MXene-based binder, tungsten-based delay powder and method

Abstract

The invention provides an MXene-based binder, a tungsten-based delay powder and a preparation method, and the preparation method of the MXene-based binder specifically comprises the following steps: mixing a vinyl chloride-vinyl acetate resin solution, a polyvinylidene fluoride-hexafluoropropylene solution and an MXene suspension to obtain a mixed solution; and adding a plasticizer into the mixed solution, stirring, drying, freezing and crushing to obtain the Mxene-based binder. The preparation method of the binder system is simple, large-scale production is facilitated, and the binder system is stable in combustion, high in combustion efficiency, good in mechanical property and low in gas yield when applied to the tungsten delay powder.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energetic materials, and particularly relates to a MXene-based binder and a tungsten-based delay composition and a method. BACKGROUND

[0002] As a core functional material in pyrotechnics and energetic devices, the core role of the delay composition is to accurately control the time interval of energy transmission or reaction triggering. This characteristic makes the delay composition widely used in weapon systems, civil blasting engineering, aerospace and other fields. Specifically, in the missile weapon system, the delay composition is used to control the ignition timing of each stage of the missile to ensure the accuracy of the flight trajectory; in space vehicles, the delay composition is used to realize the timing control of key actions such as separation and unlocking; in conventional weapons, the delay composition also plays an irreplaceable role, such as controlling the detonation time of the shell fuse. As a typical slow delay composition, the tungsten-based delay composition has become the mainstream choice in the above-mentioned fields due to its wide range of adjustable burning rate, good low-temperature combustion performance (stable combustion within the range of-60℃ to 70℃), low mechanical sensitivity and good safety performance.

[0003] However, in the practical application of the tungsten-based delay composition, especially in the case of using chlorovinyl acetate resin (PVVA, Polyvinyl Butyral Valerate) as a thermoplastic molding processing binder, there are a series of problems. Although chlorovinyl acetate resin has good bonding performance, low softening temperature, and is easy to process, it has become the mainstream bonding system for thermoplastic molding processing of tungsten-based delay composition, but it will produce a large amount of CO2, H2O(g), HCl and other low molecular weight hydrocarbon gas during combustion. The production of these gases will increase the environmental pressure in the closed space, which will affect the combustion wave, and seriously reduce the delay precision. In addition, the mechanical properties of the tungsten-based delay composition during the thermoplastic molding process are also crucial. Lower mechanical properties may cause the drug column to crack, deform and other sudden conditions during mold pressing, component assembly, long-distance transportation and extreme conditions, which may cause local drug column disintegration during combustion, resulting in combustion channel interruption or acceleration, and serious consequences such as significant shortening of delay time (early explosion) or delay failure (non-explosion).

[0004] In view of the above problems, the existing technology mainly tries to solve the problems by optimizing the binder formula and processing technology. On the one hand, researchers are committed to developing new binders to reduce the amount of gas produced during combustion, thereby reducing the impact on delay precision. On the other hand, by improving the thermoplastic molding process, the mechanical properties of the tungsten-based delay composition are improved to enhance its stability and reliability in practical application. For example, more advanced pressing techniques and post-processing processes are used to reduce internal defects and stress concentration in the drug column, and to improve its resistance to cracking and deformation.

[0005] Although the prior art alleviates the problems caused by chlorovinyl resin as a binder to some extent, there are still many deficiencies. First, the development of new binders is often accompanied by a substantial increase in cost, and its long-term stability and compatibility still need to be verified. Second, although improving the thermoplastic molding process can improve the mechanical properties of tungsten-based delay composition, it cannot fundamentally solve the influence of chlorovinyl resin combustion gas on the delay precision. Therefore, how to maintain the excellent performance of tungsten-based delay composition while further reducing the gas production and improving the mechanical properties is still a technical problem to be solved. SUMMARY

[0006] In order to solve the problems existing in the prior art, the present application provides a MXene-based binder and a tungsten-based delay composition and method, which has a simple preparation method, is easy to mass produce, is stable in combustion and has high combustion efficiency, good mechanical properties and low gas production when applied to tungsten-based delay composition.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a preparation method of MXene-based binder, the specific steps are as follows: Mixing chlorovinyl resin solution, polyvinylidene hexafluoropropylene solution and Mxene suspension to obtain a mixed solution; Adding a plasticizer to the mixed solution, stirring and drying, freezing and crushing to obtain a Mxene-based binder.

[0008] Further, the preparation of the chlorovinyl resin solution and the polyvinylidene hexafluoropropylene solution is as follows: The same amount of chlorovinyl resin and polyvinylidene hexafluoropropylene is added to the acetone solution respectively, and the chlorovinyl resin solution and the polyvinylidene hexafluoropropylene solution are obtained by stirring.

[0009] Further, the preparation of the Mxene suspension is as follows: Mxene is added to acetone, ultrasonic stirring to obtain a uniformly dispersed Mxene suspension.

[0010] Further, the Mxene is multilayered accordion-shaped Ti3C2, multilayered clay-shaped Ti3C2 or multilayered Ti3CN; the amount of Mxene is 1%-3% of the total mass of chlorovinyl resin, polyvinylidene hexafluoropropylene and Mxene.

[0011] Further, in the mixed solution, the total mass of chlorovinyl resin, polyvinylidene hexafluoropropylene and Mxene in 1ml of solvent is 0.112g.

[0012] Further, the plasticizer is dibutyl phthalate; the ratio of the amount of the plasticizer to the total mass of the chlorovinyl acetate resin, polyvinylidene fluoride-hexafluoropropylene and Mxene is 3:7.

[0013] The application further provides a MXene-based binder prepared by the preparation method.

[0014] The application further provides a MXene-based binder composite tungsten-based delay composition, which comprises metal powder, retardant, oxidant, functional additive and the MXene-based binder prepared by the preparation method.

[0015] Further, the mass ratio of the metal powder, the retardant, the oxidant, the functional additive and the MXene-based binder is 42:48:8:2:10.

[0016] Further, the metal powder is tungsten powder with a particle size of 2-4 μm, the retardant is barium chromate with a particle size of 1-2 μm, the oxidant is potassium perchlorate with a particle size of 3-6 μm, and the functional additive is polytetrafluoroethylene; the rolling temperature of the rolling thermoplastic forming is 90 ℃, and the rolling is performed for 40 rounds.

[0017] Compared with the prior art, the application has at least the following beneficial effects: The application provides a preparation method of a MXene-based binder, which uses chlorovinyl acetate resin (PVVA), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and Mxene as raw materials, the high F content of PVDF-HFP can replace part of the C and H elements in PVVA, thereby reducing the generation of CO2 and H2O (g). Meanwhile, the generated HF in the combustion can erode the oxide film on the surface of the W powder, thereby enhancing the combustion efficiency. The PVDF-HFP and PVVA form a blended crosslinked structure in the solution, the high molecular chains can be interpenetrated and crosslinked, thereby forming a blended crosslinked binder, which can improve the material structure and performance to a certain extent. The addition of Mxene can further reduce the gas generation and improve the mechanical properties. The Mxene has excellent thermal stability and physical shielding effect, can reduce the heat release rate and reduce the gas release. The metal-carbon chemical bond can endow high strength, high toughness and anti-fracture ability, and improve the tensile strength of the polymer. The Mxene can also reduce the decomposition temperature of potassium perchlorate, accelerate the generation of oxygen, and make the combustion more stable. The synthesis method is safe and simple, and is convenient for large-scale production. In the preparation process, the solutions are mixed to obtain a mixed solution, the plasticizer is added and stirred, and then the mixed solution is dried, frozen and crushed to obtain the MXene-based binder. The steps are simple and clear, the requirements for the equipment are relatively low, the operation and control are easy, and the application in the actual production is facilitated, thereby reducing the production cost.

[0018] The application provides a MXene-based binder composite tungsten-based delay composition, which applies the prepared MXene-based binder, is stable in combustion and has high combustion efficiency. Mxene can reduce the decomposition temperature of potassium perchlorate, accelerate the decomposition of potassium perchlorate to generate oxygen, provide guarantee for stable combustion of the delay composition, and ensure efficient combustion process. The composite tungsten-based delay composition has good mechanical properties, the excellent mechanical properties of Mxene improve the tensile strength of the polymer, and the delay composition has good mechanical properties. Meanwhile, the problem of large gas production in the combustion process of the tungsten-based delay composition is effectively solved, the requirement that the tungsten-based delay composition generates as little gas as possible in the combustion process of the closed delay element is met, the delay precision is ensured, and a feasible scheme is provided for preparation of the high-precision tungsten-based delay composition. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a binder diagram of the comparative example 1, the comparative example 3 and the example 1, wherein (a) is the comparative example 1, (b) is the comparative example 3, (c) is the comparative example 3, and (d) is the example 1. Figure 2 It is a tungsten-based delay composition tablet formed by hot rolling of several binders, wherein (a) is the comparative example 1, (b) is the comparative example 3, (c) is the comparative example 2, (d) is the example 1, (e) is the example 2, and (f) is the example 3. Figure 3 It is a SEM diagram of a cross section of a tungsten-based delay composition tablet formed by hot rolling of several binders, wherein (a) is the comparative example 1, (b) is the comparative example 3, and (c) is the example 3.

[0020] Figure 4 It is a force-deformation curve diagram of a tungsten-based delay composition tablet formed by hot rolling of several binders, wherein (a) is the comparative example 1, (b) is the comparative example 3, (c) is the example 1, (d) is the example 2, and (e) is the example 3. Figure 5 It is a TG curve diagram of several binders, wherein (a) is the comparative example 1, (b) is the comparative example 3, (c) is the example 1, (d) is the example 2, and (e) is the example 3. Figure 6 It is a TG curve diagram of the comparative example 1, the comparative example 3, the example 1, the example 2 and the example 3 delay composition. Figure 7 It is an XRD diagram of unburned and burned products of the comparative example 1, the comparative example 3 and the example 3. Figure 8 It is a TG curve diagram of pure potassium perchlorate and potassium perchlorate+Mxene. Figure 9 It is a binder diagram prepared by the comparative example 4 and the comparative example 5.

[0021] Figure 10For Comparative Example 1, Comparative Example 3, Example 1, Example 2, Example 3. DETAILED DESCRIPTION

[0022] For the purposes of promoting an understanding of the principles of the application, reference will now be made to the embodiments illustrated in the drawings. There is shown in the drawings, by way of illustration, a preferred embodiment of the application. It should be noted, however, that the application can be practiced in a variety of forms that will be apparent to those skilled in the art. No limitations are intended to the details of construction or the arrangements of components illustrated in the drawings. Rather, the intent is to cover all modifications, equivalents, and alternatives falling within the scope of the application.

[0023] The present application provides a MXene-based binder, and the preparation steps are as follows: The same amount of chlorovinyl resin (PVVA) and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) were added to acetone solution respectively, stirred on a magnetic stirrer for 1 h at a speed of 600 r / min, to obtain uniform solutions A and B.

[0024] Mxene was added to acetone, mixed uniformly under stirring and ultrasonic oscillation, to obtain Mxene suspension.

[0025] Solutions A, B and Mxene suspension were mixed, plasticizer dibutyl phthalate DBP was added, stirred for 10 h, and then the mixed solution was poured into a culture dish for drying, removal of solvent, freezing in liquid nitrogen, and crushing to obtain Mxene-based binder fragments.

[0026] Preferably, the Mxene suspension is prepared by the following process: Mxene is added to acetone, ultrasonic oscillation for 1 h, and stirring for 1 h, to form a uniformly dispersed Ti3CN Mxene suspension, wherein the mass fraction of Mxene in the total mass of PVVA, PVDF-HFP and Mxene is 1%-3%.

[0027] Preferably, the Mxene is multi-layered accordion-like Ti3C2 (HF etching), multi-layered clay-like Ti3C2 (LiF / HCl etching) or multi-layered Ti3CN commercially available from Foshan Xinyan Technology Co., Ltd.

[0028] Preferably, the total mass of PVVA, PVDF-HFP and Ti3CN Mxene in 1 ml of acetone is 0.112 g after mixing the acetone solutions of chlorovinyl resin (PVVA), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and Ti3CN Mxene.

[0029] Preferably, the mass ratio of the plasticizer to the total mass of PVVA, PVDF-HFP and Mxene is 3:7.

[0030] The application provides a MXene-based binder composite tungsten-based delay composition, and preparation steps are as follows: The metal powder, the retardant, the oxidant, the functional additive and the MXene-based binder are mixed according to a formula ratio, and are rolled and hot-pressed by a hot rolling device to obtain the MXene-based binder composite tungsten-based delay composition tablet.

[0031] Preferably, the mass ratio of the metal powder, the retardant, the oxidant, the functional additive and the MXene-based binder is 42:48:8:2:10.

[0032] Preferably, the metal powder is tungsten powder with a particle size of 2-4 mu, the retardant is barium chromate with a particle size of 1-2 mu, the oxidant is potassium perchlorate with a particle size of 3-6 mu, and the functional additive is polytetrafluoroethylene (PTFE).

[0033] Preferably, the rolling temperature of the rolling and hot-pressing is 90 DEG C, and the rolling is performed for 40 rounds.

[0034] In the application, chlorovinyl resin (PVVA) and polyvinylidene-hexafluoropropylene (PVDF-HFP) are used as binders, and Ti3CN Mxene is used as a functional additive, so that the delay composition has low gas production and high combustion efficiency.

[0035] The application takes chlorovinyl acetate resin (PVVA), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and Mxene as raw materials, and a MXene-based binder with mechanical properties and low gas production is prepared by a simple solvent blending method. In the system, the high F content in polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) can replace part of the C and H elements in chlorovinyl acetate resin (PVVA), thereby reducing the production of CO2 and H2O (g). At the same time, the HF produced in the combustion process of PVDF-HFP can effectively erode the WO3 oxide film on the surface of W powder, so that the W powder can better contact with O2, and the combustion efficiency is enhanced. And PVDF-HFP and PVVA can be interpenetrated and cross-linked between the polymer chains in the solution to form a blended cross-linked binder. However, the HFP unit in the structure of PVDF-HFP will destroy the close crystalline structure of PVDF, reduce the intermolecular force, and the existence of C-F bond makes PVDF-HFP rigid and brittle, resulting in a decrease in tensile strength. Adding too much PVDF-HFP will reduce the overall mechanical properties of the binder, and the softening temperature of PVDF-HFP is relatively high, which is not enough to replace the chlorovinyl acetate resin commonly used in hot rolling. Although PVVA and PVDF-HFP as a blended binder can reduce the gas production during the combustion process to a certain extent, in the actual application process, the tungsten-based delay composition needs to produce as little gas as possible during the combustion in the sealed delay element to ensure the accuracy of the delay precision. In order to improve this defect, the application further reduces the gas production during the combustion process and improves the mechanical properties by adding Mxene, a functional additive. As a kind of two-dimensional transition metal carbide / nitride, Mxene has excellent thermal stability and physical shielding effect, which can reduce the heat release rate during the combustion process of the polymer, promote the formation of a tight carbon layer, and reduce the release of CO2 and CO gas. In addition, the metal-carbon chemical bond in Mxene has stronger binding force, and has high strength, high toughness and anti-fracture ability. Its toughness is derived from the plastic deformation ability of the metal bond, which can withstand a large external force without brittle fracture. The excellent mechanical properties of Mxene improve the tensile strength of the polymer and the mechanical properties of the tungsten-based delay composition. At the same time, Mxene can reduce the decomposition temperature of potassium perchlorate (oxidizer) in the tungsten-based delay composition, accelerate the decomposition of catalytic potassium perchlorate to produce oxygen, and further make the delay composition burn stably. The synthesis method of the application is safe, simple and convenient for large-scale production, which can effectively solve the problem of large gas production of tungsten-based delay composition during the combustion process, and provides a train of thought for the preparation of high-precision tungsten-based delay composition.

[0036] The following is a specific embodiment to further explain and illustrate the technical solutions of the application.

[0037] Example 1 (1) 1.386 g PVVA and 1.386 g PVDF-HFP were dispersed in 10 mL of acetone, respectively, stirred at 600 rpm for 60 min to obtain PVVA acetone solution and PVDF-HFP acetone solution. Then the two solutions were blended, stirred at 800 rpm for 30 min to obtain PVVA / PVDF-HFP blended solution.

[0038] (2) 0.028 g Ti3CN Mxene was added to 5 ml of acetone solution, and Ti3CN Mxene was dispersed in an ultrasonic device for 1 h to obtain Ti3CN Mxene suspension, which was added to the above-mentioned PVVA and PVDF-HFP blended solution, and 1.2 g of DBP was added dropwise, and stirred for 8 h to obtain PVVA / PVDF-HFP / Mxene (1%) blended acetone solution; (3) The PVVA / PVDF-HFP / Mxene (1%) blended acetone solution was poured into a culture dish, a plastic wrap was placed on the hole, and the binder was dried in a vacuum drying oven at 60°C for 8 h. The binder was frozen in liquid nitrogen and broken to obtain PVVA / PVDF-HFP / Mxene (1%) blended binder fragments; (4) Tungsten powder, barium chromate, potassium perchlorate, polytetrafluoroethylene, and PVVA / PVDF-HFP / Mxene (1%) blended binder were mixed according to the formula ratio of 42:48:8:2:10, and an appropriate amount of acetone was added to make the mixture into a dough. The dough was placed on a hot rolling device and rolled for 40 rounds to form the delay drug tablet; Figure 1 (d) PVVA / PVDF-HFP / Mxene (1%) blended binder.

[0039] Figure 2 (d) It can be seen that the delay drug formed after the PVVA / PVDF-HFP / Mxene (1%) blended binder was hot rolled has no obvious bubbles, the surface is smooth and uniform, and the rolling degree is good.

[0040] Figure 4 (c) The force-deformation curve of the tungsten-based delay drug prepared by the PVVA / PVDF-HFP / Mxene (1%) blended binder shows that the delay drug starts to yield at a tensile force of 40.32 N, and the maximum force deformation is 12.4 mm. Compared with Comparative Example 3, the maximum tensile force and the maximum deformation are increased by 5.36 N and 0.5 mm, respectively, indicating that the mechanical force of the delay drug can be improved after adding Mxene.

[0041] Figure 5 (c), Figure 6It can be seen that the weight loss rate of the PVVA / PVDF-HFP / Mxene (1%) blended binder is 79.2%, and the weight loss rate of the tungsten-based delay composition prepared by the PVVA / PVDF-HFP / Mxene (1%) blended binder is 14.2%. Compared with Comparative Example 3 (PVVA / PVDF-HFP and PVVA / PVDF-HFP delay composition), the weight loss rate is reduced by 7.6% and 2.5%, respectively, indicating that the addition of Mxene reduces the gas generated by the decomposition of the binder and the delay composition.

[0042] Figure 8 It can be seen that after adding Mxene, the decomposition temperature of potassium perchlorate is reduced from 615.8°C to 555.9°C, and the temperature is advanced by 59.9°C. The catalytic effect of Mxene helps the decomposition of potassium perchlorate, which helps the combustion process of the delay composition.

[0043] Figure 10 It can be seen that the average peak pressure of the PVVA / PVDF-HFP / Mxene (1%) delay composition is 436Kpa, which is reduced by 41Kpa compared with Comparative Example 3, which is consistent with the above TG curve analysis.

[0044] Example 2 (1) 1.372g of PVVA and 1.372g of PVDF-HFP were dispersed in 10mL of acetone, respectively, and stirred at 600rpm for 60min to obtain PVVA acetone solution and PVDF-HFP acetone solution. Then the two solutions were blended, and stirred at 800rpm for 30min to obtain PVVA / PVDF-HFP blended solution.

[0045] (2) 0.056g of Ti3CN Mxene was added to 5ml of acetone solution, and ultrasonic device was used to disperse Ti3CN Mxene for 1h to obtain Ti3CN Mxene suspension, which was then added to the above-mentioned PVVA and PVDF-HFP blended solution, and 1.2g of DBP was added dropwise, and stirred for 8h to obtain PVVA / PVDF-HFP / Mxene (2%) blended acetone solution; (3) The PVVA / PVDF-HFP / Mxene (2%) blended acetone solution was poured into a culture dish, a hole was made in the plastic wrap, and it was placed in a vacuum drying box at 60°C for 8h. The binder was taken out, frozen in liquid nitrogen and crushed to obtain PVVA / PVDF-HFP / Mxene (2%) blended binder fragments; (4) The tungsten powder, barium chromate, potassium perchlorate, polytetrafluoroethylene, PVVA / PVDF-HFP / Mxene (2%) blending binder were mixed according to the formula proportion 42:48:8:2:10, and a proper amount of acetone was added to make the mixture into a dough, which was placed on a hot rolling device and rolled for 40 rounds to form the delay granules; Figure 2 (e) It can be seen that the delay granules prepared by the PVVA / PVDF-HFP / Mxene (2%) blending binder after hot rolling have no obvious bubbles, the surface is smooth and uniform, and the rolling degree is good.

[0046] Figure 4 (d) The force-deformation curve of the tungsten-based delay granules prepared by the PVVA / PVDF-HFP / Mxene (2%) blending binder shows that the delay granules start to yield at a pulling force of 43.12 N, and the maximum force deformation is 13.5 mm. Compared with Example 1, the maximum pulling force and the maximum deformation are increased by 2.8 N and 1.1 mm, respectively.

[0047] Figure 5 (d), Figure 6 It can be seen that the weight loss rate of the PVVA / PVDF-HFP / Mxene (2%) blending binder is 78.2%, and the weight loss rate of the tungsten-based delay granules prepared by the PVVA / PVDF-HFP / Mxene (2%) blending binder is 12.9%. Compared with Example 1 (PVVA / PVDF-HFP Mxene (1%) and PVVA / PVDF-HFP Mxene (1%) delay granules), the weight loss rates are decreased by 1% and 1.3%, respectively, and the gas generated by decomposition is further reduced.

[0048] Figure 10 It can be seen that the average peak pressure of the PVVA / PVDF-HFP / Mxene (2%) delay granules is 414 Kpa, which is reduced by 22 Kpa compared with Example 1, which is consistent with the TG curve analysis above.

[0049] Example 3 (1) 1.358g of PVVA and 1.358g of PVDF-HFP were dispersed in 10mL of acetone, respectively, and stirred at 600rpm for 60min to obtain PVVA acetone solution and PVDF-HFP acetone solution. Then the two solutions were blended and stirred at 800rpm for 30min to obtain PVVA / PVDF-HFP blending solution.

[0050] (2) Add 0.084g Ti3CN Mxene to 5ml acetone solution, sonicate in an ultrasonic device for 1h to disperse Ti3CN Mxene, and obtain Ti3CN Mxene suspension. Add it to the above PVVA and PVDF-HFP mixed solution, add 1.2g DBP dropwise, stir for 8h to obtain PVVA / PVDF-HFP / Mxene (3%) mixed acetone solution; (3) Pour the PVVA / PVDF-HFP / Mxene (3%) blended acetone solution into a petri dish, cover it with plastic wrap and poke holes in it, place it in a vacuum drying oven at 60°C for 8 hours, take out the binder and freeze it with liquid nitrogen to obtain PVVA / PVDF-HFP / Mxene (3%) blended binder fragments. (4) Mix tungsten powder, barium chromate, potassium perchlorate, polytetrafluoroethylene, and PVVA / PVDF-HFP / Mxene (3%) blended binder in a formula ratio of 42:48:8:2:10. Add an appropriate amount of acetone to make the mixture into a dough-like consistency. Place it on a hot rolling device and roll it 40 times to form the delayed drug tablet. Figure 2 (f) shows that the PVVA / PVDF-HFP / Mxene (3%) blend binder, after being hot rolled, has no obvious bubbles, a smooth and uniform surface, and good rolling degree.

[0051] Figure 4 (e) Force-deformation curves of the tungsten-based delay agent prepared with PVVA / PVDF-HFP / Mxene (3%) blend binder. The delay agent begins to yield under a tensile force of 44.06 N, with a maximum force-deformation of 14.5 mm. Compared to Example 2, the maximum tensile force and maximum deformation increased by 0.94 N and 1 mm, respectively. Figure 5 (e) Figure 6 It can be seen that the weight loss rate of the PVVA / PVDF-HFP / Mxene (3%) blend binder is 75.2%, and the weight loss rate of the tungsten-based delay agent prepared by the PVVA / PVDF-HFP / Mxene (3%) blend binder is 12.2%. Compared with the delay agents of Example 2 (PVVA / PVDF-HFP / Mxene (2%) and PVVA / PVDF-HFP / Mxene (2%)), the weight loss rate decreased by 3% and 0.7%, respectively.

[0052] Figure 10 It can be seen that the average peak pressure of the PVVA / PVDF-HFP / Mxene (3%) delay drug is 386 kPa, which is 28 kPa lower than that of Example 2, consistent with the above TG curve analysis.

[0053] Comparative Example 1 (1) Disperse 2.8g PVVA in 25mL acetone, stir at 600rpm for 60min, then add 1.2g DBP dropwise and stir for 8h to obtain PVVA acetone solution; (2) Pour the PVVA acetone solution into a petri dish, cover it with plastic wrap and poke holes, place it in a vacuum drying oven at 60°C for 8 hours, take out the adhesive and freeze it with liquid nitrogen to obtain PVVA adhesive fragments. (3) Mix tungsten powder, barium chromate, potassium perchlorate, polytetrafluoroethylene, and PVVA binder thoroughly according to the formula ratio of 42:48:8:2:10, add an appropriate amount of acetone to make the mixture into a dough, place it on a hot rolling device and roll it 40 times to form the delayed drug tablet. Figure 1 (a) is PVVA powder, and is composed of Figure 2 (a) It can be seen that the tungsten-based delay agent prepared by hot rolling with PVVA as a binder has a small number of bubbles on its surface, which is due to uneven rolling.

[0054] Figure 3 (a) A cross-sectional SEM image of the tungsten-based delay drug prepared with PVVA binder. It can be seen that the cross-sectional filamentary adhesion effect is very poor under the action of PVVA binder, which is consistent with the phenomenon of bubbles on the surface of the delay drug mentioned above.

[0055] Figure 4 (a) Force-deformation curve of tungsten-based delay agent prepared with PVVA binder. Under a tensile force of 53.82 N, the delay agent begins to yield, and the maximum force deformation is 24.8 mm.

[0056] Figure 5 (a), Figure 6 It can be seen that the weight loss rate of PVVA binder is 95.5%, and the weight loss rate of tungsten-based delay agent prepared with PVVA binder is 17.8%. During the heating process, PVVA decomposes to produce gases such as CO2, HCl, and H2O(g). The large amount of gas flow has a significant impact on the combustion interface, thus affecting the instability of the delay accuracy.

[0057] Figure 7 (c) The XRD pattern shows that the diffraction peaks of W powder at 40°, 58°, 73° and 87° in the combustion products are still higher than those of the unburned PVVA delay agent. This indicates that the combustion products of the PVVA delay agent still contain a large amount of unreacted W powder, and that PVVA has a low combustion efficiency as a binder for tungsten-based delay agents.

[0058] Figure 10It can be seen that the average peak pressure of the PVVA delay agent is 491 kPa, which is the highest among the five groups of samples, indicating that the PVVA delay agent produces the most gas during combustion.

[0059] Comparative Example 2 (1) Disperse 2.8g of PVDF-HFP in 25mL of acetone and stir at 600rpm for 60min to obtain PVDF-HFP acetone solution. Then add 1.2g of DBP and stir for 8h to obtain PVDF-HFP acetone solution. (2) Pour the PVDF-HFP acetone solution into a petri dish, cover it with plastic wrap and poke holes in it, place it in a vacuum drying oven at 60°C for 8 hours, take out the adhesive and freeze it with liquid nitrogen to obtain PVDF-HFP adhesive fragments. (3) Mix tungsten powder, barium chromate, potassium perchlorate, polytetrafluoroethylene, and PVDF-HFP binder thoroughly according to the formula ratio of 42:48:8:2:10, add an appropriate amount of acetone to make the mixture into a dough, place it on a hot rolling device and roll it 40 times to form the delayed drug tablet. Figure 2 (c) It can be seen that the delayed drug after hot rolling as a binder cannot be formed. This is because the softening temperature of PVDF-HFP is high and its hardness is high at 90℃, so it cannot be formed.

[0060] Comparative Example 3 (1) Dissolve 1.4g of PVVA and 1.4g of PVDF-HFP in 12.5mL of acetone respectively, and stir at 600rpm for 60min to obtain PVVA acetone solution and PVDF-HFP acetone solution. Then mix the two solutions together, stir at 800rpm for 30min, and then add 1.2g of DBP dropwise, and stir for 8h to obtain PVVA / PVDF-HFP blended acetone solution; (2) Pour the PVVA / PVDF-HFP blended acetone solution into a petri dish, cover it with plastic wrap and poke holes, place it in a vacuum drying oven at 60°C for 8 hours, take out the adhesive and freeze it with liquid nitrogen to obtain PVVA / PVDF-HFP blended adhesive fragments. (3) Mix tungsten powder, barium chromate, potassium perchlorate, polytetrafluoroethylene, and PVVA binder thoroughly according to the formula ratio of 42:48:8:2:10, add an appropriate amount of acetone to make the mixture into a dough, place it on a hot rolling device and roll it 40 times to form a tungsten-based delayed pill. Figure 1 (b) Figure 1 (c) is a diagram of the PVVA / PVDF-HFP blend binder being broken down and demolded.

[0061] Figure 2(b) It can be seen that the PVVA / PVDF-HFP blend binder, after being hot rolled, has no obvious bubbles, a smooth and uniform surface, and a good degree of rolling.

[0062] Figure 3 (b) is a SEM image of the cross section of the tungsten-based delay propellant prepared by the PVVA / PVDF-HFP blend binder. It can be seen that the cross section has obvious filamentous adhesion effect under the action of the PVVA / PVDF-HFP blend binder, indicating that the PVVA / PVDF-HFP blend binder can effectively bind the components uniformly, which is beneficial to improving the combustion efficiency of the tungsten-based delay propellant.

[0063] Figure 4 (b) Force-deformation curve of tungsten-based delay agent prepared with PVVA / PVDF-HFP blend binder. Under a tensile force of 34.96 N, the delay agent begins to yield, with a maximum force deformation of 11.9 mm. The tensile strength is lower than that of Comparative Example 1 because PVDF-HFP is relatively rigid and prone to fracture.

[0064] Figure 5 (b) Figure 6 It can be seen that the weight loss rate of the PVVA / PVDF-HFP blend binder is 86.8%, and the weight loss rate of the tungsten-based delay agent prepared by the PVVA / PVDF-HFP blend binder is 16.7%. Compared with Comparative Example 1 (PVVA and PVVA delay agent), the weight loss rates decreased by 8.7% and 1.1%, respectively, indicating that the addition of PVDF-HFP resulted in more solid residue and less gas generated during decomposition.

[0065] Figure 7 (c) It can be seen that, compared with PVVA, the intensity of the diffraction peak of W powder in the XRD pattern of PVVA / PVDF-HFP combustion products is significantly reduced, indicating that the addition of PVDF-HFP enhances the combustion efficiency of tungsten-based delay propellant.

[0066] Figure 10 It can be seen that the average peak pressure of the PVVA / PVDF-HFP delay agent is 477 kPa, which is 14 kPa lower than that of Comparative Example 1. This indicates that the gas production is reduced after adding PVDF-HFP, which is consistent with the above TG curve analysis.

[0067] Comparative Example 4 (1) Disperse 1.358g of PVVA and 1.358g of PVDF-HFP in 10mL of acetone respectively, and stir at 600rpm for 60min to obtain PVVA acetone solution and PVDF-HFP acetone solution. Then mix the two solutions together and stir at 800rpm for 30min to obtain PVVA / PVDF-HFP blend solution.

[0068] (2) Add 0.084g GO to 5ml acetone solution and sonicate in an ultrasonic device for 1h to disperse GO to obtain graphene oxide suspension. Add the above PVVA and PVDF-HFP mixed solution, add 1.2g DBP dropwise, stir for 8h to obtain PVVA / PVDF-HFP / GO (3%) mixed acetone solution. (3) Pour the PVVA / PVDF-HFP / GO (3%) blended acetone solution into a petri dish, cover it with plastic wrap and poke holes, place it in a vacuum drying oven at 60°C for 8 hours, take out the binder and freeze it with liquid nitrogen to obtain PVVA / PVDF-HFP / GO (3%) blended binder fragments. Extremely strong van der Waals forces (intermolecular attraction) exist between the layers of graphene oxide sheets. (Electron interactions between conjugated systems). This force drives adjacent GO sheets to spontaneously move closer together, eventually forming tight aggregates. Figure 9 (a) It can be seen that GO agglomerates severely during the acetone volatilization process and is unevenly distributed in the binder, so it is not suitable for this system.

[0069] Comparative Example 5 (1) Disperse 1.358g of PVVA and 1.358g of PVDF-HFP in 10mL of acetone respectively, and stir at 600rpm for 60min to obtain PVVA acetone solution and PVDF-HFP acetone solution. Then mix the two solutions together and stir at 800rpm for 30min to obtain PVVA / PVDF-HFP blend solution.

[0070] (2) Add 0.084 g g-C3N4 to 5 ml acetone solution, sonicate in an ultrasonic device for 1 h to disperse g-C3N4, and obtain g-C3N4 suspension. Add the suspension to the above PVVA and PVDF-HFP mixed solution, add 1.2 g DBP dropwise, stir for 8 h to obtain PVVA / PVDF-HFP / g-C3N4 (3%) mixed acetone solution; (3) Pour the acetone solution of PVVA / PVDF-HFP / g-C3N4 (3%) into a petri dish, cover it with plastic wrap and poke holes, place it in a vacuum drying oven at 60°C for 8 hours, take out the binder and freeze it with liquid nitrogen to obtain PVVA / PVDF-HFP / g-C3N4 (3%) blended binder fragments. Carbon nitride (g-C3N4) exhibits a high specific surface area due to its two-dimensional layered structure, strong van der Waals forces and hydrogen bonds between layers, and poor solvent compatibility due to its low surface polarity, making it highly prone to aggregation. Figure 9 (b) It can be seen that g-C3N4 agglomerates severely during the acetone volatilization process and is unevenly distributed in the binder, so it is not suitable for this system.

[0071] This invention employs a simple solvent blending method to synthesize a low-gas-generating Mxene-based binder system using functional additives Mxene, binders PVVA and PVDF-HFP, and plasticizer DBP. This system, applied to tungsten-based delay propellants, effectively solves the problems of high gas generation and low combustion efficiency during combustion. PVDF-HFP, with its high fluorine content, reduces the proportion of carbon and hydrogen elements when blended with PVVA, thus reducing the release of H2O(g) and CO2. Simultaneously, the HF generated during PVDF-HFP combustion effectively erodes the WO3 oxide film on the surface of the W powder, facilitating contact between the O2 generated from oxide decomposition and the W powder, thereby enhancing the combustion efficiency of the W powder. Mxene, as a unique two-dimensional layered material, possesses abundant functional groups on its surface, enabling it to act as a polymer reinforcing agent. The metal-carbon chemical bonds in Mxene exhibit stronger bonding forces, combining high strength, high toughness, and fracture resistance, allowing it to withstand significant external forces without brittle fracture. The excellent mechanical properties of Mxene improve the tensile strength of the polymer and enhance the mechanical properties of the tungsten-based delay propellant. Meanwhile, MXene promotes polymer char formation during combustion, resulting in a thick, deposited char layer. This mechanism effectively reduces the release of gases such as CO2 and CO, thereby lowering gas production. This method is green, safe, and simple to operate, representing a novel approach for preparing MXene-based binders with low gas production characteristics and improved mechanical properties.

[0072] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0073] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for preparing an MXene-based adhesive, characterized in that, The specific steps are as follows: A mixed solution was obtained by mixing chloroacetic acid resin solution, polyvinylidene fluoride-hexafluoropropylene solution, and Mxene suspension; A plasticizer is added to the mixed solution, stirred, dried, frozen, and pulverized to obtain an Mxene-based binder.

2. The method for preparing an MXene-based adhesive according to claim 1, characterized in that, The preparation of the chloroacetic acid resin solution and the polyvinylidene fluoride-hexafluoropropylene solution is as follows: Take equal amounts of chloroacetic acid resin and polyvinylidene fluoride-hexafluoropropylene, add them separately to acetone solution, and stir to obtain chloroacetic acid resin solution and polyvinylidene fluoride-hexafluoropropylene solution.

3. The method for preparing an MXene-based adhesive according to claim 1, characterized in that, The preparation of the Mxene suspension is as follows: Mxene was added to acetone, and the mixture was sonicated and stirred to obtain a uniformly dispersed Mxene suspension.

4. The method for preparing an MXene-based adhesive according to claim 3, characterized in that, The Mxene is a multilayer accordion-shaped Ti3C2, a multilayer clay-shaped Ti3C2, or a multilayer Ti3CN; the amount of Mxene used is 1%-3% of the total mass of chloroacetic acid resin, polyvinylidene fluoride-hexafluoropropylene, and Mxene.

5. The method for preparing an MXene-based adhesive according to claim 1, characterized in that, In the mixed solution, the total mass of chloroacetic acid resin, polyvinylidene fluoride-hexafluoropropylene, and Mxene in each 1 ml of solvent is 0.112 g.

6. The method for preparing an MXene-based adhesive according to claim 1, characterized in that, The plasticizer is dibutyl phthalate; the ratio of the amount of plasticizer to the total mass of vinyl acetate resin, polyvinylidene fluoride-hexafluoropropylene, and Mxene is 3:

7.

7. An MXene-based adhesive, characterized in that, It is prepared by any one of claims 1 to 6.

8. A tungsten-based delay agent composite with an MXene-based binder, characterized in that, The raw materials include metal powder, flame retardant, oxidant, and functional additives. According to claim 7, an MXene-based binder is obtained by mixing the raw materials according to the formula ratio and then rolling and thermoforming to obtain an MXene-based binder composite tungsten-based delay agent.

9. The MXene-based binder composite tungsten-based delay agent according to claim 8, characterized in that, The mass ratio of metal powder, flame retardant, oxidant, functional additive, and MXene-based binder is 42:48:8:2:

10.

10. The MXene-based binder composite tungsten-based delay agent according to claim 8, characterized in that, The metal powder is tungsten powder with a particle size of 2μm-4μm, the flame retardant is barium chromate with a particle size of 1μm-2μm, the oxidant is potassium perchlorate with a particle size of 3μm-6μm, and the functional additive is polytetrafluoroethylene; the rolling temperature of the roll forming thermoplastic molding is 90℃, and the rolling is performed for 40 rolls.

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