A novel mixed bonding agent of fluorine-containing polymer and amino-containing polymer and preparation method thereof

Abstract

The present invention provides a mixed bonding agent of a fluorine-containing polymer and an amino-containing polymer and a preparation method thereof. The present invention synthesizes a fluorine-containing polymer and an amino-containing polymer separately, and obtains the mixed bonding agent by mixing the two polymers in different ratios. This novel polymer mixed bonding agent is suitable for a solid propellant system composed of RDX as an oxidant and fluoropolymer F2313 as a binder. The mixed bonding agent contains both fluorine-based groups and amino groups. The fluorine-based groups increase the number of fluorine-containing segments in the binder F2313 that migrate to and accumulate on the surface, making the fluorine-containing polymer bonding agent and the binder F2313 more easily bonded. The amino groups form intermolecular hydrogen bonds with the oxidant RDX, thereby improving the adhesion work with the oxidant RDX. The mixed bonding agent can improve the "dewetting" phenomenon at the F2313 / RDX solid propellant interface, thereby improving the mechanical properties of the F2313 / RDX solid propellant.

Description

Technical Field

[0001] The present invention relates to the technical field of solid propellants, in particular to a novel polymer mixed bonding agent for improving the mechanical properties of solid propellants and a preparation thereof. Background Art

[0002] Composite solid propellants are energetic composite polymer materials with a polymer matrix and a solid particulate oxidizer as a filler. RDX (Hexafluoroquinoline) is the most powerful oxidizer used in military high explosives and represents the mainstream oxidizer market. Fluoropolymers are widely used as adhesive matrices for solid propellants due to their high thermal stability, good chemical compatibility, strong mechanical properties, and antioxidant, radiation, and aging resistance. The combination of the oxidizer RDX and the binder F2313 imparts excellent high-strength mechanical properties and safety to solid propellants. However, the strong electronegativity of fluorine atoms severely weakens the intermolecular cohesion, surface tension, and bonding strength of the fluoropolymer. This often leads to interfacial "dewetting" of the composite propellant at high RDX filling ratios or under high launch load stress, potentially causing solid grain collapse, mechanical structural fracture, center of gravity shift, and even explosion. To address these issues, bonding agents are often added to the propellant system to address interfacial "dewetting" in composite propellants.

[0003] The commonly used bonding agent is the neutral polymer bonding agent proposed by Kim et al. The structure of this neutral polymer bonding agent (NPBA) proposed by Kim contains a large number of active groups such as -CN and -OH. The active hydroxyl groups can participate in the curing reaction of the adhesive and form a highly chemically cross-linked transition layer with the adhesive. The cyano group can strongly adsorb on the surface of the nitramine molecule, inhibiting the dissolution of the nitramine molecule in the plasticizer system. Therefore, NPBA significantly improves the mechanical properties of high-energy nitrate polyether (NEPE) system propellants. However, NPBAs lack functional groups that can directly interact with the dense fluorine atoms and have difficulty forming a reinforcing effect with the high-energy fluorine-containing polymer binder matrix. RDX and the adhesive have similar cohesive energy densities, making NPBAs very difficult to adsorb. Therefore, existing polymer bonding agents NPBAs cannot meet the requirements of the F2313 / RDX propellant system, and there is an urgent need to develop new bonding agents suitable for improving the mechanical properties of the F2313 / propellant system. Summary of the Invention

[0004] The present invention aims to overcome the above-mentioned deficiencies of the prior art and provides a mixed bonding agent comprising a fluorine-containing polymer and an amino-containing polymer and a preparation method thereof. The present invention synthesizes a fluorine-containing polymer and an amino-containing polymer separately and mixes the two polymer groups in different ratios to obtain a mixed bonding agent. This novel polymer mixed bonding agent is suitable for use in a solid propellant system comprising RDX as an oxidant and fluoropolymer F2313 as a binder. The mixed bonding agent contains both fluorine-containing groups and amino groups. The fluorine-containing groups increase the number of fluorine-containing segments in the binder F2313 that migrate and accumulate toward the surface, making it easier for the fluorine-containing polymer bonding agent to adhere to the binder F2313. The amino groups form intermolecular hydrogen bonds with the oxidant RDX, thereby increasing the work of adhesion to the oxidant RDX. The mixed bonding agent can improve the "dewetting" phenomenon at the F2313 / RDX solid propellant interface, thereby improving the mechanical properties of the F2313 / RDX solid propellant.

[0005] The above-mentioned purpose of the present invention is mainly achieved through the following technical solutions:

[0006] A mixed bonding agent containing fluorine-based and amino-based polymers, characterized by:

[0007] The mixed bonding agent is prepared by mixing 2 to 5 parts of a fluorine-containing polymer and 4 to 8 parts of an amino-containing polymer by weight. In particular, the optimal ratio of 3 parts of a fluorine-containing polymer to 7 parts of an amino-containing polymer by weight is the best, and the performance of the mixed bonding agent is the best.

[0008] Among them, the structural formula of the fluorine-containing polymer bonding agent is:

[0009]

[0010] The amino-containing polymer structural formula is:

[0011]

[0012] Among them: a is 50-250, b is 15-75, c is 10-50, and d is 5-25.

[0013] In the above-mentioned fluorine-containing polymer and amino polymer, the molecular weight of the fluorine-containing polymer and amino polymer is 8×10 3 ~4×10 4 .

[0014] The preparation method of the above-mentioned fluorine-containing polymer and amino-containing polymer comprises the following steps:

[0015] (1) adding 60 to 180 parts of acrylonitrile, 18 to 54 parts of methyl acrylate, 12 to 48 parts of hydroxyethyl acrylate, and 6 to 24 parts of a fluorine-containing / amino compound into a reactor according to the molar ratio to obtain a mixed monomer solution;

[0016] (2) adding 100 to 300 parts of acetone solvent and 1 to 5 parts of azobisisobutyronitrile (AIBN) as an initiator to the mixed solution obtained in step (1), and stirring the solution in a constant temperature water bath at a speed of about 300 r / min to react;

[0017] (3) When the temperature of the solution in the reactor of step (2) reaches the water bath temperature, 1 to 5 parts of β-mercaptoethanol (β-Me) are added and the reaction is continued;

[0018] (4) After the solution obtained in step (3) is cooled to room temperature, it is slowly added dropwise to 300-600 parts of ethanol solution, mechanically stirred for 15-25 minutes, allowed to stand until the upper layer is clear, and the product is filtered out;

[0019] (5) The product obtained in step (4) was placed in a vacuum oven at 80° C. and dried to a constant weight, and the product was crushed by a crusher to obtain a fluorine-containing / amino polymer.

[0020] In the above-mentioned preparation method of the fluorine-containing polymer and the amino polymer, the fluorine-containing compound and the amino compound in step (1) are trifluoroethyl methacrylate and acrylamide, respectively.

[0021] In the above-mentioned preparation method of the fluorine-containing polymer and the amino-containing polymer, the constant temperature water bath in step (2) is 50-70°C.

[0022] In the above-mentioned method for preparing the fluorine-containing polymer and the amino-containing polymer, the reaction time in step (3) is 4 to 9 hours.

[0023] The preparation method of the polymer mixed bonding agent comprises: physically blending the fluorine-containing polymer and the amino-containing polymer in a certain proportion under certain conditions.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention synthesizes a fluorine-containing polymer and an amino-containing polymer respectively, and obtains a mixed bonding agent by mixing the two polymer groups in different ratios. This novel polymer mixed bonding agent is suitable for a solid propellant system composed of RDX as an oxidant and fluoropolymer F2313 as an adhesive. The mixed bonding agent contains both fluorine-containing groups and amino groups. The fluorine-containing groups increase the number of fluorine-containing segments that migrate and accumulate to the surface of the adhesive F2313, making it easier for the fluorine-containing polymer bonding agent to adhere to the adhesive F2313; the amino groups form intermolecular hydrogen bonds with the oxidant RDX, thereby improving the adhesion work with the oxidant RDX. The mixed bonding agent can effectively improve the "dehumidification" phenomenon of the F2313 / RDX solid propellant, thereby improving the mechanical properties of the F2313 / RDX solid propellant.

[0026] (2) The fluorine-containing / amino-containing polymer of the present invention is prepared by a free radical copolymerization method. Acrylonitrile, methyl acrylate, hydroxyethyl acrylate, trifluoroethyl methacrylate / acrylamide are added to a solvent containing an initiator in a certain proportion for reaction to obtain a fluorine-containing / amino-containing polymer. By controlling the molar ratio of the raw materials, the relative content of the functional groups in the fluorine-containing / amino-containing polymer can be effectively controlled. The reaction is quantitative and controllable, and the molecular weight of the product is effectively controllable. It can be reasonably adjusted according to the actual needs of the solid propellant to meet the requirements for solid propellant use.

[0027] (3) The present invention optimizes the performance of the bonding agent by adjusting the ratio of the fluorine-containing polymer and the amino polymer in the mixed bonding agent. Experiments have shown that, by weight, the optimal ratio is 3 parts of fluorine-containing polymer and 7 parts of amino polymer, and the performance of the mixed bonding agent is optimal. When the amino content is too high, the hydrogen bond content in the system is too high, the cross-linking density is high, and it is difficult to disperse. When the fluorine segment content is too high, the long chain structure formed causes the steric hindrance to increase, making it difficult to form hydrogen bonds with RDX.

[0028] (4) The preparation method of the mixed bonding agent of the fluorine-containing and amino polymers of the present invention is simple, easy to implement, has strong practicality, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 FT-IR spectrum of the fluorine-containing neutral polymer prepared in Example 1 of the present invention;

[0030] Figure 2 The fluorine-containing neutral polymer prepared in Example 1 of the present invention is 1 H-NMR spectrum;

[0031] Figure 3 FT-IR spectrum of the neutral polymer containing amino groups prepared in Example 2 of the present invention;

[0032] Figure 4 The amino-containing neutral polymer prepared in Example 2 of the present invention is 1 H-NMR spectrum. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in conjunction with the following examples, but the examples are not all examples.

[0034] Example 1

[0035] A fluorine-based polymer with the following chemical structure:

[0036]

[0037] The preparation method of the above polymer comprises the following steps:

[0038] (1) In a four-necked flask (500 ml) equipped with a mechanical stirrer, a reflux condenser, and a thermometer, 44.62 g of acrylonitrile, 21.72 g of methyl acrylate, 19.53 g of hydroxyethyl acrylate, and 14.14 g of trifluoroethyl methacrylate were added to obtain a mixed monomer solution;

[0039] (2) adding 100 ml of acetone solvent and 4.004 g of initiator azobisisobutyronitrile (AIBN) to the mixed solution obtained in step (1), and stirring the solution in a constant temperature water bath at a speed of about 300 r / min to react;

[0040] (3) When the temperature of the solution in the reactor of step (2) reaches 65°C, 0.5 g of β-mercaptoethanol (β-Me) is added and the reaction is continued for 7 hours;

[0041] (4) After the solution obtained in step (3) is cooled to room temperature, it is slowly added dropwise to 1500 ml of ethanol solution, mechanically stirred for 15 to 25 minutes, allowed to stand until the upper layer is clear, and the product is filtered out;

[0042] (5) The product obtained in step (4) was placed in a vacuum oven at 80° C. and dried to constant weight, and the product was crushed by a crusher to obtain a fluorine-containing polymer NPBA2-1.

[0043] The fluorine-containing polymer prepared by this method was tested by GPC, and the viscosity-average molecular weight Mn of the polymer was 16706 g / mol.

[0044] like Figure 1 Shown is the FT-IR spectrum of NPBA2-1 prepared in Example 1 of the present invention; Figure 2 The NPBA2-1 prepared in Example 1 of the present invention is shown. 1H-NMR spectrum.

[0045] Example 2

[0046] An amino-containing polymer having the following chemical structure:

[0047]

[0048] The preparation method of the above polymer comprises the following steps:

[0049] (1) In a four-necked flask (500 ml) equipped with a mechanical stirrer, a reflux condenser, and a thermometer, 48.58 g of acrylonitrile, 23.65 g of methyl acrylate, 21.26 g of hydroxyethyl acrylate, and 6.5 l of acrylamide were added to obtain a mixed monomer solution;

[0050] (2) adding 100 ml of acetone solvent and 4.0 g of initiator azobisisobutyronitrile (AIBN) to the mixed solution obtained in step (1), and stirring the solution in a constant temperature water bath at a speed of about 300 r / min to react;

[0051] (3) When the temperature of the solution in the reactor of step (2) reaches 65°C, 0.5 g of β-mercaptoethanol (β-Me) is added and the reaction is continued for 7 hours;

[0052] (4) After the solution obtained in step (3) is cooled to room temperature, it is slowly added dropwise to 1500 ml of ethanol solution, mechanically stirred for 15 to 25 minutes, allowed to stand until the upper layer is clear, and the product is filtered out;

[0053] (5) The product obtained in step (4) was placed in a vacuum oven at 80° C. and dried to constant weight, and the product was crushed by a crusher to obtain an amino-containing neutral polymer bonding agent NPBA3-1.

[0054] The fluorine-containing polymer prepared by this method was tested by GPC, and the viscosity-average molecular weight Mn of the polymer was 12763 g / mol.

[0055] like Figure 3 Shown is the FT-IR spectrum of NPBA3-1 prepared in Example 2 of the present invention; Figure 4 Shown is the NPBA2-1 prepared in Example 2 of the present invention. 1 H-NMR spectrum.

[0056] Example 3

[0057] A mixed bonding agent of a fluorine-containing polymer and an amino-containing polymer, wherein the mass ratio of the fluorine-containing polymer to the amino-containing polymer is controlled to be 1:4, and the preparation method thereof comprises the following steps:

[0058] (1) 8 g and 32 g of NPBA2-1 and NPBA3-1 prepared in Example 1 and Example 2, respectively, were weighed and placed in a four-necked flask (250 ml) equipped with a mechanical stirrer, a reflux condenser, and a thermometer;

[0059] (2) Add 80 ml of acetone solvent to the four-necked flask in step (1), then set a constant temperature water bath to 65°C, stir at 300 r / min, and stir and mix for 2 hours until NPBA2-1 and NPBA3-1 are evenly mixed.

[0060] (3) After the solution obtained in step (2) is cooled to room temperature, it is slowly added dropwise to 1500 ml of ethanol solution, mechanically stirred for 15 to 25 minutes, allowed to stand until the upper layer is clear, and the product is filtered out;

[0061] (4) The product obtained in step (3) was placed in a vacuum oven at 80° C. and dried to constant weight, and the product was crushed by a crusher to obtain a mixed bonding agent NPBA-1.

[0062] Example 4

[0063] A mixed bonding agent of a fluorine-containing polymer and an amino-containing polymer, wherein the mass ratio of the fluorine-containing polymer to the amino-containing polymer is controlled to be 3:7, and the preparation method thereof comprises the following steps:

[0064] (1) 9 g and 27 g of NPBA2-1 and NPBA3-1 prepared in Example 1 and Example 2, respectively, were weighed and placed in a four-necked flask (250 ml) equipped with a mechanical stirrer, a reflux condenser, and a thermometer;

[0065] (2) Add 72 ml of acetone solvent to the four-necked flask in step (1), then set a constant temperature water bath to 65°C, stir at 300 r / min, and stir and mix for 2 hours until NPBA2-1 and NPBA3-1 are evenly mixed.

[0066] (3) After the solution obtained in step (2) is cooled to room temperature, it is slowly added dropwise to 1500 ml of ethanol solution, mechanically stirred for 15 to 25 minutes, allowed to stand until the upper layer is clear, and the product is filtered out;

[0067] (4) The product obtained in step (3) was placed in a vacuum oven at 80° C. and dried to constant weight, and the product was crushed by a crusher to obtain a mixed bonding agent NPBA-2.

[0068] Example 5

[0069] A mixed bonding agent of a fluorine-containing polymer and an amino-containing polymer, wherein the fluorine-containing polymer and the amino-containing polymer are controlled to have a mass ratio of 5:4, and the preparation method thereof comprises the following steps:

[0070] (1) Weigh 20 g and 16 g of NPBA2-1 and NPBA3-1 prepared in Example 1 and Example 2, respectively, and place them in a four-necked flask (250 ml) equipped with a mechanical stirrer, a reflux condenser, and a thermometer;

[0071] (2) Add 72 ml of acetone solvent to the four-necked flask in step (1), then set a constant temperature water bath to 65°C, stir at 300 r / min, and stir and mix for 2 hours until NPBA2-1 and NPBA3-1 are evenly mixed.

[0072] (3) After the solution obtained in step (2) is cooled to room temperature, it is slowly added dropwise to 1500 ml of ethanol solution, mechanically stirred for 15 to 25 minutes, allowed to stand until the upper layer is clear, and the product is filtered out;

[0073] (4) The product obtained in step (3) was placed in a vacuum oven at 80° C. and dried to constant weight, and the product was crushed by a crusher to obtain a mixed bonding agent NPBA3.

[0074] Comparative Example 1

[0075] The chemical structure of traditional neutral polymer bonding agent is:

[0076]

[0077] The preparation method of the above-mentioned bonding agent comprises the following steps:

[0078] 5.78g of azobisisobutyronitrile (AIBN) initiator, 200g of acetone solvent, 103.93g of AN monomer, 50.59g of MA monomer, and 45.49g of HEA monomer were added sequentially to a 500ml four-necked flask equipped with a mechanical stirrer, a reflux cold flow tube, and a thermometer. The solution was stirred at approximately 300 rpm in a 65°C water bath. When the temperature reached 65°C, 0.5g of chain transfer agent β-Me was added. The reaction was allowed to proceed for 7 hours before being terminated.

[0079] After the reaction mixture cools to room temperature, slowly pour it into a large beaker containing 1500ml of ethanol. After mechanical stirring for 20 minutes, let it stand until the upper layer is relatively clear, then filter the product with fine gauze. Dry the product in an 80°C vacuum oven for 2 hours, remove it, crush it, and then transfer it to an 80°C vacuum oven to dry to constant weight. Finally, crush the product using a grinder to obtain the traditional neutral polymer bonding agent NPBA.

[0080] Performance Testing

[0081] The hydroxyl value of the bonding agent sample was determined using a ZDJ-4B automatic potentiometric titrator; the solubility parameters of the mixed bonding agent, adhesive F2313, and oxidant RDX were calculated using the group attraction factor superposition method; the contact angles of different reference solutions on the mixed bonding agent sample film were measured at 20°C using a DSA20 contact angle meter, and the surface tension was calculated according to Young's formula. The adhesion work of different bonding agents with adhesives or oxidants was further calculated. The adhesion work is an important parameter for characterizing interfacial interactions, reflecting the wettability of the material, and can be used to evaluate the strength of the interaction between two substances.

[0082] Comparing the mixed polymer bonding agent of the present invention with a traditional bonding agent, the hydroxyl value, solubility parameter of the bonding agent, and the adhesion work of the bonding agent to the adhesive F2313 and the oxidant RDX are listed in Table 1.

[0083] Table 1 Structural parameters of different bonding agents and adhesion work of oxidants and adhesives

[0084]

[0085] As can be seen from the data in Figure 1, compared to traditional bonding agents, the hybrid polymer bonding agent prepared in the present invention exhibits greater adhesion work with the binder F2313 and the oxidizer RDX. This indicates that the bonding agent prepared in the present invention exhibits stronger interfacial bonding with the oxidizer and binder, further enhancing the mechanical properties of the propellant. Furthermore, the solubility parameters of the hybrid polymer bonding agent are closer to those of the binder F2313 and the oxidizer RDX, increasing the compatibility between the bonding agent and the binder, and between the bonding agent and the oxidizer, and improving the bonding effectiveness of the bonding agent. This demonstrates particularly good bonding effectiveness for the F2313 / RDX solid propellant system.

[0086] The Brazilian test was used to characterize the bonding effects of different types of bonding agents with the adhesive F2313 and the oxidizer RDX, exploring their effects on the mechanical properties of the F2313 / RDX propellant system. The Brazilian test is a commonly used method for measuring the tensile strength of materials and is often used to verify the bonding effectiveness of bonding agents in propellants. The experimental results are listed in Table 2.

[0087] Table 2 Mechanical properties of different types of bonding agents and F2313 / RDX propellant

[0088] bonding agent Brazilian strength / MPa Brazilian strain / % Brazilian modulus / GPa Example 3 6.88 0.067 10.48 Example 4 7.75 0.0785 10.71 Example 5 7.14 0.071 10.55 Comparative Example 1 5.66 0.063 9.84

[0089] As shown in Table 2, the three mixed bonding agents synthesized in the examples of the present invention all significantly improved the mechanical properties of F2313 / RDX propellants compared to traditional neutral polymer bonding agents. Among them, Example 4, with a 3:7 mass ratio of fluorine-containing polymer to amino polymer, achieved the greatest improvement in mechanical properties, with Brazilian strength increased by 36.9% and Brazilian modulus by 8.8%.

[0090] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, and they should be covered by the scope of protection of the present invention.

Claims

1. A mixed bonding agent of a fluorine-containing polymer and an amino-containing polymer, characterized in that: By weight, it is prepared by mixing 2 to 5 parts of fluorine-containing polymer and 4 to 8 parts of amino-containing polymer: Among them, the structural formula of the fluorine-containing polymer is: The amino-containing polymer structural formula is: Among them: a is 50-250, b is 15-75, c is 10-50, d is 5-25; The molecular weight of the fluorine-containing polymer and the amino-containing polymer is 8×10 3 ~4×10 4 .

2. The hybrid bonding agent according to claim 1, characterized in that: By mass, the fluorine-containing polymer is 3 parts and the amino-containing polymer is 7 parts.

3. The hybrid bonding agent according to claim 1, characterized in that: The preparation method of the fluorine-containing polymer and the amino-containing polymer comprises the following steps: (1) adding 60 to 180 parts of acrylonitrile, 18 to 54 parts of methyl acrylate, 12 to 48 parts of hydroxyethyl acrylate, and 6 to 24 parts of a fluorine-containing / amino compound into a reactor according to the molar ratio to obtain a mixed monomer solution; (2) adding 100 to 300 parts of acetone solvent and 1 to 5 parts of azobisisobutyronitrile (AIBN) as an initiator to the mixed solution obtained in step (1), and stirring the solution in a constant temperature water bath at a speed of about 300 r / min to react; (3) When the temperature of the solution in the reactor of step (2) reaches the water bath temperature, 1 to 5 parts of β-mercaptoethanol (β-Me) are added and the reaction is continued; (4) After the solution obtained in step (3) is cooled to room temperature, it is slowly added dropwise to 300-600 parts of ethanol solution, mechanically stirred for 15-25 minutes, allowed to stand until the upper layer is clear, and the product is filtered out; (5) The product obtained in step (4) was placed in a vacuum oven at 80° C. and dried to a constant weight, and the product was crushed by a crusher to obtain a fluorine-containing / amino polymer.

4. The method for preparing a mixed bonding agent of a fluorine-containing polymer and an amino-containing polymer according to claim 3, wherein: The fluorine-containing compound and the amino-containing compound in step (1) are trifluoroethyl methacrylate and acrylamide, respectively.

5. The method for preparing a mixed bonding agent of a fluorine-containing polymer and an amino-containing polymer according to claim 3, wherein: The constant temperature of the water bath in step (2) is 50-70°C.

6. The method for preparing a mixed bonding agent of a fluorine-containing polymer and an amino-containing polymer according to claim 3, wherein: The reaction time in step (3) is 4 to 9 hours.

7. The method for preparing a mixed bonding agent according to claim 1, wherein: The invention is prepared by physically blending a fluorine-containing polymer and an amino-containing polymer in the proportion under certain conditions.

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