A sulfur-containing epoxy resin system compatible with liquid oxygen and preparation method thereof

Abstract

The invention discloses a sulfur-containing epoxy resin system compatible with liquid oxygen and a preparation method thereof, and belongs to the field of chemical and material technology. The method for preparing a sulfur-containing epoxy resin system compatible with liquid oxygen according to the present invention comprises the following steps: (1) cross-linking reaction of 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) and epoxy resin at high temperature to obtain an epoxy resin containing sulfur element; (2) adding diaminodiphenylmethane (DDM) to the epoxy resin containing sulfur element, fully dissolving; obtaining a clear liquid; (3) removing bubbles from the clear liquid, solidifying, and obtaining a sulfur-containing epoxy resin system compatible with liquid oxygen. The present invention introduces sulfur element into the epoxy resin matrix through thiadiazole ring-modified epoxy resin, effectively solving the problem that ordinary epoxy resin is incompatible with liquid oxygen; moreover, the method of the present invention is efficient and environmentally friendly.

Description

Technical Field

[0001] The invention relates to a sulfur-containing epoxy resin system compatible with liquid oxygen and a preparation method thereof, belonging to the technical field of chemical industry and materials. Background Art

[0002] The replacement of launch vehicle cryogenic propellant tanks from "metal" to "composite materials" has become an inevitable development trend in the world's aerospace industry. With the huge advantages of composite materials in terms of weight reduction and cost savings, composite propellant tanks are regarded as an important guarantee for future large-scale aerospace missions such as deep space exploration and large space station construction.

[0003] Liquid oxygen tanks are the components with the largest mass and volume in launch vehicles, and their weight reduction effect directly determines the rocket's lightweight level. Due to the limitations of the material properties of traditional metal tanks, the weight reduction effect achieved by means of structural optimization design is approaching the upper limit. Therefore, replacing traditional metal tanks with advanced composite materials with high specific strength and high specific stiffness can greatly improve the rocket's carrying efficiency and reduce launch costs.

[0004] Compared with fuels such as liquid hydrogen and liquid methane, in addition to its cryogenic properties, liquid oxygen also has strong oxidizing properties. Therefore, in addition to focusing on the mechanical properties of composite materials at low temperatures and the permeability of composite materials to cryogenic media, the development of composite liquid oxygen tanks must also address the incompatibility between composite materials and liquid oxygen. The incompatibility between the composite matrix and liquid oxygen has always been a bottleneck restricting the development of composite liquid oxygen tanks. Therefore, the work on the compatibility of resin matrix liquid oxygen is of great significance to the manufacture of a new generation of lightweight composite tanks.

[0005] Commonly used liquid oxygen compatible resins are usually achieved by modifying epoxy resins; for example: CN103694638A is an epoxy resin that can be used in a liquid oxygen environment prepared by reacting a phosphorus-containing flame retardant with an epoxy resin; CN103467923A provides a liquid oxygen compatible epoxy resin, which is mainly modified by using flame retardants such as octabromoether; CN109721711A is an epoxy resin that is liquid oxygen compatible obtained by polymerizing an epoxy resin with a flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; however, the introduction of halogen elements such as bromine into epoxy resins is harmful to the environment, and the preparation of liquid oxygen compatible phosphorus-containing resins requires higher temperatures and longer reaction times.

[0006] Therefore, how to efficiently prepare an environmentally friendly liquid oxygen-compatible epoxy resin system is a problem that needs to be solved urgently. Summary of the invention

[0007] [Technical issues]

[0008] Commonly used liquid oxygen compatible resins require the introduction of some halogen elements or phosphorus; halogen elements are harmful to the environment, and phosphorus-containing resins require higher temperatures and longer reaction times.

[0009] [Technical solution]

[0010] In order to solve the above problems, the present invention provides a sulfur-containing epoxy resin system compatible with liquid oxygen and a preparation method thereof; specifically, the present invention introduces sulfur into the epoxy resin matrix by modifying the epoxy resin with a thiadiazole ring, thereby effectively solving the problem of incompatibility between ordinary epoxy resin and liquid oxygen; moreover, the method of the present invention is highly efficient and environmentally friendly.

[0011] The first object of the present invention is to provide a method for preparing a sulfur-containing epoxy resin system compatible with liquid oxygen, comprising the steps of:

[0012] (1) subjecting 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) and epoxy resin to a cross-linking reaction at high temperature to obtain an epoxy resin containing sulfur;

[0013] (2) adding diaminodiphenylmethane (DDM) to the sulfur-containing epoxy resin and fully dissolving it to obtain a clear liquid;

[0014] (3) removing bubbles from the clarified liquid and solidifying it to obtain a sulfur-containing epoxy resin system that is compatible with liquid oxygen.

[0015] In one embodiment of the present invention, 2-amino-5-mercapto-1,3,4-thiadiazole is added in step (1) so that the sulfur content in the resin system is 1 wt%-1.5 wt%.

[0016] In one embodiment of the present invention, the epoxy resin in step (1) is bisphenol A epoxy resin (DGEBA).

[0017] In one embodiment of the present invention, the cross-linking reaction in step (1) is carried out by stirring at 150-180° C. and 500-1000 rpm for 20-40 min.

[0018] In one embodiment of the present invention, the amount of diaminodiphenylmethane (DDM) added in step (2) is such that the molar ratio of active hydrogen in DDM to epoxy groups in the sulfur-containing epoxy resin is 1:1.

[0019] In one embodiment of the present invention, the sufficient dissolution in step (2) is performed by stirring and dissolving at 80-90° C. and 500-1000 rpm for 15-30 min.

[0020] In one embodiment of the present invention, the bubbles are removed in step (3) by evacuating the resin to -0.1 MPA at 80-100°C and maintaining the pressure for 5-10 minutes to remove the bubbles in the resin.

[0021] In one embodiment of the present invention, the curing in step (3) is step curing, specifically, first curing at 100° C. for 2 hours, then curing at 130° C. for 2 hours, and finally curing at 160° C. for 4 hours.

[0022] The second object of the present invention is a sulfur-containing epoxy resin system compatible with liquid oxygen prepared by the method of the present invention.

[0023] The third object of the present invention is the application of the sulfur-containing epoxy resin system compatible with liquid oxygen in the field of aerospace.

[0024] In one embodiment of the present invention, the application is for liquid oxygen tanks, spacecraft, rocket engines, etc.

[0025] A fourth object of the present invention is to provide a liquid oxygen tank, which uses the sulfur-containing epoxy resin system compatible with liquid oxygen described in the present invention.

[0026] A fifth object of the present invention is to provide an ultra-low temperature environment material, which adopts the sulfur-containing epoxy resin system compatible with liquid oxygen described in the present invention.

[0027] A sixth object of the present invention is a method for improving the compatibility of epoxy resin with liquid oxygen, comprising the following steps:

[0028] (1) subjecting 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) and epoxy resin to a cross-linking reaction at high temperature to obtain an epoxy resin containing sulfur;

[0029] (2) adding diaminodiphenylmethane (DDM) to the sulfur-containing epoxy resin and fully dissolving it to obtain a clear liquid;

[0030] (3) removing bubbles from the clarified liquid and solidifying it to obtain a sulfur-containing epoxy resin system that is compatible with liquid oxygen.

[0031] [Beneficial Effects]

[0032] (1) The present invention introduces sulfur into the epoxy resin matrix by modifying the epoxy resin with a thiadiazole ring, thereby effectively solving the problem of incompatibility between ordinary epoxy resin and liquid oxygen.

[0033] (2) The method of the present invention is highly efficient and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1The present invention is a flow chart for preparing a sulfur-containing epoxy resin system compatible with liquid oxygen.

[0035] Figure 2 The figure is a reaction mechanism diagram for preparing a sulfur-containing epoxy resin system compatible with liquid oxygen in the present invention.

[0036] Figure 3 TG curves of the epoxy resin systems prepared in Examples 1, 2 and Comparative Example 1.

[0037] Figure 4 The DTG curves of the epoxy resin systems prepared in Examples 1 and 2 and Comparative Example 1 are shown.

[0038] Figure 5 The mechanical properties test results of the epoxy resin systems prepared in Examples 1 and 2 and Comparative Example 1 are shown.

[0039] Figure 6 This is a physical picture of the epoxy resin system prepared in Example 1.

[0040] Figure 7 This is a physical picture of the epoxy resin system prepared in Example 2. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0042] Test method:

[0043] 1. Liquid oxygen compatibility test:

[0044] Liquid oxygen compatibility testing was performed according to ASTM G86-17 standard;

[0045] All sample discs had a thickness of 2 ± 0.1 mm and a diameter of 19.4-19.5 mm;

[0046] IRS is expressed as liquid oxygen sensitivity coefficient, which is calculated as follows:

[0047]

[0048] Among them, ω i is the weighting coefficient of different phenomena during impact (combustion corresponds to ω 1 , the weight is 1.0; explosion corresponds to ω 2 , weight is 0.9; spark corresponds to ω 3 , weight is 0.7; burnt black corresponds to ω 4 , the weight is 0.4; no phenomenon corresponds to ω 5 , weight is 0.0), n i is the frequency of occurrence of each phenomenon.

[0049] 2. Mechanical properties test:

[0050] Using the LD24.204 microcomputer-controlled electronic universal testing machine produced by Shanghai Lishi Scientific Instrument Co., Ltd., the sulfur-containing resin casting was tensile tested at 2mm / min at room temperature with reference to ASTM D-638. The specimen size type was a standard type IV specimen, and the average value was taken when more than 5 samples were tested.

[0051] 3. Thermal stability test:

[0052] The TG test of sulfur-containing epoxy resin was carried out using a Mettler TGA2 fully automatic thermogravimetric analyzer produced by Swiss Mettler-Toledo Company, with a heating rate of 10°C / min and a test temperature of 30-600°C.

[0053] The raw materials used in the embodiment:

[0054] 2-Amino-5-mercapto-1,3,4-thiadiazole (AMT): purity>98%, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0055] Bisphenol A epoxy resin (DGEBA): brand 0164, epoxy equivalent weight 185 g / mol, purchased from Nantong Xingchen Synthetic Materials Co., Ltd.;

[0056] Diaminodiphenylmethane (DDM): analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0057] Example 1

[0058] A method for preparing a sulfur-containing epoxy resin system compatible with liquid oxygen comprises the following steps:

[0059] (1) 2.63 g of 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) and 100 g of bisphenol A epoxy resin (DGEBA) were mixed and stirred at 150° C. and 1000 rpm for a cross-linking reaction for 30 min, so that some epoxy groups of DGEBA were ring-opened and cross-linked with active hydrogen in AMT to obtain a sulfur-containing epoxy resin with a sulfur content of 1 wt %;

[0060] (2) Add 23.83 g of diaminodiphenylmethane (DDM) to the sulfur-containing epoxy resin (the molar ratio of active hydrogen in DDM to epoxy group in the sulfur-containing epoxy resin is 1:1), and stir and dissolve at 80° C. and 800 rpm for 30 min until DDM is completely dissolved to obtain a clear liquid;

[0061] (3) The clarified liquid was placed in a vacuum oven at 90° C. and evacuated to -0.1 MPA, and the pressure was maintained for 10 min to remove the bubbles in the resin to obtain a degassed resin; finally, the degassed resin was poured into a vacuum oven covered with a release cloth, and cured at 100° C. for 2 h, 130° C. for 2 h, and 160° C. for 4 h to obtain a sulfur-containing epoxy resin system compatible with liquid oxygen, which was labeled EP-S1.

[0062] Example 2

[0063] A method for preparing a sulfur-containing epoxy resin system compatible with liquid oxygen comprises the following steps:

[0064] (1) 3.94 g of 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) and 100 g of bisphenol A epoxy resin (DGEBA) were mixed and stirred at 150° C. and 1000 rpm for a cross-linking reaction for 30 min, so that some epoxy groups of DGEBA were ring-opened and cross-linked with active hydrogen in AMT to obtain a sulfur-containing epoxy resin with a sulfur content of 1.5 wt %;

[0065] (2) Add 22.36 g of diaminodiphenylmethane (DDM) to the sulfur-containing epoxy resin (the molar ratio of active hydrogen in DDM to epoxy group in the sulfur-containing epoxy resin is 1:1), and stir and dissolve at 80° C. and 800 rpm for 30 min until DDM is completely dissolved to obtain a clear liquid;

[0066] (3) The clarified liquid was placed in a vacuum oven at 90° C. and evacuated to -0.1 MPA, and the pressure was maintained for 10 min to remove the bubbles in the resin to obtain a degassed resin; finally, the degassed resin was poured into a vacuum oven covered with a release cloth, and cured at 100° C. for 2 h, 130° C. for 2 h, and 160° C. for 4 h to obtain a sulfur-containing epoxy resin system compatible with liquid oxygen, which was labeled EP-S1.5.

[0067] Comparative Example 1

[0068] A method for preparing epoxy resin comprises the following steps:

[0069] Add 26.79 g of diaminodiphenylmethane (DDM) to 100 g of bisphenol A epoxy resin (DGEBA), and stir and dissolve at 80°C and 800 rpm for 30 min until DDM is completely dissolved to obtain a clear liquid;

[0070] The clarified liquid was placed in a vacuum oven at 90°C and evacuated to -0.1MPA, and the pressure was maintained for 10 minutes to remove the bubbles in the resin to obtain a degassed resin; finally, the degassed resin was poured into a vacuum oven covered with a release cloth, and cured at 100°C for 2 hours, 130°C for 2 hours, and 160°C for 4 hours to obtain a sulfur-free epoxy resin.

[0071] The liquid oxygen compatibility test was performed on Examples 1, 2 and Comparative Example 1, and the test results are as follows:

[0072] Table 1 Test results of liquid oxygen compatibility

[0073] example combustion explode flash Carbonization Number of experiments IRS (%) Comparative Example 1 1 0 2 0 20 12 Example 1 0 0 0 0 20 0 Example 2 0 0 0 0 20 0

[0074] It can be seen from Table 1 that the sulfur-containing epoxy resin system prepared in Examples 1 and 2 had no sensitive phenomenon in 20 liquid oxygen impact tests and passed the liquid oxygen impact test, proving that it is compatible with liquid oxygen.

[0075] Table 2 Thermal stability test results

[0076] example sample <![CDATA[T 5％ (℃)]]> <![CDATA[T max (℃)]]> <![CDATA[R max (% / ℃)]]> Char(%) Comparative Example 1 EP 366.04 386.17 -1.44 16.31 Example 1 EP-S1 346.24 373.50 -1.25 16.82 Example 2 EP-S1.5 338.91 371.50 -1.09 15.92

[0077] Figure 3 TG curves of the epoxy resin systems prepared in Examples 1 and 2 and Comparative Example 1; Figure 4 Table 2 is the DTG curve of the epoxy resin system prepared in Examples 1, 2 and Comparative Example 1; Table 3 is the thermal stability test results; Figure 3 , Figure 4 It can be seen from Table 2 that the sulfur-containing epoxy resin systems prepared in Examples 1 and 2 have good thermal stability; the maximum thermal weight loss rate of the epoxy resin system prepared in Example 1 is increased from -1.44% to -1.25%; the maximum thermal weight loss rate of the epoxy resin system prepared in Example 2 is increased from -1.44% to -1.09%.

[0078] Figure 5 The mechanical properties test results of the epoxy resin system prepared in Examples 1 and 2 and Comparative Example 1 are shown in FIG. Figure 5 It can be seen that the mechanical property test results of the epoxy resin systems prepared in Examples 1 and 2 and Comparative Example 1 are not much different.

[0079] Figure 6 , Figure 7 This is a physical picture of the epoxy resin system prepared in Examples 1 and 2. Figure 6 and Figure 7 It can be seen that the epoxy resin systems prepared in Examples 1 and 2 are clear solutions in light yellow to orange.

[0080] Although the present invention has been disclosed as above in the form of a preferred embodiment, 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 improving the compatibility of epoxy resin with liquid oxygen, characterized in that: The steps include: (1) AMT and an epoxy resin are cross-linked at high temperature to obtain an epoxy resin containing sulfur. The addition of 2-amino-5-mercapto-1,3,4-thiadiazole results in a sulfur content of 1 wt% to 1.5 wt% in the resin system. The cross-linking reaction is carried out at 150 to 180° C. and 500 to 1000 rpm for 20 to 40 minutes. (2) Add diaminodiphenylmethane (DDM) to the sulfur-containing epoxy resin and fully dissolve it to obtain a clear liquid; (3) The clarified liquid is debubbled and solidified to obtain a sulfur-containing epoxy resin system that is compatible with liquid oxygen.

2. The method according to claim 1, characterized in that In step (2), the amount of diaminodiphenylmethane (DDM) added is such that the molar ratio of active hydrogen in DDM to epoxy groups in the sulfur-containing epoxy resin is 1:

1.

3. The method according to claim 1, characterized in that The complete dissolution in step (2) is carried out by stirring and dissolving at 80-90°C and 500-1000 rpm for 15-30 min.

4. The method according to claim 1, characterized in that: The epoxy resin in step (1) is bisphenol A epoxy resin.

5. The method according to claim 1, characterized in that The curing in step (3) is step curing, specifically, first curing at 100°C for 2h, then curing at 130°C for 2h, and finally curing at 160°C for 4h.

6. A liquid oxygen tank, characterized in that: A sulfur-containing epoxy resin system compatible with liquid oxygen is used; the preparation method of the sulfur-containing epoxy resin system compatible with liquid oxygen is as follows: (1) AMT and an epoxy resin are cross-linked at high temperature to obtain an epoxy resin containing sulfur. The addition of 2-amino-5-mercapto-1,3,4-thiadiazole results in a sulfur content of 1 wt% to 1.5 wt% in the resin system. The cross-linking reaction is carried out at 150 to 180° C. and 500 to 1000 rpm for 20 to 40 minutes. (2) Add diaminodiphenylmethane (DDM) to the sulfur-containing epoxy resin and fully dissolve it to obtain a clear liquid; (3) The clarified liquid is debubbled and solidified to obtain a sulfur-containing epoxy resin system that is compatible with liquid oxygen.

7. The liquid oxygen tank according to claim 6, characterized in that: In step (2), the amount of diaminodiphenylmethane (DDM) added is such that the molar ratio of active hydrogen in DDM to epoxy groups in the sulfur-containing epoxy resin is 1:

1.

8. The liquid oxygen tank according to claim 6, characterized in that: The complete dissolution in step (2) is carried out by stirring and dissolving at 80-90°C and 500-1000 rpm for 15-30 min.

9. The liquid oxygen tank according to claim 6, characterized in that: The epoxy resin in step (1) is bisphenol A epoxy resin (DGEBA).

10. The liquid oxygen tank according to claim 6, characterized in that: The curing in step (3) is step curing, specifically, first curing at 100°C for 2h, then curing at 130°C for 2h, and finally curing at 160°C for 4h.

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