A method for the preparation of an epoxy resin matrix for cryogenic fuel tanks

Abstract

The application discloses a preparation method of an epoxy resin matrix for a low-temperature fuel tank, and belongs to the technical field of high polymer materials. The application coats Ti3AlC2 with formaldehyde and resorcinol to obtain RF@Ti3AlC2-MXene; then, the RF@Ti3AlC2-MXene is added into an epoxy resin system, and is cured to obtain the epoxy resin matrix. The epoxy resin matrix prepared by the application has good low-temperature resistance and good mechanical properties in a low-temperature environment, and can be used for the preparation of a low-temperature fuel tank. The epoxy resin / carbon fiber composite material prepared by using the epoxy resin matrix of the application has good mechanical properties after cold and hot cycles, and the carbon fiber and the resin have good interface bonding, which is beneficial to improving the stability of the low-temperature fuel tank.

Description

Technical Field

[0001] The invention relates to a method for preparing an epoxy resin matrix for a low-temperature fuel storage tank, belonging to the technical field of polymer materials. Background Art

[0002] Cryogenic fuel tanks are key components in liquid rockets, used to store and supply cryogenic liquid propellants (such as liquid hydrogen and liquid oxygen). Cryogenic fuels, such as liquid hydrogen and liquid oxygen, offer high specific impulse and are gradually replacing traditional nitrogen tetroxide and UDMH fuels. Cryogenic fuel tanks account for over 60% of the total weight of a rocket, making their lightweighting crucial for enhancing a rocket's payload capacity.

[0003] Compared to metal materials, epoxy resin / carbon fiber composites offer advantages such as lower density, higher specific strength, and improved fatigue resistance, potentially reducing the weight of cryogenic fuel tanks by 30%. However, at ultra-low temperatures, ordinary epoxy resins freeze their molecular chains, reducing molecular network mobility and increasing their brittleness, making them difficult to use in ultra-low temperature environments and significantly impacting the reliability of cryogenic fuel tanks.

[0004] Currently, silica is commonly used as a toughening agent, effectively improving the toughness of epoxy resin at low temperatures. However, this has drawbacks such as high addition levels and high resin viscosity. Furthermore, conventional epoxy resin composites are prone to interfacial cracking and porosity damage after thermal cycling, resulting in a decrease in mechanical properties and making them difficult to use in cryogenic fuel tanks. Furthermore, the difference in thermal expansion coefficients between the carbon fibers and the resin matrix, as well as poor adhesion between the two, can lead to cracking and separation in cryogenic fuel tanks during thermal cycling, compromising their usability.

[0005] Therefore, the preparation of epoxy resins with low reinforcement addition, good toughness and low-temperature resistance, as well as epoxy resin / carbon fiber composite materials are of great significance for low-temperature fuel tanks. Summary of the Invention

[0006] [Technical Issues]

[0007] Conventional low-temperature resistant epoxy resins have the problem of large amount of reinforcement added and poor toughness;

[0008] Conventional epoxy resin composites have problems such as poor mechanical properties and poor adhesion after hot and cold cycles.

[0009] [Technical solution]

[0010] To address these issues, the present invention first coats Ti3AlC2 with formaldehyde and resorcinol to produce RF@Ti3AlC2-MXene. The RF@Ti3AlC2-MXene is then added to an epoxy resin system and cured to form an epoxy resin matrix. The epoxy resin matrix prepared in this invention exhibits excellent low-temperature resistance and mechanical properties at low temperatures, making it suitable for use in the manufacture of cryogenic fuel tanks. The epoxy resin / carbon fiber composite material prepared using this epoxy resin matrix exhibits excellent mechanical properties after thermal cycling, with good interfacial bonding between the carbon fibers and the resin, contributing to improved stability in cryogenic fuel tanks.

[0011] The first object of the present invention is to provide a method for preparing RF@Ti3AlC2-MXene / epoxy resin for cryogenic fuel tanks, comprising the following steps:

[0012] (1) Dispersing Ti3AlC2-MXene in an ethanol aqueous solution, then adding an ammonia aqueous solution and mixing evenly; then adding formaldehyde and resorcinol, and reacting at 50-100 °C for 12-24 h; after the reaction, centrifuging, washing, and drying to obtain RF@Ti3AlC2-MXene;

[0013] (2) Dispersing RF@Ti3AlC2-MXene in a solvent to obtain a dispersion of RF@Ti3AlC2-MXene; then adding the dispersion of RF@Ti3AlC2 to the epoxy resin, mixing evenly, and removing the solvent to obtain RF@Ti3AlC2-MXene / epoxy resin.

[0014] In one embodiment of the present invention, the preparation method of Ti3AlC2 in step (1) is as follows:

[0015] Dissolving LiF in HCl solution to obtain a LiF solution;

[0016] Ti3AlC2 is added to the LiF solution and etched at 35-40°C for 24-48 hours. After the reaction, the solution is washed by centrifugation, dispersed again, centrifuged, and the supernatant is collected and freeze-dried to obtain Ti3AlC2-MXene.

[0017] Wherein, the HCl solution is a 9M hydrochloric acid aqueous solution;

[0018] The particle size of LiF is 50 μm;

[0019] The particle size of Ti3AlC2 is 400 mesh;

[0020] The dosage ratio of Ti3AlC2, LiF and HCl solution is 1g:1-1.5g:20-25mL;

[0021] Centrifugal washing is centrifugal washing to 6-7;

[0022] Centrifugal speed is 3500-5000 rpm;

[0023] Redispersion is carried out in water by ultrasonic dispersion, and the ultrasonic time is 30-60 min.

[0024] In one embodiment of the present invention, the mass ratio of water to ethanol in the ethanol aqueous solution in step (1) is 8-15:1.

[0025] In one embodiment of the present invention, the amount of the ammonia solution in step (1) is 0.1-1% (volume percentage) of the ethanol aqueous solution; the volume concentration of the ammonia solution is 20-30%.

[0026] In one embodiment of the present invention, the ratio of Ti3AlC2-MXene to ethanol aqueous solution in step (1) is 5 g:300-500 mL.

[0027] In one embodiment of the present invention, the mass ratio of Ti3AlC2-MXene, formaldehyde, and resorcinol in step (1) is 1:1-3:1-4.

[0028] In one embodiment of the present invention, the mixing in step (1) is carried out by stirring at 20-30°C (normal temperature) for 20-40 minutes.

[0029] In one embodiment of the present invention, the centrifugal speed in step (1) is 3500-5000 rpm, and washing is performed with water.

[0030] In one embodiment of the present invention, the solvent in step (2) is acetone or ethanol.

[0031] In one embodiment of the present invention, the mass concentration of the dispersion of RF@Ti3AlC2-MXene in step (2) is 5-10 wt%.

[0032] In one embodiment of the present invention, the mass ratio of the epoxy resin to the dispersion of RF@Ti3AlC2-MXene in step (2) is 100:0.1-0.8.

[0033] In one embodiment of the present invention, the solvent is removed in step (2) by heating.

[0034] In one embodiment of the present invention, the epoxy resin in step (2) is E-51.

[0035] The second object of the present invention is RF@Ti3AlC2-MXene / epoxy resin prepared by the method described in the present invention.

[0036] A third object of the present invention is to provide a method for preparing an epoxy resin matrix for a cryogenic fuel tank, comprising the following steps:

[0037] A curing agent is added to RF@Ti3AlC2-MXene / epoxy resin and cured to obtain an epoxy resin matrix for low-temperature fuel tanks.

[0038] In one embodiment of the present invention, the mass ratio of the curing agent to the epoxy resin is 15-25:100.

[0039] In one embodiment of the present invention, the curing agent is diethyltoluenediamine.

[0040] In one embodiment of the present invention, the curing is step curing, specifically curing at 110° C. for 2 h and curing at 150° C. for 2 h.

[0041] The fourth object of the present invention is the epoxy resin matrix for cryogenic fuel tanks prepared by the method of the present invention.

[0042] A fifth object of the present invention is to provide a method for preparing an epoxy resin / carbon fiber composite material, which uses the RF@Ti3AlC2 / epoxy resin described in the present invention.

[0043] In one embodiment of the present invention, a method for preparing an epoxy resin / carbon fiber composite material comprises the following steps:

[0044] Mix RF@Ti3AlC2 / epoxy resin and curing agent in a mass ratio of 4-6:1, remove bubbles, and obtain a mixed solution;

[0045] The carbon fiber is placed in a mold, and then the mixed solution is poured in and cured to form an epoxy resin / carbon fiber composite material.

[0046] In one embodiment of the present invention, the bubbles are removed by mechanically stirring the mixture and placing the mixture in a vacuum oven with a vacuum degree of -0.1 MPa to remove tiny bubbles.

[0047] In one embodiment of the present invention, the curing agent is diethyltoluenediamine.

[0048] In one embodiment of the present invention, the curing is step curing, specifically curing at 110° C. for 2 h and curing at 150° C. for 2 h.

[0049] In one embodiment of the present invention, the mass ratio of carbon fiber to mixed solution is 1:100.

[0050] The sixth object of the present invention is the epoxy resin / carbon fiber composite material prepared by the method of the present invention.

[0051] A seventh object of the present application is the use of the RF@Ti3AlC2-MXene / epoxy resin, the epoxy resin matrix for cryogenic fuel tank or the epoxy resin / carbon fiber composite material of the present application in aerospace field.

[0052] An eighth object of the present application is to provide a cryogenic fuel tank using the RF@Ti3AlC2-MXene / epoxy resin, the epoxy resin matrix for cryogenic fuel tank or the epoxy resin / carbon fiber composite material of the present application.

[0053] A ninth object of the present application is to provide a method for improving the low-temperature resistance of epoxy resin and fuel tank using the RF@Ti3AlC2-MXene / epoxy resin, the epoxy resin matrix for cryogenic fuel tank or the epoxy resin / carbon fiber composite material of the present application.

[0054] [Advantages]

[0055] (1) The formaldehyde and resorcinol used in the present application are precursors for coating the surface of Ti3AlC2-MXene with polymers, which effectively improves the dispersibility of Ti3AlC2-MXene in the epoxy resin.

[0056] (2) The RF@Ti3AlC2 used in the present application as a toughening agent for epoxy resin can achieve good low-temperature mechanical properties of the epoxy resin with less addition amount.

[0057] (3) The epoxy resin matrix for cryogenic fuel tank or the epoxy resin / carbon fiber composite material prepared by the present application can be used to prepare a cryogenic fuel tank. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 Atomic force scanning electron microscope image of Ti3AlC2-MXene.

[0059] Figure 2 Atomic force scanning electron microscope image of RF@Ti3AlC2-MXene in Example 1.

[0060] Figure 3 Infrared spectrum of Ti3AlC2-MXene, RF@Ti3AlC2-MXene in Example 1.

[0061] Figure 4 Stress-strain curves of Example 1-4 and Control Example 1 at 90 K.

[0062] Figure 5 Stress test results of Example 5-7 at 90 K.

[0063] Figure 6Prepare molds and test specimens for composite materials.

[0064] Figure 7 The tensile test results (90K) of the composite materials of Example 8 and Comparative Example 4 are shown.

[0065] Figure 8 is the tensile strength (90K) of the composite materials of Example 8 and Comparative Example 4 after thermal cycling. DETAILED DESCRIPTION

[0066] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0067] Test method:

[0068] 1. Stress-strain test:

[0069] According to ASTM-D638, the epoxy resin matrix was subjected to a tensile test at 90K.

[0070] 2. Thermal cycle test:

[0071] The samples were thermally cycled 80 times; specifically, one cycle consisted of immersing the samples in liquid nitrogen for 1.5 minutes and then exposing them to ambient temperature for 6.5 minutes.

[0072] The raw materials used in the embodiments and comparative examples are:

[0073] Epoxy resin: E-51;

[0074] Curing agent: diethyltoluenediamine;

[0075] LiF: particle size 50 μm;

[0076] Ti3AlC2: particle size is 400 mesh;

[0077] HCl solution: 9M hydrochloric acid aqueous solution;

[0078] Ammonia solution: 28% ammonia solution;

[0079] Carbon fiber: T300, 1K;

[0080] The preparation of Ti3AlC2-MXene is as follows:

[0081] Dissolve 2 g LiF in 40 mL HCl solution to obtain a LiF solution; add 2 g Ti3AlC2 in the LiF solution, etch at 40℃ for 24 h; after the reaction is completed, centrifuge (4000 rpm) the solution to wash to pH 6, re-disperse in deionized water, ultrasonic for 40 min, then centrifuge at 4000 rpm for 1 h, obtain the supernatant, freeze-dry to obtain Ti3AlC2-MXene.

[0082] The stirring mentioned in the examples and the control example is magnetic stirring, the purpose is to mix uniformly, the speed has little effect; the speed used in the examples is 500 rpm.

[0083] Example 1

[0084] A method for preparing an epoxy resin matrix for a cryogenic fuel tank, comprising the following steps:

[0085] (1) Disperse 5 g Ti3AlC2-MXene in 300 mL aqueous ethanol solution (mass ratio of ethanol to water is 14:1), then add 3 mL ammonia solution, magnetic stirring at 25℃ (room temperature) for 30 min; then add 10 g formaldehyde and 8 g resorcinol, react at 60℃ for 15 h; after the reaction is completed, centrifuge (4000 rpm), wash with water, dry to obtain RF@Ti3AlC2-MXene;

[0086] (2) Disperse 8 g RF@Ti3AlC2-MXene in 100 g acetone to obtain a dispersion solution of RF@Ti3AlC2-MXene with a concentration of 8 wt%; then add 0.1 g of the dispersion solution of RF@Ti3AlC2-MXene in 100 g epoxy resin, mix uniformly, heat at 60℃ to remove acetone to obtain RF@Ti3AlC2-MXene / epoxy resin; then add 20 g curing agent, heat to 70℃ to dissolve the curing agent; vacuum degassing, pour into a mold, cure at 110℃ for 2 h, then at 150℃ for 2 h to obtain an epoxy resin matrix for a cryogenic fuel tank.

[0087] Example 2

[0088] Adjust the addition amount of the dispersion solution of RF@Ti3AlC2-MXene in step (2) of Example 1 to 0.2 g; other conditions remain the same as in Example 1 to obtain an epoxy resin matrix for a cryogenic fuel tank.

[0089] Example 3

[0090] The addition amount of the RF@Ti3AlC2-MXene dispersion in step (2) of Example 1 was adjusted to 0.4 g; the other conditions remained the same as in Example 1, and an epoxy resin matrix for a low-temperature fuel tank was obtained.

[0091] Example 4

[0092] The addition amount of the RF@Ti3AlC2-MXene dispersion in step (2) of Example 1 was adjusted to 0.6 g; the other conditions remained the same as in Example 1, and an epoxy resin matrix for a low-temperature fuel tank was obtained.

[0093] Comparative Example 1

[0094] The RF@Ti3AlC2-MXene in Example 1 was omitted, and the rest was kept consistent with Example 1 to obtain an epoxy resin matrix.

[0095] The obtained RF@Ti3AlC2-MXene and epoxy resin matrix were subjected to performance tests, and the test results are as follows:

[0096] Figure 2 This is an atomic force scanning electron microscope image of RF@Ti3AlC2-MXene in Example 1. Figure 2 It can be seen that the thickness of RF@Ti3AlC2-MXene increases, indicating that the polymer is successfully coated on the Ti3AlC2 surface.

[0097] Figure 3 The infrared spectra of Ti3AlC2-MXene and RF@Ti3AlC2 in Example 1 are shown in Figure 1. Figure 3 It can be seen that the polymer is successfully coated on the Ti3AlC2 surface.

[0098] Figure 4 The stress-strain curves of Examples 1-4 and Comparative Example 1 at 90 K are shown in FIG. Figure 4 It can be seen that the epoxy resin matrix prepared in Example 1 reached a stress of 154.6 MPa and a strain of 2.5%; the epoxy resin matrix prepared in Example 2 reached a stress of 147.4 MPa and a strain of 2.2%; the epoxy resin matrix prepared in Example 3 reached a stress of 133.3 MPa and a strain of 2.1%; the epoxy resin matrix prepared in Example 4 reached a stress of 110.1 MPa and a strain of 1.6%; and the epoxy resin matrix prepared in Control Example 1 reached a stress of 119.1 MPa and a strain of 2%. It can be seen that the epoxy resin matrices prepared in Examples 1-3 have good low-temperature resistance and good mechanical properties at low temperatures. The epoxy resin matrix prepared in Example 4 has a reduced crosslinking density, resulting in weakened mechanical properties at low temperatures.

[0099] Comparative Example 2

[0100] Omitting step (1) of Example 1, Ti3AlC2-MXene is dispersed in acetone to form a dispersion liquid, then epoxy resin is added, and the rest is consistent with Example 1.

[0101] It is found that Ti3AlC2-MXene is difficult to be directly dispersed in the epoxy resin system; if a dispersant is added, the mechanical properties of the epoxy resin will be affected.

[0102] Comparative Example 3

[0103] Omitting step (1) of Example 1, adjusting RF-Ti3AlC2-MXene in step (2) of Example 1 to silicon dioxide (50 μm), and adjusting the mass ratio of silicon dioxide and epoxy resin to 15:100, and the rest is consistent with Example 1, to obtain an epoxy resin matrix.

[0104] The obtained epoxy resin matrix is tested for performance, and the test structure is as follows:

[0105] When the mass of silicon dioxide in the epoxy resin is 15%, the effect is equivalent to that of Example 1, and the effect at low temperature is still not as good as that of Example 1.

[0106] Example 5

[0107] Adjusting “10 g of formaldehyde and 8 g of resorcinol” in step (1) of Example 1 to “5 g of formaldehyde and 4 g of resorcinol”; the rest is consistent with Example 1, to obtain an epoxy resin matrix for low-temperature fuel storage tank.

[0108] Example 6

[0109] Adjusting “10 g of formaldehyde and 8 g of resorcinol” in step (1) of Example 1 to “20 g of formaldehyde and 16 g of resorcinol”; the rest is consistent with Example 1, to obtain an epoxy resin matrix for low-temperature fuel storage tank.

[0110] Example 7

[0111] Adjusting “10 g of formaldehyde and 8 g of resorcinol” in step (1) of Example 1 to “15 g of formaldehyde and 15 g of resorcinol”; the rest is consistent with Example 1, to obtain an epoxy resin matrix for low-temperature fuel storage tank.

[0112] The obtained epoxy resin matrix is tested for performance at 90 K, and the test results are as follows:

[0113] From Figure 5It can be seen that the reduction in the amount of formaldehyde and resorcinol in Example 5 leads to incomplete coating of Ti3C2, which deteriorates the dispersibility of Ti3C2 in the resin and reduces the mechanical properties of the epoxy resin matrix; in Examples 7 and 8, the increase in the amount of aldehyde and resorcinol leads to an increase in the amount of polymer coated with Ti3C2, a decrease in the relative mass of Ti3C2, and the failure to maximize the toughening effect.

[0114] Example 8

[0115] A method for preparing an epoxy resin / carbon fiber composite material comprises the following steps:

[0116] (1) The carbon fiber and the obtained RF@Ti3AlC2-MXene epoxy resin were dried at 60 °C for 4 h;

[0117] (2) RF@Ti3AlC2-MXene epoxy resin and curing agent were mixed in a mass ratio of 5:1, mechanically stirred, and placed in a vacuum oven with a vacuum degree of -0.1 MPa to remove tiny bubbles to obtain a mixed solution;

[0118] (3) 0.1 g of carbon fiber bundle was embedded in a silicone rubber mold with a pre-reserved cut; 10 g of the mixed solution was introduced into the mold, and then placed in an oven for curing. The curing procedure was: 110 °C (2 h), 150 °C (2 h);

[0119] (4) The surface of the cured sample was polished until the fibers were exposed, and then dried at 60 °C for 8 h to obtain an epoxy resin / carbon fiber composite material.

[0120] Comparative Example 4

[0121] The RF@Ti3AlC2-MXene epoxy resin in Example 8 was adjusted to E-51 resin, and the other parameters were kept consistent with Example 8 to obtain a composite material.

[0122] The obtained epoxy resin / carbon fiber composite material was subjected to performance testing, and the test results are as follows:

[0123] from Figure 7 and Figure 8 It can be seen that compared with the pure epoxy resin of Control Example 4 (stress reaches 8.6 MPa, strain is 0.13%, and tensile strength reaches 6.9 MPa after 80 thermal cycles), Example 8 has excellent mechanical properties at 90K, with stress reaching 9.8 MPa and strain of 0.15%; the tensile strength after 80 thermal cycles reaches 9.6 MPa, indicating that there is good interfacial performance between RF@Ti3C2-MXene epoxy resin and carbon fiber, and the mechanical properties of thermal cycling are excellent.

[0124] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing RF@Ti3AlC2-MXene / epoxy resin for cryogenic fuel tanks, characterized in that: The steps include: (1) Dispersing Ti3AlC2-MXene in an ethanol aqueous solution, then adding an ammonia aqueous solution and mixing evenly; then adding formaldehyde and resorcinol, and reacting at 50-100 °C for 12-24 h; after the reaction, centrifuging, washing, and drying to obtain RF@Ti3AlC2-MXene; (2) Dispersing RF@Ti3AlC2-MXene in a solvent to obtain a dispersion of RF@Ti3AlC2-MXene; then adding the dispersion of RF@Ti3AlC2 to the epoxy resin, mixing them evenly, and removing the solvent to obtain RF@Ti3AlC2-MXene / epoxy resin; Wherein, in step (1), the mass ratio of Ti3AlC2-MXene, formaldehyde, and resorcinol is 1:1-3:1-4; The mass concentration of the dispersion of RF@Ti3AlC2-MXene in step (2) is 5-10 wt%; The mass ratio of the epoxy resin and the RF@Ti3AlC2-MXene dispersion in step (2) is 100:0.1-0.

8.

2. The method according to claim 1, characterized in that The mass ratio of water to ethanol in the ethanol aqueous solution in step (1) is 8-15:

1.

3. The method according to claim 1, wherein The ratio of Ti3AlC2-MXene to ethanol aqueous solution in step (1) is 5 g:300-500 mL.

4. The method according to claim 1, wherein The centrifugal speed in step (1) is 3500-5000 rpm, and washing is performed with water.

5. RF@Ti3AlC2-MXene / epoxy resin prepared by the method according to any one of claims 1 to 4.

6. A method for preparing an epoxy resin matrix for a cryogenic fuel tank, characterized in that: The steps include: A curing agent is added to the RF@Ti3AlC2-MXene / epoxy resin described in claim 5, and the mixture is cured to obtain an epoxy resin matrix for a low-temperature fuel tank.

7. The method according to claim 6, characterized in that The mass ratio of curing agent to epoxy resin is 15-25:

100.

8. The method according to claim 6, characterized in that The curing agent is diethyltoluenediamine.

9. The method according to claim 6, wherein The curing was stepwise, specifically curing at 110 °C for 2 h and then at 150 °C for 2 h.

10. An epoxy resin matrix for a cryogenic fuel tank prepared by the method according to any one of claims 6 to 9.

11. A method for preparing an epoxy resin / carbon fiber composite material, characterized in that: The steps include: Mixing the RF@Ti3AlC2 / epoxy resin according to claim 10 and a curing agent in a mass ratio of 4-6:1, removing bubbles, and obtaining a mixed solution; The carbon fiber is placed in a mold, and then the mixed solution is poured in and cured to form an epoxy resin / carbon fiber composite material.

12. The method according to claim 11, characterized in that The curing agent is diethyltoluenediamine.

13. The method according to claim 11, wherein The curing was stepwise, specifically curing at 110 °C for 2 h and then at 150 °C for 2 h.

14. The epoxy resin / carbon fiber composite material prepared by the method according to any one of claims 11 to 13.

15. Use of the RF@Ti3AlC2-MXene / epoxy resin according to claim 5, the epoxy resin matrix of the cryogenic fuel tank according to claim 10, or the epoxy resin / carbon fiber composite material according to claim 14 in the aerospace field.

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