A high-toughness and high-strength one-component epoxy structural adhesive system with high storage stability and controllable reaction and its preparation method

Abstract

The present invention discloses a high-toughness, high-strength, one-component epoxy structural adhesive system with high storage stability and controllable reaction, and a preparation method thereof. Using an epoxy resin and a hyperbranched polymer hybrid system loaded with a curing agent as the primary raw materials, the system is prepared. Compared to existing technologies, the epoxy structural adhesive provided by the present invention not only exhibits excellent storage stability and controllable reaction properties, but also possesses outstanding mechanical strength and toughness.

Description

Technical Field

[0001] The present invention belongs to the technical field of structure and performance design of thermosetting epoxy structural adhesives, and specifically relates to a high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction, and a preparation method thereof. Background Art

[0002] Epoxy structural adhesives are widely used in aerospace, electronics, automobiles and other fields. One-component epoxy structural adhesives are popular because of their advantages in construction, such as easy operation and no need for complicated adhesive preparation process before use. However, as a one-component structural adhesive, since the curing agent is generally added directly to the structural adhesive resin system, the storage period of the structural adhesive system is relatively short, generally 3-6 months, which is much lower than that of two-component structural adhesives. This greatly limits the applicability and application range of one-component structural adhesives. In addition, epoxy resin is the main component of structural adhesives, and its matrix has a high cross-linking density after curing, which makes it significantly brittle, so the impact resistance of the structural adhesive system is poor. The use of traditional toughening modification technology such as adding thermoplastic components can significantly improve the toughness of epoxy adhesives, but it will significantly reduce the strength of epoxy adhesives. Therefore, the development of epoxy adhesives with excellent storage stability and high toughness and strength is of great significance to improving the application of epoxy structural adhesives. Summary of the Invention

[0003] This invention addresses the short shelf life and poor impact properties of single-component epoxy structural adhesives, as well as the inability of existing modification technologies to combine high toughness, high strength, and excellent storage stability. By preparing a hyperbranched polymer (HPB) hybrid system (HBP-CA) loaded with a curing agent (CA) with unique structure and properties, this invention addresses the problems of poor storage stability and uncontrollable reaction in epoxy adhesive systems. Furthermore, HBP-CA is used to help address the epoxy adhesive's poor impact properties while maintaining the strength of the original structural adhesive system. To achieve these objectives, the invention prepares a CA-loaded HBP hybrid system, uses it as a curing agent, and modifies the epoxy adhesive, resulting in a high-toughness, high-strength, single-component epoxy structural adhesive system with high storage stability and controllable reaction.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A high-toughness, high-strength, one-component epoxy structural adhesive system with high storage stability and controllable reaction. The components and mass ratio are: epoxy resin (EP): chain extender: hyperbranched polymer hybrid system loaded with curing agent (HBP-CA): polyurethane prepolymer (PUP) = (30-50): (0-5): (10-50): (0-25), preferably: epoxy resin (EP): hyperbranched polymer hybrid system loaded with curing agent (HBP-CA): polyurethane prepolymer (PUP) = 50: (15-25): (0-25). When the system contains a chain extender, the ratio is not zero; when the system contains a polyurethane prepolymer, the ratio is not zero.

[0006] In the present invention, the HBP-CA preparation method comprises adding CA or a CA solution to HBP, stirring at 25-50°C for 0.5-4 hours, and then stirring at 120-160°C for 0.5-4 hours to obtain an HBP-CA hybrid structure system, wherein the weight ratio of HBP to CA is 100:(10-50), and the weight ratio of solvent to CA is (20-80):(10-50). Preferably, the solvent is a polar solvent, such as water, ethanol, acetone, formamide, N,N-dimethylformamide (DMF), or N,N-dimethylacetamide (DMAC). In the HBP-CA hybrid system, CA is contained within the nanocavities of HBP. Due to the branched structure and the ability of the HBP-CA hybrid to self-assemble into a spherical structure through hydrogen bonding, the CA particles are isolated, effectively preventing the CA from coming into contact with the epoxy resin system and causing a curing reaction, thereby improving the storage stability of the structural adhesive. Furthermore, under the influence of heat or external forces, the hydrogen bonds in the HBP-CA hybrid system are forcibly broken, allowing the HBP-CA hybrid system to release the CA particles, triggering the curing of the structural adhesive and achieving controlled curing of the structural adhesive system. Furthermore, the active end groups of the HBP-CA hybrid system ensure strong interfacial interactions with the epoxy resin, significantly toughening the structural adhesive system and effectively maintaining its strength.

[0007] In the present invention, the preparation method of the above-mentioned epoxy structural adhesive system is as follows: the epoxy resin and the polyurethane prepolymer are reacted at 100-120°C for 0.5-2h, followed by vacuum stirring for 20-50min, and then the HBP-CA hybrid structural system is added at room temperature to obtain the structural adhesive, which is sealed and stored for use. Alternatively, the epoxy resin and the chain extender are stirred and reacted at room temperature to 140°C for 10-30min, and then the polyurethane prepolymer is added at 100-120°C and the reaction is continued for 0.5-2h, followed by vacuum stirring for 20-50min, and then the HBP-CA hybrid structural system is added at room temperature to obtain the structural adhesive, which is sealed and stored for use; or the epoxy resin is mixed with a hyperbranched polymer hybrid system loaded with a curing agent at room temperature to obtain the high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction. Preferably, the HBP-CA hybrid structural system is added at room temperature and stirred for 3-10min to obtain the structural adhesive.

[0008] The present invention discloses a high-toughness and high-strength single-component epoxy material, which is obtained by curing the high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction. Preferably, the curing temperature is 120-180°C, the curing time is 2-6 hours, and the curing adopts a step-curing process; for example, the high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction adopts a temperature program of 120-140°C / 1-4h+170-180°C / 1-2h to obtain the high-toughness and high-strength single-component epoxy material.

[0009] In the present invention, the epoxy resin includes one or more of glycidyl ether epoxy resin (such as bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin), glycidyl ester epoxy resin, glycidyl amine epoxy resin, alicyclic epoxy resin, and linear aliphatic epoxy compound; the curing agent is one or more of aromatic amine (such as diaminodiphenyl ether, diaminodiphenyl sulfone, diaminodiphenylmethane, etc.), dicyandiamide and its derivatives, organic hydrazides (such as succinic acid hydrazide, adipic acid dihydrazide, phenylaminoacetic acid hydrazide, dimethylaminoacetic acid hydrazide, 4-aminobenzoic acid hydrazide, phenylacetic acid hydrazide, 3-aminophenylhydrazide, 4-aminosalicylic acid hydrazide, 3-aminopyrazine-2-carbohydrazide, etc.), imidazole and its derivatives; the chain extender is an amino and imino compound, such as ethylenediamine, N,N-dihydroxy(diisopropyl)aniline, iminodiacetonitrile, N,N'-dimethylethylenediamine, tert-butoxybis(dimethylamino)methane, 1,9-nonanediamine, 3,3'-iminobis(N,N-dimethylpropylamine), etc.; the HBP is a functional group-terminated hyperbranched polyester, a functional group-terminated hyperbranched polyether, a functional group-terminated hyperbranched polyamide ester, a functional group-terminated hyperbranched polyamide, a functional group-terminated hyperbranched polyurethane, etc., and the functional groups are carboxyl, hydroxyl, amino, etc.; the polyurethane prepolymer is a prepolymer with different -NCO contents and a mixture thereof, such as a polyether-type polyurethane prepolymer, a polyester-type polyurethane prepolymer, a polytetramethylene diisocyanate (MDI)-type polyurethane prepolymer, a polycaprolactone-type polyurethane prepolymer, and a mixture thereof.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] This invention discloses for the first time a HBP-CA hybrid system. CA is contained within the nanocavities of HBP, effectively resolving the dispersion problem of the curing agent CA in the structural adhesive system and preventing direct contact between the curing agent and the epoxy system during the storage period of the structural adhesive system, thereby extending the storage period of the structural adhesive and improving the storage stability of the structural adhesive. Furthermore, the self-assembled HBP-CA hybrid system can release the curing agent component under the action of heat and force, thereby controlling the curing of the epoxy structural adhesive. Furthermore, the HBP-CA hybrid system, as a second phase, can also improve the toughness of the structural adhesive while maintaining its strength, thereby more effectively enhancing the overall performance of the epoxy structural adhesive. The epoxy structural adhesive system of the present invention is easy to industrialize, and other micro-nano inorganic fillers can also be added to obtain a high-toughness, high-strength, single-component epoxy structural adhesive system with high storage stability and controllable reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1FTIR images of CHBPE, DICY, and CHBPE-DICY (a), optical microscopy (LM) images of CHBPE-DICY (b) and DICY (c), transmission electron microscopy (TEM) images (d, e) and N element distribution map (f) of CHBPE-DICY, and TEM (g) of CHBPE-DICY after ultrasonic treatment and water washing.

[0013] Figure 2 LM diagrams of CHBPE-DICY hybrid system dispersed in bisphenol A epoxy resin E-51 at 0h (a) and 7d (b); LM diagrams after treatment at 120℃ (c), 150℃ (d) and ultrasonic treatment for 1min (e).

[0014] Figure 3 These are optical microscopes and 3D images of the cross-sections of the epoxy structural adhesive materials of Example 1 (a, a΄), Comparative Example 1-1 (b, b΄), and Comparative Example 1-2 (c, c΄).

[0015] Figure 4 FTIR spectra of DDS, mixture of CHBPE and DDS, and CHBPE-DICY / DDS hybrid system (a), LM diagram of CHBPE-DICY / DDS hybrid system (b), LM diagram of DDS (c), TEM diagram of CHBPE-DICY / DDS system (d), and distribution diagram of N element (e) and S element (f) of CHBPE-DICY / DDS system.

[0016] Figure 5 LM diagrams of CHBPE-DICY / DDS hybrid system dispersed in bisphenol A epoxy resin E-51 at 0h (a) and 7d (b), and LM diagrams after treatment at 140℃ (c), 150℃ (d) and ultrasonic treatment for 1min (e).

[0017] Figure 6 These are optical microscope and 3D images of the cross-section of the epoxy adhesive materials of Example 2 (a, a΄), Comparative Example 2-1 (b, b΄), and Comparative Example 2-2 (c, c΄). DETAILED DESCRIPTION

[0018] In the present invention, the hyperbranched polymer has a distinct micro-nano porous structure that can serve as a natural storage site. In particular, the hyperbranched polymer ends contain a large number of functional groups such as carboxyl, amino, and hydroxyl groups. The presence of these groups allows the hyperbranched polymer to self-assemble into capsules or aggregates through hydrogen bonding. The structure and performance characteristics of the hyperbranched polymer make it of great application significance as a material carrier and transporter. Because hydrogen bonding can depolymerize under the action of heat and force, the curing agent stored in the hyperbranched structure can be released to trigger the curing reaction of the epoxy adhesive, which makes the control of the epoxy adhesive curing reaction have significant practical value.

[0019] The technical solution of the present invention is further described below with reference to the accompanying figures and examples. The raw materials used in this invention are all commercially available, and the specific preparation operations and performance testing are conventional techniques. Blower oven curing is employed. The following materials include carboxyl-terminated hyperbranched polyester (CHBPE) (HyperC20, molecular weight 5200), tetrahydrofuran-based polyurethane prepolymer (PTMEG) (HJ2185 or HJ2195), and hyperbranched polyamide (HPBPA) (HyPer HPN202, molecular weight 2700).

[0020] Example 1

[0021] (1) Preparation of carboxyl-terminated hyperbranched polyester (CHBPE)-dicyandiamide (DICY) hybrid system

[0022] A solution of the curing agent dicyandiamide (DICY) in N,N-dimethylformamide (DMF) was added to 1 kg of carboxyl-terminated hyperbranched polyester (CHBPE) (HyperC20), stirred at room temperature for 2 hours, and then heated to 120°C and stirred for 2 hours to obtain a CHBPE-DICY hybrid system, in which the weight ratio of CHBPE, DMF, and DICY was 100:80:30.

[0023] Figure 1 The following are infrared (FTIR) images of CHBPE, DICY, and CHBPE-DICY, optical microscope (LM) images of CHBPE-DICY and DICY, transmission electron microscope (TEM) images of CHBPE-DICY, and N element distribution map. Figure 1 As can be seen in Figure a, compared with DICY and CHBPE, the CHBPE-DICY hybrid system not only shows the characteristic absorption peaks of CHBPE, such as =CH (2862 cm -1 ), C=O and COC (1722 cm -1 and 1240 cm -1 ) stretching vibration absorption peak, CH (1098cm -1) bending vibration absorption peak, and also shows the characteristic absorption peaks of DICY, such as -NH2 (3480-3025cm -1 ), -C≡N (2197 cm -1 and 2146cm -1 ), which shows that the CHBPE-DICY hybrid system was successfully prepared and the DICY particles were embedded in the pores of CHBPE. In DMF, CHBPE and DICY have good solubility. DICY can easily penetrate into the internal pores of CHBPE and directly use the pores as a storage chamber. Due to the presence of the hyperbranched structure of CHBPE, DICY particles can be effectively dispersed, avoiding their aggregation and sedimentation, ensuring that DICY has good dispersion in the structural adhesive system. In addition, from Figure 1 It can be found in Figure a that the CHBPE-DICY system exhibits a weaker -COOH (1722 cm -1 ) and -NH2 (3480-3025cm -1 ) characteristic peak and enhanced CN (1355 cm -1 ) characteristic peak, while the CHBPE-DICY system is still at 1780cm -1 A weak imide structure characteristic peak appears at the bottom, which indicates that a small amount of -COOH and -NH2 react to form imide groups. The formation of such imide groups is also conducive to the formation of hydrogen bonds between and within molecules, thereby preventing DICY from reacting with the epoxy resin system. The LM diagram of the CHBPE-DICY hybrid system shows that there are no large DICY particles in the CHBPE-DICY hybrid system ( Figure 1 b and 1c), which further demonstrates that DICY has been dispersed in the CHBPE system. Figure 1 d shows that the shape of the CHBPE-DICY sample (with water as the dispersant) is close to spherical. Since CHBPE has abundant terminal carboxyl groups and possibly a small amount of imide groups, the CHBPE-DICY system can be easily assembled together ( Figure 1 The N element distribution diagram shows that the CHBPE-DICY system clearly contains N components, which further confirms the successful synthesis of the hybrid system ( Figure 1 d). The CHBPE-DICY hybrid system was dispersed in water and then ultrasonically treated and washed with water for multiple times. Figure 1 By comparing the middle e, we can find that the solid particles in the hybrid system disappear ( Figure 1 (g), which further confirmed that DICY was loaded in the CHBPE system, that is, the CHBPE-DICY hybrid system was successfully synthesized and the system could release DICY.

[0024] (2) Preparation of epoxy structural adhesive system

[0025] At room temperature, 100 g of CHBPE-DICY was added to 300 g of bisphenol A epoxy resin (E-51), and the mixture was stirred in a vacuum atmosphere for 10 minutes. The obtained structural adhesive was sealed and stored for later use. The mass ratio of epoxy resin to CHBPE-DICY was 30:10.

[0026] Figure 2 LM diagrams of CHBPE-DICY hybrid system dispersed in bisphenol A epoxy resin E-51 at 0h (a) and 7d (b); LM diagrams after treatment at 120℃ (c), 150℃ (d) or ultrasonic treatment (e) for 1min. Figure 2 As can be observed in Figure a, the CHBPE-DICY system is dispersed in the epoxy resin (E-51) in the form of capsules, indicating that CHBPE self-assembles into spheres in the epoxy resin system, which helps to avoid contact between DICY and the resin system, delaying the curing of the resin system and increasing the storage period. Figure 2 Figure b is the LM diagram of the CHBPE-DICY system after storage in the epoxy resin system for 7 days. It can be observed that the CHBPE-DICY system is still stably dispersed in the epoxy resin system, which means that the CHBPE-DICY system has a stable structure, good dispersion and is not prone to sedimentation in the epoxy resin system. Figure 2 Figures cd in the figure are the morphologies of the CHBPE-DICY system in the epoxy resin system after being treated at 120℃, 150℃ or ultrasonically for 1 min. Figure 2 As can be observed in the middle cd, after heat treatment and ultrasonic treatment, the structure of the CHBPE-DICY system in the epoxy resin system can be destroyed, releasing DICY particles. This shows that heat and ultrasonic treatment can control the release of DICY from the CHBPE-DICY system.

[0027] Comparative Example 1-1

[0028] At room temperature, 76.9 g of CHBPE (HyperC20) and 23.1 g of DICY were added to 300 g of bisphenol A epoxy resin (E-51). The mixture was stirred in a vacuum chamber for 10 minutes. The resulting structural adhesive was sealed and stored for later use. The mass ratio of epoxy:CHBPE:DICY was 30:7.69:2.31, and the amounts of CHBPE and DICY used were similar to those in the CHBPE-DICY hybrid system in the structural adhesive of Example 1.

[0029] Comparative Example 1-2

[0030] At room temperature, add the DICY solution dissolved in DMF to 300g of bisphenol A epoxy resin (E-51). Stir under vacuum for 10 minutes. The resulting structural adhesive is sealed and stored until ready for use. The epoxy:DICY mass ratio is 30:2.31. The DICY content is equivalent to that of the CHBPE-DICY hybrid system in the structural adhesive of Example 1.

[0031] Comparative Examples 1-3

[0032] At room temperature, CHBPE was added to 300g of bisphenol A epoxy resin (E-51) and stirred under vacuum for 10 minutes. The resulting structural adhesive was sealed and stored until ready for use. The epoxy:CHBPE mass ratio was 30:7.69. The DICY content was equivalent to the CHBPE content in the CHBPE-DICY hybrid system in the structural adhesive of Example 1.

[0033] The above structural adhesive is cured at 140° C. / 2 h+180° C. / 2 h respectively to obtain epoxy structural adhesive material.

[0034] Table 1 lists the mechanical properties, gel time and storage period of the structural adhesives in Example 1 and Comparative Examples 1-1, 1-2 and 1-3. Figure 3 Scanning electron microscope (SEM) images of cross-sections of the epoxy structural adhesive materials in Example 1, Comparative Examples 1-1, and 1-2 are shown. The addition of the CHBPE-DICY hybrid system to the epoxy resin significantly improves its mechanical properties. The impact strength of the material in Example 1 increases by 181% and 275% compared to Comparative Examples 1-1 and 1-2, respectively. The flexural strength of the epoxy structural adhesive in Example 1 increases by 12% and 303% compared to Comparative Examples 1-1 and 1-2, respectively. The tensile strength of the epoxy structural adhesive in Example 1 increases by 27% and 145% compared to Comparative Examples 1-1 and 1-2, respectively. At 120°C, the gel time of the epoxy structural adhesive in Example 1 is significantly longer than that of Comparative Examples 1-1 and 1-2, by 55-59 minutes. At 150°C, the gel time of the epoxy structural adhesive in Example 1 is similar to that of the structural adhesives in Comparative Examples 1-1 and 1-2, and both gel times are significantly shorter than those tested at 120°C. Obviously, the introduction of CHBPE-DICY hybrid system into epoxy resin can more effectively improve the comprehensive performance of pure epoxy structural adhesive materials than DICY and DICY / CHBPE mixture, and at the same time, it can also control the release of DICY by heating to cure the epoxy resin. In Comparative Examples 1-3, the added CHBPE is difficult to achieve effective curing of the epoxy resin, and the mechanical properties of the prepared structural adhesive system cannot be obtained, that is, it cannot be used. Figure 3From the fracture morphology images of the materials, it can be found that the fracture morphology of the material in Example 1 is rougher than that in Comparative Examples 1-1 and 1-2, which also means that the material in Example 1 can consume more energy, indicating that the structural adhesive system in Example 1 has higher toughness.

[0035]

[0036] a : The test was carried out using a simply supported beam impact testing machine in accordance with GB / T 2567-2008.

[0037] b : Measured using a universal testing machine in accordance with GB / T 2567-2008.

[0038] c : Measured using a universal testing machine in accordance with GB / T 2567-2008.

[0039] d : Gel time was obtained at different temperatures using the flat knife method.

[0040] e : Determined in accordance with GB / T 7123.2-2002.

[0041] Example 2

[0042] (1) Preparation of CHBPE-DICY / diaminodiphenyl sulfone (DDS) hybrid system

[0043] A DMF solution of DICY and DDS was added to 3.2 kg of carboxyl-terminated hyperbranched polyester (CHBPE) (HyperC20), stirred at room temperature for 2 hours, and then heated to 120°C for 4 hours to obtain a CHBPE-DICY / DDS hybrid system. The weight ratio of CHBPE:DMF:DICY:DDS was 32:16:8:8.

[0044] Figure 4 FTIR spectra of DDS, CHBPE and DDS mixture, CHBPE-DICY / DDS hybrid system, LM diagram of CHBPE-DICY / DDS hybrid system, LM diagram of DDS, TEM diagram of CHBPE-DICY / DDS system, and distribution diagram of N and S elements in CHBPE-DICY / DDS system. Figure 4 As can be seen in a, compared with the FTIR spectra of DICY, DDS, and CHBPE ( Figure 4 A and Figure 1 Compared with (a), the FTIR spectrum of CHBPE-DICY / DDS hybrid system not only shows the characteristic absorption peaks of CHBPE, such as =CH (2862cm-1 ), C=O and COC (1722 cm -1 and 1240 cm -1 ) stretching vibration absorption peak, CH (1098cm -1 ) bending vibration absorption peak; there are also characteristic absorption peaks of DICY, such as -NH2 (3480-3025cm -1 ), -C≡N (2197 cm -1 and 2146cm -1 ); and characteristic peaks of DDS, such as benzene ring (1590cm -1 ), S=O(1150 cm -1 ), -NH2 (3480-3025cm -1 ) characteristic peaks, which indicates that DICY and DDS are embedded in the cavity of CHBPE, and the CHBPE-DICY / DDS hybrid system is successfully prepared. The reason why DICY and DDS are embedded in the cavity of CHBPE is that CHBPE, DICY and DDS have good compatibility in DMF solution, so DICY and DDS can easily penetrate into the internal cavity of CHBPE and directly use the cavity as a storage chamber. Due to the restriction effect of the branched structure of CHBPE, the aggregation of DICY and DDS particles can be avoided, ensuring that the DICY and DDS particles have good dispersion. In addition, since some -COOH and -NH2 can react to form imide groups, -COOH (1722 cm -1 ) and -NH2 (3480-3025cm -1 ) characteristic peak weakened and CN (1355 cm -1 ) characteristic peaks are enhanced, and the CHBPE-DICY / DDS system has a peak at 1780 cm -1 A weak imide structure characteristic peak appears at the . The formation of imide groups is also conducive to the formation of hydrogen bonds between and within molecules, thereby preventing the reaction of DICY / DDS with epoxy resin system. Figure 4 b and c, Figure 1 c) It can be found that there are no large DDS and DICY particles in the CHBPE-DICY / DDS system, which indicates that DDS and DICY are well dispersed in CHBPE. Figure 4 d shows that the CHBPE-DICY / DDS sample is easy to assemble into flocs. This is because CHBPE has abundant terminal carboxyl groups and possibly a small number of imide groups, which are easy to self-assemble through hydrogen bonds. Element distribution diagram ( Figure 4(d) and (e) show that the CHBPE-DICY / DDS system contains N and S elements, which means that DICY and DDS are stored in the CHBPE system.

[0045] (2) Preparation of epoxy structural adhesive

[0046] At room temperature, ethylenediamine was added to 500 g of bisphenol A epoxy resin (E-51), and the mixture was stirred at room temperature for 30 min. Then, tetrahydrofuran-type polyurethane prepolymer (PTMEG) (HJ-2185, NCO content of about 3.5%) was added at 100°C, and the mixture was stirred for 2 h. The mixture was then stirred in a vacuum for 50 min, and CHBPE-DICY / DDS was added at room temperature and stirred in a vacuum for 6 min. The obtained structural adhesive was sealed and stored for later use. The mass ratio of epoxy resin: ethylenediamine: polyurethane prepolymer: CHBPE-DICY / DDS was 50:1:15:16.

[0047] Figure 5 This is the LM diagram of CHBPE-DICY / DDS system dispersed in epoxy resin E-51. Figure 5 As can be observed in Figure a, CHBPE-DICY / DDS is dispersed in the epoxy resin in the form of spherical capsules. This is mainly due to the amphiphilicity of CHBPE, which can self-assemble into spheres in the epoxy resin system. This helps to avoid contact between DICY and DDS and the resin system, and can improve the storage life of the resin system. Figure 5 Figure b is the LM diagram of the CHBPE-DICY / DDS system after storage in the epoxy resin system for 7 days. It can be observed that the CHBPE-DICY / DDS system is still stably dispersed in the epoxy resin system, which means that the CHBPE-DICY / DDS system has a stable structure, good dispersion and is not prone to sedimentation in the epoxy resin system. Figure 5 cd in the figure are the morphologies of CHBPE-DICY / DDS system in epoxy resin system after being treated at 140℃, 150℃ or ultrasonic treatment for 1min. Figure 5 As can be observed in the graphs (cd), the structure of the CHBPE-DICY / DDS system in the epoxy resin system can be disrupted after heat and ultrasound treatment, primarily due to the disruption of hydrogen bonding between the CHBPEs. The disrupted CHBPE-DICY / DDS system releases DICY / DDS particles, enabling controlled curing of the epoxy resin. Clearly, the curing behavior of epoxy systems containing the CHBPE-DICY / DDS system can be controlled by controlling the release of DICY / DDS from the CHBPE-DICY / DDS system through heat and ultrasound treatment.

[0048] Comparative Example 2-1

[0049] At room temperature, ethylenediamine was added to 500g of bisphenol A epoxy resin (E-51), and the mixture was stirred at room temperature for 30 minutes. Then, tetrahydrofuran-based polyurethane prepolymer (PTMEG) (HJ-2185, NCO content approximately 3.5%) was added at 100°C and stirred for 2 hours. The mixture was then stirred under vacuum for 50 minutes. CHBPE (HyperC20), DICY, and DDS were then added at room temperature and stirred under vacuum for 6 minutes. The resulting structural adhesive was sealed and stored until ready for use. The mass ratio of epoxy: ethylenediamine: polyurethane prepolymer: CHBPE: DICY: DDS was 50:1:15:8:4:4. The CHBPE, DICY, and DDS contents were similar to those in the CHBPE-DICY / DDS structural adhesive in Example 2.

[0050] Comparative Example 2-2

[0051] At room temperature, ethylenediamine was added to 500g of bisphenol A epoxy resin (E-51). The mixture was stirred at room temperature for 30 minutes. Then, tetramethylene glycol (PTMEG) (HJ-2185, NCO content approximately 3.5%) was added at 100°C. After stirring for 2 hours, the mixture was stirred under vacuum for 50 minutes. DICY and DDS were then added at room temperature and stirred under vacuum for 6 minutes. The resulting structural adhesive was sealed and stored until ready for use. The structural adhesive was cured using a temperature program of 150°C / 2h followed by 180°C / 2h to produce an epoxy structural adhesive. The mass ratio of epoxy:ethylenediamine:polyurethane prepolymer:DICY:DDS was 50:1:15:4:4. The DICY and DDS contents were similar to those in the CHBPE-DICY / DDS structural adhesive in Example 2.

[0052] Comparative Example 2-3

[0053] At room temperature, ethylenediamine was added to 500g of bisphenol A epoxy resin (E-51). The mixture was stirred at room temperature for 30 minutes. Then, tetrahydrofuran-based polyurethane prepolymer (PTMEG) (HJ2185, NCO content approximately 3.5%) was added at 100°C and stirred for 2 hours. The mixture was then stirred under vacuum for 50 minutes. CHBPE (HyperC20) was then added at room temperature and stirred under vacuum for 6 minutes. The resulting structural adhesive was sealed and stored until ready for use. The mass ratio of epoxy: ethylenediamine: polyurethane prepolymer: CHBPE was 50:1:15:8. The CHBPE content was similar to that in the CHBPE-DICY / DDS structural adhesive in Example 2.

[0054] The above structural adhesive is cured at 150° C. / 2 h+180° C. / 2 h respectively to obtain epoxy structural adhesive material.

[0055] Table 2 lists the mechanical properties of the structural adhesive materials, the gel time and the storage period of the structural adhesive in Example 2 and Comparative Examples 2-1, 2-2 and 2-3. Figure 6 The following are SEM images of cross-sections of the epoxy structural adhesive materials used in Example 2 and Comparative Examples 2-1 and 2-2. The addition of the CHBPE-DICY / DDS hybrid system to the epoxy adhesive significantly improves its mechanical properties. The impact strength of the material in Example 2 increases by 36% and 61% compared to Comparative Examples 2-1 and 2-2, respectively. The flexural strength of the epoxy structural adhesive in Example 2 increases by 144% and 175% compared to Comparative Examples 2-1 and 2-2, respectively. The tensile strength of the epoxy structural adhesive in Example 2 increases by 63% and 93% compared to Comparative Examples 2-1 and 2-2, respectively. At 140°C, the gel time of the epoxy structural adhesive in Example 2 is longer than that of Comparative Examples 2-1 and 2-2. At 150°C, the gel time of the epoxy structural adhesive in Example 2 is similar to that of the structural adhesives in Comparative Examples 2-1 and 2-2. Obviously, the CHBPE-DICY / DDS hybrid system can more effectively improve the comprehensive performance of epoxy structural adhesive materials than DICY / DDS and DICY / DDS / CHBPE mixtures and can control the release of DICY / DDS to cure epoxy resin. In Comparative Examples 2-3, the added CHBPE is difficult to achieve effective curing of epoxy resin, and the mechanical properties of the prepared structural adhesive system cannot be obtained. Figure 6 From the fracture morphology images of the materials, it can be found that the fracture morphology of the material in Example 2 is rougher than that in Comparative Examples 2-1 and 2-2, which also means that the material in Example 2 can consume more energy and has higher toughness.

[0056] Example 3

[0057] (1) Preparation of carboxyl-terminated hyperbranched polyester (CHBPE)-dicyandiamide (DICY) hybrid system

[0058] Add 1 kg of molecular weight (M) of curing agent dicyandiamide (DICY) in N, N-dimethylformamide (DMF) solution to n The CHBPE-DICY hybrid system was prepared by stirring a carboxyl-terminated hyperbranched polyester (CHBPE) (HyperC20) with a DMF content of 5200 at 50°C for 4 hours, then heating to 160°C and stirring for 4 hours. The weight ratio of CHBPE, DMF, and DICY was 100:80:50.

[0059] (2) Preparation of epoxy structural adhesive

[0060] Tert-butoxybis(dimethylamino)methane was added to 500g of bisphenol A epoxy resin (E-51), stirred at 140°C for 10 minutes, cooled to 120°C, and tetrahydrofuran-type polyurethane prepolymer (PTMEG) (HJ2195, OCN content of 6%) was added. After stirring for 0.5h, vacuum stirring was performed for 20min, and CHBPE-DICY was added at room temperature. The obtained structural adhesive was sealed and stored for later use. The mass ratio of epoxy: tert-butoxybis(dimethylamino)methane: polyurethane prepolymer: CHBPE-DICY was 50:5:25:15.

[0061] Comparative Example 3-1

[0062] 500g of bisphenol A epoxy resin (E-51) was added with tert-butoxybis(dimethylamino)methane and stirred at 140°C for 10 minutes. The mixture was then cooled to 120°C and a tetrahydrofuran-based polyurethane prepolymer (PTMEG) (HJ2195, 6% OCN content) was added. The mixture was stirred for 0.5 hours and then vacuum-stirred for 20 minutes. CHBPE and DICY were then added at room temperature and stirred for 10 minutes. The resulting structural adhesive was sealed and stored for later use. The mass ratio of epoxy: tert-butoxybis(dimethylamino)methane: polyurethane prepolymer: CHBPE: DICY was 50:5:25:10:5. The CHBPE and DICY contents were similar to those in the CHBPE-DICY structural adhesive in Example 3.

[0063] Comparative Example 3-2

[0064] Tert-butoxybis(dimethylamino)methane was added to 500g of bisphenol A epoxy resin (E-51) and stirred at 140°C for 10 minutes. The mixture was then cooled to 120°C and a tetrahydrofuran-based polyurethane prepolymer (PTMEG) (HJ2195, 6% OCN content) was added. The mixture was stirred for 0.5 hours and then vacuum-stirred for 20 minutes. DICY was then added at room temperature and stirred for 10 minutes. The resulting structural adhesive was sealed and stored for later use. The mass ratio of epoxy:tert-butoxybis(dimethylamino)methane:polyurethane prepolymer:DICY was 50:1:25:5. The DICY content was similar to that in the CHBPE-DICY structural adhesive in Example 3.

[0065] Comparative Example 3-3

[0066] Tert-butoxybis(dimethylamino)methane was added to 500g of bisphenol A epoxy resin (E-51) and stirred at 140°C for 10 minutes. The mixture was then cooled to 120°C and a tetrahydrofuran-based polyurethane prepolymer (PTMEG) (HJ2195, 6% OCN content) was added. The mixture was stirred for 0.5 hours and then vacuum-stirred for 200 minutes. CHBPE was then added at room temperature and vacuum-stirred for 6 minutes. The resulting structural adhesive was sealed and stored until ready for use. The mass ratio of epoxy: tert-butoxybis(dimethylamino)methane: polyurethane prepolymer: CHBPE was 50:1:25:10. The CHBPE content was similar to that in the CHBPE-DICY structural adhesive in Example 3.

[0067] The above structural adhesive is cured at 120° C. / 4 h+180° C. / 2 h to obtain epoxy structural adhesive material.

[0068] Table 3 lists the mechanical properties of the structural adhesive materials, the gel time and the storage period of the structural adhesive in Example 3 and Comparative Examples 3-1, 3-2 and 3-3. Figure 6 The following are SEM images of cross-sections of the epoxy structural adhesive materials used in Example 3 and Comparative Examples 3-1 and 3-2. The addition of the CHBPE-DICY hybrid system to the epoxy adhesive significantly improves its mechanical properties. The impact strength of the material in Example 3 is 60% and 124% higher than that of Comparative Examples 3-1 and 3-2, respectively. The flexural strength of the epoxy structural adhesive in Example 2 is 80% and 93% higher than that of Comparative Examples 3-1 and 3-2, respectively. The tensile strength of the epoxy structural adhesive in Example 3 is 64% and 84% higher than that of Comparative Examples 3-1 and 3-2, respectively. At 140°C, the gel time of the epoxy structural adhesive in Example 3 is longer than that of Comparative Examples 3-1 and 3-2. At 150°C, the gel time of the epoxy structural adhesive in Example 3 is similar to that of the structural adhesives in Comparative Examples 3-1 and 3-2. Obviously, the CHBPE-DICY hybrid system can more effectively improve the comprehensive performance of epoxy structural adhesive materials than DICY and DICY / CHBPE mixtures and can control the release of DICY to cure epoxy resin. In Comparative Example 3-3, the added CHBPE is difficult to achieve effective curing of epoxy resin, and the mechanical properties of the prepared structural adhesive system cannot be obtained. Figure 6 From the SEM images, it can be found that the fracture morphology of the material in Example 3 is rougher than that of Comparative Examples 3-1 and 3-2, which also means that the material in Example 3 can consume more energy and has higher toughness.

[0069] Example 4

[0070] (1) Preparation of hyperbranched polyamide (HPBPA)-imidazole (MZ) hybrid system

[0071] A solution of imidazole (MZ) in N,N-dimethylformamide (DMF) was added to 800 g of hydroxyl-terminated hyperbranched polyamide (HPBPA) (HyPer HPN202, molecular weight 2700), stirred at 50°C for 0.5 h, and then heated and stirred at 160°C for 0.5 h to obtain an HPBPA-MZ hybrid system; the weight ratio of AHPBPA, DMF, and MZ was 80:40:20.

[0072] (2) Preparation of epoxy structural adhesive

[0073] HPBPA-MZ was added to 1000 g of bisphenol A epoxy resin (E-44) at room temperature and stirred in vacuum for 3 minutes. The obtained structural adhesive was sealed and stored for later use; wherein the mass ratio of epoxy:HPBPA-MZ was 100:40.

[0074] Comparative Example 4-1

[0075] HPBPA (HyPer HPN202, molecular weight 2700) and MZ were added to 1000 g of bisphenol A epoxy resin (E-44) at room temperature and stirred in a vacuum for 3 minutes. The resulting structural adhesive was sealed and stored for later use. The mass ratio of epoxy:HPBPA:MZ was 100:32:8, and the HPBPA and MZ contents were similar to those in the HPBPA-MZ structural adhesive in Example 4.

[0076] Comparative Example 4-2

[0077] At room temperature, MZ was added to 1000g of bisphenol A epoxy resin (E-44) and stirred under vacuum for 3 minutes. The resulting structural adhesive was sealed and stored until ready for use. The mass ratio of epoxy to MZ was 1000:8. The MZ content was similar to that in the HPBPA-MZ structural adhesive in Example 4.

[0078] Comparative Example 4-3

[0079] HPBPA (HyPer HPN202, molecular weight 2700) was added to 1000g of bisphenol A epoxy resin (E-44) at room temperature and stirred under vacuum for 3 minutes. The resulting structural adhesive was sealed and stored until ready for use. The mass ratio of epoxy to HPBPA was 100:32. The HPBPA content was similar to the BPET content in the HPBPA-MZ structural adhesive in Example 4.

[0080] The above structural adhesive is cured at 120° C. / 1 h+170° C. / 1 h respectively to obtain epoxy structural adhesive material.

[0081] Table 4 lists the mechanical properties, gel time, and shelf life of the structural adhesive materials in Example 4 and Comparative Examples 4-1, 4-2, and 4-3. The addition of the HPBPA-MZ hybrid system to the epoxy adhesive significantly improves its mechanical properties. The impact strength of the material in Example 4 increases by 142% and 950% compared to Comparative Examples 4-1 and 4-2, respectively. The flexural strength of the epoxy structural adhesive in Example 4 increases by 26% and 37% compared to Comparative Examples 4-1 and 4-2, respectively. The tensile strength of the epoxy structural adhesive in Example 4 increases by 54% and 80% compared to Comparative Examples 4-1 and 4-2, respectively. At 120°C, the gel time of the epoxy structural adhesive in Example 4 is longer than that of Comparative Examples 4-1 and 4-2. At 150°C, the gel time of the epoxy structural adhesive in Example 4 is similar to that of the structural adhesives in Comparative Examples 4-1 and 4-2. Clearly, the HPBPA-MZ hybrid system is more effective than MZ and HPBPA / MZ mixtures in improving the overall performance of epoxy structural adhesives and enabling controlled release of MZ to cure epoxy resins. In Comparative Example 4-3, the added HPBPA made it difficult to effectively cure the epoxy resin, and the mechanical properties of the prepared structural adhesive system were not achieved.

[0082]

[0083] The present invention embeds a curing agent into the pores of a hyperbranched polymer and further utilizes the self-assembly behavior of the amphiphilic hyperbranched polymer to further isolate the curing agent from the epoxy resin, thereby improving the shelf life of the epoxy adhesive. Furthermore, the curing behavior of the epoxy adhesive can be controlled by controlling the release of the curing agent from the hyperbranched polymer through thermal and mechanical manipulation. Furthermore, the hyperbranched polymer has abundant active end groups that react with the resin system and form a strong interfacial interaction with the resin matrix, thereby improving the structure and performance of the epoxy adhesive.

Claims

1. A high-toughness, high-strength, one-component epoxy structural adhesive system with high storage stability and controllable reaction, characterized in that: The high-toughness and high-strength one-component epoxy structural adhesive system with high storage stability and controllable reaction comprises an epoxy resin, a chain extender, a hyperbranched polymer hybrid system loaded with a curing agent, and a polyurethane prepolymer; or the high-toughness and high-strength one-component epoxy structural adhesive system with high storage stability and controllable reaction comprises an epoxy resin and a hyperbranched polymer hybrid system loaded with a curing agent; The preparation process of the hyperbranched polymer hybrid system loaded with a curing agent comprises the following steps: adding a curing agent or a curing agent solution to a hyperbranched polymer, stirring at 25-50° C. for 0.5-4 hours, and then stirring at 120-160° C. for 0.5-4 hours to obtain the hyperbranched polymer hybrid system loaded with a curing agent; the preparation method of the high-toughness, high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction comprises the following steps: stirring an epoxy resin and a chain extender at room temperature to 140° C. for 10-30 minutes, then adding a polyurethane prepolymer at 100-120° C. and continuing the reaction for 0.5-2 hours, then vacuum stirring for 20-50 minutes, and then adding the hyperbranched polymer hybrid system loaded with a curing agent at room temperature to obtain the high-toughness, high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction; Alternatively, the epoxy resin is mixed with a hyperbranched polymer hybrid system loaded with a curing agent at room temperature to obtain the high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction; The hyperbranched polymer includes a functional group-terminated hyperbranched polyester, wherein the functional group is a hydroxyl group or an amino group, or the hyperbranched polymer includes a functional group-terminated hyperbranched polyether, a functional group-terminated hyperbranched polyamide ester, a functional group-terminated hyperbranched polyamide, or a functional group-terminated hyperbranched polyurethane, wherein the functional group is a carboxyl group, a hydroxyl group or an amino group.

2. The high-toughness, high-strength, one-component epoxy structural adhesive system with high storage stability and controllable reaction according to claim 1, characterized in that: The mass ratio of epoxy resin, chain extender, hyperbranched polymer hybrid system loaded with curing agent and polyurethane prepolymer is (30-50): (0-5): (10-50): (0-25).

3. The high-toughness, high-strength, one-component epoxy structural adhesive system with high storage stability and controllable reaction according to claim 1, characterized in that: The weight ratio of the hyperbranched polymer to the curing agent is 100:(10-50), and the weight ratio of the solvent to the curing agent is (20-80):(10-50).

4. The high-toughness, high-strength, one-component epoxy structural adhesive system with high storage stability and controllable reaction according to claim 1, characterized in that: The epoxy resin includes one or more of glycidyl ether epoxy resin, glycidyl ester epoxy resin, glycidyl amine epoxy resin, alicyclic epoxy resin, and linear aliphatic epoxy compound; the curing agent is one or more of aromatic amine, dicyandiamide and its derivatives, organic hydrazide, imidazole and its derivatives; the chain extender is an amino or imino compound; and the polyurethane prepolymer is a prepolymer with different -NCO contents and a mixture thereof.

5. The method for preparing the high-toughness and high-strength one-component epoxy structural adhesive system with high storage stability and controllable reaction according to claim 1, characterized in that: The epoxy resin and the chain extender are stirred and reacted at room temperature to 140° C. for 10 to 30 minutes, and then a polyurethane prepolymer is added at 100 to 120° C. and the reaction is continued for 0.5 to 2 hours. The mixture is then vacuum stirred for 20 to 50 minutes, and then a hyperbranched polymer hybrid system loaded with a curing agent is added at room temperature to obtain the high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction; Alternatively, the epoxy resin is mixed with a hyperbranched polymer hybrid system loaded with a curing agent at room temperature to obtain the high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction.

6. A high-toughness and high-strength single-component epoxy material, characterized in that: The adhesive is obtained by curing the high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction as described in claim 1.

7. The high-toughness and high-strength single-component epoxy material according to claim 6, characterized in that: The curing temperature is 120-180° C., the curing time is 2-6 hours, and the curing adopts a step curing process.

8. Use of the high-toughness and high-strength one-component epoxy structural adhesive system with high storage stability and controllable reaction according to claim 1 or the high-toughness and high-strength one-component epoxy material according to claim 6 in the preparation of structural adhesive materials.

9. The method for applying the high-toughness and high-strength one-component epoxy structural adhesive system with high storage stability and controllable reaction according to claim 1, characterized in that: The high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction is placed at a target position, and the application of the high-toughness and high-strength single-component epoxy structural adhesive system with high storage stability and controllable reaction is completed by curing.

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