Silicon dioxide / polyhedral oligomeric silsesquioxane composite epoxy resin, high-temperature-resistant damp-heat-resistant high-modulus epoxy resin and preparation method thereof

Abstract

The invention provides silicon dioxide / polyhedral oligomeric silsesquioxane composite epoxy resin, high-temperature-resistant damp-heat-resistant high-modulus epoxy resin as well as a preparation method and application thereof. The silicon dioxide / polyhedral oligomeric silsesquioxane composite epoxy resin is prepared from the following raw materials: an epoxy silane coupling agent, phenyltriethoxysilane, epoxy modified nano silicon dioxide and polyfunctional epoxy resin; the high-temperature-resistant damp-heat-resistant high-modulus epoxy resin is prepared from raw materials including silicon dioxide / polyhedral oligomeric silsesquioxane composite epoxy resin, polyethersulfone resin, high-temperature-resistant structural epoxy resin and a curing agent, the prepared polyhedral oligomeric silsesquioxane epoxy resin can reduce the internal stress of the epoxy resin, increase the toughness of the epoxy resin, improve the brittleness of a system and increase the elongation at break of the system; the prepared high-temperature-resistant damp-heat-resistant high-modulus epoxy resin has good temperature resistance and damp-heat resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resins. Further, it relates to a silica / silsesquioxane composite epoxy resin, a high-temperature and high-humidity resistant high-modulus epoxy resin, and their preparation methods and applications. Background Art

[0002] Advanced resin matrix composites have performance characteristics such as high specific modulus, high specific strength, fatigue resistance, corrosion resistance, and strong designability, and are widely used. They are one of the preferred lightweight and high-performance materials for the main load-bearing structural components of aerospace aircraft, and are widely used in many fields such as aerospace, military, and automotive lightweighting, and the application proportion is increasing day by day. In practical applications, carbon fiber composites have successfully achieved the development from secondary load-bearing components to main load-bearing components. Many structural materials are more subjected to compression, and higher requirements for compressive composites are put forward in practice. The compressive strength of composites is one of the important parameters in structural design and application. Studying and solving the problem of low compressive strength of resin matrix composites can more effectively exert the superior performance of resin matrix composites. The compressive strength and tensile strength of high-strength and medium-modulus carbon fiber composites are seriously unbalanced, and the mechanical properties related to compression have become the performance short board of high-strength and medium-modulus carbon fiber composites, greatly restricting the efficient application of high-strength and medium-modulus carbon fiber composites. The modulus of the resin matrix is one of the main factors affecting the composite material, so it is of great significance to develop a high-modulus epoxy resin matrix.

[0003] Conventional high-modulus epoxy resins often lead to an increase in resin brittleness and a decrease in the fracture elongation process with the increase in resin modulus. In addition, the aerospace field has high requirements for the high-temperature resistance and high-humidity resistance of composite materials. Therefore, the development of high-temperature and high-humidity resistant high-modulus epoxy resins with a relatively high fracture elongation rate has become an urgent need in high-end application fields such as aerospace. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the present invention provides a silica / silsesquioxane composite epoxy resin, a high-temperature and high-humidity resistant high-modulus epoxy resin, and their preparation methods and applications, and solves the problems of increased system brittleness and decreased system fracture elongation rate caused by increasing the modulus of the resin system.

[0005] The present invention prepares a silica / silsesquioxane composite epoxy resin, and stably disperses a relatively high content of epoxy group silica in silsesquioxane epoxy and polyfunctional epoxy resins, solving the problems that nano-fillers are easy to agglomerate and difficult to be uniformly dispersed in epoxy resins, and the addition amount is limited, enabling the epoxy group silica and silsesquioxane epoxy to uniformly participate in the cross-linking network, significantly reducing the free volume of the system, and thereby increasing the modulus of the epoxy resin.

[0006] The cage - type silsesquioxane epoxy resin prepared by the present invention combines the characteristics of both inorganic and organic substances. It can reduce the internal stress of the epoxy resin, improve the brittleness of the system, increase the toughness of the epoxy resin, and thus enhance the elongation at break of the system. The cage - type silsesquioxane epoxy resin and nano - silica can significantly reduce the water absorption rate of the system. At the same time, in combination with multi - functional epoxy resins with good heat and humidity resistance and high - temperature - resistant structural epoxy resins, the prepared epoxy resin system has good heat and humidity resistance and high - temperature resistance.

[0007] One of the purposes of the present invention is to provide a silica / cage - type silsesquioxane composite epoxy resin, which is prepared from raw materials including an epoxy - silane coupling agent A, an arylalkoxysilane, epoxy - modified nano - silica, and a multi - functional epoxy resin.

[0008] In a preferred embodiment of the present invention,

[0009] The epoxy - silane coupling agent A is a mixture of 3 - (2,3 - epoxypropoxypropyl)trimethoxysilane and β - (3,4 - epoxycyclohexyl)ethyltrimethoxysilane; preferably, the molar ratio of 3 - (2,3 - epoxypropoxypropyl)trimethoxysilane to β - (3,4 - epoxycyclohexyl)ethyltrimethoxysilane is (0.25 - 4):1;

[0010] The arylalkoxysilane is a phenylalkoxysilane, preferably phenyltriethoxysilane;

[0011] The average particle size of the epoxy - modified nano - silica is 10 - 100 nm, preferably 20 - 40 nm;

[0012] The epoxy - modified nano - silica is fumed nano - silica modified by an epoxy - silane coupling agent B; preferably, the mass ratio of the silane coupling agent B to the fumed nano - silica is (2 - 7):100, more preferably (4 - 6):100; the epoxy - silane coupling agent B is at least one of 3 - (2,3 - epoxypropoxypropyl)trimethoxysilane and β - (3,4 - epoxycyclohexyl)ethyltrimethoxysilane;

[0013] The multi - functional epoxy resin is at least one of a trifunctional epoxy resin and a tetrafunctional epoxy resin, preferably at least one of N,N,N',N' - tetra - glycidyl - 4,4 - diamino - diphenylmethane epoxy resin (TGDDM), 4,5 - epoxyhexane - 1,2 - dicarboxylic acid diglycidyl ester (TDE85), and triglycidyl - p - aminophenol (MY0510).

[0014] Another purpose of the present invention is to provide a preparation method of the silica / cage - type silsesquioxane composite epoxy resin, which includes the following steps:

[0015] (1) After adding epoxy silane coupling agent A and arylalkoxysilane to an aqueous solution for hydrolysis reaction, the aqueous solution is removed and an organic solvent is added to obtain an organic solution of cage-like silsesquioxane epoxy resin.

[0016] (2) Epoxy-modified nano-silica and multi-functional epoxy resin are added to the organic solution of cage-like silsesquioxane epoxy resin obtained in step (1), dispersed evenly, and then the solvent is removed to obtain the silica / cage-like silsesquioxane composite epoxy resin.

[0017] In a preferred embodiment of the present invention,

[0018] Step (1),

[0019] The molar ratio of the epoxy silane coupling agent A to the arylalkoxysilane is 1:(1 - 3);

[0020] The aqueous solution is a mixed solution of ethanol, methanol, water and hydrochloric acid; preferably, the molar ratio of water to arylalkoxysilane is (3 - 4):1; the pH value of the aqueous solution is 3 - 4;

[0021] The ratio of the mass of the aqueous solution to the sum of the masses of the epoxy silane coupling agent A and the arylalkoxysilane is not less than 1:1;

[0022] The temperature of the hydrolysis reaction is 30 - 40 °C;

[0023] The hydrolysis reaction time is 36 - 60 h;

[0024] After hydrolysis, the pH value is adjusted to neutral, and an alkaline reagent such as sodium hydroxide solution can be used to adjust the pH value;

[0025] The method for removing the aqueous solution is to wash with water and then perform vacuum distillation;

[0026] The organic solvent is at least one of acetone, tetrahydrofuran, and toluene;

[0027] The mass of the added organic solvent accounts for not less than 40% of the mass of the organic solution of cage-like silsesquioxane epoxy resin.

[0028] In a preferred embodiment of the present invention,

[0029] Step (2),

[0030] The mass ratio of the cage-like silsesquioxane epoxy resin to the multi-functional epoxy resin is (1 - 3):5;

[0031] The mass ratio of the epoxy-modified nano-silica to the multi-functional epoxy resin is (2 - 4):5;

[0032] Dispersion is carried out by high-speed stirring. Preferably, the dispersion time is 15 min to 60 min;

[0033] The solvent can be removed by methods in the prior art, such as vacuum distillation.

[0034] The third object of the present invention is to provide a high-temperature and high-humidity resistant high-modulus epoxy resin, which is prepared from raw materials including silica / cage-like silsesquioxane composite epoxy resin, polyethersulfone resin, high-temperature resistant structural epoxy resin and curing agent; the silica / cage-like silsesquioxane composite epoxy resin is the above-mentioned silica / cage-like silsesquioxane composite epoxy resin or the silica / cage-like silsesquioxane composite epoxy resin obtained by the above-mentioned preparation method.

[0035] In a preferred embodiment of the present invention,

[0036] Based on 100 parts by weight of the silica / cage-like silsesquioxane composite epoxy resin, the high-temperature and high-humidity resistant high-modulus epoxy resin includes:

[0037]

[0038] In a preferred embodiment of the present invention,

[0039] The weight-average molecular weight of the polyethersulfone resin is 10,000 to 80,000, preferably 30,000 to 50,000;

[0040] The high-temperature resistant structural epoxy resin contains at least one group among biphenyl group, naphthyl group, hetero-naphthyl group, fluorene group, adamantyl group, and triazine ring, preferably at least one of condensed-ring naphthalene-type epoxy resin and biphenyl phenol-type epoxy resin;

[0041] The curing agent is an aromatic amine curing agent, preferably at least one of 4,4'-diaminodiphenyl sulfone and 3,3'-diaminodiphenyl sulfone.

[0042] The fourth object of the present invention is to provide a preparation method of a high-temperature and high-humidity resistant high-modulus epoxy resin, including:

[0043] (1) Mix the silica / cage-like silsesquioxane composite epoxy resin, high-temperature resistant structural epoxy resin and polyethersulfone resin, heat up and stir to dissolve the polyethersulfone resin to obtain a mixture; the mixing temperature is preferably 100 to 180 °C, more preferably 140 to 160 °C;

[0044] (2) Cool the mixture obtained in step (1), then add the curing agent and mix evenly to obtain the high-temperature and high-humidity resistant high-modulus epoxy resin; preferably cool to 50 to 90 °C, more preferably 65 to 75 °C.

[0045] A fifth object of the present invention is to provide an application of a high-temperature and high-humidity-resistant high-modulus epoxy resin in the field of prepregs, preferably in high-performance carbon fiber prepregs for aerospace.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] (1) Through a unique preparation method, the present invention stably disperses a relatively high content of epoxy-functionalized silica in cage-like silsesquioxane epoxy and polyfunctional epoxy resins, solving the problems that nano-fillers are prone to agglomeration and difficult to be uniformly dispersed in epoxy resins, as well as the limitation of the addition amount. This enables the epoxy-modified silica and cage-like silsesquioxane epoxy to uniformly participate in the crosslinking network, significantly reducing the free volume of the system and thereby enhancing the modulus of the epoxy resin.

[0048] (2) The cage-like silsesquioxane epoxy resin prepared by the present invention combines the characteristics of both inorganic and organic substances, which can reduce the internal stress of the epoxy resin. At the same time, the cage-like silsesquioxane epoxy increases the toughness of the epoxy resin, can improve the brittleness of the system, and enhance the elongation at break of the system.

[0049] (3) The cage-like silsesquioxane epoxy resin and the high-temperature-resistant structural epoxy resin of the present invention have good heat resistance. At the same time, the polyfunctional epoxy resin enables the curing system to have a relatively high crosslinking density, which can significantly improve the temperature resistance of the resin system.

[0050] (4) The cage-like silsesquioxane epoxy resin and nano-silica of the present invention can significantly reduce the water absorption rate of the system. At the same time, in combination with polyfunctional epoxy resins and high-temperature-resistant structural epoxy resins with good heat and humidity resistance, the prepared epoxy resin system has good heat and humidity resistance. Specific Embodiments

[0051] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0052] The raw materials used in the examples and comparative examples of the present invention are all conventional commercially available raw materials.

[0053] The tetrafunctional AG-80 epoxy resin is N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane epoxy resin, and the production company is Shanghai Huayi Resin Co., Ltd.;

[0054] The trifunctional TDE85 epoxy resin is diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate, and the production company is Hubei Xingdongcheng Chemical Co., Ltd.;

[0055] The trifunctional MY0510 epoxy resin is triglycidyl p-aminophenol, and the production company is Huntsman;

[0056] The epoxy-modified nano-silica was purchased from Hangzhou Hengge Nano Technology Co., Ltd., model HN-SP30S, which is fumed nano-silica modified by epoxy silane coupling agent.

[0057] Test methods:

[0058] Tensile modulus and elongation at break: Conducted according to GB / T 2567-2008;

[0059] Glass transition temperature: Using a dynamic mechanical analyzer, the thermomechanical properties of the resin spline were analyzed to characterize the glass transition temperature of the resin cured product;

[0060] Retention rate of flexural strength after boiling in water at 95°C for 7 days: The flexural spline was placed in pure water at 95°C, and after 7 days of heat preservation, the flexural strength was tested according to GB / T 2567-2008. The ratio of the flexural strength of the spline after boiling in water to that of the spline without boiling in water is the retention rate of flexural strength after boiling in water at 95°C for 7 days.

[0061] The parts in the examples and comparative examples of the present invention all refer to parts by weight.

[0062]

Example 1

[0063] (1) Preparation of silica / polyhedral oligomeric silsesquioxane composite epoxy resin

[0064] The pH value of the mixed solution of ethanol, methanol, water and hydrochloric acid was adjusted to 4, and the temperature was kept at 35°C. Then, epoxy silane coupling agent and phenyltriethoxysilane were added. The epoxy silane coupling agent was 3-(2,3-epoxypropoxypropyl)trimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (molar ratio 1:1). The molar ratio of the epoxy silane coupling agent to phenyltriethoxysilane was 1:1, and the molar ratio of water to phenyltriethoxysilane in the mixed solution was 3:1. The hydrolysis reaction time was 48 h. The pH value was adjusted to neutral with sodium hydroxide aqueous solution, and the aqueous solution was removed by vacuum distillation. Acetone was added to obtain a polyhedral oligomeric silsesquioxane epoxy resin acetone solution. Epoxy-modified nano-silica (average particle size 20 nm) and tetrafunctional AG-80 epoxy resin were added thereto and dispersed at high speed for 30 min. The solvent was removed by vacuum distillation to obtain silica / polyhedral oligomeric silsesquioxane composite epoxy resin.

[0065] The mass ratio of polyhedral oligomeric silsesquioxane epoxy resin to tetrafunctional AG-80 epoxy resin was 2:5, and the mass ratio of epoxy-modified nano-silica to tetrafunctional AG-80 epoxy resin was 3:5.

[0066] (2) Preparation of High Temperature and Humidity Resistant High Modulus Epoxy Resin

[0067] The formulation is as follows:

[0068]

[0069] Mix silica / cage - type silsesquioxane composite epoxy resin, polycyclic naphthalene - type epoxy resin and polyethersulfone resin, heat up and stir, the mixing temperature is 160 °C, and dissolve the polyethersulfone to obtain a mixture;

[0070] Adjust the temperature of the mixture to 75 °C, add 4,4'-diaminodiphenyl sulfone, stir and mix evenly to obtain high temperature and humidity resistant high modulus epoxy resin.

[0071] (3) Performance Testing of High Temperature and Humidity Resistant High Modulus Epoxy Resin Cured Product

[0072] The curing process of high temperature and humidity resistant high modulus epoxy resin is 120 °C / 1h + 180 °C / 2h.

[0073] Carry out tensile and bending tests on the resin cured product according to the standard GB / T 2567 - 2008.

[0074] Use a dynamic mechanical analyzer to conduct thermomechanical performance analysis on the resin spline to characterize the glass transition temperature of the resin cured product.

[0075] Use the bending strength retention rate of the resin cured product boiled in water at 95 °C for 7 days to characterize the moisture and heat resistance of the resin cured product.

[0076]

Example 2

[0077] (1) Preparation of Cage - type Silsesquioxane Epoxy Resin

[0078] Adjust the pH value of the mixed solution of ethanol, methanol, water and hydrochloric acid to 3, keep the temperature at 40 °C, add epoxy silane coupling agent and phenyltriethoxysilane. The epoxy silane coupling agent is 3-(2,3 - epoxypropoxypropyl)trimethoxysilane and β-(3,4 - epoxycyclohexyl)ethyltrimethoxysilane (molar ratio 4:1), the molar ratio of the epoxy silane coupling agent to phenyltriethoxysilane is 1:3, the molar ratio of water to phenyltriethoxysilane in the mixed solution is 3:1, the hydrolysis reaction time is 60h, adjust the pH value to neutral with sodium hydroxide aqueous solution, distill off the aqueous solution under reduced pressure, add acetone to obtain a cage - type silsesquioxane epoxy resin acetone solution, add epoxy - modified nano - silica (average particle size 40nm) and tetra - functional AG - 80 epoxy resin to it for high - speed dispersion, the dispersion time is 30min, and distill off the solvent under reduced pressure to obtain silica / cage - type silsesquioxane composite epoxy resin.

[0079] The mass ratio of the cage - type silsesquioxane epoxy resin to the tetra - functional AG - 80 epoxy resin is 1:5, and the mass ratio of the epoxy - modified nano - silica to the tetra - functional AG - 80 epoxy resin is 4:5.

[0080] (2) The preparation of the high - temperature, high - humidity - resistant and high - modulus epoxy resin and (3) the performance test of the cured product of the high - temperature, high - humidity - resistant and high - modulus epoxy resin are the same as those in Example 1.

[0081]

Example 3

[0082] (1) Preparation of silica / cage - type silsesquioxane composite epoxy resin

[0083] Adjust the pH value of the mixed solution of ethanol, methanol, water and hydrochloric acid to 4, keep the temperature at 30 °C, add epoxy silane coupling agent and phenyltriethoxysilane. The epoxy silane coupling agent is 3 - (2,3 - epoxypropoxypropyl)trimethoxysilane and β - (3,4 - epoxycyclohexyl)ethyltrimethoxysilane (molar ratio 1:4). The molar ratio of the epoxy silane coupling agent to phenyltriethoxysilane is 1:1. The molar ratio of water to phenyltriethoxysilane in the mixed solution is 4:1. The hydrolysis reaction time is 36 h. Adjust the pH value to neutral with sodium hydroxide aqueous solution, remove the aqueous solution by vacuum distillation, add acetone to obtain a cage - type silsesquioxane epoxy resin acetone solution. Add epoxy - modified nano - silica (average particle size 20 nm) and tetra - functional AG - 80 epoxy resin to it for high - speed dispersion. The dispersion time is 30 min. Remove the solvent by vacuum distillation to obtain silica / cage - type silsesquioxane composite epoxy resin.

[0084] The mass ratio of the cage - type silsesquioxane epoxy resin to the tetra - functional AG - 80 epoxy resin is 3:5, and the mass ratio of the epoxy - modified nano - silica to the tetra - functional AG - 80 epoxy resin is 2:5.

[0085] (2) The preparation of the high - temperature, high - humidity - resistant and high - modulus epoxy resin and (3) the performance test of the cured product of the high - temperature, high - humidity - resistant and high - modulus epoxy resin are the same as those in Example 1.

[0086]

Example 4

[0087] The differences from Example 1 are: (1) The multi - functional epoxy used in the preparation of silica / cage - type silsesquioxane composite epoxy resin is trifunctional TDE85 epoxy resin; (2) The formulation composition of the preparation of the high - temperature, high - humidity - resistant and high - modulus epoxy resin is:

[0088]

[0089] Except for the above differences, other conditions in Example 4 are the same as those in Example 1. The performance of the cured product of the high - temperature, high - humidity - resistant and high - modulus epoxy resin obtained is tested.

[0090]

Example 5

[0091] The differences from Example 1 are as follows: (1) The multifunctional epoxy used in the preparation of the silica / silsesquioxane composite epoxy resin is the trifunctional MY0510 epoxy resin;

[0092] Except for the above differences, other conditions of Example 5 are the same as those of Example 1, and the properties of the obtained high-temperature and high-humidity resistant high-modulus epoxy resin curing agent are tested.

[0093]

Example 6

[0094] The differences from Example 1 are as follows: (2) The formulation of the high-temperature and high-humidity resistant high-modulus epoxy resin is different;

[0095] The specific formulation is as follows:

[0096]

[0097]

[0098] Except for the above differences, other conditions of Example 6 are the same as those of Example 1, and the properties of the obtained high-temperature and high-humidity resistant high-modulus epoxy resin cured product are tested.

[0099]

Example 7

[0100] The differences from Example 1 are as follows: (2) The formulation and preparation conditions of the high-temperature and high-humidity resistant high-modulus epoxy resin are different;

[0101] The specific formulation is as follows:

[0102] (2) Preparation of high-temperature and high-humidity resistant high-modulus epoxy resin

[0103] The formulation is as follows:

[0104]

[0105] Mix the silica / silsesquioxane composite epoxy resin, biphenyl phenol type epoxy resin and polyethersulfone resin, heat up and stir, the mixing temperature is 140 °C, and dissolve the polyethersulfone to obtain a mixture;

[0106] Adjust the temperature of the mixture to 65 °C, add 3,3'-diaminodiphenyl sulfone, stir and mix evenly to obtain a high-temperature and high-humidity resistant high-modulus epoxy resin.

[0107] Except for the above differences, other conditions of Example 7 are the same as those of Example 1, and the properties of the obtained high-temperature and high-humidity resistant high-modulus epoxy resin cured product are tested.

[0108]

Comparative Example 1

[0109] The differences from Example 1 are as follows: (1) In the preparation of the cage - type silsesquioxane composite epoxy resin, epoxy - modified nano - silica was not added.

[0110] Except for the above differences, other conditions in Comparative Example 1 were the same as those in Example 1, and the properties of the obtained high - temperature - resistant, high - humidity - resistant, and high - modulus epoxy resin cured product were tested.

[0111]

Comparative Example 2

[0112] (1) Preparation of silica composite epoxy resin

[0113] Disperse epoxy - modified nano - silica (average particle size 20 nm) in acetone, add tetra - functional AG - 80 epoxy resin to it and conduct high - speed dispersion, and remove the solvent by reduced - pressure distillation to obtain silica composite epoxy resin.

[0114] The mass ratio of epoxy - modified nano - silica to tetra - functional AG - 80 epoxy resin is 3:5.

[0115] (2) Preparation of high - temperature - resistant, high - humidity - resistant, and high - modulus epoxy resin

[0116] The formulation composition is as follows:

[0117]

[0118] (3) The performance test of the high - temperature - resistant, high - humidity - resistant, and high - modulus epoxy resin cured product is the same as that in Example 1.

[0119]

Comparative Example 3

[0120] The differences from Example 1 are as follows: (1) In the preparation of the cage - type silsesquioxane composite epoxy resin, tetra - functional AG - 80 epoxy resin was replaced by difunctional 128 epoxy resin, the mass ratio of cage - type silsesquioxane epoxy resin to difunctional 128 epoxy resin is 2:5, and the mass ratio of epoxy - modified nano - silica to difunctional 128 epoxy resin is 3:5;

[0121] Except for the above differences, other conditions in Comparative Example 3 were the same as those in Example 1, and the properties of the obtained high - temperature - resistant, high - humidity - resistant, and high - modulus epoxy resin cured product were tested.

[0122]

Comparative Example 4

[0123] The differences from Example 1 are as follows: (2) The formulation of the high - temperature - resistant, high - humidity - resistant, and high - modulus epoxy resin preparation is different;

[0124] The specific formulation composition is as follows:

[0125] Silica / cage - type silsesquioxane composite epoxy resin 100 parts by weight;

[0126] 2 parts by weight of polyethersulfone resin (weight average molecular weight 50,000);

[0127] 32 parts by weight of 4,4'-diaminodiphenylsulfone;

[0128] Except for the above differences, other conditions of Comparative Example 4 were the same as those of Example 1, and the properties of the high-temperature and high-humidity resistant high-modulus epoxy resin cured product obtained were tested.

[0129]

Comparative Example 5

[0130] The differences from Example 1 were as follows: (1) In the preparation of the cage-like silsesquioxane composite epoxy resin, nano-silica (average particle size 20 nm, surface untreated with epoxy groups) was used to replace the epoxy-modified nano-silica;

[0131] Except for the above differences, other conditions of Comparative Example 5 were the same as those of Example 1, and the properties of the high-temperature and high-humidity resistant high-modulus epoxy resin cured product obtained were tested.

[0132] The laminate was evaluated for its properties according to the method of Example 1, and the results are shown in Table 1.

[0133] Table 1 Test Results of Resin Cured Products

[0134]

[0135] When preparing the cage-like silsesquioxane epoxy resin, no epoxy-modified nano-silica was added in Comparative Example 1, and the nano-silica in Comparative Example 5 was not epoxy-modified. Compared with Example 1, the bending strength retention rate after boiling in water at 95 °C for 7 days was higher, proving that Example 1 had better moisture and heat resistance and lower water absorption; the tensile modulus was higher, proving that the epoxy-modified nano-silica in Example 1 was more uniformly dispersed in the epoxy resin matrix, significantly reducing the free volume of the system and thus improving the modulus of the epoxy resin.

[0136] In Comparative Example 2, a silica composite epoxy resin was prepared instead of using an epoxy silane coupling agent and phenyltriethoxysilane to prepare the cage-like silsesquioxane composite epoxy resin. Compared with Example 1, the bending strength retention rate was higher, proving that Example 1 had better moisture and heat resistance and lower water absorption; the tensile fracture elongation rate was higher, proving that the cage-like silsesquioxane epoxy increased the toughness of the epoxy resin, could improve the brittleness of the system, and enhance the fracture elongation rate of the system.

[0137] In Comparative Example 3, a bifunctional 128 epoxy resin was used to replace the tetrafunctional AG-80 epoxy resin to prepare the cage-shaped silsesquioxane epoxy resin. Compared with Example 1, the bending strength retention rate was higher, indicating that the heat and humidity resistance of Example 1 was better and the water absorption rate was lower; the tensile modulus was higher and the glass transition temperature was higher, indicating that the multifunctional epoxy resin made the curing system have a higher crosslinking density and could significantly improve the temperature resistance of the resin system.

[0138] In Comparative Example 4, when preparing the high-temperature and high-humidity resistant high-modulus epoxy resin, the polycyclic naphthalene-type epoxy resin was not added. Compared with Example 1, the tensile modulus was higher and the glass transition temperature was higher, indicating that the addition of the high-temperature resistant structural epoxy resin could significantly improve the temperature resistance of the resin system.

[0139] For the high-temperature and high-humidity resistant high-modulus epoxy resins prepared in Examples 1 to 7, a relatively high content of epoxy-functionalized silica was stably dispersed in the cage-shaped silsesquioxane epoxy and multifunctional epoxy resins, solving the problems that nano-fillers are prone to agglomeration and difficult to be uniformly dispersed in the epoxy resin and the addition amount is limited, enabling the epoxy-modified silica and the cage-shaped silsesquioxane epoxy to uniformly participate in the crosslinking network, significantly reducing the free volume of the system, and thus enhancing the modulus of the epoxy resin; the cage-shaped silsesquioxane epoxy increases the toughness of the epoxy resin, can improve the brittleness of the system, and enhance the elongation at break of the system; the cage-shaped silsesquioxane epoxy resin and the high-temperature resistant structural epoxy resin have good heat resistance, and at the same time, the multifunctional epoxy resin makes the curing system have a higher crosslinking density, which can significantly improve the temperature resistance of the resin system; the cage-shaped silsesquioxane epoxy resin and nano-silica can significantly reduce the water absorption rate of the system. At the same time, combined with the multifunctional epoxy resin and the high-temperature resistant structural epoxy resin with good heat and humidity resistance, the prepared epoxy resin system has good heat and humidity resistance and can be applied to high-end application fields such as aerospace.

Claims

1. A silica / cage-like silsesquioxane composite epoxy resin is prepared from raw materials including epoxy silane coupling agent A, arylalkoxysilane, epoxy-modified nano-silica, and polyfunctional epoxy resin.

2. The silica / cage-like silsesquioxane composite epoxy resin according to claim 1, characterized in that: the epoxy silane coupling agent A is a mixture of 3-(2,3-epoxypropoxypropyl)trimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; preferably, the molar ratio of 3-(2,3-epoxypropoxypropyl)trimethoxysilane to β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane is (0.25 - 4):1; and / or, the arylalkoxysilane is phenylalkoxysilane, preferably phenyltriethoxysilane; and / or, the average particle size of the epoxy-modified nano-silica is 10 - 100 nm, preferably 20 - 40 nm; and / or, the epoxy-modified nano-silica is fumed nano-silica modified by epoxy silane coupling agent B; preferably, the mass ratio of the epoxy silane coupling agent B to the fumed nano-silica is (2 - 7):100, more preferably (4 - 6):100; the epoxy silane coupling agent B is at least one of 3-(2,3-epoxypropoxypropyl)trimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and / or, the polyfunctional epoxy resin is at least one of trifunctional epoxy resin and tetrafunctional epoxy resin, preferably at least one of N,N,N',N'-tetraglycidyl-4,4-diaminodiphenylmethane epoxy resin, diglycidyl 4,5-epoxyhexane-1,2-dicarboxylate, and triglycidyl p-aminophenol.

3. A method for preparing the silica / cage-like silsesquioxane composite epoxy resin according to claim 1 or 2, comprising the following steps: (1) After adding epoxy silane coupling agent A and arylalkoxysilane to an aqueous solution for hydrolysis reaction, the aqueous solution is removed and an organic solvent is added to obtain a cage-like silsesquioxane epoxy resin organic solution; (2) Epoxy-modified nano-silica and polyfunctional epoxy resin are added to the cage-like silsesquioxane epoxy resin organic solution obtained in step (1) and dispersed evenly, and then the solvent is removed to obtain the silica / cage-like silsesquioxane composite epoxy resin.

4. The method for preparing the silica / cage-like silsesquioxane composite epoxy resin according to claim 3, characterized in that: in step (1), the molar ratio of the epoxy silane coupling agent A to the arylalkoxysilane is 1:(1 - 3); and / or, the aqueous solution is a mixed solution of ethanol, methanol, water, and hydrochloric acid; preferably, the molar ratio of water to arylalkoxysilane is (3 - 4):1; and / or, the pH value of the aqueous solution is 3 - 4; and / or, the mass ratio of the aqueous solution to the sum of the masses of epoxy silane coupling agent A and arylalkoxysilane is not less than 1:1; and / or, the temperature of the hydrolysis reaction is 30 - 40 °C; and / or, the hydrolysis reaction time is 36 - 60 h; and / or, Adjust the pH value to neutral after hydrolysis; and / or, The method for removing the aqueous solution is to perform vacuum distillation after water washing; and / or, The organic solvent is at least one of acetone, tetrahydrofuran, and toluene; and / or, The mass of the added organic solvent accounts for no less than 40% of the mass of the silsesquioxane epoxy resin organic solution.

5. The method for preparing the silica / silsesquioxane composite epoxy resin according to claim 3, characterized in that: Step (2), The mass ratio of the silsesquioxane epoxy resin to the polyfunctional epoxy resin is (1-3):5; and / or, The mass ratio of the epoxy-modified nano-silica to the polyfunctional epoxy resin is (2-4):

5.

6. A high-temperature and high-humidity resistant high-modulus epoxy resin is prepared from raw materials including a silica / silsesquioxane composite epoxy resin, a polyethersulfone resin, a high-temperature resistant structural epoxy resin, and a curing agent; the silica / silsesquioxane composite epoxy resin is the silica / silsesquioxane composite epoxy resin according to claim 1 or 2 or the silica / silsesquioxane composite epoxy resin obtained by the preparation method of any one of claims 3-5.

7. The high-temperature and high-humidity resistant high-modulus epoxy resin according to claim 6, characterized in that: Based on 100 parts by weight of the silica / silsesquioxane composite epoxy resin, the high-temperature and high-humidity resistant high-modulus epoxy resin includes: Silica / silsesquioxane composite epoxy resin 100 parts by weight; Polyethersulfone resin 1-10 parts by weight; preferably 2-5 parts by weight; High-temperature resistant structural epoxy resin 10-50 parts by weight; preferably 20-30 parts by weight; Curing agent 30-60 parts by weight; preferably 35-45 parts by weight.

8. The high-temperature and high-humidity resistant high-modulus epoxy resin according to claim 6, characterized in that: The weight-average molecular weight of the polyethersulfone resin is 10,000-80,000, preferably 30,000-50,000; and / or, The high-temperature resistant structural epoxy resin contains at least one group of biphenyl, naphthyl, hetero-naphthyl, fluorene, adamantyl, and triazine ring, preferably at least one of condensed ring naphthalene type epoxy resin and biphenyl phenol type epoxy resin; and / or, The curing agent is an aromatic amine curing agent, preferably at least one of 4,4'-diaminodiphenyl sulfone and 3,3'-diaminodiphenyl sulfone.

9. A method for preparing a high-temperature and high-humidity resistant high-modulus epoxy resin according to any one of claims 6-8, comprising: (1) Mix and heat the silica / silsesquioxane composite epoxy resin, the high-temperature resistant structural epoxy resin, and the polyethersulfone resin with stirring; the mixing temperature is preferably 100-180°C, more preferably 140-160°C; (2) Cool the mixture obtained in step (1) and then add the curing agent and mix evenly to obtain the high-temperature and high-humidity resistant high-modulus epoxy resin; preferably cool to 50-90°C, more preferably 65-75°C.

10. Use of a high-temperature and high-humidity resistant high-modulus epoxy resin as described in any one of claims 6 to 8 or a high-temperature and high-humidity resistant high-modulus epoxy resin obtained by the preparation method as described in claim 9 in the field of prepregs, preferably in high-performance carbon fiber prepregs for aerospace applications.

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