High-strength paraffin-containing fuel based on azide adhesive and preparation method of high-strength paraffin-containing fuel

Abstract

The invention provides a high-strength paraffin-containing fuel based on an azide adhesive and a preparation method of the high-strength paraffin-containing fuel. The fuel is prepared from the following raw materials in percentage by mass: 50-70% of solid paraffin, 20-40% of the azide adhesive, 5-8% of a cosolvent, 1-3% of sodium cocoyl isethionate, 1-3% of nano carbon powder, 0.1-0.3% of a curing catalyst and the balance of a curing agent, the cosolvent is hydrogenated C5 petroleum resin or hydroxy acrylic resin. According to the invention, sodium cocoyl isethionate and the cosolvent are added into the paraffin-containing fuel, so that the compatibility of paraffin and the adhesive can be improved, and the mechanical property of the paraffin-containing fuel can be improved; by adding the azide adhesive, the fuel gas generation amount can be remarkably increased, and the performance of the solid fuel ramjet engine is improved; the nano carbon powder is added, so that the heat radiation absorption capacity of the fuel is enhanced, and the combustion efficiency is further improved; and meanwhile, the use of metal fuel additives is avoided, so that the fuel cost is reduced, and the performance loss of the engine and possible safety problems are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of methods for preparing propellants for solid fuel ramjet engines, and in particular relates to a high-strength paraffin-containing fuel based on an azide adhesive and a method for preparing the paraffin-containing fuel. Background Art

[0002] Solid fuel ramjet is an air-breathing propulsion system that carries its own solid fuel and uses oxygen in the air for combustion. It has the advantages of simple structure, high safety and reliability, and high specific impulse. However, most traditional solid fuels use inert polymers, which have a low gasification rate, resulting in a low fuel combustion surface retreat rate, which is difficult to meet the thrust requirements of the engine.

[0003] Paraffin-containing fuel is one of the ideal fuels for solid fuel ramjet engines. Its advantages are reflected in two aspects: after the fuel is heated, an unstable molten layer with low viscosity and surface tension is formed on its surface. Under the shearing action of the high-speed incoming flow, the molten layer becomes unstable and breaks into droplets, which are then entrained into the boundary layer. This droplet mixing mechanism significantly increases the recession rate of the combustion surface, thereby enhancing the combustion efficiency; by adding adhesives, the structural strength of the fuel is further improved, ensuring its stability under the scouring of high-speed airflow.

[0004] Chinese patent 202010447511.3 discloses "a paraffin-containing fuel formula and preparation method", which improves the viscosity and ductility of paraffin by introducing modified polyethylene, and realizes uniform mixing of adhesive and paraffin, thereby preparing paraffin-containing fuel with good mechanical properties. The formula uses polyazide glycidyl ether as an adhesive, biuret polyisocyanate as a curing agent, stannous octoate as a catalyst, and aluminum powder as a metal additive. The prepared paraffin-containing fuel has a high rate of combustion surface regression. This scheme uses an energetic adhesive, which improves its thermal decomposition performance and meets the demand for large gas production, but 25% of metallic aluminum powder is introduced, and there are more condensed phase combustion products, which may damage the engine flow path. In addition, although modified polyethylene can significantly improve the mechanical properties of paraffin-containing fuel, it will have a large side effect on combustion performance, and modified polyethylene needs to be prepared in advance with boric acid and octadecyl alcohol as catalysts, polyethylene and ozone as the main raw materials. The overall formulation process is complicated, the cost is high, and there is a problem of difficulty in thermal decomposition. At the same time, since the formula only contains one energetic binder, the scope of application of the formula is limited. Summary of the invention

[0005] The object of the present invention is to solve the above-mentioned multiple problems existing in the paraffin-containing fuel used in the existing solid fuel ramjet engine, and to provide a high-strength paraffin-containing fuel based on an azide adhesive and a method for preparing the paraffin-containing fuel.

[0006] To achieve the above object, the technical solution provided by the present invention is as follows:

[0007] A high-strength paraffin-containing fuel based on azide binder is provided, which is composed of the following raw materials in mass percentage: 50-70% of solid paraffin, 20-40% of azide binder, 5-8% of cosolvent, 1-3% of sodium cocoamphoacetate, 1-3% of nano-carbon powder, 0.1-0.3% of curing catalyst, and the balance is curing agent; the cosolvent is hydrogenated C5 petroleum resin or hydroxyacrylic resin.

[0008] Further, the azide binder is poly(3,3-bis(azidomethyl)oxetane) or a copolymer of 3,3-bis(azidomethyl)oxetane and tetrahydrofuran or poly(azidoglycidyl ether).

[0009] Further, the curing agent is stannous octoate or dibutyltin dilaurate.

[0010] Further, the curing catalyst is polyisocyanate or toluene diisocyanate.

[0011] A preparation method of the above high-strength paraffin-containing fuel based on azide binder is also provided, including the following steps:

[0012] Step 1. Melting and mixing:

[0013] After heating the solid paraffin until it is completely melted, add the cosolvent according to the mass percentage and stir until it is evenly mixed to obtain a molten liquid;

[0014] Step 2. Adding azide binder:

[0015] Add the azide binder to the molten liquid obtained in Step 1 according to the mass percentage, increase the stirring rate and stir until the azide binder and paraffin are fully dissolved and dispersed to obtain a solution;

[0016] Step 3. Interface optimization:

[0017] Add sodium cocoamphoacetate to the solution obtained in Step 2 according to the mass percentage, stir evenly, then add nano-carbon powder according to the mass percentage, and continue to stir until it is completely mixed to obtain a mixed liquid;

[0018] Step 4. Curing and forming:

[0019] Add the corresponding content of curing agent to the mixed liquid obtained in Step 3 according to the curing parameters, stir and then add the curing catalyst to catalyze the curing reaction; finally, pour the mixed slurry into a mold for vacuum casting and cure at 70-80 °C for 3-5 d to obtain the paraffin-containing fuel.

[0020] Further, in Step 1, the stirring rate is 80-100 r / min and the stirring time is 15-20 min.

[0021] Further, in step 2, the stirring rate is 130 - 150 r / min, and the stirring time is 30 - 40 min.

[0022] Further, in step 2, the liquid temperature is maintained at 60 - 65 °C during stirring.

[0023] Further, in step 4, the range of the curing parameter is 1 - 1.2.

[0024] The advantages of the present invention are as follows:

[0025] By introducing a co-solvent, the present invention improves the compatibility between solid paraffin and azide adhesives, increases the viscosity of the system, and is beneficial to the formation of a homogeneous fuel system; the co-solvent is a resin. On the one hand, its high molecular weight structure can entangle and interact with azide adhesives, enhancing the adhesive force of the adhesives and promoting mixing. On the other hand, the melting characteristics of the resin match those of paraffin, facilitating blending. Using such a co-solvent is more prone to thermal decomposition. By using sodium cocoyl hydroxyethyl sulfonate as an interfacial modifier, the interfacial properties of the fuel system can be improved. By using the rapid gasification reaction of azide adhesives, a paraffin-containing fuel with a high gas generation amount can be obtained. Adding an interfacial modifier and a co-solvent to the paraffin-containing fuel of the present invention can improve the compatibility between paraffin and the adhesive, which is beneficial to improving the mechanical properties of the paraffin-containing fuel; using azide adhesives can significantly increase the gas generation amount and improve the performance of solid fuel ramjet engines; adding nano-carbon powder enhances the heat radiation absorption ability of the fuel and further improves the combustion efficiency. At the same time, avoiding the use of metal fuel additives not only reduces the fuel cost but also reduces the damage to the engine flow path and possible safety problems; and using azide adhesives in the paraffin-containing fuel formulation increases the applicable range of the paraffin-containing fuel formulation. Description of the Drawings

[0026] Through the following description with reference to the drawings, the features and advantages of the present invention will become more easily understood. In the attached

[0027] In the figure:

[0028] Figure 1 is the preparation flow chart of the high-strength paraffin-containing fuel based on azide adhesives of the present invention. Detailed Embodiments

[0029] The present invention will be described in detail below with reference to the exemplary embodiments of the present invention with the aid of the drawings. It should be noted that the following detailed description of the present invention is only for the purpose of illustration and does not limit the present invention.

[0030] The present invention provides a high-strength paraffin-containing fuel based on an azide binder, which is composed of the following raw materials in mass percentages: 50-70% of solid paraffin, 20-40% of azide binder, 5-8% of co-solvent, 1-3% of sodium cocoamphoacetate, 1-3% of nano-carbon powder, 0.1-0.3% of curing catalyst, and the balance is curing agent; the co-solvent is hydrogenated C5 petroleum resin or hydroxyacrylic resin.

[0031] The azide binder is poly(3,3-bis(azidomethyl)oxetane) (PBAMO) or poly(3,3-bis(azidomethyl)oxetane) -co-tetrahydrofuran (PBT) or poly(glycidyl azide ether) (GAP). Preferably, PBT is used as the azide binder.

[0032] The curing agent is stannous octoate or dibutyltin dilaurate.

[0033] The curing catalyst is polyisocyanate (N-100) or toluene diisocyanate (TDI).

[0034] The present invention also provides a preparation method of the above high-strength paraffin-containing fuel based on an azide binder, referring to Figure 1 , and the preparation method includes the following steps:

[0035] Step 1. Melting and mixing:

[0036] After heating the solid paraffin until it is completely melted, add the co-solvent according to the mass percentage, and stir at a rate of 80-100 r / min for 15-20 min until it is evenly mixed to obtain a molten liquid;

[0037] Step 2. Adding azide binder:

[0038] Add the azide binder to the molten liquid obtained in Step 1 according to the mass percentage, keep the temperature at 60-65 °C and stir at a rate of 130-150 r / min for 30-40 min until the azide binder is fully dissolved and dispersed in the paraffin to obtain a solution;

[0039] Step 3. Interface optimization:

[0040] Add sodium cocoamphoacetate to the solution obtained in Step 2 according to the mass percentage, stir evenly for 20-25 min, then add nano-carbon powder according to the mass percentage, and continue to stir for 15-20 min until it is completely mixed evenly to obtain a mixed liquid;

[0041] Step 4. Curing and forming:

[0042] Add a corresponding amount of curing agent to the mixed solution obtained in Step 3 according to the curing parameters, stir for 15 - 20 min, then add a curing catalyst and stir for 10 min to catalyze the curing reaction; finally, pour the mixed slurry into a mold and perform vacuum casting, and cure at 70 - 80 °C for 3 - 5 d to obtain a paraffin fuel.

[0043] Among them, the curing parameter refers to the parameter for calculating the ratio of the mixed solution to the curing agent based on the molar equivalent ratio of the active hydroxyl group (—OH) in the binder to the isocyanate group (—NCO) in the curing agent. The range of the curing parameter can be 1 - 1.2.

[0044] In the present invention, a co - solvent is introduced to improve the compatibility between solid paraffin and azide - based binders. Both hydrogenated C5 petroleum resin and hydroxyacrylic resin have polar and non - polar structures in their molecules. When used as a co - solvent, it can help form a bridge between the non - polar paraffin substances and the polar substances of the azide - based binder, enhance their compatibility, and increase the viscosity of the system, which is beneficial to the formation of a homogeneous fuel system; the co - solvent is a resin. On the one hand, its high - molecular - weight structure can entangle and interact with the azide - based binder, enhancing the adhesive force of the binder and promoting mixing at the same time. On the other hand, the melting characteristics of the resin match those of paraffin, facilitating blending. By using such a co - solvent, compared with the existing modified polyethylene, the problem of difficult thermal decomposition is solved. By using sodium cocoamphoacetate as an interfacial modifier, the interfacial properties of the fuel system can be improved; by using the rapid gasification reaction of the azide - based binder, a paraffin - containing fuel with a high gas - generating amount can be obtained. Adding an interfacial modifier and a co - solvent to the paraffin - containing fuel in the present invention can improve the compatibility between paraffin and the binder, which is beneficial to improving the mechanical properties of the paraffin - containing fuel, ensuring the integrity of the grain during the transportation, storage, ignition, and overload of the solid fuel ramjet engine; using the azide - based binder can significantly increase the gas - generating amount and improve the performance of the solid fuel ramjet engine; adding nano - carbon powder enhances the heat radiation absorption ability of the fuel, further improving the combustion efficiency; at the same time, avoiding the use of metal fuel additives not only reduces the fuel cost but also reduces the engine performance loss and potential safety problems; using nano - carbon powder as a functional filler to increase heat radiation absorption, improve combustion efficiency, and enhance the performance of the solid fuel ramjet engine.

[0045] The following further illustrates the preparation method of the high - strength paraffin - containing fuel based on azide binder provided by the present invention with reference to Examples 1 to 5. In Examples 1 to 5, when curing and forming, the curing agent is added according to the index of a curing parameter of 1.

[0046] Example 1

[0047] Weigh solid paraffin 53.8%, PBT 35.6%, hydrogenated C5 petroleum resin 4%, sodium cocoyl hydroxyethyl sulfonate 2%, nano carbon powder 2%, N-100 2.4%, and stannous octoate 0.2% by mass fraction. Treat the above raw materials according to the following method: Place the solid paraffin in a reaction kettle at 70 °C and stir at a rate of 100 r / min until the paraffin is completely melted. Then add the hydrogenated C5 petroleum resin to the melted paraffin and stir for 20 min to mix them evenly; add PBT and increase the stirring speed to 150 r / min, and stir for 30 min to fully disperse PBT and paraffin; then successively add sodium cocoyl hydroxyethyl sulfonate, nano carbon powder, and N-100, and stir for 20 min each time after adding. Finally, add stannous octoate and stir for 10 min to complete the addition and mixing of all raw materials. After the stirring is completed, turn off the stirrer of the reaction kettle, pour the mixed slurry into the mold through a vacuum casting cylinder, and cure at 70 °C for 5 d to obtain the paraffin-containing fuel.

[0048] Example 2

[0049] Weigh solid paraffin 53.8%, PBT 35.6%, hydroxy acrylic resin 4%, sodium cocoyl hydroxyethyl sulfonate 2%, nano carbon powder 2%, N-100 2.4%, and stannous octoate 0.2% by mass fraction. Treat the above raw materials according to the following method: Place the solid paraffin in a reaction kettle at 70 °C and stir at a speed of 100 r / min until the paraffin is completely melted. Then add the hydroxy acrylic resin to the melted paraffin and stir for 20 min to mix them evenly; add PBT and increase the stirring speed to 150 r / min, and stir for 30 min to fully disperse PBT and paraffin; then successively add sodium cocoyl hydroxyethyl sulfonate, nano carbon powder, and N-100, and stir for 20 min each time after adding. Finally, add stannous octoate and stir for 10 min to complete the addition and mixing of all raw materials. After the stirring is completed, turn off the stirrer of the reaction kettle, pour the mixed slurry into the mold through a vacuum casting cylinder, and cure at 70 °C for 5 d to obtain the paraffin-containing fuel.

[0050] Example 3

[0051] Weigh solid paraffin 55.8%, GAP 34.7%, hydrogenated C5 petroleum resin 4%, sodium cocoyl isethionate 2%, nano-carbon powder 2%, TDI 1.3%, and dibutyltin dilaurate 0.2% by mass fraction. Treat the above raw materials according to the following method: Place the solid paraffin in a reaction kettle at 70°C and stir at a speed of 100 r / min until the paraffin is completely melted. Then add the hydrogenated C5 petroleum resin to the melted paraffin and stir for 20 min to mix them evenly; add GAP and increase the stirring speed to 150 r / min, and stir for 30 min to fully disperse GAP and paraffin; then add sodium cocoyl isethionate, nano-carbon powder, and TDI in sequence, and stir for 20 min after each addition. Finally, add dibutyltin dilaurate and stir for 10 min to complete the addition and mixing of all raw materials. After the stirring is completed, turn off the stirrer of the reaction kettle, pour the mixed slurry into the mold through a vacuum casting cylinder, and cure at 70°C for 5 days to obtain the paraffin-containing fuel.

[0052] Example 4

[0053] Weigh solid paraffin 55.8%, GAP 34.7%, hydroxyacrylic resin 4%, sodium cocoyl isethionate 2%, carbon powder 2%, TDI 1.3%, and dibutyltin dilaurate 0.2% by mass percentage. Treat the above raw materials according to the following method: Place the solid paraffin in a reaction kettle at 70°C and stir at a speed of 100 r / min until the paraffin is completely melted. Then add the hydroxyacrylic resin to the melted paraffin and stir for 20 min to mix them evenly; add GAP and increase the stirring speed to 150 r / min, and stir for 30 min to fully disperse GAP and paraffin; then add sodium cocoyl isethionate, carbon powder, and TDI in sequence, and stir for 20 min after each addition. Finally, add dibutyltin dilaurate and stir for 10 min to complete the addition and mixing of all raw materials. After the stirring is completed, turn off the stirrer of the reaction kettle, pour the mixed slurry into the mold through a vacuum casting cylinder, and cure at 70°C for 5 days to obtain the paraffin-containing fuel.

[0054] Example 5

[0055] Weigh solid paraffin 68.8%, PBT 22.5%, hydrogenated C5 petroleum resin 3%, sodium cocoyl isethionate 2%, nano-carbon powder 2%, N-100 1.5%, and stannous octoate 0.2 by mass percentage. Treat the above raw materials according to the following method: Place the solid paraffin in a reaction kettle at 70°C and stir at a speed of 100 r / min until the paraffin is completely melted. Then add the hydrogenated C5 petroleum resin to the melted paraffin and stir for 20 min to mix the two evenly; add PBT and increase the stirring speed to 150 r / min, and stir for 30 min to fully disperse PBT and paraffin; then add sodium cocoyl isethionate, nano-carbon powder, and N-100 in sequence, and stir for 20 min after each addition. Finally, add stannous octoate and stir for 10 min to complete the addition and mixing of all raw materials. After the stirring is completed, turn off the stirrer of the reaction kettle, pour the mixed slurry into the mold through a vacuum casting cylinder, and cure at 70°C for 5 days to obtain paraffin-containing fuel.

[0056] Control example

[0057] Use the invention patent formula with the publication number CN111718226B as the control example; specifically: Weigh solid paraffin 62%, modified polyethylene 2%, polyazide glycidyl ether 10%, biuret polyisocyanate 0.8%, low-particle-size aluminum powder 25%, and stannous octoate 0.2% by mass percentage. The modified polyethylene is made of high-density polyethylene 87.7%, octadecanol 5.3%, and boric acid 7% by mass fraction. Treat the above raw materials according to the following method: Put the weighed solid paraffin and modified polyethylene into a reaction kettle at 120°C and stir at a speed of 80 r / min to accelerate the melting of solid paraffin and modified polyethylene and make them fully mixed; after the solid paraffin and modified polyethylene are melted, lower the temperature in the reaction kettle to 80°C, then add polyazide glycidyl ether binder and keep stirring at a speed of 80 r / min for 2 hours, and then add aluminum powder and stir for 0.5 hours; before pouring, add biuret polyisocyanate and stannous octoate to the reaction kettle and stir evenly, and then pour the mixed slurry into the mold; put the mold filled with slurry into a vacuum curing box and cure at 70°C for 7 days, and demold and shape to obtain paraffin-containing fuel with a certain charge configuration.

[0058] In the control example, adding modified polyethylene makes one end of the modified polyethylene connect to paraffin and the other end connect to the binder, so as to achieve the effect of mutual dissolution and modification of the two. However, the pre-modification step of the modified polyethylene is complex, and there is a problem of difficult thermal decomposition.

[0059] Using the relevant specified methods, the paraffin-containing fuels prepared in Examples 1 to 5 and the comparative examples were respectively made into dumbbell-shaped Type B specimens. The engineering gauge length of the specimens was 70 mm ± 0.5 mm, and the thickness was 10 mm ± 0.5 mm. After the specimens were prepared, they were placed in an environment at 25 °C for 24 hours and subjected to mechanical property experiments at room temperature, with the tensile rate set at 5 mm / min. In the comparative example, the content of polyglycidyl azide was 10%, so its maximum tensile strength could reach 0.91 MPa, but the elongation at break did not exceed 25%. The tensile strengths of the specimens prepared with the formulations of Examples 1 to 5 were all greater than or equal to 0.7 MPa, and the elongation at break of the fuel system with PBT as the binder was 45%, and that of the fuel system with GAP as the binder was 40%, meeting the usage requirements of solid fuels. Compared with the GAP binder, the fuel system with PBT as the binder had better mechanical properties. Moreover, as the content of the binder increased, the tensile strength decreased but the elongation at break increased. Therefore, the paraffin-containing fuels prepared in Examples 1 and 2 had the optimal mechanical properties.

[0060] Finally, it should be noted that the features mentioned and / or shown in the above description of the exemplary embodiments of the present invention can be combined in the same or similar manner into one or more other embodiments, combined with the features in other embodiments or replace the corresponding features in other embodiments. The technical solutions obtained through such combination or substitution should also be regarded as being included within the protection scope of the present invention.

Claims

1. A high-strength paraffin-containing fuel based on an azide binder, characterized in that: The method is composed of the following raw materials in percentage by weight: 50-70% of solid paraffin, 20-40% of azide adhesive, 5-8% of cosolvent, 1-3% of sodium cocoyl isethionate, 1-3% of nano carbon powder, 0.1-0.3% of curing catalyst, and the balance is curing agent; The cosolvent is hydrogenated C5 petroleum resin or hydroxy acrylic resin.

2. A high-strength paraffin-containing fuel based on an azide binder according to claim 1, characterized in that: The azide adhesive is poly 3,3-bis(azidomethyl)oxybutylene or 3,3-bis(azidomethyl)oxybutylene and tetrahydrofuran copolymer or polyazido glycidyl ether.

3. The high-strength paraffin-containing fuel based on an azide binder according to claim 1, characterized in that: The curing agent is stannous octoate or dibutyltin dilaurate.

4. The high-strength paraffin-containing fuel based on an azide binder according to claim 1, characterized in that: The curing catalyst is polyisocyanate or toluene diisocyanate.

5. A method for preparing a high-strength paraffin-containing fuel based on an azide binder according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1. Melt and mix: After the solid paraffin is heated until completely melted, a co-solvent is added according to the mass percentage and stirred until the mixture is uniform to obtain a molten liquid; Step 2. Add azide adhesive: Adding an azide adhesive according to the mass percentage to the molten liquid obtained in step 1, increasing the stirring rate and stirring until the azide adhesive and the paraffin wax are fully dissolved and dispersed to obtain a dissolved liquid; Step 3. Interface optimization: Adding sodium cocoyl isethionate according to the mass percentage to the solution obtained in step 2, stirring evenly, and then adding nano carbon powder according to the mass percentage, and continuing to stir until completely mixed to obtain a mixed solution; Step 4. Curing and molding: Add a corresponding amount of curing agent to the mixed solution obtained in step 3 according to the curing parameters, and add a curing catalyst after stirring to catalyze the curing reaction; finally, pour the mixed slurry into a mold for vacuum casting, and cure it at 70-80° C. for 3-5 days to obtain a paraffin-containing fuel.

6. The preparation method according to claim 5, characterized in that: In step 1, the stirring rate is 80-100 r / min, and the stirring time is 15-20 min.

7. The preparation method according to claim 5, characterized in that: In step 2, the stirring rate is 130-150 r / min, and the stirring time is 30-40 min.

8. The preparation method according to claim 5, characterized in that: In step 2, the liquid temperature is maintained at 60-65° C. during stirring.

9. The preparation method according to claim 5, characterized in that: In step 4, the curing parameter ranges from 1 to 1.2.

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