A method for solving vacuum degassing of space flexible materials based on double network

Abstract

A method for solving the vacuum degassing of space flexible materials based on a double network belongs to the field of space deployment material preparation. The method is: after mixing a photocuring agent, an imidazole derivative curing agent, an acrylate resin and an epoxy resin, evacuate the mixture, remove bubbles, pour it into a mold, and irradiate it with ultraviolet light for 10-20 minutes to prepare a flexible material of the first network, and then pre-cure it at 110°C for 3 hours and post-cure it at 150°C for 3 hours to obtain a rigid material. After the first stage of light initiation, an acrylate material of the first network is obtained. At this time, the synthetic product will be embedded in the acrylate resin network. When the flexible material is launched and deployed in orbit, under vacuum conditions, the second stage curing agent in the material will not be drawn into the vacuum environment due to its higher molecular weight. Then, the imidazole derivative is triggered by heating to cure the epoxy resin, completing the formation of the second network of the material in the space environment, that is, the soft-rigid conversion.

Description

Technical Field

[0001] The invention belongs to the field of preparation of space expansion materials, and in particular relates to a method for solving vacuum degassing of space flexible materials based on a double network. Background Art

[0002] As humans continue to explore space, various types of spacecraft tend to be larger, with increasingly complex structures and larger masses. Due to the limitations of factors such as the effective space and carrying mass of the carrier, traditional spacecraft structures have encountered huge difficulties in development and launch. To resolve this contradiction, the technology of building a double network is introduced, that is, firstly, the monomers and initiators are mixed and reacted on the ground to form the first network to obtain a flexible material; after the spacecraft enters orbit, the reaction of the second network is triggered. The initiation reaction at this stage gradually transforms the flexible material into a rigid material, completing the process of rigidification and shape preservation on orbit.

[0003] At present, in the preparation process of the double network, the initiator used in the preparation process of the second network is mainly an additive initiator. This type of initiator exists in a free form in the flexible material obtained from the first network. However, once the flexible material is launched from the ground and enters orbit, there is an important problem: the free initiator may be affected by negative pressure and thus be extracted into the space environment, resulting in the emergence of vacuum degassing problems. What is more serious is that the loss of this initiator may cause the curing process of the second network to get out of control, and thus the expected material performance cannot be effectively achieved. This situation may significantly degrade the structural strength, durability and other key properties of the material, which is particularly critical for space applications. Summary of the invention

[0004] The purpose of the present invention is to solve the problems of vacuum outgassing of initiators in the second network curing process of flexible materials and short storage period in the first network, and provide a method for solving vacuum outgassing of space flexible materials based on a double network. The material system of the present invention is selected as an acrylate-epoxy resin system. After triggering the first stage of curing, a flexible polyacrylate material is obtained (at this time, the epoxy resin monomer has not been cured), and this material can be flexibly folded on the ground; after the flexible material is launched into orbit, the imidazole substances are triggered by heating to trigger the anionic curing of the epoxy resin, and the second stage of curing is completed to obtain a rigid material. The imidazole latent curing agent is synthesized by molecular design. When the polymerization of the first stage acrylate monomer is triggered, this type of imidazole curing agent can be connected to the acrylate resin network, that is, the initiator of the second stage epoxy resin is connected to the first stage acrylate resin network. At this time, after the flexible material is launched into orbit, under the action of vacuum, the second stage curing agent in the material will not be drawn into the vacuum environment, and there is no problem of vacuum outgassing. Further, the imidazole curing epoxy resin is triggered by heating to complete the soft-rigid conversion of the material in the space environment. The invention provides a solution to the vacuum degassing problem of space flexible-rigid conversion materials.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for solving the vacuum degassing of space flexible materials based on a double network, the method comprising: a double network system: an acrylate resin is used in the first network, the mass ratio of a photocuring agent to acrylate is 2:100, an epoxy resin is used in the second network, the curing agent is a synthetic imidazole derivative curing agent, the mass ratio of the curing agent to the epoxy resin is 7-15:100, the total amount of resin is 100%, and the epoxy resin is 50%-90%. After mixing the photocuring agent, the imidazole derivative curing agent, the acrylate resin and the epoxy resin, vacuuming is performed to remove bubbles, and the mixture is poured into a mold and irradiated with ultraviolet light for 10-20 minutes to prepare a flexible material of the first network, and then pre-cured at 110°C for 3 hours and post-cured at 150°C for 3-5 hours to obtain a rigid material.

[0007] Furthermore, the photocuring agent is one or more of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0008] Furthermore, the preparation method of the imidazole derivative curing agent is: dissolving toluene-2,4-diisocyanate in a solvent, adding dropwise a solvent containing polyethylene glycol-400 and diethylene glycol under reflux condensation, nitrogen atmosphere and 60°C, and reacting for 4-5 hours; then adding dropwise a solvent containing 2-ethyl-4-methylimidazole under reflux condensation, nitrogen atmosphere and 40°C, and reacting for 4-5 hours to obtain the imidazole derivative curing agent.

[0009] Furthermore, the molar ratio of toluene-2,4-diisocyanate, polyethylene glycol-400, diethylene glycol, and 2-ethyl-4-methylimidazole is 20:9:1:20.

[0010] Furthermore, the solvent is one or more of tetrahydrofuran, dioxane, pyridine, N,N-dimethylformamide, N,N-dimethylacetamide, and acetonitrile.

[0011] Further, the reaction solution was added dropwise to a mixed solution of petroleum ether and ethyl acetate (V1:V2=3:1) for precipitation treatment, followed by suction filtration. The yellow filter cake in the funnel was taken and dried in a vacuum oven at 60°C for 24 hours to obtain the product TPU-EMI.

[0012] The beneficial effects of the present invention compared to the prior art are:

[0013] 1. Through molecular synthesis scheme design, a high molecular weight imidazole derivative was prepared. The molecular chain was a polyurethane structure and was end-capped with 2-ethyl-4-methylimidazole (EMI). The hydrogen nuclear magnetic spectrum was as follows: Figure 1 As shown, the Fourier infrared spectrum is as follows Figure 2 As shown, the molecular weight elution curve is as follows Figure 3 As shown. After the first stage of light initiation, the first network of acrylic material is obtained. At this time, the synthetic product will be embedded in the acrylic resin network. When the flexible material is launched and deployed in orbit, under vacuum conditions, the second stage curing agent in the material will not be drawn into the vacuum environment due to its high molecular weight. Then, the imidazole derivative is triggered by heating to cure the epoxy resin, completing the formation of the second network of the material in the space environment, that is, the soft-rigid conversion. The schematic diagram is shown as Fig.11 shown.

[0014] 2. Compared with imidazoles, imidazole derivative curing agents are latent. For example, when 15wt% imidazole is mixed with epoxy resin at room temperature, the system is completely cured within 6-8h, and the non-isothermal DSC test shows that the peak exothermic temperature of the system is about 124℃. Figure 4As shown. When 15wt% of imidazole derivatives are mixed with epoxy resin at room temperature, the system still has a certain fluidity within 20 days. The main chain of the synthesized imidazole derivatives is a polyurethane structure with a certain flexibility, which can embed the end-capped EMI in the system, thereby greatly reducing its activity, thereby extending the storage life and processing time of the system. Further non-isothermal DSC testing shows that the peak exothermic temperature of the imidazole derivative curing agent is 164°C, as shown in Figure 5 As shown, it indicates that the imidazole derivative curing agent needs to absorb more energy to cure the epoxy resin, that is, the synthetic product has latency, which can extend the storage life of the first network flexible material.

[0015] 3. Compared with imidazole substances, imidazole derivative curing agents have a certain toughening effect. For example, the elongation at break of the sample after EMI curing based on the double network is only 5%; while the elongation at break of the synthetic imidazole derivatives at the same ratio reaches 10%, which is 1 times higher. Figure 8 As shown. Because of the molecular synthesis scheme design, Fig.12 As shown, the molecular chain is a polyurethane structure formed by the reaction of isocyanate groups and hydroxyl groups, and is capped with EMI. Because the polyurethane structure has the advantage of high toughness, the synthesized imidazole derivatives have a certain toughening effect after curing the epoxy resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The results of H NMR spectrum data of the synthetic products TPU-EMI and EMI are shown in FIG.

[0017] Figure 2 The Fourier infrared test data result diagram of the synthetic product TPU-EMI and EMI;

[0018] Figure 3 It is the molecular weight outflow curve of TPU-EMI;

[0019] Figure 4 This is the DSC graph of 2-ethyl-4-methylimidazole cured epoxy resin;

[0020] Figure 5 This is the DSC graph of the synthetic product TPU-EMI cured epoxy resin;

[0021] Figure 6 is a comparison diagram of the modulus of the flexible material and the rigid material of Example 1;

[0022] Figure 7 This is a strength comparison diagram of the flexible material and the rigid material of Example 1;

[0023] Figure 8This is a comparison chart of the elongation at break of the curing agent EMI and TPU-EMI cured samples of Comparative Example 1;

[0024] Fig. 9 is a comparison diagram of the modulus of the flexible material and the rigid material of Example 2;

[0025] Fig.10 This is a strength comparison diagram of the flexible material and the rigid material of Example 2;

[0026] Fig.11 It is a schematic diagram of a dual network;

[0027] Fig.12 Schematic diagram of the synthesis scheme of imidazole derivative curing agent TPU-EMI. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0029] Double network: A network structure formed by inducing a reaction between two blended polymers so that their molecular chains penetrate each other and the two polymer molecular chains are cross-linked by chemical bonds.

[0030] Embodiment 1:

[0031] Reaction scheme: Dissolve an appropriate amount of toluene-2,4-diisocyanate in 80 ml of tetrahydrofuran, add 20 ml of tetrahydrofuran containing polyethylene glycol-400 and diethylene glycol under reflux condensation, nitrogen atmosphere and 60°C within 1 hour, and react for 4 hours; then add 25 ml of tetrahydrofuran containing 2-ethyl-4-methylimidazole under reflux condensation, nitrogen atmosphere and 40°C within 1 hour, and react for 4 hours. The molar ratio of toluene-2,4-diisocyanate, polyethylene glycol-400, diethylene glycol and 2-ethyl-4-methylimidazole is controlled to be 20:9:1:20.

[0032] Post-treatment scheme: the reaction solution was added dropwise to a mixed solution of petroleum ether and ethyl acetate (V1: V2 = 3: 1) for precipitation treatment, followed by suction filtration, the yellow filter cake in the funnel was taken and placed in a 60°C vacuum oven for drying for 24 hours to obtain the product TPU-EMI.

[0033] Characterization test: Through nuclear magnetic resonance hydrogen spectrum test, such as Figure 1 As shown in the figure, the peak a in the EMI H NMR spectrum does not appear in TPU-EMI, indicating that EMI is successfully terminated. Figure 2 As shown in the EMI spectrum, 3000cm -1 Nearby and 1574cm -1 The absorption peaks of (NH) appeared, while these two absorption peaks disappeared in TPU-EMI, indicating that EMI was successfully terminated, and no (-NCO) in isocyanate was observed at 2200cm in the TPU-EMI spectrum. -1 The absorption peak at 3300cm is due to the reaction of -NCO and -OH to form an urethane bond. -1 With 1720cm -1 A new absorption peak appeared near, indicating that TPU-EMI was successfully synthesized. Figure 3 As shown, the molecular weight of the synthesized product is 26584, which meets the requirement of high molecular weight and can solve the vacuum degassing problem.

[0034] Preparation of sample strips: Weigh 0.9g of product TPU-EMI and dissolve it in 10ml of N,N-dimethylformamide, then add 6g of epoxy resin, stir thoroughly and ultrasonicate for 30min, put it in a vacuum oven and treat it at 80℃ for 4h to remove N,N-dimethylformamide from the system, weigh 9g of difunctional acrylate resin and 0.5g of pentafunctional acrylate resin, add 0.22g of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone, ultrasonicate for 10min to dissolve the photoinitiator in the acrylate resin, mix the prepared acrylate resin and epoxy resin in a ratio of 2:8, evacuate and remove bubbles for 30min, pour it into a silicone mold, and use 365nm ultraviolet light with a light intensity of 50mW / cm 2 , irradiated for 10 minutes, and obtained the first network of flexible material, the material was cured at 110 ° C for 3 hours, and cured at 150 ° C for 3 hours, and obtained the second network of rigid material. The tensile modulus and strength of the first network of flexible material were 0.19 MPa and 0.16 MPa, respectively. The tensile modulus and strength of the second network of rigid material were 1939.8 MPa and 48.5 MPa, respectively. Figure 6 , Figure 7 As shown. It can be concluded that the material successfully completes the transition from the flexible state of the first network to the rigid state of the second network.

[0035] Embodiment 2:

[0036] The difference between this embodiment and embodiment 1 is that the mass ratio of the acrylate used for the synthesis of the first network to the epoxy resin of the second network is adjusted to 3:7, and the flexible material of the first network is obtained by photoinitiation, and then the rigid material of the second network is obtained by thermal initiation. The tensile modulus and strength of the flexible material of the first network are 1.59MPa and 0.65MPa respectively. The tensile modulus and strength of the rigid material of the second network are 1855.05MPa and 44.01MPa respectively. Fig. 9 , Fig.10 As shown. It can be concluded that the material successfully completes the transition from the flexible state of the first network to the rigid state of the second network.

[0037] Comparative Example 1:

[0038] Weigh 0.9 g of 2-ethyl-4-methylimidazole (EMI), add 6 g of epoxy resin, stir thoroughly and ultrasonicate for 30 min to make it completely dissolved in the epoxy resin; weigh 9 g of difunctional acrylate resin and 0.5 g of pentafunctional acrylate resin, add 0.22 g of photoinitiator 2-hydroxy-2-methyl-1-phenyl-1-propanone, ultrasonicate for 10 min to dissolve the photoinitiator in the acrylate resin, mix the prepared acrylate resin and epoxy resin in a ratio of 2:8, vacuumize and remove bubbles for 30 min, pour into a silicone mold, and use 365 nm ultraviolet light with a light intensity of 50 mW / cm 2 , irradiated for 10 minutes to obtain a flexible material of the first network, the material was cured at 80°C for 3 hours, and at 120°C for 3 hours to obtain a rigid material of the second network.

[0039] The elongation at break of the double network cured samples of curing agent 2-ethyl-4-methylimidazole (EMI) and TPU-EMI based on a ratio of 2:8 were 5.84% and 10.3%, respectively. Figure 8 It can be concluded that the synthesized high molecular weight imidazole derivative TPU-EMI has an obvious toughening effect, which doubles its elongation at break.

Claims

1. A method for solving vacuum degassing of space flexible materials based on a double network, characterized in that: The method comprises: a double network system: an acrylate resin is used in the first network, the mass ratio of the photocuring agent to the acrylate is 2:100, an epoxy resin is used in the second network, the curing agent is a synthetic imidazole derivative curing agent, the mass ratio of the curing agent to the epoxy resin is 7-15:100, the total amount of resin is 100%, and the epoxy resin is 50%-90%, the photocuring agent, the imidazole derivative curing agent, the acrylate resin and the epoxy resin are mixed, vacuumized, bubbles are removed, poured into a mold, and then irradiated with ultraviolet light for 10-20 minutes to prepare a flexible material of the first network, and then pre-cured at 110°C for 3 hours and post-cured at 150°C for 3-5 hours to obtain a rigid material; The preparation method of the imidazole derivative curing agent is as follows: toluene-2,4-diisocyanate is dissolved in a solvent, and a solvent containing polyethylene glycol-400 and diethylene glycol is added dropwise under reflux condensation, nitrogen atmosphere and 60° C., and the reaction is performed for 4-5 hours; then, a solvent containing 2-ethyl-4-methylimidazole is added dropwise under reflux condensation, nitrogen atmosphere and 40° C., and the reaction is performed for 4-5 hours to obtain the imidazole derivative curing agent.

2. According to claim 1, a method for solving vacuum degassing of space flexible materials based on double network, characterized in that: The photocuring agent is one or more of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

3. The method for solving vacuum degassing of space flexible materials based on double network according to claim 1, characterized in that: The molar ratio of toluene-2,4-diisocyanate, polyethylene glycol-400, diethylene glycol and 2-ethyl-4-methylimidazole is 20:9:1:

20.

4. The method for solving vacuum degassing of space flexible materials based on double network according to claim 1, characterized in that: The solvent is one or more of tetrahydrofuran, dioxane, pyridine, N,N-dimethylformamide, N,N-dimethylacetamide and acetonitrile.

5. A method for solving vacuum degassing of space flexible materials based on double network according to claim 1, 3 or 4, characterized in that: The reaction solution was added dropwise to a mixed solution of petroleum ether and ethyl acetate for precipitation treatment, followed by suction filtration. The yellow filter cake in the funnel was taken and dried in a vacuum oven at 60° C. for 24 h.

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