A high-strength adhesive aerogel, its preparation method and application

Abstract

This invention belongs to the field of aerogel materials technology, specifically relating to a high-strength aerogel for adhesives, its preparation method, and its application. The method includes the following steps: (1) preparing polyamic acid using amide-containing diamine monomers and phenol-containing hydroxyl diamine monomers as raw materials; (2) adding polyamic acid to deionized water, precipitating it to obtain polyamic acid powder; (3) adding the polyamic acid powder and an organic alkaline compound to deionized water, dispersing it, adding inorganic nanofillers, and then sol-gelling it to obtain a polyamic acid hydrogel; (4) drying the polyamic acid hydrogel, partially thermal imidizing it, and pulverizing it to obtain a high-strength aerogel for adhesives. The addition of inorganic fillers can enhance the mechanical properties of the polyimide aerogel, increase its porosity, facilitate the full wetting of adhesive materials, and improve bonding strength.

Description

Technical Field

[0001] This invention belongs to the field of aerogel materials technology, specifically relating to a high-strength adhesive aerogel, its preparation method, and its application. Background Technology

[0002] Adhesives are organic or inorganic, natural or synthetic substances that can bond two or more homogeneous or heterogeneous parts or materials together, achieving sufficient strength after curing. Adhesives bond to materials through surface adhesion, chemical bonding, diffusion, and physical adsorption. Compared to other bonding methods, they offer high strength and ease of use, and are widely used in the automotive, aerospace, home appliance, biomedical, and dental industries.

[0003] Currently, in the manufacturing industry, adhesives are widely used for bonding various materials due to their unique properties, such as curing time, bond strength, weather resistance, and moisture resistance. Research on adhesives focuses on enhancing their bond strength and tensile stress, improving corrosion resistance, reducing curing time, and reducing the thickness of adhesives used. These research advances have greatly met the diverse market demands for adhesive applications.

[0004] Adhesives used in the market mainly include inorganic adhesives and organic adhesives. Inorganic adhesives are primarily composed of inorganic salts, inorganic alkali metals, inorganic acids, metal oxides, and hydroxides. Based on the type of inorganic salt, they can be further classified into sulfate, phosphate, silicate, and borate adhesives. Due to the significant advantages of inorganic materials, inorganic adhesives possess excellent high and low temperature resistance, allowing use in a temperature range of -180℃ to 3000℃. They also exhibit low curing shrinkage, simple application processes, and low cost, making them widely used in machinery manufacturing and repair, architectural coatings, and other fields. However, inorganic adhesives suffer from poor acid and alkali resistance, water resistance, brittleness, poor impact resistance, and insufficient bonding strength, making performance improvement difficult and limiting their application.

[0005] CN119391347A discloses a fast-curing epoxy resin adhesive, composed of component A and component B. The raw materials for preparing component A include at least: epoxy resin, filler A, diluent, toughening agent, and coupling agent A. The raw materials for preparing component B include at least: curing agent, filler B, accelerator, and coupling agent B. The curing agent is a combination of at least one of polythiol curing agent, phenolic amine curing agent, and polyamide curing agent. By optimizing the formulation system, the product's workability (potential life), curing speed, and post-curing hardness are effectively balanced. It achieves rapid curing within a suitable workability time while ensuring post-curing hardness, meeting the practical application needs of emergency repair of cold-welded pipelines. CN119592272A uses tetramethyltri-3-trifluoropropylcyclotetrasiloxane as a raw material to prepare hydroxyl-terminated organofluorosilicone oil, which modifies epoxy resin. Fluorine atoms are tightly arranged around its main chain in an umbrella shape, which synergistically improves the waterproof and heat-resistant effects with organosilicon. The hydroxyl groups on the oxidized carbon nanofibers react with thiocyanate in the vulcanized rubber powder to form a hybrid filler. The remaining active groups on the surface of the oxidized carbon fibers are then combined and crosslinked with the epoxy resin, which greatly improves the heat resistance of the epoxy resin. Secondly, phenyl maleic anhydride is used as a crosslinking agent to form a three-dimensional crosslinked structure. At the same time, phenyl groups are introduced into the structure to further improve the heat resistance and waterproof effect of the epoxy resin. As a result, the adhesive prepared from this epoxy resin has excellent waterproof and heat-resistant properties. Summary of the Invention

[0006] This invention provides an aerogel for high-strength adhesives, its preparation method, and its application. The preparation process is simple, low-cost, and easy to operate, and the raw materials are readily available, which is conducive to industrial production. Furthermore, the adhesives modified with this aerogel have excellent mechanical properties and broad application prospects, especially in the field of epoxy resin adhesives, where they exhibit superior performance.

[0007] This objective of the invention is achieved through the following technical solution:

[0008] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0009] (1) Add the amide-containing diamine monomer and the phenol-hydroxyl-containing diamine monomer to an organic solvent to obtain a mixed solution of diamine monomers; then add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained;

[0010] (2) Polyamic acid was added to deionized water and precipitated to obtain polyamic acid powder;

[0011] (3) Add polyamic acid powder and organic alkaline compound to deionized water, disperse them, add inorganic nanofiller, stir evenly, and then obtain polyamic acid hydrogel after sol-gelation;

[0012] (4) Dry the polyamic acid hydrogel, partially heat imidize it, and pulverize it to obtain a high-strength adhesive aerogel.

[0013] Polyimide typically cannot be directly fused with epoxy resin, while polyamic acid, the precursor of polyimide, is a liquid substance with a certain viscosity that can be uniformly mixed in epoxy resin, making the process extremely simple. The inventors previously used polyamic acid to modify adhesives. However, polyamic acid is mostly in a liquid state, exhibiting extremely poor stability and requiring immediate preparation, which limits its large-scale application. Aerogel materials, as lightweight materials with porous structures, are widely used as reinforcing stabilizers in bonding resin composites. Traditional inorganic aerogel materials have low strength, are brittle, and are difficult to process. Although common polymer aerogels are easier to process than inorganic aerogels, they still suffer from poor heat resistance. In contrast, polyimide-based aerogels retain the general properties of aerogel materials and, thanks to the excellent mechanical properties and high-temperature thermal stability of polyimide, overcome the shortcomings of traditional aerogels, such as low strength.

[0014] Therefore, this invention prepares an active polyimide aerogel using amide-containing diamine monomers and phenol-hydroxyl-containing diamine monomers as raw materials and inorganic nanofillers as reinforcing agents. Due to the presence of phenolic hydroxyl groups, the polyimide powder can react with the epoxy groups of the epoxy resin to form covalent bonds, thereby improving the compatibility between the two and achieving a good toughening effect in the epoxy resin system. However, the introduction of a large number of phenolic hydroxyl groups also leads to a decrease in the mechanical strength of the polyimide itself. To solve this problem, this invention selects to add a certain amount of amide-containing diamine monomers. The introduction of amide-containing diamine monomers breaks the regularity of the polyimide main chain, which not only improves the mechanical properties of the polyimide material but also helps to form a gel network, increases gel porosity, and facilitates the wetting of the adhesive resin. Furthermore, the amide-containing diamine monomers contain a large number of active amide bonds, which are conducive to further forming hydrogen bonds with the epoxy resin, promoting the formation of the hydrogen bond network of the adhesive, and further improving the mechanical strength of the adhesive. Simultaneously, the addition of inorganic nanofillers further improves the stability of the gel structure, promotes the formation of a porous structure, and increases the porosity of the aerogel.

[0015] Further, the phenolic hydroxy diamine monomer mentioned in step (1) is one or more of the following: 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 3,3-diamino-4,4-dihydroxydiphenyl sulfone, 9,9-bis(3-amino-4-hydroxyphenyl)fluorene, 3,3-diamino-4,4-dihydroxybiphenyl, 3,3-dihydroxy-4,4-diaminodiphenylmethane, 4,4-diamino-4-hydroxytriphenylmethane, bis(5-amino-2-hydroxyphenyl)methane, 3,3-diamino-4,4-dihydroxydiphenyl sulfide, and 3,3-diamino-4,4-dihydroxydiphenyl ether.

[0016] Furthermore, the amide-containing diamine monomer mentioned in step (1) is one or more of 4,4-diaminobenzoyl aniline, 2-chloro-4,4-diaminobenzoyl aniline, 3,4-diaminobenzoyl aniline, 2-methyl-4,4-diaminobenzoyl aniline, and 3-methyl-4,4-diaminobenzoyl aniline;

[0017] Furthermore, the molar ratio of the amide-containing diamine monomer to the phenol-containing hydroxyl diamine monomer is (0-0.5):1, and the amount of the amide-containing diamine monomer is not 0.

[0018] Furthermore, the organic solvent mentioned in step (1) is one or more of N,N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone;

[0019] Further, the dianhydride monomers mentioned in step (1) are pyromellitic dianhydride, 3,3,4,4-diphenyl ether tetracarboxylic dianhydride, 3,3,4,4-biphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, 4,4-hexafluoroisopropylphthalic anhydride, 2,3,3,4-benzophenone tetracarboxylic dianhydride, 3,3,4,4-benzophenone tetracarboxylic dianhydride, 3,3,4,4-biphenyl tetracarboxylic dianhydride, and p- One or more of the following: phenylene-bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)phenyl dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phenyl dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, and 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride. Specifically, the dianhydride monomer is pyromellitic dianhydride, 3,3,4,4-diphenyl ether tetracarboxylic dianhydride, 3,3,4,4-biphenyltetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride, 4,4-hexafluoroisopropylphthalic anhydride, 2,3,3,4-benzophenone tetracarboxylic dianhydride, 3,3,4,4-benzophenone tetracarboxylic dianhydride, 3,3,4,4-biphenyltetracarboxylic dianhydride, and p-phenylene-bisphenyltrilate dianhydride. Further, it is selected from biphenyl dianhydrides and ester-based dianhydrides. Further, the dianhydride is selected from 3,3,4,4-biphenyltetracarboxylic dianhydride and p-phenylene-bisphenyltrilate dianhydride. Furthermore, the molar ratio of 3,3,4,4-biphenyltetracarboxylic dianhydride to p-phenylene-bisphenyltriester dianhydride is (0.1-1):1; further, it is (0.3-0.5):1. By selecting ester-containing dianhydrides and biphenyl dianhydrides, the formation of hydrogen bonds in the system can be further promoted, improving the stability of the aerogel structure; and the combination of flexible ester-containing dianhydrides and rigid biphenyl dianhydrides can improve the stiffness and toughness of the aerogel network, thereby enhancing the mechanical properties of the adhesive.

[0020] Furthermore, in step (1), the dianhydride monomer is added to the diamine monomer mixture in 2-6 portions (all dianhydride monomers are evenly distributed), with an interval of 2-6 minutes between each addition; the molar ratio of the dianhydride monomer to the diamine monomer is (1-1.04):1.

[0021] Furthermore, the reaction temperature in step (1) is 25-35℃, and the reaction time is 6-10h;

[0022] Furthermore, the precipitation process described in step (2) also includes subsequent washing and drying processes.

[0023] Furthermore, the organic alkaline compound mentioned in step (3) is at least one of triethylamine, tripropylamine, diethylenetriamine, triethylenetetramine, and triethylenediamine; the mass ratio of the polyamic acid powder to the organic alkaline compound is 1:(0.1-1).

[0024] Furthermore, the inorganic nanofiller mentioned in step (3) is one or more of granular fillers, lamellar fillers, or fibrous fillers. The addition of inorganic fillers can enhance the mechanical properties of polyimide aerogel and improve the stability of the aerogel structure.

[0025] Furthermore, the inorganic nanofiller mentioned in step (3) is one or more of the following: nano-calcium carbonate particles, nano-silica particles, nano-alumina particles, nano-boron carbide particles, graphene, graphene oxide, carbon nanofibers, carbon nanotubes, and bacterial cellulose. In particular, fibrous fillers can be selected. The addition of fibrous nanofillers can better promote the formation of gel pore structures, increase the porosity of polyimide aerogel, and facilitate the full wetting of adhesive materials.

[0026] Furthermore, the inorganic nanofiller described in step (3) is modified by a coupling agent; the mass ratio of the modified inorganic nanofiller to the polyamic acid powder is (0.01-0.2):1.

[0027] Furthermore, the coupling agent mentioned in step (3) is one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents. The type of coupling agent is not particularly limited, but can specifically be one or more of KH550, KH551, KH560, and KH570. Modification with coupling agents can improve the interfacial interaction between inorganic nanofillers and polyamic acid. Further, aminosilane coupling agents or epoxysilane coupling agents can be selected. The selection of the above coupling agents can improve the hydrogen bond network structure of the system and promote the gelation process.

[0028] Furthermore, the specific process of modifying the inorganic nanofiller with a coupling agent in step (3) is as follows:

[0029] Inorganic nanofillers were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), then a coupling agent was added, the mixture was ultrasonically dispersed, heated to react, and then filtered, washed, and dried to obtain modified inorganic nanofillers.

[0030] Furthermore, in step (3), the mass ratio of the inorganic nanofiller to the coupling agent is 1:(0.1-1); the heating reaction temperature is 50-60℃, and the reaction time is 1-2h.

[0031] Furthermore, the drying process described in step (4) is freeze-drying or supercritical drying.

[0032] Furthermore, the partial thermal imidization described in step (4) involves holding at 100-180℃ for 1-3 hours. Specifically, it involves holding at 140-160℃ for 1.5-2.5 hours. In particular, the carboxyl groups on the partially imidized aerogel mainly react with the epoxy groups. Each unit has two active hydrogens at different positions, which may react simultaneously, thus forming a complex macromolecular ester graft copolymer and an interpenetrating network structure. When the temperature reaches 200-300℃, the carboxyl groups that have not reacted with the epoxy and the amino groups on the adjacent benzene ring undergo a condensation reaction to form a five-membered ring group. The formation of this stable five-membered ring further improves the stability of the system, which is particularly beneficial to the improvement of heat resistance. Due to the presence of imide groups, the heat resistance of the system can be improved by modifying the epoxy resin adhesive with partially imidized aerogel.

[0033] On the other hand, the present invention also provides an aerogel for high-strength adhesives and its application therein. The aerogel for high-strength adhesives is used in the field of adhesives, wherein the adhesive comprises a bonding resin and an aerogel, which can greatly improve the mechanical properties of resin adhesives.

[0034] Specifically, the adhesive may optionally contain components such as bonding resin, aerogel, curing agent, and a small amount of diluent.

[0035] Specifically, the adhesive resin is polyurethane, epoxy resin, phenolic resin, silicone resin, acrylic resin, etc.

[0036] Beneficial effects:

[0037] (1) Polyimide-based aerogels retain the general properties of aerogel materials and benefit from the excellent mechanical properties and high-temperature thermal stability of polyimide, thus overcoming the shortcomings of traditional aerogels such as low strength.

[0038] (2) An active polyimide aerogel was prepared using amide-containing diamine monomers and phenol-hydroxyl-containing diamine monomers as raw materials. Due to the presence of phenolic hydroxyl groups, the polyimide powder can react with the epoxy groups of the epoxy resin to form covalent bonds, thereby improving the compatibility between the two and enabling the epoxy resin system to achieve a good toughening effect. The introduction of amide-containing diamine monomers breaks the regularity of the polyimide main chain, which not only improves the mechanical properties of the polyimide material, but also helps to form a gel network, increases the gel porosity, and facilitates the wetting of the adhesive resin. In addition, the amide-containing diamine monomers contain a large number of active amide bonds, which are conducive to further forming hydrogen bonds with the epoxy resin, promoting the formation of the hydrogen bond network of the adhesive, and further improving the mechanical strength of the adhesive.

[0039] (3) The addition of inorganic nanofillers further improves the stability of the gel structure, promotes the formation of porous structure, and increases the porosity of aerogel. Detailed Implementation

[0040] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0041] Unless otherwise specified, the raw material types and specific process parameters of the following examples and comparative examples are consistent. The product performance testing method is as follows: under the same conditions, the effect of the aerogel prepared in Examples 1-10 and Comparative Example 1 on the performance of the epoxy resin adhesive is tested. The epoxy resin adhesive comprises: 100 parts E-51 epoxy resin, 4.2 parts aerogel, 20 parts 4,4'-diaminodiphenyl sulfone, etc. After the epoxy resin and aerogel are mixed evenly, the curing agent 4,4'-diaminodiphenyl sulfone is added, and the mixture is stirred at 95°C for 0.6 hours to obtain the epoxy resin adhesive. The epoxy resin adhesive is uniformly coated on the treated aluminum alloy surface and cured at 120°C for 0.5 hours, 150°C for 0.5 hours, 170°C for 1.5 hours, 210°C for 1.5 hours, and 250°C for 1.5 hours; the curing pressure is 0.2 MPa. The shear strength is tested according to GB7124-86.

[0042] Example 1

[0043] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0044] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.1:1; the phenol-hydroxy diamine monomer is 2,2-bis(3-amino-4-hydroxyphenyl)propane; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is a mixture of 3,3,4,4-benzophenone tetracarboxylic dianhydride and 3,3,4,4-diphenyl ether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the mixed solution of diamine monomers in 4 batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 25℃ and the reaction time is 10h;

[0045] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0046] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.4. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 50°C for 2 hours. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.3.

[0047] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 145℃ for 3 hours, and then pulverized to obtain a high-strength adhesive aerogel. The shear strength of the aerogel-modified adhesive was tested to be 28.6 MPa.

[0048] Example 2

[0049] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0050] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N-methylpyrrolidone to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.5:1; the phenol-hydroxy diamine monomer is 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is a mixture of 3,3,4,4-biphenyltetracarboxylic dianhydride and 3,3,4,4-diphenyl ether tetracarboxylic dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the mixed solution of diamine monomers in four batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 35℃ and the reaction time is 6h;

[0051] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0052] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.8. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 60°C for 1 hour. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.6.

[0053] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 160℃ for 1 hour, and then pulverized to obtain a high-strength adhesive aerogel. The shear strength of the aerogel-modified adhesive was tested to be 30.9 MPa.

[0054] Example 3

[0055] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0056] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenolic hydroxyl diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenolic hydroxyl diamine monomer is 0.3:1; the phenolic hydroxyl diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is 3,3,4,4-biphenyltetracarboxylic dianhydride; the dianhydride monomer is added to the mixed solution of diamine monomers in 4 batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0057] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0058] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.6. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 55°C for 1.5 h. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.5.

[0059] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain a high-strength adhesive aerogel. The shear strength of the aerogel-modified adhesive was tested to be 30.1 MPa.

[0060] Example 4

[0061] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0062] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.5:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is a mixture of pyromellitic dianhydride and 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the mixed solution of diamine monomers in 4 batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 25℃ and the reaction time is 6h;

[0063] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0064] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.5. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 50°C for 1 hour. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.6.

[0065] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 150°C for 1.3 h, and then pulverized to obtain a high-strength adhesive aerogel. The shear strength of the aerogel-modified adhesive was tested to be 28.9 MPa.

[0066] Example 5

[0067] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0068] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenolic hydroxyl diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenolic hydroxyl diamine monomer is 0.3:1; the phenolic hydroxyl diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is p-phenylene-bisphenyltriester dianhydride; the dianhydride monomer is added to the mixed solution of diamine monomers in 4 batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0069] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0070] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.6. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 55°C for 1.5 h. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.5.

[0071] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain a high-strength adhesive aerogel. The shear strength of the aerogel-modified adhesive was tested to be 29.5 MPa.

[0072] Example 6

[0073] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0074] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N-methylpyrrolidone to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.2:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxybiphenyl; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is a mixture of 2,3,3,4-benzophenone tetracarboxylic dianhydride and 3,3,4,4-biphenyl tetracarboxylic dianhydride in a molar ratio of 2:1; the dianhydride monomer is added to the mixed solution of diamine monomers in four batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 28℃ and the reaction time is 9h;

[0075] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0076] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.5. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 52°C for 1.8 h. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.4.

[0077] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 149℃ for 2.8h, and then pulverized to obtain a high-strength aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 30.2MPa.

[0078] Example 7

[0079] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0080] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.3:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is a mixture of 3,3,4,4-biphenyltetracarboxylic dianhydride and p-phenylene-bisphenyltriterpenoid dianhydride in a molar ratio of 1:0.5; the dianhydride monomer is added to the mixed solution of diamine monomers in 4 batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0081] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0082] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.6. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 55°C for 1.5 h. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.5.

[0083] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain a high-strength aerogel for adhesives. The shear strength of the aerogel-modified adhesive was tested to be 30.6 MPa.

[0084] Example 8

[0085] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0086] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.4:1; the phenol-hydroxy diamine monomer is 2,2-bis(3-amino-4-hydroxyphenyl)propane; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is a mixture of 2,2-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride and 3,3,4,4-biphenyltetracarboxylic acid dianhydride in a molar ratio of 1:1; the dianhydride monomer is added to the mixed solution of diamine monomers in 4 batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 31℃ and the reaction time is 7h;

[0087] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0088] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.7. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 58°C for 1.2 h. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.5.

[0089] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 155℃ for 2.5h, and then pulverized to obtain a high-strength adhesive aerogel. The shear strength of the aerogel-modified adhesive was tested to be 31.1 MPa.

[0090] Example 9

[0091] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0092] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.2:1; the phenol-hydroxy diamine monomer is 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is a mixture of 3,3,4,4-benzophenone tetracarboxylic dianhydride and 3,3,4,4-biphenyltetracarboxylic dianhydride in a molar ratio of 1:3; the dianhydride monomer is added to the mixed solution of diamine monomers in 4 batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 29°C and the reaction time is 7.5 h;

[0093] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0094] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.6. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 54°C for 1.6 h. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.5.

[0095] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 155℃ for 2.2 h, and then pulverized to obtain a high-strength adhesive aerogel. The shear strength of the aerogel-modified adhesive was tested to be 30.8 MPa.

[0096] Example 10

[0097] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0098] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 0.3:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is a mixture of 3,3,4,4-biphenyltetracarboxylic dianhydride and p-phenylene-bisphenyltriterpenoid dianhydride in a molar ratio of 0.5:1; the dianhydride monomer is added to the mixed solution of diamine monomers in 4 batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0099] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0100] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.6. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 55°C for 1.5 h. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.5.

[0101] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain a high-strength adhesive aerogel. The shear strength of the aerogel-modified adhesive was tested to be 32.7 MPa.

[0102] Comparative Example 1

[0103] A method for preparing aerogel for high-strength adhesives includes the following steps:

[0104] (1) Add the amide-containing diamine monomer 4,4-diaminobenzoyl aniline and the phenol-hydroxy diamine monomer to the organic solvent N,N-dimethylacetamide to obtain a mixed solution of diamine monomers; the molar ratio of the amide-containing diamine monomer to the phenol-hydroxy diamine monomer is 1:1; the phenol-hydroxy diamine monomer is 3,3-diamino-4,4-dihydroxydiphenyl sulfone; add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the dianhydride monomer is a mixture of 3,3,4,4-biphenyltetracarboxylic dianhydride and p-phenylene-bisphenyltriterpenoid dianhydride in a molar ratio of 0.5:1; the dianhydride monomer is added to the mixed solution of diamine monomers in 4 batches, with an interval of 4 minutes between each batch; the molar ratio of the dianhydride monomer to all diamine monomers is 1.02:1; the reaction temperature is 30℃ and the reaction time is 8h;

[0105] (2) Polyamic acid is added to deionized water, and after precipitation, washing and drying, polyamic acid powder is obtained;

[0106] (3) Polyamic acid powder and triethylamine, an organic alkaline compound, were added to deionized water, dispersed, and then inorganic nanofiller was added. The mixture was stirred evenly and then sol-gelled to obtain polyamic acid hydrogel. The mass ratio of polyamic acid powder to organic alkaline compound was 1:0.6. The inorganic nanofiller was modified carbon nanotubes, and the mass ratio of modified carbon nanotubes to polyamic acid powder was 0.1:1. The specific preparation process was as follows: carbon nanotubes were placed in a mixed solvent of ethanol and deionized water (volume ratio 1:1), and then coupling agent KH550 was added. The mixture was ultrasonically dispersed evenly and reacted at 55°C for 1.5 h. After filtration, washing, and drying, modified carbon nanotubes were obtained. The mass ratio of carbon nanotubes to coupling agent was 1:0.5.

[0107] (4) The polyamic acid hydrogel was freeze-dried, partially thermally imidized at 152℃ for 2 hours, and then pulverized to obtain a high-strength adhesive aerogel. The shear strength of the aerogel-modified adhesive was tested to be 23.3 MPa.

[0108] As can be seen from the above examples and comparative examples, this invention uses amide-containing diamine monomers and phenol-hydroxyl-containing diamine monomers as raw materials, and inorganic nanofillers as improving additives to prepare active polyimide aerogels. Due to the presence of phenolic hydroxyl groups, the polyimide powder can react with the epoxy groups of the epoxy resin to form covalent bonds, thereby improving the compatibility between the two and enabling the epoxy resin system to achieve a good toughening effect. However, the introduction of a large number of phenolic hydroxyl groups also leads to a decrease in the mechanical strength of the polyimide itself. To solve this problem, this invention selects to add a certain amount of amide-containing diamine monomers. The introduction of amide-containing diamine monomers breaks the regularity of the polyimide main chain, which not only improves the mechanical properties of the polyimide material but also helps in the formation of a gel network, increases gel porosity, and facilitates the wetting of the adhesive resin. In addition, the amide-containing diamine monomers contain a large number of active amide bonds, which are conducive to further forming hydrogen bonds with the epoxy resin, promoting the formation of the hydrogen bond network of the adhesive, and further improving the mechanical strength of the adhesive. Meanwhile, the addition of inorganic fillers can enhance the mechanical properties of polyimide aerogel, increase its porosity, and facilitate the full wetting of adhesive materials, thereby improving bonding strength. However, the amount of amide-diamine monomer should not be excessive, otherwise it will lead to the formation of polyimide with amide-diamine monomer as the main structure, affecting the interaction between phenolic hydroxyl diamine monomer and epoxy adhesive, and hindering the improvement of mechanical properties. Compared with Example 10, the excessive amount of amide-diamine monomer in Comparative Example 1 affected the interaction between phenolic hydroxyl diamine monomer and epoxy adhesive, resulting in a decrease in the shear strength of the adhesive.

[0109] The above description is merely a preferred embodiment of the invention and is not intended to limit the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should be considered within the technical scope of this invention.

Claims

1. A method for preparing aerogel for high-strength adhesives, characterized in that, Includes the following steps: (1) Add the amide-containing diamine monomer and the phenol-hydroxyl-containing diamine monomer to an organic solvent to obtain a mixed solution of diamine monomers; then add the dianhydride monomer in batches to the mixed solution of diamine monomers, and after the reaction, polyamic acid is obtained; the molar ratio of the amide-containing diamine monomer and the phenol-hydroxyl-containing diamine monomer is (0-0.5):1, and the amount of the amide-containing diamine monomer is not 0; (2) Polyamic acid was added to deionized water and precipitated to obtain polyamic acid powder; (3) Add polyamic acid powder and organic alkaline compound to deionized water, disperse them, add inorganic nanofiller, stir evenly, and then obtain polyamic acid hydrogel after sol-gelation; (4) Dry the polyamic acid hydrogel, partially heat imidize it, and pulverize it to obtain a high-strength adhesive aerogel; The phenolic hydroxy diamine monomer mentioned in step (1) is one or more of the following: 2,2-bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 3,3-diamino-4,4-dihydroxydiphenyl sulfone, 9,9-bis(3-amino-4-hydroxyphenyl)fluorene, 3,3-diamino-4,4-dihydroxybiphenyl, 3,3-dihydroxy-4,4-diaminodiphenylmethane, 4,4-diamino-4-hydroxytriphenylmethane, bis(5-amino-2-hydroxyphenyl)methane, 3,3-diamino-4,4-dihydroxydiphenyl sulfide, and 3,3-diamino-4,4-dihydroxydiphenyl ether. The amide-containing diamine monomer mentioned in step (1) is one or more of 4,4-diaminobenzoyl aniline, 2-chloro-4,4-diaminobenzoyl aniline, 3,4-diaminobenzoyl aniline, 2-methyl-4,4-diaminobenzoyl aniline, and 3-methyl-4,4-diaminobenzoyl aniline.

2. The method for preparing a high-strength adhesive aerogel as described in claim 1, characterized in that, The inorganic nanofiller mentioned in step (3) is one or more of the following: particulate filler, lamellar filler, or fibrous filler.

3. The method for preparing a high-strength adhesive aerogel as described in claim 1, characterized in that, The inorganic nanofiller mentioned in step (3) is one or more of the following: nano-calcium carbonate particles, nano-silica particles, nano-alumina particles, nano-boron carbide particles, graphene, graphene oxide, carbon nanofibers, carbon nanotubes, and bacterial cellulose.

4. The method for preparing a high-strength adhesive aerogel as described in claim 1, characterized in that, The inorganic nanofiller in step (3) is modified by a coupling agent; the mass ratio of the modified inorganic nanofiller to the polyamic acid powder is (0.01-0.2):

1.

5. The method for preparing a high-strength adhesive aerogel as described in claim 4, characterized in that, The coupling agent mentioned in step (3) is one or more of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

6. The method for preparing a high-strength adhesive aerogel as described in claim 4, characterized in that, The specific process of modifying the inorganic nanofiller with a coupling agent in step (3) is as follows: The inorganic nanofiller was placed in a mixed solvent of ethanol and deionized water, then a coupling agent was added, and the mixture was ultrasonically dispersed and heated to react. After filtration, washing, and drying, the modified inorganic nanofiller was obtained.

7. The method for preparing a high-strength adhesive aerogel as described in claim 6, characterized in that, The mass ratio of the inorganic nanofiller to the coupling agent in step (3) is 1:(0.1-1); the heating reaction temperature is 50-60℃ and the reaction time is 1-2h.

8. An aerogel for high-strength adhesives, characterized in that, It is prepared by any one of the methods for preparing a high-strength adhesive aerogel according to claims 1-7.

9. An application of the aerogel for high-strength adhesives as described in claim 8, characterized in that, High-strength adhesive aerogels are used in the field of epoxy resin adhesives.

10. An adhesive, characterized in that, The aerogel comprises epoxy resin and high-strength adhesive, wherein the high-strength adhesive aerogel is the high-strength adhesive aerogel as described in claim 8.