Self-repairing phenolic epoxy resin, preparation method and application thereof

Abstract

The application provides a self-repairing phenolic epoxy resin and a preparation method and application thereof. The self-repairing phenolic epoxy resin of the application can introduce a dynamic covalent bond borate into the phenolic epoxy resin through 4-hydroxymethylphenylboronic acid. Under certain temperature conditions, the borate bond can be dissociated and a crosslinking network can be re-built, so that the interface of the broken phenolic epoxy resin is re-healed, and the problems of non-repeated processing, recycling and utilization and environmental pollution of the phenolic epoxy resin are solved. Hexamethylenetetramine is used as a permanent covalent crosslinking agent of the phenolic epoxy resin. The hexamethylenetetramine can be decomposed into ammonia and formaldehyde in a weak acid solution. The formaldehyde can be used as a methylene formed by the reaction of the phenolic epoxy resin, and can be used as a permanent covalent crosslinking point, so that the permanent covalent crosslinking density is increased to improve the mechanical properties of the material. By adjusting the proportion and content of the two kinds of crosslinking, good mechanical strength and a certain degree of self-repairing effect can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of epoxy phenolic resin technology, and particularly relates to a self-healing phenolic epoxy resin, its preparation method, and its application. Background Technology

[0002] Phenolic epoxy resin is a condensation product of linear low molecular weight phenolic resin and epichlorohydrin, and is a light brownish-yellow viscous liquid at room temperature. It is a type of multifunctional epoxy resin, which can provide more crosslinking points during curing, readily forming a highly crosslinked three-dimensional structure. It combines the properties of both phenolic and epoxy resins, exhibiting excellent heat resistance, corrosion resistance, and good strength. Traditional phenolic epoxy resins typically use permanent covalent crosslinking agents for crosslinking, achieving good mechanical properties but also resulting in the material's inability to self-heal and be reused. Using non-covalent crosslinking agents alone yields materials with relatively low mechanical properties, making it difficult to meet practical production requirements.

[0003] Boronates undergo rapid transesterification at room temperature and are considered among the most promising candidates for self-healing materials. Dynamic covalent bonds have emerged as an innovative strategy for preparing covalently adaptive networks, potentially providing an effective method for developing self-healing materials. The reversible conversion of BO bonds under certain conditions makes them highly advantageous for designing self-repairing polymer materials; however, the strength of dynamic covalent bonds is often weaker than that of permanent covalent bonds, which affects the mechanical properties required for their application.

[0004] Given the current problems with phenolic epoxy resins, it is necessary to improve them. Summary of the Invention

[0005] In view of this, the present invention proposes a self-healing phenolic epoxy resin, its preparation method and application, in order to solve the technical problems existing in the prior art.

[0006] In a first aspect, the present invention provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 2-40 parts of hexamethylenetetramine, 5-35 parts of 4-hydroxymethylphenylboronic acid, 100 parts of phenolic epoxy resin, 200-400 parts of solvent, and 1-5 parts of catalyst.

[0007] Preferably, the self-healing phenolic epoxy resin contains a catalyst comprising zinc acetate and / or nano zinc oxide.

[0008] Preferably, the self-healing phenolic epoxy resin is an alcohol-soluble phenolic epoxy resin with a solid content ≥50%, a viscosity ≤2.5 Pa·s, and an epoxy value of 0.42 to 53.

[0009] Preferably, in the self-healing phenolic epoxy resin, the solvent is an alcohol solvent, and the alcohol solvent includes at least one of methanol, ethanol, and isopropanol.

[0010] Secondly, the present invention also provides a method for preparing the self-healing phenolic epoxy resin, comprising the following steps:

[0011] Phenolic epoxy resin is added to a solvent, and the pH is adjusted to 4-6 using an acid solution. Then, 4-hydroxymethylphenylboronic acid, hexamethylenetetramine, and a catalyst are added and stirred to obtain a phenolic epoxy resin prepolymer solution.

[0012] After concentrating the phenolic epoxy resin prepolymer solution, it was dried to obtain uncured phenolic epoxy resin.

[0013] Uncured phenolic epoxy resin is cured by hot pressing to obtain self-healing phenolic epoxy resin.

[0014] Preferably, the method for preparing the self-healing phenolic epoxy resin involves hot-pressing uncured phenolic epoxy resin at a temperature of 110–170°C and a pressure of 3–7 MPa for 20–40 minutes to obtain the self-healing phenolic epoxy resin.

[0015] Preferably, the method for preparing the self-healing phenolic epoxy resin involves concentrating the phenolic epoxy resin prepolymer solution and then vacuum drying it at 70–90°C to obtain uncured phenolic epoxy resin.

[0016] Preferably, in the method for preparing the self-healing phenolic epoxy resin, the concentration step of the phenolic epoxy resin prepolymer solution is performed by vacuum distillation.

[0017] Thirdly, the present invention also provides the application of the self-healing phenolic epoxy resin described above or the self-healing phenolic epoxy resin prepared by the preparation method described above in encapsulation materials or building materials.

[0018] The method for preparing a self-healing phenolic epoxy resin according to the present invention has the following advantages over the prior art:

[0019] 1. This invention relates to a self-healing phenolic epoxy resin, comprising hexamethylenetetramine, 4-hydroxymethylphenylboronic acid, phenolic epoxy resin, solvent, and catalyst. In this self-healing phenolic epoxy resin, 4-hydroxymethylphenylboronic acid introduces dynamic covalent borate esters into the phenolic epoxy resin. Under certain temperature conditions, the borate ester bonds dissociate and rebuild a cross-linking network, causing the broken phenolic epoxy resin interface to heal again. This solves the problems of non-recyclability, non-recyclability, and environmental pollution associated with phenolic epoxy resin. Hexamethylenetetramine, as a permanent covalent cross-linking agent for phenolic epoxy resin, decomposes into ammonia and formaldehyde in a weak acid solution. Formaldehyde can react with the phenolic epoxy resin to form methylene groups, which can serve as permanent covalent cross-linking points, thereby increasing the density of permanent covalent cross-links and improving the mechanical properties of the material. This invention controls the dynamic covalent bonds and cross-linking structure of covalent bonds in phenolic epoxy resin by adjusting the addition ratio and content of 4-hydroxymethylphenylboronic acid and hexamethylenetetramine. By controlling the ratio and content of the two cross-linking components, good mechanical strength and a certain degree of self-healing effect are obtained.

[0020] 2. The preparation method of the self-healing phenolic epoxy resin of the present invention uses hexamethylenetetramine and 4-hydroxymethylphenylboronic acid to co-cur the phenolic epoxy resin, forming a complementary structural network of permanent covalent crosslinking and dynamic crosslinking, which has stronger mechanical properties and healing ability. Traditional phenolic epoxy resin crosslinking agents are usually permanently covalently crosslinked, forming irreversible permanent covalent bonds, which cannot be repeatedly processed and reused. The present invention introduces dynamic exchangeable borate ester bonds, enabling the phenolic epoxy resin to have self-healing function, achieving the effect of recycling and saving resources. The self-healing phenolic epoxy resin of the present invention has good mechanical properties and self-healing effect. After repeated processing, the mechanical properties and self-healing effect only decrease slightly compared with the raw materials. The preparation method of the present invention is simple, requiring no complex synthesis, with short reaction time and simple reaction equipment. Therefore, the method of the present invention is easy to promote, has low time cost, low energy consumption, and is expected to be industrialized. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0023] This invention provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 2-40 parts hexamethylenetetramine, 5-35 parts 4-hydroxymethylphenylboronic acid, 100 parts phenolic epoxy resin, 200-400 parts solvent, and 1-5 parts catalyst.

[0024] In some embodiments, the catalyst is a powder or an alcohol-soluble liquid, and specific catalysts include zinc acetate and / or nano zinc oxide.

[0025] In some embodiments, the phenolic epoxy resin is an alcohol-soluble phenolic epoxy resin, wherein the phenolic epoxy resin has a solid content ≥50%, a viscosity ≤2.5 Pa·s, and an epoxy value of 0.42 to 53.

[0026] In some embodiments, the solvent is an alcohol solvent, which includes at least one of methanol, ethanol, and isopropanol, preferably ethanol.

[0027] The self-healing phenolic epoxy resin of this invention utilizes 4-hydroxymethylphenylboronic acid to introduce dynamic covalent borate esters into the phenolic epoxy resin. Under certain temperature conditions, the borate ester bonds dissociate and rebuild a crosslinking network, allowing the broken phenolic epoxy resin interface to heal. This solves the problems of non-recyclability, non-reusability, and environmental pollution associated with phenolic epoxy resin. Hexamethylenetetramine, as a permanent covalent crosslinking agent for phenolic epoxy resin, decomposes into ammonia and formaldehyde in weak acid conditions. Formaldehyde can react with the phenolic epoxy resin to form methylene groups, which can serve as permanent covalent crosslinking points, thereby increasing the density of permanent covalent crosslinks and improving the material's mechanical properties. The mechanism of hexamethylenetetramine forming methylene permanent covalent crosslinks with phenolic epoxy resin is as follows:

[0028] c6H 12 N4+4H ++6H₂O→6HCHO+4NH₄ +

[0029]

[0030] This invention controls the dynamic covalent bonds and cross-linking structure of phenolic epoxy resin by adjusting the addition ratio and content of 4-hydroxymethylphenylboronic acid and hexamethylenetetramine. By regulating the ratio and content of the two cross-linking components, good mechanical strength and a certain degree of self-healing effect are obtained.

[0031] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned self-healing phenolic epoxy resin, comprising the following steps:

[0032] S1. Add phenolic epoxy resin to a solvent, adjust the pH to 4-6 with acid, and then add 4-hydroxymethylphenylboronic acid, hexamethylenetetramine and catalyst. Stir and mix to obtain phenolic epoxy resin prepolymer solution.

[0033] S2. After concentrating the phenolic epoxy resin prepolymer solution, dry it to obtain uncured phenolic epoxy resin.

[0034] S3. The uncured phenolic epoxy resin is hot-pressed and cured to obtain a self-healing phenolic epoxy resin.

[0035] Specifically, the acid used in step S1 includes, but is not limited to, hydrochloric acid, sulfuric acid, and nitric acid.

[0036] In some embodiments, uncured phenolic epoxy resin is hot-pressed and cured at a temperature of 110–170°C and a pressure of 3–7 MPa for 20–40 min to obtain self-healing phenolic epoxy resin.

[0037] Specifically, in some embodiments, uncured phenolic epoxy resin is pulverized into powder with a particle size of 80-150 mesh. The pulverized phenolic epoxy resin is then placed in a mold (length, width, and height are 50mm, 50mm, and 10mm, respectively), and the mold is placed in a flat vulcanizing apparatus. The mixture is then hot-pressed and cured for 20-40 minutes at a temperature of 110-170℃ and a pressure of 3-7MPa to obtain self-healing phenolic epoxy resin.

[0038] In some embodiments, the phenolic epoxy resin prepolymer solution is concentrated and then vacuum dried at 70–90°C to obtain uncured phenolic epoxy resin.

[0039] In some embodiments, the concentration of the phenolic epoxy resin prepolymer solution is carried out by vacuum distillation.

[0040] The preparation method of the self-healing phenolic epoxy resin of this invention uses hexamethylenetetramine and 4-hydroxymethylphenylboronic acid to co-cur the phenolic epoxy resin, forming a complementary structural network of permanent covalent crosslinking and dynamic crosslinking, which has stronger mechanical properties and healing ability. Traditional phenolic epoxy resin crosslinking agents are usually permanently covalently crosslinked, forming irreversible permanent covalent bonds, which cannot be reused. This invention introduces dynamic exchangeable borate ester bonds, enabling the phenolic epoxy resin to have self-healing function, achieving the effect of recycling and saving resources. The self-healing phenolic epoxy resin of this invention has good mechanical properties and self-healing effect. After repeated processing, the mechanical properties and self-healing effect only decrease slightly compared with the raw materials. The preparation method of this invention is simple, does not require complex synthesis, has a short reaction time, and requires simple reaction equipment. Therefore, the method of this invention is easy to promote, has low time cost, low energy consumption, and is expected to be industrialized.

[0041] Based on the same inventive concept, the present invention also provides the application of the above-mentioned self-healing phenolic epoxy resin or the self-healing phenolic epoxy resin prepared by the above-mentioned preparation method in encapsulation materials or building materials.

[0042] The following detailed embodiments further illustrate the self-healing phenolic epoxy resin and its preparation method. This section further explains the invention with reference to specific embodiments, but should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in the art. The phenolic epoxy resin used in the following embodiments is an alcohol-soluble phenolic epoxy resin, purchased from Jining Baichuan Chemical Co., Ltd.

[0043] Example 1

[0044] This application provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 2 parts hexamethylenetetramine, 30 parts 4-hydroxymethylphenylboronic acid, 100 parts phenolic epoxy resin, 250 parts solvent, and 3 parts catalyst.

[0045] The solvent is anhydrous ethanol, and the catalyst is zinc acetate.

[0046] The preparation method of the above-mentioned self-healing phenolic epoxy resin includes the following steps:

[0047] S1. At room temperature, 100 parts of phenolic epoxy resin were added to 250 parts of anhydrous ethanol and stirred. The pH was adjusted to 5 with hydrochloric acid. Then, 30 parts of 4-hydroxymethylphenylboronic acid, 2 parts of hexamethyltetramine and 3 parts of zinc acetate catalyst were added and stirred for 30 minutes to obtain a phenolic epoxy resin prepolymer solution.

[0048] S2. The phenolic epoxy resin prepolymer solution is concentrated by vacuum distillation and then dried in a vacuum furnace at 80°C to constant weight to obtain uncured phenolic epoxy resin.

[0049] S3. After crushing the uncured phenolic epoxy resin into powder, place it in a mold (length, width, and height are 50mm, 50mm, and 10mm respectively) and hot press it at 170℃ and 5MPa for 30 minutes to obtain a cured phenolic epoxy resin film, which is the self-healing phenolic epoxy resin.

[0050] Example 2

[0051] This application provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 5 parts hexamethylenetetramine, 30 parts 4-hydroxymethylphenylboronic acid, 100 parts phenolic epoxy resin, 250 parts solvent, and 3 parts catalyst.

[0052] The solvent is anhydrous ethanol, and the catalyst is zinc acetate.

[0053] The preparation method of the above-mentioned self-healing phenolic epoxy resin includes the following steps:

[0054] S1. At room temperature, 100 parts of phenolic epoxy resin were added to 250 parts of anhydrous ethanol and stirred. The pH was adjusted to 5 with hydrochloric acid. Then, 30 parts of 4-hydroxymethylphenylboronic acid, 5 parts of hexamethyltetramine and 3 parts of zinc acetate catalyst were added and stirred for 30 minutes to obtain a phenolic epoxy resin prepolymer solution.

[0055] S2. The phenolic epoxy resin prepolymer solution is concentrated by vacuum distillation and then dried in a vacuum furnace at 80°C to constant weight to obtain uncured phenolic epoxy resin.

[0056] S3. After crushing the uncured phenolic epoxy resin into powder, place it in a mold (length, width, and height are 50mm, 50mm, and 10mm respectively) and hot press it at 170℃ and 5MPa for 30 minutes to obtain a cured phenolic epoxy resin film, which is the self-healing phenolic epoxy resin.

[0057] Example 3

[0058] This application provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 10 parts hexamethylenetetramine, 30 parts 4-hydroxymethylphenylboronic acid, 100 parts phenolic epoxy resin, 250 parts solvent, and 3 parts catalyst.

[0059] The solvent is anhydrous ethanol, and the catalyst is zinc acetate.

[0060] The preparation method of the above-mentioned self-healing phenolic epoxy resin includes the following steps:

[0061] S1. At room temperature, 100 parts of phenolic epoxy resin were added to 250 parts of anhydrous ethanol and stirred. The pH was adjusted to 5 with hydrochloric acid. Then, 30 parts of 4-hydroxymethylphenylboronic acid, 10 parts of hexamethyltetramine and 3 parts of zinc acetate catalyst were added and stirred for 30 minutes to obtain a phenolic epoxy resin prepolymer solution.

[0062] S2. The phenolic epoxy resin prepolymer solution is concentrated by vacuum distillation and then dried in a vacuum furnace at 80°C to constant weight to obtain uncured phenolic epoxy resin.

[0063] S3. After crushing the uncured phenolic epoxy resin into powder, place it in a mold (length, width, and height are 50mm, 50mm, and 10mm respectively) and hot press it at 170℃ and 5MPa for 30 minutes to obtain a cured phenolic epoxy resin film, which is the self-healing phenolic epoxy resin.

[0064] Example 4

[0065] This application provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 15 parts hexamethylenetetramine, 30 parts 4-hydroxymethylphenylboronic acid, 100 parts phenolic epoxy resin, 250 parts solvent, and 3 parts catalyst.

[0066] The solvent is anhydrous ethanol, and the catalyst is zinc acetate.

[0067] The preparation method of the above-mentioned self-healing phenolic epoxy resin includes the following steps:

[0068] S1. At room temperature, 100 parts of phenolic epoxy resin were added to 250 parts of anhydrous ethanol and stirred. The pH was adjusted to 5 with hydrochloric acid. Then, 30 parts of 4-hydroxymethylphenylboronic acid, 15 parts of hexamethyltetramine and 3 parts of zinc acetate catalyst were added and stirred for 30 minutes to obtain a phenolic epoxy resin prepolymer solution.

[0069] S2. The phenolic epoxy resin prepolymer solution is concentrated by vacuum distillation and then dried in a vacuum furnace at 80°C to constant weight to obtain uncured phenolic epoxy resin.

[0070] S3. After crushing the uncured phenolic epoxy resin into powder, place it in a mold (length, width, and height are 50mm, 50mm, and 10mm respectively) and hot press it at 170℃ and 5MPa for 30 minutes to obtain a cured phenolic epoxy resin film, which is the self-healing phenolic epoxy resin.

[0071] Example 5

[0072] This application provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 20 parts hexamethylenetetramine, 30 parts 4-hydroxymethylphenylboronic acid, 100 parts phenolic epoxy resin, 250 parts solvent, and 3 parts catalyst.

[0073] The solvent is anhydrous ethanol, and the catalyst is zinc acetate.

[0074] The preparation method of the above-mentioned self-healing phenolic epoxy resin includes the following steps:

[0075] S1. At room temperature, 100 parts of phenolic epoxy resin were added to 250 parts of anhydrous ethanol and stirred. The pH was adjusted to 5 with hydrochloric acid. Then, 30 parts of 4-hydroxymethylphenylboronic acid, 20 parts of hexamethyltetramine and 3 parts of zinc acetate catalyst were added and stirred for 30 minutes to obtain a phenolic epoxy resin prepolymer solution.

[0076] S2. The phenolic epoxy resin prepolymer solution is concentrated by vacuum distillation and then dried in a vacuum furnace at 80°C to constant weight to obtain uncured phenolic epoxy resin.

[0077] S3. After crushing the uncured phenolic epoxy resin into powder, place it in a mold (length, width, and height are 50mm, 50mm, and 10mm respectively) and hot press it at 170℃ and 5MPa for 30 minutes to obtain a cured phenolic epoxy resin film, which is the self-healing phenolic epoxy resin.

[0078] Example 6

[0079] This application provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 30 parts hexamethylenetetramine, 30 parts 4-hydroxymethylphenylboronic acid, 100 parts phenolic epoxy resin, 250 parts solvent, and 3 parts catalyst.

[0080] The solvent is anhydrous ethanol, and the catalyst is zinc acetate.

[0081] The preparation method of the above-mentioned self-healing phenolic epoxy resin includes the following steps:

[0082] S1. At room temperature, 100 parts of phenolic epoxy resin were added to 250 parts of anhydrous ethanol and stirred. The pH was adjusted to 5 with hydrochloric acid. Then, 30 parts of 4-hydroxymethylphenylboronic acid, 30 parts of hexamethyltetramine and 3 parts of zinc acetate catalyst were added and stirred for 30 minutes to obtain a phenolic epoxy resin prepolymer solution.

[0083] S2. The phenolic epoxy resin prepolymer solution is concentrated by vacuum distillation and then dried in a vacuum furnace at 80°C to constant weight to obtain uncured phenolic epoxy resin.

[0084] S3. After crushing the uncured phenolic epoxy resin into powder, place it in a mold (length, width, and height are 50mm, 50mm, and 10mm respectively) and hot press it at 170℃ and 5MPa for 30 minutes to obtain a cured phenolic epoxy resin film, which is the self-healing phenolic epoxy resin.

[0085] Example 7

[0086] This application provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 40 parts hexamethylenetetramine, 30 parts 4-hydroxymethylphenylboronic acid, 100 parts phenolic epoxy resin, 250 parts solvent, and 3 parts catalyst.

[0087] The solvent is anhydrous ethanol, and the catalyst is zinc acetate.

[0088] The preparation method of the above-mentioned self-healing phenolic epoxy resin includes the following steps:

[0089] S1. At room temperature, 100 parts of phenolic epoxy resin were added to 250 parts of anhydrous ethanol and stirred. The pH was adjusted to 5 with hydrochloric acid. Then, 30 parts of 4-hydroxymethylphenylboronic acid, 40 parts of hexamethyltetramine and 3 parts of zinc acetate catalyst were added and stirred for 30 minutes to obtain a phenolic epoxy resin prepolymer solution.

[0090] S2. The phenolic epoxy resin prepolymer solution is concentrated by vacuum distillation and then dried in a vacuum furnace at 80°C to constant weight to obtain uncured phenolic epoxy resin.

[0091] S3. After crushing the uncured phenolic epoxy resin into powder, place it in a mold (length, width, and height are 50mm, 50mm, and 10mm respectively) and hot press it at 170℃ and 5MPa for 30 minutes to obtain a cured phenolic epoxy resin film, which is the self-healing phenolic epoxy resin.

[0092] Comparative Example 1

[0093] This comparative example provides a self-healing phenolic epoxy resin, comprising the following raw materials in parts by weight: 30 parts of 4-hydroxymethylphenylboronic acid, 100 parts of phenolic epoxy resin, 250 parts of solvent, and 3 parts of catalyst.

[0094] The solvent is anhydrous ethanol, and the catalyst is zinc acetate.

[0095] The preparation method of the above-mentioned self-healing phenolic epoxy resin includes the following steps:

[0096] S1. At room temperature, 100 parts of phenolic epoxy resin were added to 250 parts of anhydrous ethanol and stirred. The pH was adjusted to 5 with hydrochloric acid. Then, 30 parts of 4-hydroxymethylphenylboronic acid and 3 parts of zinc acetate catalyst were added and stirred for 30 minutes to obtain a phenolic epoxy resin prepolymer solution.

[0097] S2. The phenolic epoxy resin prepolymer solution is concentrated by vacuum distillation and then dried in a vacuum furnace at 80°C to constant weight to obtain uncured phenolic epoxy resin.

[0098] S3. After crushing the uncured phenolic epoxy resin into powder, place it in a mold (length, width, and height are 50mm, 50mm, and 10mm respectively) and hot press it at 170℃ and 5MPa for 30 minutes to obtain a cured phenolic epoxy resin film, which is the self-healing phenolic epoxy resin.

[0099] Mechanical property testing

[0100] Tensile tests were conducted on the self-healing phenolic epoxy resins prepared in Examples 1-7 and Comparative Example 1 at room temperature using a universal testing instrument to detect the tensile strength and elongation at break of the samples. The sample size was 50×10mm (length×width), the initial test distance between the two clamps was 20mm, and the samples were tested at a loading speed of 5mm / min. The test results are shown in Table 1.

[0101] Table 1 - Mechanical properties of self-healing phenolic epoxy resins in different embodiments

[0102] Example Tensile strength (MPa) Elongation at break (%) Example 1 27.65 10.42 Example 2 29.84 9.89 Example 3 33.69 9.37 Example 4 37.34 8.58 Example 5 40.15 8.02 Example 6 46.72 7.56 Example 7 48.87 7.04 Comparative Example 1 24.83 11.62

[0103] As can be seen from Table 1, the mechanical properties of phenolic epoxy resin are enhanced with the increase of hexamethyltetramine content. This is because hexamethyltetramine increases the crosslinking density of methylene covalent bonds in phenolic epoxy resin, thereby enhancing its mechanical properties. In addition, while the tensile strength of the prepared phenolic epoxy resin is improved, the fracture strength is only slightly reduced.

[0104] Self-repair performance test

[0105] The self-healing phenolic epoxy resins prepared in Examples 1-7 and Comparative Example 1 were cut into 50×10mm (length×width) shapes. The cut samples were then severed in the middle with a blade, and the cuts were immediately rejoined. The samples were then subjected to self-healing at 170℃ for 30 minutes. The repaired samples were then subjected to tensile testing using a universal testing instrument until fracture. The ratio of the tensile strength after repair to the tensile strength of the original sample is the repair effect. The evaluation criteria for repair effect are: ≥95% is excellent, 80%–95% is good, 65%–80% is good, 40%–65% is average, and ≤40% is poor. The test results are shown in Table 2.

[0106] Table 2 - Self-healing performance test of self-healing phenolic epoxy resin in different embodiments

[0107] Example Tensile strength (MPa) Repair effect (%) Example 1 25.26 91.36 Example 2 26.77 89.71 Example 3 28.58 84.83 Example 4 30.74 82.32 Example 5 32.36 80.60 Example 6 36.85 78.87 Example 7 37.63 77.00 Comparative Example 1 23.10 93.03

[0108] As can be seen from Table 2, at a certain value of 4-hydroxymethylphenylboronic acid content, the self-healing performance weakens with the increase of hexamethyltetramine content. This is because the ratio of covalent bonds to dynamic covalent bonds increases, resulting in more permanent covalent cross-linked structures and a decrease in self-healing performance.

[0109] Heat resistance test

[0110] The self-healing phenolic epoxy resin samples prepared in Examples 1-7 and Comparative Example 1 were placed in a thermogravimetric analyzer (TGA, model NETZSCH TG 209C) and tested for heat resistance at a heating rate of 10℃ / min under a nitrogen atmosphere. The results are shown in Table 3.

[0111] Table 3 - Heat resistance test of self-healing phenolic epoxy resin in different embodiments

[0112]

[0113]

[0114] As shown in Table 3, with the increase of hexamethyltetramine content, the temperature at which the weight loss reaches 10% gradually decreases, while the remaining weight content increases after reaching 800℃. This is because the ammonium ions produced by hexamethyltetramine easily generate ammonia gas at high temperatures, causing the material's weight loss rate to reach 10% more quickly. Simultaneously, the introduction of more methylene covalent cross-linked networks into the phenolic epoxy resin makes the remaining phenolic epoxy resin more heat-resistant after the ammonia gas escapes, resulting in a gradual increase in the remaining weight at 800℃.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-healing phenolic epoxy resin, characterized in that, The raw materials include the following parts by weight: 2-40 parts hexamethylenetetramine, 5-35 parts 4-hydroxymethylphenylboronic acid, 100 parts phenolic epoxy resin, 200-400 parts solvent, and 1-5 parts catalyst; The catalyst is zinc acetate; The phenolic epoxy resin is an alcohol-soluble phenolic epoxy resin; The solvent is an alcohol solvent, and the alcohol solvent is ethanol; The preparation method of the self-healing phenolic epoxy resin includes the following steps: Phenolic epoxy resin was added to a solvent, the pH was adjusted to 5 with an acid solution, and then 4-hydroxymethylphenylboronic acid, hexamethylenetetramine and catalyst were added and stirred to obtain a phenolic epoxy resin prepolymer solution. After concentrating the phenolic epoxy resin prepolymer solution, it was dried to obtain uncured phenolic epoxy resin. Uncured phenolic epoxy resin is hot-pressed at a temperature of 110~170 ℃ and a pressure of 3~7MPa for 20~40 min to obtain self-healing phenolic epoxy resin. The phenolic epoxy resin has a solid content of ≥50%, a viscosity of ≤2.5 Pa·s, and an epoxy value of 0.42~53.

2. A method for preparing the self-healing phenolic epoxy resin as described in claim 1, characterized in that, Includes the following steps: Phenolic epoxy resin was added to a solvent, the pH was adjusted to 5 with an acid solution, and then 4-hydroxymethylphenylboronic acid, hexamethylenetetramine and catalyst were added and stirred to obtain a phenolic epoxy resin prepolymer solution. After concentrating the phenolic epoxy resin prepolymer solution, it was dried to obtain uncured phenolic epoxy resin. Uncured phenolic epoxy resin is hot-pressed at a temperature of 110~170 ℃ and a pressure of 3~7MPa for 20~40 min to obtain self-healing phenolic epoxy resin.

3. The method for preparing the self-healing phenolic epoxy resin as described in claim 2, characterized in that, After concentrating the phenolic epoxy resin prepolymer solution, it was vacuum dried at 70~90℃ to obtain uncured phenolic epoxy resin.

4. The method for preparing the self-healing phenolic epoxy resin as described in claim 2, characterized in that, In the step of concentrating the phenolic epoxy resin prepolymer solution, the concentration is carried out by vacuum distillation.

5. The application of a self-healing phenolic epoxy resin as described in claim 1 or a self-healing phenolic epoxy resin prepared by any of the preparation methods described in claims 2 to 4 in encapsulation materials or building materials.

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