Epoxy resin with liquid oxygen compatibility and low-temperature toughening and preparation method thereof

Abstract

The invention discloses epoxy resin with liquid oxygen compatibility and low-temperature toughening and a preparation method thereof, and belongs to the technical field of functional materials. The preparation method comprises the following steps: carrying out hyperbranched treatment on a thermoplastic material polyethersulfone (PES), grafting a flame retardant 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) into the hyperbranched PES, and blending with epoxy resin to form the epoxy resin. The epoxy resin prepared by the invention has both liquid oxygen compatibility and low-temperature toughening performance, and can be better used for low-temperature storage tanks.

Description

Technical Field

[0001] The invention relates to an epoxy resin having both liquid oxygen compatibility and low-temperature toughening and a preparation method thereof, belonging to the technical field of functional materials. Background Art

[0002] Traditional epoxy resins face challenges such as high low-temperature brittleness, strong microcrack propagation, and flammability and explosion in liquid oxygen (-183°C) environments. When epoxy resin is exposed to low-temperature working environments, low-temperature shrinkage causes large thermal stresses within the polymer-based composite material. Large thermal stresses can cause microcracks to appear within the composite material, weakening the composite material's ability to resist crack propagation and causing tank leakage and failure. The common and traditional method for toughening tanks is to directly introduce a second phase (toughening agent) into the epoxy resin matrix. Toughening agents commonly used by researchers include rubber (also known as elastomer, RE), thermoplastics (TP), core-shell polymers (CSP), nanomaterials (NM), etc. Toughening agents and epoxy resins form a heterogeneous toughening system, which means that the two are incompatible. The toughening agent appears in the epoxy resin in the form of phase separation, and its toughening effect on the epoxy resin is limited.

[0003] DOPO is the most commonly used flame retardant in liquid oxygen tanks. Since liquid oxygen itself is a strong oxidant, when it comes into contact with organic components in traditional epoxy resins (such as hydrocarbon segments), it may cause violent combustion or even explosion, especially when sparks are generated by mechanical impact or friction. In addition, the carbon-based skeleton of epoxy resin is more easily ignited in an oxygen-rich environment, and the energy released by combustion may further increase the risk. Therefore, DOPO is often used to achieve flame retardant effects by realizing free radical quenching and carbon layer strengthening functions through gas phase flame retardancy and condensed phase flame retardancy. Although the technology of using DOPO to improve the liquid oxygen compatibility of epoxy resin is relatively mature, DOPO does not have the function of improving the low-temperature mechanical properties of epoxy resin.

[0004] Therefore, how to simultaneously improve the liquid oxygen compatibility and low-temperature toughening of epoxy resin is a problem that needs to be solved at present. Summary of the Invention

[0005] [Technical Issues]

[0006] Conventional epoxy resins cannot combine liquid oxygen compatibility with low-temperature toughening.

[0007] [Technical solution]

[0008] To address the above problems, the present invention provides an epoxy resin having both liquid oxygen compatibility and low-temperature toughening properties and a preparation method thereof. Specifically, the present invention hyperbranched the thermoplastic material polyethersulfone (PES), then introduced the flame retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) into the hyperbranched PES, and then blended it with the epoxy resin to form the epoxy resin. The epoxy resin prepared by the present invention has both liquid oxygen compatibility and low-temperature toughening properties, and can be better used in cryogenic storage tanks (liquid oxygen storage tanks).

[0009] The first object of the present invention is to provide a method for preparing a hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide composite for increasing the liquid oxygen compatibility and low-temperature toughness of an epoxy resin, comprising the following steps:

[0010] Hyperbranched polyethersulfone (HB-PES) is dissolved in a solvent, and then a catalyst and a dehydrating agent are added for activation; then 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is added for reaction. After the reaction is completed, the reaction solution is centrifuged, precipitated, washed, and dried to obtain a hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES).

[0011] In one embodiment of the present invention, the solvent is one or both of N-methylpyrrolidone (NMP) and tetrahydrofuran (THF).

[0012] In one embodiment of the present invention, the catalyst is one or both of p-toluenesulfonic acid (PTSA) and 4-dimethylaminopyridine (DMAP).

[0013] In one embodiment of the present invention, the dehydrating agent is N,N'-dicyclohexylcarbodiimide (DCC).

[0014] In one embodiment of the present invention, the usage ratio of hyperbranched polyethersulfone (HB-PES), solvent, catalyst, dehydrating agent and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is 3-7 g:40-60 mL:0.6-1.0 g:1-2 g:3-3.5 g; more preferably 5 g:50 mL:0.8 g:1.5 g:3.2 g.

[0015] In one embodiment of the present invention, the activation is performed at 20-30° C. (normal temperature) for 1-3 hours.

[0016] In one embodiment of the present invention, the reaction is carried out at 75-85° C. for 10-15 hours.

[0017] In one embodiment of the present invention, the centrifugation is performed at 5000-8000 rpm for 10-20 min.

[0018] In one embodiment of the present invention, the precipitation is carried out by dropping the reaction solution into water.

[0019] In one embodiment of the present invention, washing is washing with water.

[0020] In one embodiment of the present invention, the drying is performed at 20-30° C. (normal temperature).

[0021] In one embodiment of the present invention, the preparation method of hyperbranched polyethersulfone (HB-PES) is as follows:

[0022] The hydroxyl-terminated PES was dissolved in a solvent and stirred until transparent; then a hyperbranched modified monomer and an initiator were added to react; after the reaction was completed, the reaction solution was dropped into methanol for precipitation, filtered, and dried to obtain hyperbranched polyethersulfone (HB-PES);

[0023] Among them, the molecular weight of hydroxyl-terminated PES is 50,000-80,000;

[0024] The solvent is one or both of N-methylpyrrolidone (NMP) and tetrahydrofuran (THF);

[0025] The hyperbranched modification monomer is one or both of trimethylolpropane triacrylate (TMPTA) and hyperbranched polyester (Boltorn H30);

[0026] The initiator is azobisisobutyronitrile (AIBN);

[0027] The usage ratio of hydroxyl-terminated PES, solvent, hyperbranched modified monomer and initiator is 10g:90-110mL:2-3g:0.1-0.15g, more preferably 10g:100mL:2.5g:0.12g.

[0028] Stirring until transparent is stirring at 70-90℃ until transparent;

[0029] The reaction is carried out under nitrogen protection by heating to 115-125°C for 6-10 hours;

[0030] Drying is performed at 55-65°C in vacuum for 20-30 hours.

[0031] The second object of the present invention is a hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) prepared by the method of the present invention.

[0032] A third object of the present invention is to provide a method for preparing an epoxy resin having both liquid oxygen compatibility and low-temperature toughening, comprising the following steps:

[0033] Epoxy resin and hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) are premixed, a curing agent is added, the mixture is degassed, poured into a mold, and cured to obtain an epoxy resin with both liquid oxygen compatibility and low-temperature toughening.

[0034] In one embodiment of the present invention, the mass ratio of epoxy resin, hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES), and curing agent is 20g:1-10g:3-5g, more preferably 20g:5g:4g.

[0035] In one embodiment of the present invention, the curing agent is polyetheramine D230; and the premixing is performed at 55-65° C. for 20-30 minutes.

[0036] In one embodiment of the present invention, the degassing is vacuum degassing.

[0037] In one embodiment of the present invention, the curing is performed at 75-85°C for 1-3 hours, followed by curing at 110-130°C for 3-6 hours, more preferably at 80°C for 2 hours, followed by curing at 120°C for 4 hours.

[0038] The fourth object of the present invention is to prepare an epoxy resin having both liquid oxygen compatibility and low-temperature toughening by the method of the present invention.

[0039] A fifth object of the present invention is to apply the epoxy resin having both liquid oxygen compatibility and low-temperature toughening in the field of aerospace.

[0040] A sixth object of the present invention is to provide a liquid oxygen tank, which uses the epoxy resin having both liquid oxygen compatibility and low-temperature toughening according to the present invention.

[0041] A seventh object of the present invention is to provide a method for simultaneously improving the liquid oxygen compatibility and low-temperature toughening of epoxy resins, which uses the hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) described in the present invention or an epoxy resin with both liquid oxygen compatibility and low-temperature toughening.

[0042] [Beneficial Effects]

[0043] (1) The present invention overcomes the performance contradiction between toughening and flame retardancy through the topological design of hyperbranched PES;

[0044] (2) The process of the present invention is simple, and the hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) can be directly blended with epoxy resin without the need for complex surface treatment;

[0045] (3) The epoxy resin prepared by the present invention, which has both liquid oxygen compatibility and low-temperature toughening properties, passes stringent tests such as ASTM D2512 and MIL-STD-810G, and meets the long-term service requirements of liquid oxygen tanks, that is, it has both good liquid oxygen compatibility and low-temperature toughening properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is the synthetic route of hyperbranched polyethersulfone (HB-PES).

[0047] Figure 2 The synthetic route of hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex.

[0048] Figure 3 It is an SEM image of the impact section at -183℃; among them, a is the room temperature tensile section of the epoxy resin of comparative example 1; b is the room temperature tensile section of the epoxy resin of embodiment 3; c is the low temperature tensile section of the epoxy resin of comparative example 1; d is the low temperature tensile section of the epoxy resin of embodiment 3. DETAILED DESCRIPTION

[0049] 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.

[0050] Test method:

[0051] 1. Liquid oxygen compatibility test:

[0052] ASTM D2512: Test method for impact sensitivity of materials in liquid oxygen; the IRS value is the sensitivity index of the test material to impact in liquid oxygen.

[0053] 2. Low temperature toughness test:

[0054] ASTM D638: Plastic tensile properties test;

[0055] The chuck of the tensile testing machine is placed in a low-temperature environmental box. The temperature is controlled to -183°C by controlling the flow rate of liquid nitrogen in the environmental box. The tensile properties of the sample are tested using the tensile testing machine.

[0056] The raw materials used in the embodiment are:

[0057] Hydroxyl-terminated polyethersulfone (PES): industrial grade, Mw = 30,000-80,000;

[0058] DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide): purity ≥98%;

[0059] Azobisisobutyronitrile (AIBN): purity ≥99%;

[0060] Epoxy resin: E-51.

[0061] Example 1

[0062] A method for preparing hyperbranched polyethersulfone (HB-PES) (such as Figure 1 ), including the following steps:

[0063] 10 g of hydroxyl-terminated PES (Mw = 30,000) was dissolved in 100 mL of N-methylpyrrolidone and stirred at 80°C until transparent; then 2.5 g of trimethylolpropane triacrylate and 0.12 g of azobisisobutyronitrile (AIBN) were added, and the temperature was raised to 120°C under nitrogen protection and reacted for 8 h. After the reaction, the reaction solution was dropwise added to methanol for precipitation, filtered, and vacuum dried at 60°C for 24 h to obtain hyperbranched polyethersulfone (HB-PES).

[0064] Example 2

[0065] A method for preparing a hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide composite for increasing the liquid oxygen compatibility and low-temperature toughness of epoxy resin (such as Figure 2 ), including the following steps:

[0066] 5 g of the hyperbranched polyethersulfone (HB-PES) of Example 1 was dissolved in 50 mL of tetrahydrofuran (THF), and then 0.8 g of 4-dimethylaminopyridine (DMAP) and 1.5 g of N,N'-dicyclohexylcarbodiimide (DCC) were added and activated at 25 ° C. for 2 h; then 3.2 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was added and reacted at 80 ° C. for 12 h. After the reaction, the byproduct DCU (1,3-dicyclohexylurea, a byproduct generated by DCC and water) was removed by centrifugation at 5000 rpm for 15 min. The reaction solution was then dropped into water for precipitation, washed with water, and dried to obtain a hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) (grafting rate 90%).

[0067] Example 3

[0068] A method for preparing an epoxy resin having both liquid oxygen compatibility and low-temperature toughening comprises the following steps:

[0069] 20 g of E-51 epoxy resin and 5 g of the hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) of Example 2 were premixed at 60 ° C for 30 min, and then 4 g of polyetheramine D230 was added. The mixture was vacuum degassed and poured into a mold. The mixture was cured at 80 ° C for 2 h and then cured at 120 ° C for 4 h to obtain an epoxy resin with both liquid oxygen compatibility and low-temperature toughening.

[0070] Example 4

[0071] The amount of hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) in Example 3 was adjusted to 1 g, 3 g, and 7 g, respectively, while other ingredients remained the same as in Example 3 to obtain an epoxy resin.

[0072] Comparative Example 1

[0073] The hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) in Example 3 was omitted, and the other steps were the same as in Example 3 to obtain an epoxy resin.

[0074] The obtained epoxy resin was subjected to performance testing, and the test results are as follows:

[0075] Table 1

[0076] Dosage Liquid oxygen compatibility -183℃ toughness 0 (Comparative Example 1) IRS = 30% Elongation at break = 1.2% 1g IRS=0% Elongation at break = 1.5% 3g IRS=0% Elongation at break = 1.8% 5g (Example 1) IRS=0% Elongation at break = 2.6% 7g IRS=0% Elongation at break = 2.2%

[0077] Figure 3 The SEM images of the impact section at -183°C are shown; among them, a is the room temperature tensile section of the epoxy resin of comparative example 1; b is the room temperature tensile section of the epoxy resin of embodiment 3; c is the low temperature tensile section of the epoxy resin of comparative example 1; d is the low temperature tensile section of the epoxy resin of embodiment 3. Figure 3 It can be seen that hyperbranched polyethersulfone has a toughening effect on epoxy resin, which transforms the brittle fracture of epoxy resin into tough fracture.

[0078] Comparative Example 2

[0079] The hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex in Example 3 was adjusted to 3.2 g of DOPO and 5 g of hyperbranched polyethersulfone, while remaining the same as in Example 3 to obtain an epoxy resin.

[0080] Comparative Example 3

[0081] The amount of the hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex in Example 3 was adjusted to 3.2 g of DOPO, and the other contents were kept the same as in Example 3 to obtain an epoxy resin.

[0082] Comparative Example 4

[0083] The hyperbranched polyethersulfone in Example 2 was changed to a hyperbranched polyamide, and the other steps were kept consistent with Examples 2 and 3 to obtain an epoxy resin.

[0084] Comparative Example 5

[0085] The hyperbranched polyethersulfone in Example 2 was adjusted to polyethersulfone, and the other parts were kept consistent with Examples 2 and 3 to obtain an epoxy resin.

[0086] Comparative Example 6

[0087] The DOPO in Example 2 was adjusted to triphenyl phosphate, and the other aspects remained the same as in Examples 2 and 3 to obtain an epoxy resin. The obtained epoxy resin was subjected to performance testing, and the test results are as follows:

[0088] Table 2

[0089] Comparative Example Liquid oxygen compatibility -183℃ toughness 2 IRS = 10% Elongation at break = 1.8% 3 IRS=0% Elongation at break = 1.2% 4 IRS=0% Elongation at break = 1.6% 5 IRS=0% Elongation at break = 2.1% 6 IRS = 15% Elongation at break = 2.2%

[0090] 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 a hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide composite for increasing the liquid oxygen compatibility and low-temperature toughness of epoxy resin, characterized in that: The steps include: Hyperbranched polyethersulfone (HB-PES) is dissolved in a solvent, and then a catalyst and a dehydrating agent are added for activation; then 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is added for reaction. After the reaction is completed, the reaction solution is centrifuged, precipitated, washed, and dried to obtain a hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES).

2. The method according to claim 1, characterized in that The usage ratio of hyperbranched polyethersulfone (HB-PES), solvent, catalyst, dehydrating agent and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is 3-7 g: 40-60 mL: 0.6-1.0 g: 1-2 g: 3-3.5 g.

3. The method according to claim 1, characterized in that The reaction is carried out at 75-85°C for 10-15 hours.

4. A hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) prepared by the method according to any one of claims 1 to 3.

5. A method for preparing an epoxy resin having both liquid oxygen compatibility and low-temperature toughening, characterized in that: The steps include: The epoxy resin and the hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide composite according to claim 4 are premixed, a curing agent is added, the mixture is degassed, the mixture is poured into a mold, and the mixture is cured to obtain an epoxy resin having both liquid oxygen compatibility and low-temperature toughening.

6. The method according to claim 5, characterized in that The mass ratio of epoxy resin, hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide complex (DOPO-HB-PES) and curing agent is 20g:1-10g:3-5g.

7. The epoxy resin having both liquid oxygen compatibility and low-temperature toughening prepared by the method according to claim 5 or 6.

8. Use of the epoxy resin having both liquid oxygen compatibility and low-temperature toughening according to claim 7 in the field of aerospace.

9. A liquid oxygen tank, characterized in that: It adopts the epoxy resin with liquid oxygen compatibility and low-temperature toughening as described in claim 7.

10. A method for simultaneously improving the liquid oxygen compatibility and low-temperature toughening of epoxy resin, characterized in that: The hyperbranched polyethersulfone-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide composite (DOPO-HB-PES) described in claim 4 or the epoxy resin with both liquid oxygen compatibility and low-temperature toughening described in claim 7 is used.

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