep, so that the thermal insulation gap of the solid rocket motor is fully sealed.

[0064] The mixing device with strong shear is a device that can generate macroscopic mechanical shear force. During the mixing process of the adhesive, it generates strong shear force to break the superhydrogen bonds formed inside the material, so as to achieve the purpose of mixing and shear thinning.

[0065] The main function of the device is to generate strong shear force under the premise of fully mixing the adhesive solution, so as to break the hydrogen bonds between molecules in the adhesive solution and achieve the effect of shear thinning.

[0066] The device and its usage method, through the principle of shear thinning, achieve a low viscosity after mixing of the formulated adhesive solution, which meets the requirements for effective grouting of narrow gaps <3mm under normal temperature and pressure.

[0067] The performance of the formulation in this embodiment is shown in Table 1 below:

[0068] Table 1 Performance of Example 1

[0069] project result Remark Consistency of adhesive solution during shearing and injection (25℃) 50cm GB 1749-79 Consistency of adhesive solution 3 hours after shearing and infusion (25℃) 20cm GB 1749-79 Body tensile strength 0.04MPa Elongation at break 1346％ Bond strength with nitrile rubber insulation layer 0.03MPa Body fracture Bond strength with EPDM rubber insulation layer 0.03MPa Body fracture Applicable period 60-90min Meets application requirements

[0070] Example 2:

[0071] In this embodiment, to further enhance the non-sagging properties of the formulated adhesive in the gaps after injection and the creep resistance after curing, a certain amount of modified silica (A380) filler is added based on Example 1.

[0072] The modified silica is a lightweight white powder filler with surface hydroxyl (-OH) modification, which further increases the hydrogen bond density and overall viscosity of the mixed adhesive.

[0073] After adding modified silica to the formula, the initial viscosity of the mixed adhesive solution increases. In order to ensure a good narrow-slot injection effect, the matching mixing equipment needs to be modified.

[0074] The modification of the mixing equipment requires further increase in mechanical shear force. At the same time, in order to prevent mechanical heat from affecting the pot life of the formulated adhesive, the mixing equipment also needs to add a cooling function for the mixed adhesive.

[0075] The preferred cooling function of the equipment is a sandwich cooling method. In this embodiment, the equipment modification is achieved by adding a mixing cylinder sandwich and a cooling compressor.

[0076] The reduced density of the mixed adhesive in this embodiment helps to reduce the negative mass of the solid rocket motor.

[0077] In this embodiment, the presence of modified silica increases the number of intermolecular hydrogen bonds after the adhesive has cured in the gaps, resulting in better creep resistance and further improving the long-term storage capability of the solid rocket motor.

[0078] In this embodiment, the formulation uses 4 parts by mass of modified silica, and its properties are shown in Table 2 below:

[0079] Table 2 Performance of Example 2

[0080] project result Remark Consistency of adhesive solution during shearing and injection (25℃) 30cm GB 1749-79 3 hours after shearing and infusion, the consistency of the adhesive solution 10cm GB 1749-79 Body tensile strength 0.02MPa Elongation at break 874％ Bond strength with nitrile rubber insulation layer 0.02MPa Body fracture Strong adhesion to EPDM rubber insulation layer 0.02MPa Body fracture Applicable period 30-60min Meets application requirements

[0081] Example 3:

[0082] In this embodiment, to enhance the ablation resistance of the gap filling material, further protect the insulation layer and lining, and effectively increase the operational safety of the solid rocket motor, a certain amount of carbon black filler (N330) modified with catechol (C6H4(OH)2) is added to the formulation of Example 1.

[0083] The modified carbon black is a black modified carbon black powder filler with a large number of hydroxyl groups (-OH) on its surface. The hydroxyl groups (-OH) on its surface will further increase the hydrogen bond density and overall viscosity of the mixed adhesive.

[0084] Adding a certain amount of modified carbon black to the formula can greatly increase the ablation resistance of the filling material in the insulation gap, effectively improving the safety and stability of the solid rocket motor during operation.

[0085] In this embodiment, 10 parts by mass of modified carbon black are added to the formulation, and the properties are shown in Table 3 below:

[0086] Table 3 Performance of Example 3

[0087] project result Remark Consistency of adhesive solution during shearing and injection (25℃) 45cm GB 1749-79 Consistency of adhesive solution 3 hours after shearing and infusion (25℃) 13cm GB 1749-79 Body tensile strength 0.03MPa Elongation at break 1076％ Bond strength with nitrile rubber insulation layer 0.03MPa Body fracture Strong adhesion to EPDM rubber insulation layer 0.03MPa Body fracture Applicable period 60-90min Meets application requirements

[0088] Example 4:

[0089] Based on the results of Examples 1-3 above, this example is based on Example 1, with the addition of modified silica (A380) and modified carbon black (N330) fillers.

[0090] Through the formulation optimization in this embodiment, the thermal insulation gap filling material can not only meet the shear-thinning filling requirements, but also has good filling properties, non-sagging properties, long-term storage and ablation resistance, effectively protecting the storage stability and operational safety of solid rocket motors.

[0091] In this embodiment, the formulation simultaneously adds 8 parts by mass of modified carbon black and 2 parts by mass of modified silica. The properties are shown in Table 4 below:

[0092] Table 4 Performance of Example 4

[0093] project result Remark Consistency of adhesive solution during shearing and injection (25℃) 40cm GB 1749-79 Consistency of adhesive solution 3 hours after shearing and infusion (25℃) 12cm GB 1749-79 Body tensile strength 0.04MPa Elongation at break 954％ Bond strength with nitrile rubber insulation layer 0.03MPa Body fracture Strong adhesion to EPDM rubber insulation layer 0.03MPa Body fracture Applicable period 40-70min Meets application requirements

[0094] Example 5:

[0095] In order to further improve the injection efficiency and shorten the curing cycle, this embodiment adds a certain amount of accelerator (DMP-30) and a certain amount of epoxy diluent (A100) to the basis of Example 1.

[0096] After adding the accelerator to the formula, the reaction rate of the mixed adhesive solution is accelerated, which can shorten the curing cycle.

[0097] After adding epoxy diluent to the formula, the initial viscosity of the mixed adhesive solution is reduced, which can improve the injection efficiency.

[0098] This embodiment improves injection efficiency and shortens curing cycle, which helps to improve the assembly efficiency of solid rocket motors.

[0099] In this embodiment, the formulation uses an accelerator added at a mass ratio of 2 parts;

[0100] In this embodiment, an epoxy diluent with a mass ratio of 7 parts is added. The properties are shown in Table 5 below:

[0101] Table 5 Performance of Example 5

[0102] project result Remark Consistency of adhesive solution during shearing and injection (25℃) 65cm GB 1749-79 Consistency of adhesive solution 3 hours after shearing and infusion (25℃) 10cm GB 1749-79 Body tensile strength 0.05MPa Elongation at break 1045％ Bond strength with nitrile rubber insulation layer 0.04MPa Body fracture Bond strength with EPDM rubber insulation layer 0.04MPa Body fracture Applicable period 30-60min Meets application requirements

[0103] Example 6:

[0104] While keeping other conditions unchanged in Example 1, this example selects another terminal epoxy polyether as component A, where R1 is H and m = 10;

[0105] In this embodiment, another low molecular weight polyamide curing agent is selected as component B, where N = 2 and n = 2.

[0106] The performance of the formulation in this embodiment is shown in Table 6 below:

[0107] Table 6 Performance of Example 6

[0108] project result Remark Consistency of adhesive solution during shearing and injection (25℃) 35cm GB 1749-79 Consistency of adhesive solution 3 hours after shearing and infusion (25℃) 15cm GB 1749-79 Body tensile strength 0.03MPa Elongation at break 1521％ Bond strength with nitrile rubber insulation layer 0.02MPa Body fracture Bond strength with EPDM rubber insulation layer 0.02MPa Body fracture Applicable period 70-100min Meets application requirements

[0109] Example 7:

[0110] While keeping other conditions unchanged in Example 1, this example selects another terminal epoxy polyether as component A, wherein R1 is CH3 and m = 7;

[0111] In this embodiment, another low molecular weight polyamide curing agent is selected as component B, where N = 3 and n = 1;

[0112] The performance of the formulation in this embodiment is shown in Table 7 below:

[0113] Table 7 Performance of Example 7

[0114] project result Remark Consistency of adhesive solution during shearing and injection (25℃) 45cm GB 1749-79 Consistency of adhesive solution 3 hours after shearing and infusion (25℃) 18cm GB 1749-79 Body tensile strength 0.05MPa Elongation at break 1135％ Bond strength with nitrile rubber insulation layer 0.04MPa Body fracture Bond strength with EPDM rubber insulation layer 0.04MPa Body fracture Applicable period 30-60min Meets application requirements

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flow- and time-aging responsive material for use in the potting of the thermal gap of a solid rocket engine, characterized in that it comprises a mixture of a thermoplastic polymer and a thermosetting polymer. The potting material comprises A component and B component, the A component is terminal epoxy polyether, the B component is low molecular weight polyamide curing agent, the mass ratio of the A component and the B component is 100:80-200.

2. The flow and time responsive material for use in the potting of the thermal gap of a solid rocket engine according to claim 1, characterized in that: The terminal epoxy polyether structure is: Wherein, R1 is H or CH3, m=4-10.

3. The flow and time responsive material for use in the potting of the thermal gap of a solid rocket engine according to claim 1, characterized in that: The low molecular weight polyamide curing agent is obtained by condensation polymerization of dimer acid and polyamine, and the structural formula is: The number of N in the structure of low molecular weight polyamide curing agent is determined by the type of polyamine, N=2 is ethylenediamine, N=3 is diethylenetriamine, R2 is C 34 alkyl segment, n is between 1-2.

4. The flow- and time-aging responsive material for use in the gap filling of solid rocket engine insulation according to any one of claims 1 to 3, characterized in that: The potting material further comprises one or more of diluent, accelerator and reinforcing filler.

5. The flow and time responsive material for use in the potting of the thermal gap of a solid rocket engine according to claim 4, characterized in that: The accelerator is amine accelerator, including but not limited to DMP-30, DBMA, and the addition amount is 0.5%-2% of the total mass.

6. The flow and time responsive material for use in the potting of the thermal gap of a solid rocket engine according to claim 4, characterized in that: The diluent is epoxy diluent, including but not limited to A100, 5316, and the addition amount is 2%-7% of the total mass.

7. The flow and time responsive material for use in the potting of the thermal gap of a solid rocket engine according to claim 4, characterized in that: The reinforcing filler is modified carbon black and modified white carbon black, including but not limited to A380, HL-380, modified N330 and modified N220, and the addition amount is 1%-4% of the total mass.

8. The flow- and time-aging responsive material for use in the gap filling of solid rocket engine insulation according to any one of claims 1 to 7, characterized in that: Before perfusion, the mixing equipment with strong mechanical shear is used for fully mixing according to the proportion, the A component is terminal epoxy polyether, the B component is low molecular weight polyamide curing agent, and the mass ratio of the A component and the B component is 100:80-200.

9. The flow and time responsive material for use in the potting of the thermal gap of a solid rocket engine according to claim 8, characterized in that: According to the performance and application requirements, one or more of accelerator, diluent and reinforcing filler needs to be added, the accelerator is amine accelerator, the addition amount is 0.5%-2% of the total mass, the diluent is epoxy diluent, the addition amount is 2%-7% of the total mass, and the reinforcing filler is modified carbon black and modified white carbon black, the addition amount is 1%-4% of the total mass.

Images